Patent Publication Number: US-8977216-B2

Title: Limited Q factor tunable front end using tunable circuits and microelectromechanical system (MEMS)

Description:
CLAIM OF PRIORITY UNDER 35 U.S.C. 119 
     The present Application for patent claims priority to Provisional Application No. 61/612,890, entitled “NOVEL OPTIMIZED RFIC DISTRIBUTED MEMS BASED FRONT-END” filed Mar. 19, 2012, and assigned to the assignee hereof and hereby expressly incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to wireless devices for communication systems. More specifically, the present disclosure relates to systems and methods for a limited Q factor tunable front end using tunable circuits and microelectromechanical system (MEMS) in devices. 
     BACKGROUND 
     Electronic devices (cellular telephones, wireless modems, computers, digital music players, Global Positioning System units, Personal Digital Assistants, gaming devices, etc.) have become a part of everyday life. Small computing devices are now placed in everything from automobiles to housing locks. The complexity of electronic devices has increased dramatically in the last few years. For example, many electronic devices have one or more processors that help control the device, as well as a number of digital circuits to support the processor and other parts of the device. 
     These electronic devices may communicate wirelessly with each other and with a network. As the demand for information by these electronic devices has increased, the downlink throughput has also increased. One such way to increase downlink throughput is the use of carrier aggregation. In carrier aggregation, multiple carriers may be aggregated on the physical layer to provide the required bandwidth (and thus the required throughput). 
     It may be desirable for an electronic device to maximize battery life. Because an electronic device often runs on a battery with a limited operation time, reductions in the power consumption of an electronic device may increase the desirability and functionality of the electronic device. 
     The electronic devices have also become smaller and cheaper. To facilitate both the decrease in size and the decrease in cost, additional circuitry and more complex circuitry are being used on integrated circuits. Thus, any reduction in the die area used by circuitry may reduce both the size and cost of an electronic device. Benefits may be realized by improvements to electronic devices that allow an electronic device to participate in carrier aggregation while minimizing the cost and size of the electronic device while also minimizing the power consumption of the electronic device. 
     SUMMARY 
     A wireless device is described. The wireless device includes a tunable front end module. The tunable front end module includes a Tx microelectromechanical system bandpass filter and a first Rx microelectromechanical system bandpass filter. The wireless device also includes a power amplifier. The wireless device further includes a low noise amplifier. 
     The tunable front end module may include a microelectromechanical system duplexer. The microelectromechanical system duplexer may include a first tunable filter for Tx and a second tunable filter for Rx. The first tunable filter and the second tunable filter may use microelectromechanical system technology. The power amplifier may be coupled between the Tx microelectromechanical system bandpass filter and the first tunable filter. The low noise amplifier may be coupled between the first Rx microelectromechanical system bandpass filter and the second tunable filter. The first tunable filter and the second tunable filter may be coupled to an antenna. 
     The wireless device may include a radio frequency integrated circuit that includes a driver amplifier and a post-LNA amplifier. The driver amplifier may be tunable to provide higher gain to narrower chunks of bandwidth. The post-LNA amplifier may also be tunable to provide higher gain to narrower chunks of bandwidth. The power amplifier may be integrated with the tunable front end module. The low noise amplifier may also be integrated with the tunable front end module. 
     The power amplifier may be a distributed gain power amplifier. The power amplifier may include a Tx driver integrated on a radio frequency integrated circuit, a low gain power amplifier, a Tx driver filter coupled between the Tx driver and the low gain power amplifier and a Tx filter coupled to an output of the low gain power amplifier. 
     The low noise amplifier may be a distributed gain low noise amplifier. The low noise amplifier may include a post-LNA amplifier integrated on a radio frequency integrated circuit, a low gain low noise amplifier, an Rx post-LNA filter coupled between the post-LNA amplifier and the low gain low noise amplifier and an Rx filter coupled to an input of the low gain low noise amplifier. 
     The low noise amplifier and the power amplifier may be integrated with the tunable front end module. The Tx microelectromechanical system bandpass filter and the first Rx microelectromechanical system bandpass filter may be integrated on a radio frequency integrated circuit. The low noise amplifier may also be integrated on the radio frequency integrated circuit. The power amplifier may be integrated on the radio frequency integrated circuit. The power amplifier may be tunable to provide higher gain to narrower chunks of bandwidth. The power amplifier may have higher efficiency and better matching to the antenna because an output filter is not used. The power amplifier may emit less, since the response of the power amplifier is the same as a bandpass filter. 
     The power amplifier may improve Rx/Tx isolation, since the bandwidth is narrower and rejection is increased. The low noise amplifier may be tunable to provide higher gain to narrower chunks of bandwidth. The low noise amplifier may allow for the relaxation of specifications for an input filter. The low noise amplifier may have higher efficiency and lower noise figures because the low noise amplifier is better matched to the input filter and since the specification for the input filter are relaxed. The low noise amplifier may have a response that is the same as a bandpass filter. The low noise amplifier may improve Rx/Tx isolation, since the bandwidth is narrower and rejection is increased. 
     The wireless device may include a microelectromechanical system RF switch and multiple Rx surface acoustic wave duplexers. The microelectromechanical system RF switch may couple the low noise amplifier to an antenna via one of the multiple Rx surface acoustic wave duplexers. 
     The wireless device may include a Tx band select microelectromechanical system switch and multiple Tx surface acoustic wave duplexers. The Tx band select microelectromechanical system switch may couple the power amplifier to the antenna via one of the multiple Tx surface acoustic wave duplexers. 
     The wireless device may include a first antenna. The wireless device may also include a second Rx microelectromechanical bandpass filter coupled between the first antenna and the first microelectromechanical bandpass filter. The wireless device may further include a second antenna coupled to an output of the power amplifier. 
     A method for wireless communications is also described. A receive signal is received. The receive signal is routed through a first Rx microelectromechanical bandpass filter in a tunable front end module. The receive signal is provided to a modem. A transmit signal is received from the modem. The transmit signal is routed through a Tx microelectromechanical bandpass filter in the tunable front end module. The transmit signal is transmitted. 
     The method may be performed by a wireless device that includes a tunable front end module. The tunable front end module may include a power amplifier and a low noise amplifier. The wireless device may be a wireless communication device or a base station. 
     An apparatus for wireless communications is described. The apparatus includes means for receiving a receive signal. The apparatus also includes means for routing the receive signal through a first Rx microelectromechanical bandpass filter in a tunable front end module. The apparatus further includes means for providing the receive signal to a modem. The apparatus also includes means for receiving a transmit signal from the modem. The apparatus further includes means for routing the transmit signal through a Tx microelectromechanical bandpass filter in the tunable front end module. The apparatus also includes means for transmitting the transmit signal. 
     A computer-program product for wireless communications is also described. The computer-program product includes a non-transitory computer-readable medium having instructions thereon. The instructions include code for causing a wireless device to receive a receive signal. The instructions also include code for causing the wireless device to route the receive signal through a first Rx microelectromechanical bandpass filter in a tunable front end module. The instructions further include code for causing the wireless device to provide the receive signal to a modem. The instructions also include code for causing the wireless device to receive a transmit signal from the modem. The instructions further include code for causing the wireless device to route the transmit signal through a Tx microelectromechanical bandpass filter in the tunable front end module. The instructions also include code for causing the wireless device to transmit the transmit signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a wireless device for use in the present systems and methods; 
         FIG. 2  is a block diagram illustrating a distributed gain power amplifier (PA) configuration and a high gain power amplifier (PA); 
         FIG. 3  is a block diagram illustrating a distributed gain low noise amplifier (LNA) configuration and a high gain low noise amplifier (LNA); 
         FIG. 4  is a block diagram illustrating one configuration of a tunable front end module and a radio frequency integrated circuit (RFIC) on a printed circuit board (PCB); 
         FIG. 5  is a flow diagram of a method for using microelectromechanical system (MEMS) filters in a tunable front end module; 
         FIG. 6  is a block diagram illustrating a tunable front end module with an integrated power amplifier (PA); 
         FIG. 7  is a block diagram illustrating a front end module with an integrated low noise amplifier (LNA); 
         FIG. 8  is a block diagram illustrating a front end module with an integrated power amplifier (PA); 
         FIG. 9  is a block diagram illustrating a radio frequency integrated circuit (RFIC), where a portion of the front end module has been integrated into the radio frequency integrated circuit (RFIC); 
         FIG. 10  is a block diagram illustrating another radio frequency integrated circuit (RFIC), where a portion of the front end module has been integrated into the radio frequency integrated circuit (RFIC); 
         FIG. 11  is a circuit diagram illustrating a tunable low noise amplifier (LNA); 
         FIG. 12  is a circuit diagram illustrating a tunable power amplifier (PA); 
         FIG. 13  is a graph illustrating bandwidth chunks selection and tuning; 
         FIG. 14  is a block diagram illustrating a radio frequency integrated circuit (RFIC) with a fully integrated front end module; 
         FIG. 14A  is a block diagram illustrating a radio frequency integrated circuit (RFIC) where the microelectromechanical system (MEMS) radio frequency (RF) switches have been integrated with the radio frequency integrated circuit (RFIC); 
         FIG. 15  is a block diagram illustrating another radio frequency integrated circuit (RFIC) with a fully integrated front end module; 
         FIG. 15A  is a block diagram illustrating the radio frequency integrated circuit (RFIC) where the microelectromechanical system (MEMS) switches are integrated within the radio frequency integrated circuit (RFIC); 
         FIG. 16  is a block diagram illustrating yet another radio frequency integrated circuit (RFIC) with an integrated front end module; 
         FIG. 17  is a block diagram illustrating a radio frequency integrated circuit (RFIC) with an integrated front end module that does not include a duplexer; 
         FIG. 18  illustrates certain components that may be included within a wireless communication device; and 
         FIG. 19  illustrates certain components that may be included within a base station. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a wireless device  102  for use in the present systems and methods. A wireless device  102  may be a wireless communication device or a base station. A wireless communication device may also be referred to as, and may include some or all of the functionality of, a terminal, an access terminal, a user equipment (UE), a subscriber unit, a station, etc. A wireless communication device may be a cellular phone, a personal digital assistant (PDA), a wireless device, a wireless modem, a handheld device, a laptop computer, a PC card, compact flash, an external or internal modem, a wireline phone, etc. A wireless communication device may be mobile or stationary. A wireless communication device may communicate with zero, one or multiple base stations on a downlink and/or an uplink at any given moment. The downlink (or forward link) refers to the communication link from a base station to a wireless communication device, and the uplink (or reverse link) refers to the communication link from a wireless communication device to a base station. Uplink and downlink may refer to the communication link or to the carriers used for the communication link. 
     A wireless communication device may operate in a wireless communication system that includes other wireless devices  102 , such as base stations. A base station is a station that communicates with one or more wireless communication devices. A base station may also be referred to as, and may include some or all of the functionality of, an access point, a broadcast transmitter, a Node B, an evolved Node B, etc. Each base station provides communication coverage for a particular geographic area. A base station may provide communication coverage for one or more wireless communication devices. The term “cell” can refer to a base station and/or its coverage area, depending on the context in which the term is used. 
     Communications in a wireless communication system (e.g., a multiple-access system) may be achieved through transmissions over a wireless link. Such a communication link may be established via a single-input and single-output (SISO) or a multiple-input and multiple-output (MIMO) system. A multiple-input and multiple-output (MIMO) system includes transmitter(s) and receiver(s) equipped, respectively, with multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. SISO systems are particular instances of a multiple-input and multiple-output (MIMO) system. The multiple-input and multiple-output (MIMO) system can provide improved performance (e.g., higher throughput, greater capacity or improved reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized. 
     The wireless communication system may utilize both single-input and multiple-output (SIMO) and multiple-input and multiple-output (MIMO). The wireless communication system may be a multiple-access system capable of supporting communication with multiple wireless communication devices by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, wideband code division multiple access (W-CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, 3 rd  Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems and spatial division multiple access (SDMA) systems. 
     The wireless device  102  may be used for both the transmission of wireless signals and the reception of wireless signals. Thus, the wireless device  102  may include a transmit (Tx) chain and a receive (Rx) chain. The transmit (Tx) chain may route signals generated by a modem through a transmitter to be transmitted by an antenna. Likewise, the receive (Rx) chain may route signals received by an antenna through a receiver to be decoded by a modem. Portions of the receive (Rx) chain and the transmit (Tx) chain may be located on a printed circuit board (PCB)  106  in the wireless device  102 . In one configuration, portions of the receive (Rx) chain and the transmit (Tx) chain may be located on an integrated circuit on the printed circuit board (PCB)  106  (referred to as a radio frequency integrated circuit (RFIC)  108 ). 
     The wireless device  102  may include a front end module  110 . The front end module  110  may refer to all the circuitry between the antenna and a first intermediate frequency (IF) stage. The front end module  110  may be located on the printed circuit board (PCB)  106 . In one configuration, some or all of the front end module  110  may be located on the radio frequency integrated circuit (RFIC)  108 . As used herein, a module is an external unit to the radio frequency integrated circuit (RFIC)  108  and a block is internal to the radio frequency integrated circuit (RFIC)  108 . 
     Conventionally, in a multiband zero intermediate frequency (ZIF) or very low intermediate frequency (VLIF) architecture, the front end module  110  on a radio frequency integrated circuit (RFIC)  108  may include multiple low noise amplifiers (LNAs) and multiple power amplifier (PA) drivers that are coupled to the radio frequency integrated circuit (RFIC)  108  package pins. The radio frequency integrated circuit (RFIC)  108  pins may then be coupled to external components such as power amplifiers (PAs), duplexers, low noise amplifiers (LNAs), switches and an RF front end module. The external components naturally increase both the cost and area consumption of the printed circuit board (PCB)  106 . 
     In some architectures, a power amplifier (PA) may be reused for multiple bands (thus requiring a low efficiency). This is because the power amplifier (PA) must maintain high power for a wide band. In other architectures, multiple power amplifiers (PAs) may be used for each band, leading to an increase in the cost and area consumption of the printed circuit board (PCB)  106 . 
     Traditionally, the external power amplifier (PA) has a high gain and is cascaded directly to the PA-driver on the radio frequency integrated circuit (RFIC)  108 . This may increase the Tx out-of-band noise level (e.g., the noise density). The additional noise may be filtered by the front end Tx filter. However, the additional noise may be reduced if the power amplifier (PA) gain and filtering is distributed differently such that the power amplifier (PA) bandwidth is tunable in chunks. In other words, the additional noise may be reduced if a tunable power amplifier (PA) is used in the wireless device. Stringent specifications of high rejection at the RF front end (RFFE) duplexer to prevent Rx compression and blocking by the Tx may result in high pass-band insertion-loss (IL). The insertion-loss (IL) may resemble an increase in the Rx noise figure (NF) and the Tx insertion loss (IL), causing an increase in the Tx power amplifier (PA) gain (resulting in an increase in the power consumption of the wireless device). Noise Figure (NF) is measured in decibels (dBs). 
     Excessive insertion loss (IL) in the radio frequency front end (RFFE) and the part count in the wireless device  102  may be reduced by the present systems and methods. Furthermore, problems associated with multiple front end modules may be mitigated using the present systems and methods. A typical radio frequency integrated circuit (RFIC)  108  structure may include excessive off-chip components and in-chip front end blocks such as multiple low noise amplifiers (LNAs) and Tx drivers. Thus, a typical radio frequency integrated circuit (RFIC)  108  structure may have non-optimal performance in terms of power consumption, noise-figure (NF), insertion loss (IL), degraded sensitivity, size and cost. The present systems and methods may improve the transmit/receive performance of the wireless device  102 . 
     The wireless device  102  may include a tunable front end module  110 . In one configuration, the tunable front end module  110  may be located on the radio frequency integrated circuit (RFIC)  108 . In another configuration, the tunable front end module  110  may be located on the printed circuit board (PCB)  106  but not on the radio frequency integrated circuit (RFIC)  108 . A tunable front end module  110  may make use of a microelectromechanical system (MEMS). A microelectromechanical system (MEMS) may include moving parts such that incoming signals generate voltages that produce an electrostatic force, causing parts within the microelectromechanical system (MEMS) to move to a new position based on the electrostatic field applied on a cantilever. This may include moving beams of RF switches or high Q air capacitors. 
     A microelectromechanical system (MEMS) may be used as a bandpass filter (BPF) to reject signals with certain frequencies while passing signals with other frequencies. One advantage of using a microelectromechanical system (MEMS) is that a microelectromechanical system (MEMS) allows the wireless device  102  to process signals with minimal interference and maximum transmission efficiency. Furthermore, a microelectromechanical system (MEMS) may use considerably less space on a printed circuit board (PCB)  106  and/or on a radio frequency integrated circuit (RFIC)  108 . By using microelectromechanical system (MEMS) technology, filters may be tuned to cover the entire receive and transmit range, thus reducing the need for additional off-chip components. 
     In one configuration, a single tunable microelectromechanical system (MEMS) filter  112  along with a single distributed gain tunable power amplifier (PA)  116  and a single distributed gain tunable low noise amplifier (LNA)  114  can replace all off-chip parts as well as reduce the number of radio frequency integrated circuit (RFIC)  108  internal front end module  110  blocks. Thus, the wireless device  102  may include one or two tunable front end modules  110  and a radio frequency integrated circuit (RFIC)  108  with one or two tunable RF front end blocks such as a single internal low noise amplifier (LNA) (a post-LNA amplifier  120 ) and a single Tx driver amplifier  118 . The front end module  110  may also include a microelectromechanical (MEMS) duplexer  122 . The microelectromechanical (MEMS) duplexer  122  is discussed in additional detail below in relation to  FIG. 4 . Distributed gain power amplifiers (PAs) are discussed below in relation to  FIG. 2 . Tunable power amplifiers (PAs) are discussed below in relation to  FIG. 12 . Distributed gain low noise amplifiers (LNAs) are discussed below in relation to  FIG. 3 . Tunable low noise amplifiers (LNAs) are discussed below in relation to  FIG. 11 . 
       FIG. 2  is a block diagram illustrating a distributed gain power amplifier (PA) configuration  230  and a high gain power amplifier (PA)  235 . Traditionally, the power amplifier (PA)  237  is directly coupled to the radio frequency integrated circuit (RFIC)  208   b  Tx driver  236  (as shown in the high gain power amplifier (PA)  235 ). The wideband noise density may be expressed using Equation (1):
 
 N=kTFG+Pn (ƒ) G.   (1)
 
     In Equation (1), k is the Boltzmann constant, T is the temperature in Kelvin, F is the Tx chain equivalent noise-figure (NF) and G is the Tx gain. Pn(ƒ) is the phase noise density as a function of frequency. Equation (1) may be rewritten as Equation (2):
 
 N=kTF   1   G   1   G   2   +kTF   2   G   2   +Pn (ƒ) G   1   G   2 .  (2)
 
     In Equation (2), G 1  is the Tx gain factor within the radio frequency integrated circuit (RFIC)  208   b , F 1  is the noise figure (NF) within the radio frequency integrated circuit (RFIC)  208   b , G 2  is the power amplifier (PA)  237  gain factor and G 2  is the power amplifier (PA)  237  noise figure (NF). The noise may be filtered by the radio frequency front end (RFFE) filter  238  as described using Equation (3):
 
 N   out =( kTF   1   G   1   G   2   +kTF   2   G   2   +Pn (ƒ) G   1   G   2 ) H   t (ƒ).  (3)
 
     In Equation (3), Ht(f) is the radio frequency front end (RFFE) filter  238  response versus frequency. The radio frequency front end (RFFE) filter  238  may also reduce the undesired Tx harmonics and spurious signals created throughout the Tx chain. Harmonics and spurious signals generated within the radio frequency integrated circuit (RFIC)  208   b  are thus amplified by the external power amplifier (PA)  237  and additional harmonics are generated. 
     By distributing differently the Tx gain through the Tx chain and inserting a Tx inter-stage bandpass filter (BPF) filter (i.e., the Tx filter  234 ), the high gain power amplifier (PA)  235  may become a distributed gain power amplifier (PA) configuration  230 . In the distributed gain power amplifier (PA) configuration  230 , the wideband noise may be reduced, since the noise created by the radio frequency integrated circuit (RFIC)  208   a  and the Tx driver  231  is reduced by the inter-stage filter (i.e., the Tx driver filter  232 ) as described in Equation (4):
 
 N   out =(( Pn (ƒ) G   1   +kTF   1   G   1 ) H   1 (ƒ) G   2   +kTF   2   G   2 ) H   2 (ƒ).  (4)
 
     In Equation (4), H 1 ( f ) is the inter-stage filter (i.e., the Tx driver filter  232 ) response versus frequency and H 2 ( f ) is the Tx filter  234  response versus frequency. In the distributed gain power amplifier (PA) configuration  230 , the radio frequency integrated circuit (RFIC)  208   a  harmonics and spurious signals may be attenuated by the Tx driver filter  232  and further generation of undesired spurious signals within the power amplifier (PA)  233  may be minimized. The low gain power amplifier (PA)  233  has lower gain than the power amplifier (PA)  237 , reducing the generation of undesired spurious signals within the distributed gain power amplifier (PA) configuration  230 . 
     The Tx filter  234  may require less stringent rejection specifications, resulting in a reduced insertion loss (IL). A lower insertion loss (IL) results in a lower required power amplifier (PA) gain G 2 , resulting in reduced power consumption, as described in Equation (5):
 
 H   1 (ƒ)+ H   2 (ƒ)&lt; H   t (ƒ).  (5)
 
     In Equation (5), Ht(f) is the filter response versus frequency of a radio frequency front end (RFFE) filter  238  used in conventional Tx design. In Equation (5), H 1 ( f ), H 2 ( f ) and Ht(f) are expressed in decibels (dB). Because the power amplifier (PA) gain G 2  of the low gain power amplifier (PA)  233  is lower, the low gain power amplifier (PA)  233  is less susceptible to oscillation and emitting noise on the printed circuit board (PCB)  106  than the power amplifier (PA)  237 . 
     The gain values used in the distributed gain power amplifier (PA) configuration  230  are different than the gain values used in the high gain power amplifier (PA)  235 . In the distributed gain power amplifier (PA) configuration  230 , the power amplifier (PA) gain is reduced and the Tx driver  231  gain is increased to an optimum level. In addition, the Tx driver filter  232  and the Tx filter  234  have an optimized shape-factor that provides the required rejection while minimizing insertion loss (IL). Thus, a distributed gain power amplifier (PA) configuration  230  has advantages over a high gain power amplifier (PA)  235 . 
       FIG. 3  is a block diagram illustrating a distributed gain low noise amplifier (LNA) configuration  334  and a high gain low noise amplifier (LNA)  346 . Traditionally, the low noise amplifier (LNA)  344  is coupled directly to the post-LNA amplifier  343  in the radio frequency integrated circuit (RFIC)  308   b  (as shown in the high gain low noise amplifier (LNA)  346 ). As a result, the third order intercept point (IP 3 ) of the receive (Rx) chain is low. This is because the low noise amplifier (LNA)  344  has a high gain. The specifications for the Rx filter  345  (a radio frequency front end (RFFE) bandpass filter (BPF)) are for strong rejection, resulting in higher insertion loss (IL) that inherently increases the Rx noise figure (NF). The noise figure (NF) in dB=10 log F. 
     In the distributed gain low noise amplifier (LNA) configuration  334 , the Rx filter  342  is coupled to a low gain low noise amplifier (LNA)  341 . The output of the low gain low noise amplifier (LNA)  341  is coupled to an Rx post-LNA filter  340 . The output of the Rx post-LNA filter  340  is coupled to a high gain post-LNA amplifier  339  that includes multiple cascaded amplifier stages on the radio frequency integrated circuit (RFIC)  308   a . The distributed gain low noise amplifier (LNA) configuration  334  may have higher immunity against out-of-band jammers and Tx blocking, since the Rx filter  342  rejects jammers and Tx blocking and the input stage low noise amplifier (LNA) (i.e., the low gain low noise amplifier (LNA)  341 ) has a lower gain. For the signals and jammers at the Rx post-LNA filter  340 , if the signal is within the bandwidth of the Rx post-LNA filter  340 , insertion loss (IL) only occurs while the jammer is further attenuated, therefore protecting the post-LNA amplifiers  339  within the radio frequency integrated circuit (RFIC)  308   a . As a consequence, the overall third order intercept point (IP 3 ) is improved. This is because the low gain low noise amplifier (LNA)  341  has a lower gain and the RFFE Rx filter  342  is placed at the input of the low gain low noise amplifier (LNA)  341 . Hence, jammers are attenuated and the leaking energy of jammers is amplified using a low gain low noise amplifier (LNA)  341  instead of a high gain low noise amplifier (LNA)  344 . The Rx post-LNA filter  340  may further attenuate the jammers. Thus, the post-LNA amplifier  339 , which has a high gain compared to the low gain low noise amplifier (LNA)  341 , does not amplify high energy jammers, unlike the high gain low noise amplifier (LNA)  346 , which does amplify high energy jammers. 
     Since the Rx filter  342  has lower insertion loss (IL) due to relaxation in the specifications, the distributed gain low noise amplifier (LNA) configuration  334  has an improved noise figure (NF) and sensitivity according to Equation (6): 
     
       
         
           
             
               
                 
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     In Equation (6), H 1 ( f ) is the Rx filter  342  response versus frequency, H 2 ( f ) is the Rx post-LNA filter  340  response versus frequency, G 1  is the gain of the low gain low noise amplifier (LNA)  341 , F 1  is the noise figure (NF) of the low gain low noise amplifier (LNA)  341  and F 2  is the post-LNA amplifiers  339  noise figure (NF). In Equation (6), 0&lt;H 1 (ƒ)&lt;1 and 0&lt;H 2  (ƒ)&lt;1, where an ideal filter has a response equal to 1. Thus, it can be seen that moderate filter insertion loss (IL) adds directly to the noise figure (NF) of the low gain low noise amplifier (LNA)  341 , creating lower performance reduction as compared to a higher insertion loss (IL) Rx filter  345 , where the insertion loss is added to the low noise amplifier (LNA)  344 . Moreover, the low gain low noise amplifier (LNA)  341  in the distributed gain low noise amplifier (LNA) configuration  334  may compensate the rest of the Rx chain noise according to the third and fourth terms of Equation (6). Thus, noise figure (NF) improvement is accomplished in addition to improvements to the third order intercept point (IP 3 ). The noise figure (NF) gain due to the insertion loss (IL) in the Rx filter  342  is described in Equation (7):
 
 H   1 (ƒ)+ H   2 (ƒ)&lt; H   t (ƒ).  (7)
 
     In Equation (7), Ht(f) is the filter response versus frequency of an Rx filter  345  used in conventional Rx design (e.g., a high gain low noise amplifier (LNA)  346 ). In Equation (5), H 1 ( f ), H 2 ( f ) and Ht(f) are expressed in decibels (dB); this means that the overall low noise amplifier (LNA) gain budget in the distributed gain low noise amplifier (LNA) configuration  334  is potentially lower, resulting in saved power. 
       FIG. 4  is a block diagram illustrating one configuration of a tunable front end module  410  and a radio frequency integrated circuit (RFIC)  408  on a printed circuit board (PCB)  406 . The aim of radio frequency integrated circuit (RFIC)  408  radio integration is to minimize the number of off-chip components and provide a modular approach using a tunable front end module  410 . The tunable front end module  410  may use microelectromechanical system (MEMS) technology and provide improved performance. 
     The tunable front end module  410  may include a microelectromechanical system (MEMS) duplexer  422  coupled to an antenna  417 . The microelectromechanical system (MEMS) duplexer  422  may include a first tunable filter  428   a  for the Tx chain and a second tunable filter  428   b  for the Rx chain. Both the first tunable filter  428   a  and the second tunable filter  428   b  may use microelectromechanical system (MEMS) technology. The first tunable filter  428   a  may be coupled to the output of a power amplifier (PA)  424  that is not part of the front end module  410 . The power amplifier (PA)  424  may be the low gain power amplifier (PA)  233  as used in the distributed gain power amplifier (PA) configuration  230 . The input of the power amplifier (PA)  424  may be coupled to a Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  412   a . The input of the Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  412   a  may be coupled to the output of a driver amplifier  418  on the radio frequency integrated circuit (RFIC)  408 . Thus, this configuration represents the distributed gain power amplifier (PA) configuration  230 . 
     The second tunable filter  428   b  may be coupled to the input of a low noise amplifier (LNA)  426  that is not part of the front end module  410 . The low noise amplifier (LNA)  426  may be the low gain low noise amplifier (LNA)  341  in a distributed gain low noise amplifier (LNA) configuration  334 . The output of the low noise amplifier (LNA)  426  may be coupled to an Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  412   b . The output of the Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  412   b  may be coupled to a post-LNA amplifier  420  on the radio frequency integrated circuit (RFIC)  408 . Thus, this configuration represents the distributed gain low noise amplifier (LNA) configuration  334 . 
       FIG. 5  is a flow diagram of a method  500  for using microelectromechanical system (MEMS) filters  412  in a tunable front end module  410 . The method  500  may be performed by a wireless device  102 . The wireless device  102  may be a wireless communication device or a base station. The wireless device  102  may receive  502  a receive signal using an antenna  417 . The wireless device  102  may route  504  the receive signal through a microelectromechanical system (MEMS) duplexer  422  and a Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  412   b  in a front end module  410 . The wireless device  102  may provide  506  the receive signal to a modem. 
     The wireless device  102  may also receive  508  a transmit signal from the modem. The wireless device  102  may route  510  the transmit signal through a Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  412   a  and the microelectromechanical system (MEMS) duplexer  422  in the front end module  410 . The wireless device  102  may transmit  512  the transmit signal using the antenna  417 . 
       FIG. 6  is a block diagram illustrating a tunable front end module  610  with an integrated power amplifier (PA)  624 . The tunable front end module  610  and a radio frequency integrated circuit (RFIC)  608  may be located on a printed circuit board (PCB)  606 . The tunable front end module  610  may include a microelectromechanical system (MEMS) duplexer  622  coupled to an antenna  617 . The microelectromechanical system (MEMS) duplexer  622  may include a first tunable filter  628   a  for the Tx chain and a second tunable filter  628   b  for the Rx chain. Both the first tunable filter  628   a  and the second tunable filter  628   b  may use microelectromechanical system (MEMS) technology. The first tunable filter  628   a  may be coupled to the output of a power amplifier (PA)  624  that is integrated into the front end module  610 . The power amplifier (PA)  624  may use a distributed gain power amplifier (PA) configuration  230 . The input of the power amplifier (PA)  624  may be coupled to a Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  612   a . The input of the Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  612   a  may be coupled to the output of a driver amplifier  618  within the radio frequency integrated circuit (RFIC)  608 . 
     The second tunable filter  628   b  may be coupled to the input of a low noise amplifier (LNA)  626  that is not part of the front end module  610 . The low noise amplifier (LNA)  626  may be part of a distributed gain low noise amplifier (LNA) configuration  334 . The output of the low noise amplifier (LNA)  626  may be coupled to an Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  612   b . The output of the Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  612   b  may be coupled to a post-LNA amplifier  620  within the radio frequency integrated circuit (RFIC)  608 . Thus, this configuration represents the distributed low noise amplifier (LNA) configuration  334 . 
       FIG. 7  is a block diagram illustrating a front end module  710  with an integrated low noise amplifier (LNA)  726 . The tunable front end module  710  and a radio frequency integrated circuit (RFIC)  708  may be located on a printed circuit board (PCB)  706 . The low noise amplifier (LNA)  726  may be integrated into the front end module  710  while the power amplifier (PA)  724  is external to the front end module  710  to increase isolation between the power amplifier (PA)  724  and the low noise amplifier (LNA)  726 . The front end module  710  may include a microelectromechanical system (MEMS) duplexer  722  coupled to an antenna  717 . The microelectromechanical system (MEMS) duplexer  722  may include a first tunable filter  728   a  for the Tx chain and a second tunable filter  728   b  for the Rx chain. Both the first tunable filter  728   a  and the second tunable filter  728   b  may use microelectromechanical system (MEMS) technology. 
     The first tunable filter  728   a  may be coupled to the output of a power amplifier (PA)  724  that is not part of the front end module  710 . The power amplifier (PA)  724  may be part of a distributed gain power amplifier (PA) configuration  230 . The input of the power amplifier (PA)  724  may be coupled to a Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  712   a  which is within the front end module (FEM)  710  (similar to the Tx driver filter  232  that is coupled to the low gain power amplifier (PA)  233  in the distributed gain power amplifier (PA) configuration  230 ). The input of the Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  712   a  may be coupled to the output of a driver amplifier  718  within the radio frequency integrated circuit (RFIC)  708 . 
     The second tunable filter  728   b  may be coupled to the input of a low noise amplifier (LNA)  726  that is integrated into the front end module  710 . The low noise amplifier (LNA)  726  may be a low gain low noise amplifier (LNA)  341  that is part of a distributed gain low noise amplifier (LNA) configuration  334 . The output of the low noise amplifier (LNA)  726  may be coupled to an Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  712   b . The output of the Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  712   b  may be coupled to a post-LNA amplifier  720  within the radio frequency integrated circuit (RFIC)  708 . 
       FIG. 8  is a block diagram illustrating a front end module  810  with an integrated power amplifier (PA)  824 . The front end module  810  and a radio frequency integrated circuit (RFIC)  808  may be located on a printed circuit board (PCB)  806 . By integrating the power amplifier (PA)  824  with the front end module  810  and keeping the low noise amplifier (LNA)  826  external to the front end module  810 , losses between the power amplifier (PA)  824  and filters may be reduced at the expense of some reduction in the noise figure (NF) of the receiver due to the external connection between the front end module  810  and the low noise amplifier (LNA)  826 . The power amplifier (PA)  824  and the low noise amplifier (LNA)  826  may be separated to increase Rx/Tx isolation. However, a front end module  810  with both the power amplifier (PA)  824  and the low noise amplifier (LNA)  826  integrated may be achieved under conditions of high isolation between the power amplifier (PA)  824  and the low noise amplifier (LNA)  826  (e.g., in cases where both the power amplifier (PA)  824  and the low noise amplifier (LNA)  826  are tunable (for example, having a tunable bandwidth and a center frequency that is narrower as compared to conventional wideband solutions)). 
     The front end module  810  may not be tunable. Integrating the power amplifier (PA)  824  into the front end module  810  may optimize the Rx/Tx lineup but will not reduce the number of off-chip components. Additionally, integrating the power amplifier (PA)  824  into the front end module  810  does not obtain the performance optimizations that may be achieved by implementing microelectromechanical system (MEMS) technology into the front end module  810  to tune filters to chunks of the whole bandwidth. 
     The front end module  810  may include a duplexer  822  coupled to an antenna  817 . In one configuration, the duplexer  822  may be based on surface acoustic wave (SAW) or bulk acoustic wave (BAW) technology. This may add some relaxation on the radio frequency front end (RFFE) duplexer and add selectivity. The duplexer  822  may include a first filter  828   a  for the Tx chain and a second filter  828   b  for the Rx chain. The first filter  828   a  may be coupled to the output of a power amplifier (PA)  824  that is integrated with the front end module  810 . The power amplifier (PA)  824  may be the low gain power amplifier (PA)  233  in a distributed gain power amplifier (PA) configuration  230 . The input of the power amplifier (PA)  824  may be coupled to a Tx bandpass filter (BPF)  812   a . The input of the Tx bandpass filter (BPF)  812   a  may be coupled to the output of a driver amplifier  818  within the radio frequency integrated circuit (RFIC)  808 . 
     The second filter  828   b  may be coupled to the input of a low noise amplifier (LNA)  826  that is not part of the front end module  810 . The low noise amplifier (LNA)  826  may be low gain low noise amplifier (LNA)  341  used in a distributed gain low noise amplifier (LNA) configuration  334 . The output of the low noise amplifier (LNA)  826  may be coupled to an Rx bandpass filter (BPF)  812   b  input. The output of the Rx bandpass filter (BPF)  812   b  may be coupled to a post-LNA amplifier  820  within the radio frequency integrated circuit (RFIC)  808 . In another configuration (not shown), the low noise amplifier (LNA)  826  may be integrated with the front end module  810  and the power amplifier (PA)  824  may not be part of the front end module  810 . In yet another configuration (not shown), the low noise amplifier (LNA)  826 , the power amplifier (PA)  824  and the Rx bandpass filter (BPF)  812   b  may not be part of the front end module  810 . 
       FIG. 9  is a block diagram illustrating a radio frequency integrated circuit (RFIC)  908 , where a portion of the front end module  110  has been integrated into the radio frequency integrated circuit (RFIC)  908 . By integrating some or all of the front end module  110  on the radio frequency integrated circuit (RFIC)  908 , the number of off-chip parts may be reduced. Adding tunability to the Tx driver amplifier  918  may improve Tx noise rejection, gain optimization and RF power matching; the power efficiency of the Tx driver amplifier  918  may also be improved. 
     The front end module  110  may include a power amplifier (PA)  924  and a low noise amplifier (LNA)  926  that are not integrated on the radio frequency integrated circuit (RFIC)  908 . The front end module  110  may include a microelectromechanical system (MEMS) duplexer  922  coupled to an antenna  917 . The microelectromechanical system (MEMS) duplexer  922  may include a first tunable filter  928   a  for the Tx chain and a second tunable filter  928   b  for the Rx chain. Both the first tunable filter  928   a  and the second tunable filter  928   b  may use microelectromechanical system (MEMS) technology. The first tunable filter  928   a  may be coupled to the output of the power amplifier (PA)  924  that is not integrated with the radio frequency integrated circuit (RFIC)  908 . The power amplifier (PA)  924  may be the low gain power amplifier (PA)  233  used in a distributed gain power amplifier (PA) configuration  230 . The input of the power amplifier (PA)  924  may be coupled to a Tx microelectromechanical system (MEMS) bandpass filter (BPF)  912   a . The input of the Tx microelectromechanical system (MEMS) bandpass filter (BPF)  912   a  may be coupled to the output of a driver amplifier  918  within the radio frequency integrated circuit (RFIC)  908 . 
     The second tunable filter  928   b  may be coupled to the input of the low noise amplifier (LNA)  926  that is not integrated with the radio frequency integrated circuit (RFIC)  908 . The low noise amplifier (LNA)  926  may be a low gain low noise amplifier (LNA)  341  used in a distributed gain low noise amplifier (LNA) configuration  334 . The output of the low noise amplifier (LNA)  926  may be coupled to an Rx microelectromechanical system (MEMS) bandpass filter (BPF)  912   b . The output of the Rx microelectromechanical system (MEMS) bandpass filter (BPF)  912   b  may be coupled to a post-LNA amplifier  920  within the radio frequency integrated circuit (RFIC)  908 . 
     Adding tunability to the post-LNA amplifier  920  may improve selectivity, the noise figure (NF), matching and gain. Adding tunability to the low noise amplifier (LNA)  926  and the power amplifier (PA)  924  may make the front end module  110  a complete tunable front end. A tunable low noise amplifier (LNA)  926  may have improved gain and noise figure (NF); moreover, having a tunable matching between the low noise amplifier (LNA)  926  input and the tunable filter  928   b  output will further improve the noise figure (NF) of the low noise amplifier (LNA)  926 . A tunable power amplifier (PA)  924  may be better optimized to power matching and the Tx out-of-band noise may be reduced. Furthermore, a tunable power amplifier (PA)  924  may have lower power consumption. Additionally, tuning the power amplifier (PA)  924  for antenna matching may improve performance even further in terms of noise figure (NF), power matching, gain, duplexer performance and a further reduction in power consumption. Thus, the receiver performance and the efficiency are improved. This is because the out-of-band noise of the power amplifier (PA)  924  leaking to the receiver is reduced. Hence, the total noise power may be lower and the effective noise figure (NF) is improved. Having an optimized tuning of the power amplifier (PA)  924  may improve power saving by drawing lower current and reduce leakage of noise power, improving the effective noise figure (NF). 
     Using a tuned low noise amplifier (LNA) and a tuned power amplifier (PA) is one way to optimize performance while narrowing the bandwidth (BW). This essentially improved undesired noise emissions on the Tx path, optimizes power load matching and efficiency, optimizes gain and improves efficiency. The same is true for a low noise amplifier (LNA); the noise figure (NF) and the gain may be optimized, since matching is narrower only for a given portion of the entire bandwidth (BW). Furthermore, the selectivity and rejection of the undesired jammers may be optimized and improved. As a consequence, the overall Rx/Tx isolation may be improved for free as a byproduct. This may be common for all cases. 
       FIG. 10  is a block diagram illustrating another radio frequency integrated circuit (RFIC)  1008 , where a portion of the front end module  110  has been integrated into the radio frequency integrated circuit (RFIC)  1008 . The front end module  110  may include a low noise amplifier (LNA)  1026  that is integrated on the radio frequency integrated circuit (RFIC)  1008  and a power amplifier (PA)  1024  that is not integrated on the radio frequency integrated circuit (RFIC)  1008 . Integrating the low noise amplifier (LNA)  1026  on the radio frequency integrated circuit (RFIC)  1008  along with other portions of the front end module  110  may provide the gains discussed above while also reducing the number of off-chip components. 
     The front end module  110  may include a microelectromechanical system (MEMS) duplexer  1022  coupled to an antenna  1017 . The microelectromechanical system (MEMS) duplexer  1022  may include a first tunable filter  1028   a  for the Tx chain and a second tunable filter  1028   b  for the Rx chain. Both the first tunable filter  1028   a  and the second tunable filter  1028   b  may use microelectromechanical system (MEMS) technology. The first tunable filter  1028   a  may be coupled to the output of the power amplifier (PA)  1024  that is not integrated with the radio frequency integrated circuit (RFIC)  1008 . The power amplifier (PA)  1024  may be a low gain power amplifier (PA)  233  in a distributed gain power amplifier (PA) configuration  230 . The input of the power amplifier (PA)  1024  may be coupled to a Tx microelectromechanical system (MEMS) bandpass filter (BPF)  1012   a . The input of the Tx microelectromechanical system (MEMS) bandpass filter (BPF)  1012   a  may be coupled to the output of a driver amplifier  1018  on the radio frequency integrated circuit (RFIC)  1008 . 
     The second tunable filter  1028   b  may be coupled to the input of the low noise amplifier (LNA)  1026  that is integrated with the radio frequency integrated circuit (RFIC)  1008 . The low noise amplifier (LNA)  1026  may be low gain low noise amplifier (LNA)  341  in a distributed gain low noise amplifier (LNA) configuration  334 . The output of the low noise amplifier (LNA)  1026  may be coupled to an Rx microelectromechanical system (MEMS) bandpass filter (BPF)  1012   b . The output of the Rx microelectromechanical system (MEMS) bandpass filter (BPF)  1012   b  may be coupled to a post-LNA amplifier  1020  on the radio frequency integrated circuit (RFIC)  1008 . 
     In another configuration (not shown), the power amplifier (PA)  1024  may be integrated on the radio frequency integrated circuit (RFIC)  1008  and the low noise amplifier (LNA)  1026  may not be integrated on the radio frequency integrated circuit (RFIC)  1008 . 
       FIG. 11  is a circuit diagram illustrating a tunable low noise amplifier (LNA)  1147 . The tunable low noise amplifier (LNA)  1147  may be a low noise amplifier (LNA)  341  or a post-LNA amplifier  339 . In a tunable low noise amplifier (LNA)  1147 , efficiency may be improved by optimizing gains into chunks of bands (like those depicted in  FIG. 13 , as an example). In other words, the bandwidth of the tunable low noise amplifier (LNA)  1147  may be narrowed to achieve higher gain, better power matching, better noise figure (NF) matching and a better voltage standing wave ratio (VSWR). The chunks of bands may be narrower and overlap. As a result, the narrower low noise amplifier (LNA)  1147  is easier to optimize for noise figure (NF), voltage standing wave ratio (VSWR), third order intercept point (IP 3 ), the 1 dB compression measurement (P1 db) and power consumption is optimized. Moreover, this circuit concept improves receiver selectivity and rejection of undesired jammers and, as a byproduct, the Rx/Tx isolation is improved. 
     The tunable low noise amplifier (LNA)  1147  may be coupled to tuning circuitry  1149 . The tuning circuitry  1149  (as an example for bandwidth (BW), gain and noise figure (NF) matching optimization) may include a switch coupling the tunable low noise amplifier (LNA)  1147  to ground via one of multiple capacitors  1151 . The tuning circuitry  1149  may also include an adjustable inductor  1150  that is coupled between the tunable low noise amplifier (LNA)  1147  and ground. The tuning circuitry  1149  may also be implemented in various other ways. 
     In one configuration, a tunable bandpass filter (BPF)  1148  (also referred to as a “pre-selector”) may be coupled to an input of the tunable low noise amplifier (LNA)  1147 . The tunable bandpass filter (BPF)  1148  may also have a narrower bandwidth. The tunable bandpass filter (BPF)  1148  may reject the better of air blockers, which are undesired jamming signals called jammers or blockers, that are received at the antenna. These jammers are filtered and rejected by the radio frequency front end (RFFE) bandpass filter (such as the tunable bandpass filter (BPF)  1148 ) and further rejected by the tunable low noise amplifier (LNA)  1147 , which is optimized to a narrower bandwidth (BW) as discussed above. In one configuration, the tunable bandpass filter (BPF)  1148  may perform Tx blocking as well as blocking Tx out-of-band noise while providing higher linearity and noise figure (NF). 
       FIG. 12  is a circuit diagram illustrating a tunable power amplifier (PA)  1252 . The tunable power amplifier (PA)  1252  may be a Tx pre-amplifier (e.g., a Tx driver  231 ) or a power amplifier (PA)  233 . In a tunable power amplifier (PA)  1252 , the bandwidth of the tunable power amplifier (PA)  1252  may be divided into chunks of band that are narrower than the bandwidth and that overlap. A narrower power amplifier (PA)  1252  may be easier to optimize for power, gain, voltage standing wave ratio (VSWR), third order intercept point (IP 3 ), 1 dB compression measurement (P1 db), power consumption and efficiency. 
     The tunable power amplifier (PA)  1252  may be coupled to tuning circuitry  1249 . The tuning circuitry  1249  may include a switch coupling the tunable power amplifier (PA)  1252  to ground via one of multiple capacitors  1251 . The tuning circuitry  1249  may also include an adjustable inductor  1250  that is coupled between the tunable power amplifier (PA)  1252  and ground. The tuning circuitry may also be implemented in various other ways. 
     In one configuration, a tunable bandpass filter (BPF) (not shown) may be coupled to an input of the tunable power amplifier (PA)  1252 . In another configuration, a tunable bandpass filter (BPF) (not shown) may be coupled to an output of the tunable power amplifier (PA)  1252 . A tunable power amplifier (PA)  1252  coupled with a tunable bandpass filter (BPF) may better reject Tx out-of-band noise while providing higher linearity efficiency. 
       FIG. 13  is a graph illustrating bandwidth chunks  1353   a - c  selection and tuning. A tunable front end module  110  and a tunable radio frequency integrated circuit (RFIC) front end may be realized in several tunability resolutions. The graph depicts either the transmit band or the receive band. The band  1352  shown is a wide band covering many bands of operation such as cellular, Personal Communications Service (PCS), distributed control system (DCS), etc. A tunable front end module  110  and a tunable radio frequency integrated circuit (RFIC) front end may operate using coarse tuning or fine tuning. The tunable front end module  110  may be an external block that is not part of the radio frequency integrated circuit (RFIC)  608 . In contrast, a tunable radio frequency integrated circuit (RFIC) front end (such as the front end module  710 ) is a front end that is an integral part of the radio frequency integrated circuit (RFIC)  708 . The Rx filter  712   b , low noise amplifier (LNA)  726 ) and in some cases the tunable filter  728   b  may be internal to the radio frequency integrated circuit (RFIC)  708  with an Rx antenna and a separate Tx antenna; thus the Rx has a full radio frequency front end (RFFE) in the radio frequency integrated circuit (RFIC)  708 . 
     In such cases, the radio frequency integrated circuit (RFIC)  708  may include, on the Tx path, the Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  712   a  and, on the Rx side, the Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  712   b  and the low noise amplifier (LNA)  726 , only in order to prevent noise leakage to the receive chain from the input of the tunable filter  728   b . The radio frequency integrated circuit (RFIC)  708  may also include Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF) when the antenna  717  is an Rx only antenna. When the antenna  717  is common to both Tx and Rx and when the tunable filter  728   b  is included within the radio frequency integrated circuit (RFIC)  708 , Tx noise may leak into the Rx signal. This is applicable even though additional power arrangements are required within the radio frequency integrated circuit (RFIC)  708  to enable Tx power. Alternatively, the entire front end module  710  may be included on the radio frequency integrated circuit (RFIC)  708  while the power amplifier (PA)  724  is external to isolate the power amplifier (PA)  724  Tx noise and current hits in time division multiple access (TDMA). Other variants may also be applicable. 
     The microelectromechanical system (MEMS) topology presented herein can be further expanded for Long Term Evolution (LTE) multiple-input and multiple-output (MIMO) and carrier aggregation. For example, in a specific small frequency Rx/Tx duplexer, there is no need to split the radio frequency front end (RFFE) filters, as the narrower microelectromechanical system (MEMS) filter at the front end operates as a pre-selector. For cases of carrier aggregation (Long Term Evolution (LTE) inter and intra carrier aggregation), the tenability saves the need of multiple bulk acoustic wave (BAW)/surface acoustic wave (SAW) filters and the tuning of the microelectromechanical system (MEMS) filter according to the band chunk  1353  is available from the entire band chunk  1353  grid. 
     In coarse tuning, the tunable components (e.g., the Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  412   b , the Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  412   a , the first tunable filter  428   a , the second tunable filter  428   b , the tunable power amplifier (PA)  1252 , the tunable driver amplifier  418 , the tunable low noise amplifier (LNA)  1147  and the tunable post-LNA amplifier  420 ) may be tuned to the desired band of operation. The center frequency of the tuning may be the center frequency of the Rx band for the Rx chain and the center frequency of the Tx band for the Tx chain. 
     To achieve higher selectivity for the Rx and use the front end as a pre-selector and to optimize the Tx for higher gain over a narrower bandwidth, the Rx and Tx bands in a given standard are divided into chunks  1353  of narrower bands that overlap. Each chunk  1353  has a center frequency f 0 , f 1 , etc. The lowest bandwidth chunk  1353  center frequency f 0  is marked as the anchor point from where tuning and band selection starts. The step between two bandwidth chunks  1353  is the raster of the tuning. If the tuning is too fine (i.e., the chunks  1353  are too narrow), high loss may be created in the filters. Thus, the bandwidth of a chunk  1353  and the number of chunks  1353  may be optimized for each standard. The Rx and Tx anchor frequency of the first bandwidth chunk  1353   a  may have the same duplex separation as defined by the standard of activity (e.g., cellular 45 megahertz (MHz), Personal Communications System (PCS) 80 MHz, distributed control system (DCS) 95 MHz). 
       FIG. 14  is a block diagram illustrating a radio frequency integrated circuit (RFIC)  1408  with a fully integrated front end module  110 . In the radio frequency integrated circuit (RFIC)  1408 , microelectromechanical system (MEMS) tunability with gain and filtering distribution is partially implemented as an Rx tunable block  1454 . The Rx tunable block  1454  may include a tunable low noise amplifier (LNA)  1426 , an Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1412   b  and a tunable post-LNA  1420  integrated on the radio frequency integrated circuit (RFIC)  1408 . The Rx input may be routed by a microelectromechanical system (MEMS) RF switch  1456  with very low insertion loss. The microelectromechanical system (MEMS) RF switch  1456  may couple the Rx tunable block  1454  to an antenna  1417  via different Rx surface acoustic wave (SAW) duplexers  1457  for the Rx path. The Rx surface acoustic wave (SAW) duplexers  1457  may have relaxed specification requirements, since the Rx tunable block  1454  is tuned to an optimized bandwidth. In one configuration, the microelectromechanical system (MEMS) radio frequency (RF) switch  1456  and the surface acoustic wave (SAW) duplexers  1457  may be part of a radio frequency front end (RFFE) module  1461  that is located off the radio frequency integrated circuit (RFIC)  1408 . Because the radio frequency front end (RFFE) module  1461  is external to the radio frequency integrated circuit (RFIC)  1408 , the pin count of the radio frequency integrated circuit (RFIC)  1408  may be maintained. In one configuration, the surface acoustic wave (SAW) duplexers  1457  may be bulk acoustic wave (BAW) filters. 
     The Tx path may include a tunable power amplifier (PA)  1424 , a Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1412   a  and a tunable driver amplifier  1418 . The Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1412   a  and the tunable driver amplifier  1418  may be part of a Tx tunable block  1455 . The tunable power amplifier (PA)  1424  may be implemented externally to the radio frequency integrated circuit (RFIC)  1408  to prevent undesired effects on the receive path and the local oscillator (LO), such as current hits that may create pushing effects on the voltage controlled oscillator (VCO) and voltage standing wave ratio (VSWR) pulling of the voltage controlled oscillator (VCO). The tunable power amplifier (PA)  1424  may also be external to the radio frequency integrated circuit (RFIC)  1408  to avoid desensitization of the Rx path. 
     Since the power amplifier (PA)  1424  is tunable with bandwidth (BW) optimization, it is a narrow bandwidth (BW) amplifier that emits less than a conventional power amplifier (PA). As a result, the output filter can be saved and excessive loss between the power amplifier (PA) and the antenna may be saved. Therefore, the Tx power efficiency is improved, which directly improves talk time (and other features). 
       FIG. 14A  is a block diagram illustrating a radio frequency integrated circuit (RFIC)  1408   a  where the microelectromechanical system (MEMS) radio frequency (RF) switches  1456  have been integrated with the radio frequency integrated circuit (RFIC)  1408   a . The radio frequency integrated circuit (RFIC)  1408   a  of  FIG. 14A  may include similar components as the radio frequency integrated circuit (RFIC)  1408  of  FIG. 14 . However, the microelectromechanical system (MEMS) switches  1456  have been integrated with the radio frequency integrated circuit (RFIC)  1408   a . The radio frequency integrated circuit (RFIC)  1408   a  may reduce losses in the radio frequency integrated circuit (RFIC)  1408  because no printed circuit board (PCB) soldering is needed; however, additional pins may be required. 
       FIG. 15  is a block diagram illustrating another radio frequency integrated circuit (RFIC)  1508  with a fully integrated front end module  110 . In the radio frequency integrated circuit (RFIC)  1508 , microelectromechanical system (MEMS) tunability with gain and filtering distribution is partially implemented as an Rx tunable block  1554 . The Rx tunable block  1554  may include a tunable low noise amplifier (LNA)  1526 , an Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1512   b  and a tunable post-LNA amplifier  1520  integrated on the radio frequency integrated circuit (RFIC)  1508 . The Rx input may be routed by a microelectromechanical system (MEMS) RF switch  1556  with very low insertion loss. The microelectromechanical system (MEMS) RF switch  1556  may couple the Rx tunable block  1554  to an antenna  1517  via different Rx surface acoustic wave (SAW) duplexers  1557  for the Rx path. The Rx surface acoustic wave (SAW) duplexers  1557  may have relaxed specification requirements, since the Rx tunable block  1554  is tuned to an optimized bandwidth. The microelectromechanical system (MEMS) RF switch  1556  and the surface acoustic wave (SAW) duplexers  1557  may be part of a Rx module with MEMS selector  1563  (i.e., a first front end module (FEM)). 
     The Tx path may include a tunable power amplifier (PA)  1524 , a Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1512   a  and a tunable driver amplifier  1518 . The tunable power amplifier (PA)  1524  may be part of a first front end module (FEM) that is off chip. The Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1512   a  and the tunable driver amplifier  1518  may be part of a Tx tunable block  1555  within the radio frequency integrated circuit (RFIC)  1508 . The tunable power amplifier (PA)  1524  may be implemented external to the radio frequency integrated circuit (RFIC)  1508  to prevent undesired effects on the Rx path and the local oscillator (LO) such as current hits that may create pushing effects on the voltage controlled oscillator (VCO) and voltage standing wave ratio (VSWR) pulling of the voltage controlled oscillator (VCO). The tunable power amplifier (PA)  1524  may also be external to the radio frequency integrated circuit (RFIC)  1508  to avoid desensitization of the Rx path. 
     A Tx band select microelectromechanical system (MEMS) switch  1559  with very low insertion loss (IL) and high linearity may be used between the tunable power amplifier (PA)  1524  and different Tx surface acoustic wave (SAW) duplexers  1558 . The Tx band select microelectromechanical system (MEMS) switch  1559 , the tunable power amplifier (PA)  1524  and the surface acoustic wave (SAW) duplexers  1558  may be part of a Tx module with MEMS selector  1565  (i.e., a second front end module (FEM)) that is located external to the radio frequency integrated circuit (RFIC)  1508 . Each port of the Tx band select microelectromechanical system (MEMS) switch  1559  may route the tunable power amplifier (PA)  1524  to the appropriate Tx port of a Tx surface acoustic wave (SAW) duplexer  1558  for the Tx path. The common port of the Tx surface acoustic wave (SAW) duplexer  1558  may be routed to the antenna  1517 . 
     The complexity of the tunable power amplifier (PA)  1524  may be reduced due to the usage of the Tx microelectromechanical system (MEMS) bandpass filter (BPF)  1512   a  in the Tx tunable block  1555  within the radio frequency integrated circuit (RFIC)  1508  with compromising Tx filter insertion loss (IL). The specifications of the Tx surface acoustic wave (SAW) duplexers  1558  and the Rx surface acoustic wave (SAW) duplexers  1557  may be reduced because the bandwidth operation is divided into several sub-bands, where each sub-band includes several consecutive chunks  1353 . Thus, both the Rx insertion loss (IL) of the Rx surface acoustic wave (SAW) duplexers  1557  and the Tx insertion loss (IL) of the Tx surface acoustic wave (SAW) duplexers  1558  may be improved as the specification is relaxed on the front end filtration. This is because the tunable microelectromechanical system (MEMS) filter  1554  in the Rx tunable block  1554  and the Tx tunable block  1555  provide the selectivity and attenuation, as their bandwidth is narrower and is tuned each time to the desired chunk  1353 . Both the Tx band select microelectromechanical system (MEMS) switch  1559  and the microelectromechanical system (MEMS) RF switch  1556  may be part of a second front end module (FEM) that is off chip. 
     A tunable network to the antenna  1517  may be utilized to improve and optimize the Rx/Tx voltage standing wave ratio (VSWR), thereby further improving the Tx performance in aspects of power efficiency and Rx noise figure (NF) as well as the Rx selectivity and further reducing the Tx desensitization noise. 
     The Tx front end module (FEM), which includes the MEMS selector  1565 , and the Rx front end module (FEM), which includes the Rx MEMS selector  1563 , may be merged to a single front end module (FEM) (as illustrated in  FIG. 15A ). In this case, the microelectromechanical system (MEMS) switches  1567  are within the radio frequency integrated circuit (RFIC)  1508  (as opposed to the microelectromechanical system (MEMS) switches  1556  that are not in the radio frequency integrated circuit (RFIC)  1508 ). This saves insertion loss and further improves sensitivity and power saves, at the expense of increasing the radio frequency integrated circuit (RFIC)  1508  pin count. The power amplifier (PA)  1524  is tunable, since a tunable power amplifier (PA)  1524  with a bandpass filter (BPF) characteristic increases the immunity of the Rx path against Tx noise. Because the low noise amplifier (LNA)  1526  is also tunable with bandpass filter (BPF) characteristics, further rejection may be obtained. The solution illustrated in  FIG. 15  is full duplex that utilizes tunable microelectromechanical system (MEMS) filters (with surface acoustic wave (SAW) or band acoustic wave (BAW) filters in the front end module (FEM)). The front end module (FEM) may also include surface acoustic wave (SAW) microelectromechanical system (MEMS) filters as well. Thus, the solution illustrated in  FIG. 15  is particularly useful for LTE where duplex separation requirements are more stringent. 
       FIG. 15A  is a block diagram illustrating the radio frequency integrated circuit (RFIC)  1508   a  where the microelectromechanical system (MEMS) switches are integrated within the radio frequency integrated circuit (RFIC)  1508   a . The radio frequency integrated circuit (RFIC)  1508   a  of  FIG. 15A  may include similar components as the radio frequency integrated circuit (RFIC)  1508  of  FIG. 15 . However, the microelectromechanical system (MEMS) switches  1567  have been integrated within the radio frequency integrated circuit (RFIC)  1508   a . The radio frequency integrated circuit (RFIC)  1508   a  may reduce losses in the radio frequency integrated circuit (RFIC)  1508  at the expense of pin count. 
       FIG. 16  is a block diagram illustrating yet another radio frequency integrated circuit (RFIC)  1608  with an integrated front end module  110 . In the radio frequency integrated circuit (RFIC)  1608 , microelectromechanical system (MEMS) tunability with gain and filtering distribution is partially implemented as an Rx tunable block  1654  within the radio frequency integrated circuit (RFIC)  1608 . The Rx tunable block  1654  may include a tunable low noise amplifier (LNA)  1626 , an Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1612   b  and a post-LNA amplifier  1620  that are implemented within the radio frequency integrated circuit (RFIC)  1608 . The Rx input may be routed to an external tunable microelectromechanical system (MEMS) duplexer  1622  that includes a first tunable filter  1628   a  for the Rx and a second tunable filter  1628   b  for the Tx. Both the first tunable filter  1628   a  and the second tunable filter  1628   b  may use microelectromechanical system (MEMS) technology. The tunable microelectromechanical (MEMS) duplexer  1622  may be coupled to the antenna  1617 . 
     The Tx path may include a tunable power amplifier (PA)  1624  with bandpass filter (BPF) characteristics, a Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1612   a  and a tunable driver amplifier  1618 . The Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1612   a  and the tunable driver amplifier  1618  may be part of a Tx tunable block  1655  within the radio frequency integrated circuit (RFIC)  1608 . The tunable power amplifier (PA)  1624  may be implemented external to the radio frequency integrated circuit (RFIC)  1608  to prevent undesired effects on the Rx path and the local oscillator (LO) such as current hits that may create pushing effects on the voltage controlled oscillator (VCO) and voltage standing wave ratio (VSWR) pulling of the voltage controlled oscillator (VCO). The tunable power amplifier (PA)  1624  may also be external to the radio frequency integrated circuit (RFIC)  1608  to avoid desensitization of the Rx path. Because the tunable driver amplifier  1618  and the Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1612   a  operate with the tunable power amplifier (PA)  1624 , better rejection of wideband Tx noise leakage may be obtained while optimizing Tx matching to the load and gain optimization. This may result in higher efficiency, lower power consumption and lower desensitization of the receiver. The tunable power amplifier (PA)  1624  may be coupled to the first tunable filter  1628   a  within the tunable duplexer  1622 . The first tunable filter  1628   a  may also be coupled to the antenna  1617  at the common port of the duplexer  1622 . 
     Band selection may be accomplished by the tunability of the filters and amplifiers. Since the filters and amplifiers are tunable, further selectivity and gain optimization may be obtained. The Rx path filtration may reduce the Tx noise such that the second tunable filter  1628   b  for Rx in the tunable microelectromechanical system (MEMS) duplexer  1622  can have relaxed specifications with higher selectivity compared to an ordinary surface acoustic wave (SAW) filter. Furthermore, the use of a tunable microelectromechanical system (MEMS) duplexer  1622  in place of multiple surface acoustic wave (SAW) duplexers further reduces the number of off-chip components. 
       FIG. 17  is a block diagram illustrating a radio frequency integrated circuit (RFIC)  1708  with an integrated front end module  110  that does not include a duplexer. In the radio frequency integrated circuit (RFIC)  1708 , microelectromechanical system (MEMS) tunability with gain and filtering distribution is partially implemented as an Rx tunable block  1754 . The Rx tunable block  1754  may include a tunable low noise amplifier (LNA)  1726 , an Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1712   b  and a tunable post-LNA amplifier  1720  that are integrated within the radio frequency integrated circuit (RFIC)  1708 . The Rx input may be routed to the Rx antenna  1717   b  via an Rx microelectromechanical system (MEMS) bandpass filter (BPF)  1760 . 
     The Tx path may include a tunable power amplifier (PA)  1724 , a Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1712   a  and a tunable driver amplifier  1718 . The Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1712   a  and the tunable driver amplifier  1718  may be part of a Tx tunable module  1755  within the radio frequency integrated circuit (RFIC)  1708 . The tunable power amplifier (PA)  1724  may be implemented external to the radio frequency integrated circuit (RFIC)  1708  to prevent undesired effects on the Rx path and the local oscillator (LO) such as current hits that may create pushing effects on the voltage controlled oscillator (VCO) and voltage standing wave ratio (VSWR) pulling of the voltage controlled oscillator (VCO). The tunable power amplifier (PA)  1724  may also be external to the radio frequency integrated circuit (RFIC)  1708  to avoid desensitization of the Rx path. 
     Because the tunable driver amplifier  1718  and the Tx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1712   a  operate with the tunable power amplifier (PA)  1724 , better rejection of wideband Tx noise leakage may be obtained while optimizing Tx matching to the load and gain optimization. This may result in higher efficiency, lower power consumption and lower desensitization of the receiver. The Rx tunable block  1754  may be coupled to a receive antenna  1717   b  via an Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1760 . 
     The tunable power amplifier (PA)  1724  may be coupled directly to the transmit antenna  1717   a  without a tunable filter. Because the tunable power amplifier (PA)  1724  has a narrower bandwidth that covers the entire bandwidth of operation in chunks  1353 , the tunable filter is not required. In other words, the tunable power amplifier (PA)  1724  may operate as an RF front end bandpass filter (BPF). As a consequence, the insertion loss (IL) between the tunable power amplifier (PA)  1724  and the transmit antenna  1717   a  is lowered. This may improve the efficiency of the tunable power amplifier (PA)  1724 , since no back-off gain is needed to compensate for excessive insertion loss (IL). 
     The connection of the tunable power amplifier (PA)  1724  directly to the transmit antenna  1717   a  may improve the Tx power saving and efficiency. Tx out-of-band wideband noise and harmonics may be reduced by design, since the tunable power amplifier (PA)  1724  is a tunable narrow band power amplifier (PA) that covers the entire bandwidth of operation. The direct connection of the tunable power amplifier (PA)  1724  to a dedicated transmit antenna  1717   a  and the use of a tunable matching network may reduce the mismatch-loss and thus, further Tx power efficiency is gained. 
     The Rx path may be protected against Tx noise in several ways. For example, the Rx path uses a different receive antenna  1717   b  than the Tx path, hence there is an inherent Rx/Tx isolation between the receive antenna  1717   b  and the transmit antenna  1717   a . This is critical in current Long Term Evolution (LTE) designs and new releases. Furthermore, the tunability of the Rx path protects against Tx blocking. Because the Rx tunable block  1754  within the radio frequency integrated circuit (RFIC)  1708  is tunable, the Rx tunable block  1754  operates as a pre-selector, thereby protecting the Rx path from compression and Tx noise. Because the Rx path uses a separate receive antenna  1717   b , the insertion loss (IL) is reduced (because a duplexer is not used). By reducing the insertion loss (IL), the noise figure (NF) is improved (as demonstrated in the first term and the second term of Equation (6) above). 
     Moreover, because the transmit path and the receive path each have their own antenna  1717   a - b , better antenna matching may be accomplished. Hence, a better noise figure (NF) in the receive path and better power matching at the transmit path may be obtained. Since matching is tunable in chunks  1353 , a narrow band matching is that is superior over wideband matching is achieved. Narrow band matching has a band pass filter (BPF) characteristic that adds additional Rx/Tx isolation and selectivity. 
     An additional implementation of  FIG. 17  is to use only a single antenna. In this case, the output of the tunable power amplifier (PA)  1724  may be coupled to an Rx/Tx antenna that is shared by the input of the Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1760 . As discussed above, the isolation between the receive (Rx) and the transmit (Tx) may be accomplished due to the narrow band characteristics of the tunable power amplifier (PA)  1724  and the Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1760 . Both the tunable power amplifier (PA)  1724  and the Rx microelectromechanical system (MEMS) tunable bandpass filter (BPF)  1760  have a band pass characteristic that is tuned in chunks  1353 . 
       FIG. 18  illustrates certain components that may be included within a wireless communication device  1804 . The wireless communication device  1804  may be an access terminal, a mobile station, a user equipment (UE), etc. The wireless communication device  1804  includes a processor  1803 . The processor  1803  may be a general purpose single- or multi-chip microprocessor (e.g., an ARM), a special purpose microprocessor (e.g., a digital signal processor (DSP)), a microcontroller, a programmable gate array, etc. The processor  1803  may be referred to as a central processing unit (CPU). Although just a single processor  1803  is shown in the wireless communication device  1804  of  FIG. 18 , in an alternative configuration, a combination of processors (e.g., an ARM and DSP) could be used. 
     The wireless communication device  1804  also includes memory  1805 . The memory  1805  may be any electronic component capable of storing electronic information. The memory  1805  may be embodied as random access memory (RAM), read-only memory (ROM), magnetic disk storage media, optical storage media, flash memory devices in RAM, on-board memory included with the processor, EPROM memory, EEPROM memory, registers and so forth, including combinations thereof. 
     Data  1807   a  and instructions  1809   a  may be stored in the memory  1805 . The instructions  1809   a  may be executable by the processor  1803  to implement the methods disclosed herein. Executing the instructions  1809   a  may involve the use of the data  1807   a  that is stored in the memory  1805 . When the processor  1803  executes the instructions  1809 , various portions of the instructions  1809   b  may be loaded onto the processor  1803 , and various pieces of data  1807   b  may be loaded onto the processor  1803 . 
     The wireless communication device  1804  may also include a transmitter  1811  and a receiver  1813  to allow transmission and reception of signals to and from the wireless communication device  1804  via an antenna  1817 . The transmitter  1811  and receiver  1813  may be collectively referred to as a transceiver  1815 . The wireless communication device  1804  may also include (not shown) multiple transmitters, multiple antennas, multiple receivers and/or multiple transceivers. 
     The wireless communication device  1804  may include a digital signal processor (DSP)  1821 . The wireless communication device  1804  may also include a communications interface  1823 . The communications interface  1823  may allow a user to interact with the wireless communication device  1804 . 
     The various components of the wireless communication device  1804  may be coupled together by one or more buses, which may include a power bus, a control signal bus, a status signal bus, a data bus, etc. For the sake of clarity, the various buses are illustrated in  FIG. 18  as a bus system  1819 . 
       FIG. 19  illustrates certain components that may be included within a base station  1902 . The base station  1902  of  FIG. 19  may be one configuration of the wireless device  102  of  FIG. 1 . A base station may also be referred to as, and may include some or all of the functionality of, an access point, a broadcast transmitter, a NodeB, an evolved NodeB, etc. The base station  1902  includes a processor  1903 . The processor  1903  may be a general purpose single- or multi-chip microprocessor (e.g., an ARM), a special purpose microprocessor (e.g., a digital signal processor (DSP)), a microcontroller, a programmable gate array, etc. The processor  1903  may be referred to as a central processing unit (CPU). Although just a single processor  1903  is shown in the base station  1902  of  FIG. 19 , in an alternative configuration, a combination of processors (e.g., an ARM and DSP) could be used. 
     The base station  1902  also includes memory  1905 . The memory  1905  may be any electronic component capable of storing electronic information. The memory  1905  may be embodied as random access memory (RAM), read-only memory (ROM), magnetic disk storage media, optical storage media, flash memory devices in RAM, on-board memory included with the processor, EPROM memory, EEPROM memory, registers, and so forth, including combinations thereof. 
     Data  1907   a  and instructions  1909   a  may be stored in the memory  1905 . The instructions  1909   a  may be executable by the processor  1903  to implement the methods disclosed herein. Executing the instructions  1909   a  may involve the use of the data  1907   a  that is stored in the memory  1905 . When the processor  1903  executes the instructions  1909   a , various portions of the instructions  1909   b  may be loaded onto the processor  1903 , and various pieces of data  1907   b  may be loaded onto the processor  1903 . 
     The base station  1902  may also include a transmitter  1911  and a receiver  1913  to allow transmission and reception of signals to and from the base station  1902 . The transmitter  1911  and receiver  1913  may be collectively referred to as a transceiver  1915 . An antenna  1917  may be electrically coupled to the transceiver  1915 . The base station  1902  may also include (not shown) multiple transmitters, multiple receivers, multiple transceivers and/or multiple antennas. 
     The base station  1902  may include a digital signal processor (DSP)  1921 . The base station  1902  may also include a communications interface  1923 . The communications interface  1923  may allow a user to interact with the base station  1902 . 
     The various components of the base station  1902  may be coupled together by one or more buses, which may include a power bus, a control signal bus, a status signal bus, a data bus, etc. For the sake of clarity, the various buses are illustrated in  FIG. 19  as a bus system  1919 . 
     The term “determining” encompasses a wide variety of actions and, therefore, “determining” can include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, “determining” can include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, “determining” can include resolving, selecting, choosing, establishing and the like. 
     The systems and methods discussed herein may be realized using any technology that is tunable, such as tunable circuits using variable capacitance junction diodes, varactors, CMOS transistors, switches or tunable microelectromechanical systems (MEMS). 
     The phrase “based on” does not mean “based only on,” unless expressly specified otherwise. In other words, the phrase “based on” describes both “based only on” and “based at least on.” 
     The term “processor” should be interpreted broadly to encompass a general purpose processor, a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a controller, a microcontroller, a state machine and so forth. Under some circumstances, a “processor” may refer to an application specific integrated circuit (ASIC), a programmable logic device (PLD), a field programmable gate array (FPGA), etc. The term “processor” may refer to a combination of processing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     The term “memory” should be interpreted broadly to encompass any electronic component capable of storing electronic information. The term memory may refer to various types of processor-readable media such as random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable PROM (EEPROM), flash memory, magnetic or optical data storage, registers, etc. Memory is said to be in electronic communication with a processor if the processor can read information from and/or write information to the memory. Memory that is integral to a processor is in electronic communication with the processor. 
     The terms “instructions” and “code” should be interpreted broadly to include any type of computer-readable statement(s). For example, the terms “instructions” and “code” may refer to one or more programs, routines, sub-routines, functions, procedures, etc. “Instructions” and “code” may comprise a single computer-readable statement or many computer-readable statements. 
     The functions described herein may be implemented in software or firmware being executed by hardware. The functions may be stored as one or more instructions on a computer-readable medium. The terms “computer-readable medium” or “computer-program product” refers to any tangible storage medium that can be accessed by a computer or a processor. By way of example, and not limitation, a computer-readable medium may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray® disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. It should be noted that a computer-readable medium may be tangible and non-transitory. The term “computer-program product” refers to a computing device or processor in combination with code or instructions (e.g., a “program”) that may be executed, processed or computed by the computing device or processor. As used herein, the term “code” may refer to software, instructions, code or data that is/are executable by a computing device or processor. 
     Software or instructions may also be transmitted over a transmission medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio and microwave are included in the definition of transmission medium. 
     The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is required for proper operation of the method that is being described, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims. 
     Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein, such as those illustrated by  FIG. 5 , can be downloaded and/or otherwise obtained by a device. For example, a device may be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via a storage means (e.g., random access memory (RAM), read-only memory (ROM), a physical storage medium such as a compact disc (CD) or floppy disk, etc.), such that a device may obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized. 
     It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the systems, methods and apparatus described herein without departing from the scope of the claims.