Patent Publication Number: US-10326491-B2

Title: Transceiving device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 62/509,979, filed May 23, 2017. 
    
    
     BACKGROUND 
     Bluetooth low energy (BLE) is currently the most popular radio standard for Internet-of-Things (IoT) applications. IoT nodes are mainly battery operated but increasingly use energy harvesting to sustain their long-term operation. This places heavy emphasis on ultra-low-power (ULP) aspects of IoT Rx, which is considered the most energy-hungry subsystem. Unfortunately, those versatile high-performance RXs developed for the cellular market suffer from relatively high power dissipation, which naturally prevents their use in the emerging IoT applications that take the ULP dissipation and relatively low performance as their starting point. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  is a block diagram illustrating a Bluetooth low energy transceiver in accordance with some embodiments. 
         FIG. 2  is a circuit diagram illustrating a front end of a transceiving device in accordance with some embodiments. 
         FIG. 3  is a diagram illustrating an equivalent circuit of the front end in  FIG. 2  during the receiving mode in accordance with some embodiments. 
         FIG. 4  is a diagram illustrating a Thevenin equivalent circuit of a transmitter matching network and a low-noise transconductance amplifier during the receiving mode in accordance with some embodiments. 
         FIG. 5  is a diagram illustrating an equivalent circuit of the front end in  FIG. 2  during the transmitting mode in accordance with some embodiments. 
         FIG. 6  is a diagram illustrating a return loss at a signal port during the transmitting mode in accordance with some embodiments. 
         FIG. 7  is a diagram illustrating a return loss at a signal port during the receiving mode in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     Embodiments of the present disclosure are discussed in detail below. It should be appreciated, however, that the present disclosure provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative and do not limit the scope of the disclosure. 
     Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper”, “lower”, “left”, “right” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. It will be understood that when an element is referred to as being “connected to” or “coupled to” another element, it may be directly connected to or coupled to the other element, or intervening elements may be present. 
     Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in the respective testing measurements. Also, as used herein, the term “about” generally means within 10%, 5%, 1%, or 0.5% of a given value or range. Alternatively, the term “about” means within an acceptable standard error of the mean when considered by one of ordinary skill in the art. Other than in the operating/working examples, or unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages such as those for quantities of materials, durations of times, temperatures, operating conditions, ratios of amounts, and the likes thereof disclosed herein should be understood as modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the present disclosure and attached claims are approximations that can vary as desired. At the very least, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Ranges can be expressed herein as from one endpoint to another endpoint or between two endpoints. All ranges disclosed herein are inclusive of the endpoints, unless specified otherwise. 
     In the field of ultra-low-power (ULP) wireless transceivers (TRXs) for the Internet of Things (IoT), Bluetooth low energy (BLE) may be used for short-range IoT communications. BLE is an extension of the Bluetooth (BT) that specifies an increased channel spacing of 2 MHz and a relaxed interference tolerance to allow for low-power (LP) implementations. The present embodiments focus on implementing such a TRX in low-cost bulk CMOS technology node. The objective is to maximally reduce the system cost by fully integrating all the RF TRX building blocks, including the antenna-interfacing circuitry, such as the power amplifier (PA) matching network and transmit/receive (T/R) switch, while maximally reducing the power consumption. 
     To address the above objectives of full system integration at ULP consumption, including amenability with digital processors in face of strong push toward a sub-threshold operation, the proposed TRX may exploit all-digital and digitally intensive architectures for the frequency synthesizer, transmitter (TX), and receiver (RX). A time-to-digital converter (TDC) in an all-digital PLL (ADPLL) employs a string of inverters to convert a time difference between reference and variable (RF) clocks into a digital phase error. Power consumption and resolution of the TDC improve with technology scaling. Furthermore, at the same area, device matching improves thus reducing TDC nonlinearity and the level of fractional spurs. On the RX side, most of signal processing and filtering is done using discrete-time (DT) passive switched capacitor circuits. Waveforms required for driving the switches are also generated using digital logic. To provide signal gain, DT techniques use inverter-based gm cells that are always compatible with digital technology. 
     As the technology scales, MOS switches become faster with lower parasitic capacitance. Consequently, digital waveform generators also become faster and more power efficient. On the other hand, metal capacitor density improves by migrating to more advanced technology, resulting in a reduced area. 
       FIG. 1  is a block diagram illustrating a Bluetooth low energy transceiver (BLE TRX)  100  in accordance with some embodiments. The BLE TRX  100  comprises an antenna  102 , a matching network  104 , a receiver  106 , and a transmitter  108 . The receiver  106  comprises a low-noise transconductance amplifier (LNTA)  1062  and a down-converted circuit  1064 . The transmitter  108  comprises a digital PA (DPA)  1082  and an all-digital phase-lock loop (ADPLL)  1084 . The BLE TRX  100  integrates all the required RF (e.g. the ADPLL  1084 ) and IF (e.g. the down-converted circuit  1064 ) building blocks and further includes a T/R antenna switch having an adjustable digital PA (e.g. the digital PA  1082 ) and a low-noise transconductance amplifier (e.g. the LNTA  1062 ) matching networks such that the signal port (or RF input/output (RFIO) pin)  110  may be directly connected to the antenna  102 . In other words, the combination of the matching network  104 , the LNTA  1062 , and the digital PA  1082  is capable of switching the LNTA  1062  to the antenna  102  during a first mode, e.g. the receiving mode, and switching the digital PA  1082  to the antenna  102  during a second mode, e.g. the transmitting mode. The matching network  104  may be treated as a “soft” T/R switch. The matching network  104  may provide good impedance matching between the transmitting mode and the receiving mode of the BLE TRX  100 . The BLE TRX  100  may operate in low supply voltage and may overcome process variation easily. In addition, an external/discrete T/R antenna switch may be omitted in the present embodiment. An external/discrete antenna filter may also be omitted in the present embodiment. A serial peripheral interface (SPI) facilitates the switching between the receiving mode and the transmitting mode. 
     The DPA  1082  may be implemented by a switched-mode class-E/F2 topology with a transformer-based matching network, which may enhance its efficiency at low supply voltage. According to the present embodiments, the BLE TRX  100  has relatively low power and cost because the BLE TRX  100  is highly integrated and has small die area. The transformers of the matching network  104  is arranged to incorporate the associated active devices underneath them with no significant loss of performance or power efficiency. 
     In the receiver  106 , the intermediate frequency (IF) is increased to just beyond the flicker corner frequency and filter the IF signal using complex-domain cascaded bandpass filters (BPFs). The first of filters is clocked at multiples of the LO frequency performing sufficient filtering and harmonic rejection. 
       FIG. 2  is a circuit diagram illustrating a front end  200  of a transceiving device (e.g. the BLE TRX  100 ) in accordance with some embodiments. For brevity, the front end  200  comprises the antenna  102 , the LNTA  1062 , the matching network  104 , and the DPA  1082 . According to some embodiments, a bonding wire  112  is bonded between the signal port  110  and the antenna  102 . A capacitor  114  having a first terminal directly connected to the signal port  110  and a second terminal coupled to the LNTA  1062 . The signal port  110  is arranged to relay or transfer a radio frequency (RF) input signal during the receiving mode, and to relay or transfer an RF output signal during the transmitting mode. The capacitor  114  has a large capacitance in order to block the direct current (DC) signal from the signal port  110 . According to some embodiments, the LNTA  1062  is composed of two stages: a single-input/single-output common-source cascode low-noise amplifier (LNA) and a common-source transconductance (gm) amplifier. However, for brevity,  FIG. 2  merely shows the input stage of the LNTA  1062 . The input stage of the LNTA  1062  comprises an inductor  1063 , a resistor  1064 , a N-channel field-effect transistor  1065 , an adjustable capacitor  1066 , and an inductor  1067 . The inductor  1063  has a first terminal coupled to the second terminal of the capacitor  114 . The inductor  1063  is arranged to have an inductance L G . The resistor  1064  has a first terminal coupled to a second terminal of the inductor  1063 . The resistor  1064  may be a parasitic series resistor of the inductor  1063 , and the resistance of the resistor is r loss . The field-effect transistor  1065  has a gate terminal coupled to a second terminal of the resistor  1064 . The adjustable capacitor  1066  has a first terminal and a second terminal coupled to the gate terminal and a source terminal of the field-effect transistor  1065  respectively. The capacitance of the adjustable capacitor  1066  is C gs . The inductor  1067  has a first terminal coupled to the source terminal and a reference voltage level (e.g. a ground voltage) respectively. The inductance of the inductor  1067  is L 1 . A drain terminal of the field-effect transistor  1065  is arranged to output a receiving signal during the receiving mode, which may be a current signal. According to some embodiments, the inductor  1063 , the resistor  1064 , the adjustable capacitor  1066 , the inductor  1067 , and the field-effect transistor  1065  may form an amplifier. 
     The matching network  104  comprises a first adjustable capacitor  1041 , a first resistor  1042 , a first winding  1043 , a second winding  1044 , a third winding  1045 , a second resistor  1046 , a third resistor  1047 , a second adjustable capacitor  1048 , a third adjustable capacitor  1049 , and a capacitor  1050 . The adjustable capacitor  1041  has a first terminal directly connected to the signal port  110 , and a second terminal coupled to the ground voltage. The capacitance of the adjustable capacitor  1041  is C 2 . The resistor  1042  has a first terminal coupled to the signal port  110 . The first winding  1043  has a first terminal coupled to a second terminal of the resistor  1042 , and a second terminal coupled to the ground voltage. The resistor  1042  may be a parasitic series resistor of the first winding  1043 , and the resistance of the resistor  1042  is r s . The first winding  1043  is electromagnetically coupled to the second winding  1044  to form a transformer, in which the second winding  1044  may be the primary winding and the first winding  1043  may be the secondary winding. Moreover, the inductance of the first winding  1043  is L s , and the inductance of the second winding  1044  is L p . 
     The resistor  1046  has a first terminal coupled to a first terminal of the second winding  1044 . The resistor  1047  has a first terminal coupled to a second terminal of the second winding  1044 . The resistor  1046  and the resistor  1047  may be the parasitic series resistors of the second winding  1044 . For brevity, the resistances of the resistor  1046  and the resistor  1047  are 0.5r p . The third winding  1045  has a first terminal coupled to a middle of the second winding  1044 , and a second terminal coupled to a second reference voltage (e.g. a supply voltage VDD). The capacitor  1050  has a first terminal coupled to the second terminal of the third winding  1045 , and a second terminal coupled to the ground voltage. The adjustable capacitor  1048  has a first terminal coupled to a second terminal of the resistor  1046 . The adjustable capacitor  1049  has a first terminal coupled to a second terminal of the resistor  1047 . For brevity, the capacitances of the adjustable capacitor  1048  and the adjustable capacitor  1049  are 0.5C 1 . 
     According to some embodiments, the DPA  1082  may be a class E/F 2  power amplifier. However, for brevity,  FIG. 2  merely shows a last stage of the DPA  1082 . The last stage of the DPA  1082  comprises a first N-channel field-effect transistor  1051  and a second N-channel field-effect transistor  1052 . The field-effect transistor  1051  has a gate terminal for receiving a first pre-transmit signal during the transmitting mode, a drain terminal coupled to the second terminal of the resistor  1046 , and a source terminal coupled to the ground voltage. The field-effect transistor  1052  has a gate terminal for receiving a second pre-transmit signal during the transmitting mode, a drain terminal coupled to the second terminal of the resistor  1047 , and a source terminal coupled to the ground voltage. According to some embodiments, the aspect ratios (W/L) of the field-effect transistors  1051  and  1052  are adjustable. 
     During the receiving mode, the gate terminals of the field-effect transistors  1051  and  1052  are connected to the ground voltage to turn off the field-effect transistors  1051  and  1052 .  FIG. 3  is a diagram illustrating an equivalent circuit  300  of the front end  200  during the receiving mode in accordance with some embodiments. During the receiving mode, an RF input signal S rf   _   in  is transmitted from the antenna  102  to the LNTA  1062  via the signal port  110 . In the receiving mode, the field-effect transistors  1051  and  1052  are OFF and, consequently, the transmitter (i.e. the matching network  104  and the DPA  1082 ) is simplified to be a PA transformer-based TX matching network (TXMN)  302  acting as a second-order resonator. According to some embodiments, the main resonant frequency of the second-order resonator is arranged to be substantially equal to the operating frequency of the RF input signal S rf   _   in . In the TXMN  302 , the resistor  1046  and the resistor  1047  are simplified to be a resistor  3022  with a resistance r p . The adjustable capacitor  1048  and the adjustable capacitor  1049  are simplified to be an adjustable capacitor  3024  with a capacitance C 1 . A first equivalent input noise  3026  and a second equivalent input noise  3028  are also shown on the first winding  1043  and the second winding  1044  respectively. The value of the first equivalent input noise  3026  is 4KTr s . The value of the second equivalent input noise  3028  is 4KTr p . 
     During the receiving mode, the arrangement of the transmitter is to alleviate the side effects of TXMN  302  on the receiver&#39;s noise factor and input return loss. To analyze the system during the receiving mode, the Thevenin equivalent circuit of the TXMN  302  and LNTA  1062  are employed as shown in  FIG. 4 .  FIG. 4  is a diagram illustrating the Thevenin equivalent circuit  400  of the TXMN  302  and LNTA  1062  during the receiving mode in accordance with some embodiments. The Thevenin equivalent circuit  400  comprises a resistor  402 , a first equivalent input noise  404 , a second equivalent input noise  406 , a first transmission line  408 , and a second transmission line  410 . The resistor  402  has a resistance R s  (e.g. 50 ohm) equivalent to the antenna  102 . The equivalent input noise  404  represents an input noise of the TXMN  302 . The equivalent input noise  406  represents an input noise of the LNTA  1062 . The first transmission line  408  represents an input impedance of the TXMN  302  at an operating frequency. The second transmission line  410  represents an input impedance of the LNTA  1062  at the operating frequency. 
     The RX noise factor (F) can be calculated the following equation (1): 
     
       
         
           
             
               
                 
                   F 
                   = 
                   
                     1 
                     + 
                     
                       
                         R 
                         S 
                       
                       
                         4 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         KT 
                       
                     
                     + 
                     
                       
                         
                           V 
                           
                             n 
                             , 
                             RX 
                           
                           2 
                         
                         _ 
                       
                       
                         
                            
                           
                             Z 
                             RX 
                           
                            
                         
                         2 
                       
                     
                     + 
                     
                       
                         
                           R 
                           S 
                         
                         
                           4 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           KT 
                         
                       
                       · 
                       
                         
                           
                             V 
                             
                               n 
                               , 
                               TX 
                             
                             2 
                           
                           _ 
                         
                         
                           
                              
                             
                               Z 
                               
                                 PA 
                                 , 
                                 RX 
                               
                             
                              
                           
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
       V n,RX   2    and Z RX  are the equivalent input noise  406  and the input impedance of LNTA  1062  at the operating frequency ω 0  respectively. Z RX  and  V n,RX   2    are estimated by the following equations (2) and (3) respectively: 
     
       
         
           
             
               
                 
                   
                     Z 
                     RX 
                   
                   = 
                   
                     
                       
                         r 
                         loss 
                       
                       + 
                       
                         
                           
                             g 
                             m 
                           
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                           ( 
                           
                             
                               
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                                     1 
                                   
                                 
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                     = 
                     
                       
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                   ( 
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                       V 
                       
                         n 
                         , 
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                     _ 
                   
                   = 
                   
                     4 
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                       KT 
                       ⁡ 
                       
                         [ 
                         
                           
                             r 
                             loss 
                           
                           + 
                           
                             γ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               
                                 g 
                                 m 
                               
                               · 
                               
                                 
                                   ( 
                                   
                                     
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                                       1 
                                     
                                     ⁢ 
                                     
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                                       0 
                                     
                                   
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                                 2 
                               
                             
                           
                         
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                   ( 
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                   ) 
                 
               
             
           
         
       
     
     Furthermore, Z PA,RX  and  V n,TX   2    are the output impedance of TXMN  302  and the equivalent output noise  404  at the operating frequency ω 0  respectively. Z PA,RX  and  V n,TX   2    are estimated by the following equations (4) and (5) respectively: 
     
       
         
           
             
               
                 
                   
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                       , 
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                                             ⁢ 
                                             
                                               C 
                                               1 
                                             
                                           
                                           + 
                                           
                                             
                                               L 
                                               s 
                                             
                                             ⁢ 
                                             
                                               C 
                                               2 
                                             
                                           
                                           + 
                                           
                                             
                                               r 
                                               p 
                                             
                                             ⁢ 
                                             
                                               r 
                                               s 
                                             
                                             ⁢ 
                                             
                                               C 
                                               1 
                                             
                                             ⁢ 
                                             
                                               C 
                                               2 
                                             
                                           
                                         
                                         ) 
                                       
                                     
                                     + 
                                     
                                       s 
                                       ⁡ 
                                       
                                         ( 
                                         
                                           
                                             
                                               r 
                                               p 
                                             
                                             ⁢ 
                                             
                                               C 
                                               1 
                                             
                                           
                                           + 
                                           
                                             
                                               r 
                                               s 
                                             
                                             ⁢ 
                                             
                                               C 
                                               2 
                                             
                                           
                                         
                                         ) 
                                       
                                     
                                     + 
                                     1 
                                   
                                 
                               
                             
                              
                           
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
     In the equations (4) and (5), the parameter k m  is the magnetic coupling factor of the transformer (i.e.  1043  and  1044 ). The parameter r p  models the equivalent series resistance (i.e.  3022 ) of the primary winding  1044 . The parameter r s  models the equivalent series resistance (i.e.  1042 ) of the secondary winding  1043  respectively. To reduce the side effect of TXMN  302  on the RX&#39;s noise factor F in equation (1), the last term in equation (1) should be minimized. By employing the equations (4) and (5), then substituting parameters r p  and r s  with L p ω/Q p  and L s ω/Q s  respectively, and assuming Q p Q s &gt;&gt;1, an equation (6) is obtained as follow: 
     
       
         
           
             
               
                 
                   
                     
                       
                         V 
                         
                           n 
                           , 
                           TX 
                         
                         2 
                       
                       _ 
                     
                     
                       
                          
                         
                           Z 
                           
                             PA 
                             , 
                             RX 
                           
                         
                          
                       
                       2 
                     
                   
                   = 
                   
                     
                       
                         4 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         KT 
                       
                       
                         
                           L 
                           s 
                         
                         ⁢ 
                         ω 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           Q 
                           s 
                         
                       
                     
                     · 
                     
                       
                         
                           
                             
                               Q 
                               s 
                             
                             
                               Q 
                               p 
                             
                           
                           ⁢ 
                           
                             k 
                             m 
                             2 
                           
                           ⁢ 
                           
                             L 
                             p 
                             2 
                           
                           ⁢ 
                           
                             C 
                             1 
                             2 
                           
                           ⁢ 
                           
                             ω 
                             4 
                           
                         
                         + 
                         
                           
                             ( 
                             
                               1 
                               - 
                               
                                 
                                   L 
                                   p 
                                 
                                 ⁢ 
                                 
                                   C 
                                   1 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   2 
                                 
                               
                             
                             ) 
                           
                           2 
                         
                       
                       
                         
                           
                             1 
                             
                               Q 
                               s 
                               2 
                             
                           
                           ⁢ 
                           
                             
                               ( 
                               
                                 1 
                                 - 
                                 
                                   
                                     L 
                                     p 
                                   
                                   ⁢ 
                                   
                                     C 
                                     1 
                                   
                                   ⁢ 
                                   
                                     
                                       ω 
                                       2 
                                     
                                     ⁡ 
                                     
                                       ( 
                                       
                                         1 
                                         + 
                                         
                                           
                                             Q 
                                             s 
                                           
                                           
                                             Q 
                                             p 
                                           
                                         
                                       
                                       ) 
                                     
                                   
                                 
                               
                               ) 
                             
                             2 
                           
                         
                         + 
                         
                           
                             ( 
                             
                               1 
                               - 
                               
                                 
                                   L 
                                   p 
                                 
                                 ⁢ 
                                 
                                   C 
                                   1 
                                 
                                 ⁢ 
                                 
                                   
                                     ω 
                                     2 
                                   
                                   ⁡ 
                                   
                                     ( 
                                     
                                       1 
                                       - 
                                       
                                         k 
                                         m 
                                         2 
                                       
                                     
                                     ) 
                                   
                                 
                               
                             
                             ) 
                           
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   6 
                   ) 
                 
               
             
           
         
       
     
     According to some embodiments, a global optimum frequency ω opt  that minimizes the contribution of TXMN  302  to the system noise factor. The minimum noise factor can be obtained by using the following equation (7): 
     
       
         
           
             
               
                 
                   
                     ω 
                     opt 
                     2 
                   
                   ≈ 
                   
                     
                       1 
                       
                         
                           L 
                           p 
                         
                         ⁢ 
                         
                           C 
                           1 
                         
                       
                     
                     · 
                     
                       
                         Q 
                         p 
                       
                       
                         
                           Q 
                           p 
                         
                         + 
                         
                           Q 
                           s 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   7 
                   ) 
                 
               
             
           
         
       
     
     To achieve the minimum noise factor penalty, the capacitance C 1  of the adjustable capacitor  3024  is adjusted to make the frequency ω opt  equal or near to the frequency ω 0 . An equation (8) can be obtained by inserting the equation (7) into the equation (6) as follow: 
     
       
         
           
             
               
                 
                   
                     
                       ( 
                       
                         
                           
                             V 
                             
                               n 
                               , 
                               TX 
                             
                             2 
                           
                           _ 
                         
                         
                           
                              
                             
                               Z 
                               
                                 PA 
                                 , 
                                 RX 
                               
                             
                              
                           
                           2 
                         
                       
                       ) 
                     
                     min 
                   
                   = 
                   
                     
                       
                         
                           
                             4 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             KT 
                           
                           
                             
                               L 
                               s 
                             
                             ⁢ 
                             ω 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               Q 
                               s 
                             
                           
                         
                         · 
                         
                           
                             
                               
                                 k 
                                 m 
                                 2 
                               
                               ⁢ 
                               
                                 Q 
                                 p 
                               
                               ⁢ 
                               
                                 Q 
                                 s 
                               
                             
                             + 
                             
                               Q 
                               s 
                               2 
                             
                           
                           
                             
                               ( 
                               
                                 
                                   Q 
                                   s 
                                 
                                 + 
                                 
                                   
                                     k 
                                     m 
                                     2 
                                   
                                   ⁢ 
                                   
                                     Q 
                                     p 
                                   
                                 
                               
                               ) 
                             
                             2 
                           
                         
                       
                       ⁢ 
                       
                         → 
                         
                           
                             Q 
                             p 
                           
                           = 
                           
                             Q 
                             s 
                           
                         
                       
                       ⁢ 
                       
                         
                           ( 
                           
                             
                               
                                 V 
                                 
                                   n 
                                   , 
                                   TX 
                                 
                                 2 
                               
                               _ 
                             
                             
                               
                                  
                                 
                                   Z 
                                   
                                     PA 
                                     , 
                                     RX 
                                   
                                 
                                  
                               
                               2 
                             
                           
                           ) 
                         
                         min 
                       
                     
                     = 
                     
                       
                         4 
                         ⁢ 
                         KT 
                       
                       
                         
                           L 
                           s 
                         
                         ⁢ 
                         ω 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           
                             Q 
                             s 
                           
                           ⁡ 
                           
                             ( 
                             
                               1 
                               + 
                               
                                 k 
                                 m 
                                 2 
                               
                             
                             ) 
                           
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   8 
                   ) 
                 
               
             
           
         
       
     
     As a result, the noise factor penalty reduces with increasing Q s  and k m , which coincides with efforts to optimize the efficiency of the PA&#39;s matching network (i.e.  104 ). However, a step-down transformer, which is formed by  1043 ,  1044 , and  1045 , must be employed for the PA&#39;s matching network to scale up the load resistance seen by PA&#39;s transistor in order to achieve the highest possible efficiency at a relatively low output power of 3 dBm. The scale up of the load resistance may against the noise factor optimization, as evident from the equation (8) and clearly demonstrates a tradeoff between TX (e.g.  108 ) efficiency and RX (e.g.  106 ) noise factor. The total noise factor F may be calculated by inserting the equations (2), (3), and (8) into the equation (1), and an equation (9) is obtained as follow: 
     
       
         
           
             
               
                 
                   F 
                   = 
                   
                     1 
                     + 
                     
                       
                         r 
                         loss 
                       
                       
                         R 
                         S 
                       
                     
                     + 
                     
                       γ 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                         g 
                         m 
                       
                       ⁢ 
                       
                         
                           
                             R 
                             s 
                           
                           ⁡ 
                           
                             ( 
                             
                               
                                 
                                   L 
                                   1 
                                 
                                 ⁢ 
                                 
                                   ω 
                                   0 
                                 
                               
                               
                                 R 
                                 s 
                               
                             
                             ) 
                           
                         
                         2 
                       
                     
                     + 
                     
                       
                         R 
                         S 
                       
                       
                         
                           L 
                           s 
                         
                         ⁢ 
                         ω 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           
                             Q 
                             s 
                           
                           ⁡ 
                           
                             ( 
                             
                               1 
                               + 
                               
                                 k 
                                 m 
                                 2 
                               
                             
                             ) 
                           
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   9 
                   ) 
                 
               
             
           
         
       
     
     In addition, the input impedance of the RX (e.g.  106 ) should be matched to the antenna impedance. The input matching of LNTA  1062  is quite sensitive to the imaginary part of the impedance seen from the output pad (i.e. signal port  110 ) toward the TX (e.g.  108 ). Hence, the main resonant frequency of PA&#39;s matching network (i.e.  104 ) is adjusted to near or equal the operating frequency ω 0 . It also facilitates designing the PA  1082  and the LNTA  1062  more independently. The fundamental resonant frequency ω res  of the transformer-base resonator may be obtained by the following equation (10): 
     
       
         
           
             
               
                 
                   
                     ω 
                     res 
                     2 
                   
                   = 
                   
                     1 
                     
                       
                         
                           L 
                           p 
                         
                         ⁢ 
                         
                           C 
                           1 
                         
                       
                       + 
                       
                         
                           L 
                           s 
                         
                         ⁢ 
                         
                           C 
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   10 
                   ) 
                 
               
             
           
         
       
     
     It is noted that the term L p C 1  should be chosen to satisfy the equation (7) in order to achieve the lowest noise factor. Consequently, the capacitance C 2  of the adjustable capacitor  1041  may be varied to adjust the resonant frequency ω 0  of the PA&#39;s matching network (i.e.  104 ). By inserting the equation (7) into the equation (10), an equation (11) is obtained as follow: 
     
       
         
           
             
               
                 
                   
                     C 
                     2 
                   
                   = 
                   
                     
                       1 
                       
                         
                           L 
                           s 
                         
                         ⁢ 
                         
                           ω 
                           0 
                           2 
                         
                       
                     
                     · 
                     
                       
                         Q 
                         s 
                       
                       
                         
                           Q 
                           p 
                         
                         + 
                         
                           Q 
                           s 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   11 
                   ) 
                 
               
             
           
         
       
     
     Consequently, to simultaneously achieve the lowest noise factor and the input insertion loss, the capacitance C 1  of the adjustable capacitor  3024  and the capacitance C 2  of the adjustable capacitor  1041  may be adjusted to satisfy the equation (7) and the equation (11) respectively. Under this condition, the TX&#39;s output impedance becomes purely resistive and may be estimated by the following equation (12): 
     
       
         
           
             
               
                 
                   
                     R 
                     
                       PA 
                       , 
                       RX 
                     
                   
                   = 
                   
                     
                       L 
                       s 
                     
                     ⁢ 
                     
                       ω 
                       0 
                     
                     ⁢ 
                     
                       
                         Q 
                         s 
                       
                       · 
                       
                         ( 
                         
                           1 
                           + 
                           
                             
                               k 
                               m 
                               2 
                             
                             ⁢ 
                             
                               
                                 Q 
                                 p 
                               
                               
                                 Q 
                                 s 
                               
                             
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   ( 
                   12 
                   ) 
                 
               
             
           
         
       
     
     As a result, the input matching may be realized by adjusting the transconductance gain g m  of the LNTA  1062  by the following equation (13): 
     
       
         
           
             
               
                 
                   
                     g 
                     m 
                   
                   = 
                   
                     
                       
                         C 
                         gs 
                       
                       
                         L 
                         1 
                       
                     
                     · 
                     
                       
                         ( 
                         
                           
                             
                               
                                 R 
                                 
                                   PA 
                                   , 
                                   RX 
                                 
                               
                               · 
                               
                                 R 
                                 s 
                               
                             
                             
                               
                                 R 
                                 
                                   PA 
                                   , 
                                   RX 
                                 
                               
                               - 
                               
                                 R 
                                 s 
                               
                             
                           
                           - 
                           
                             r 
                             loss 
                           
                         
                         ) 
                       
                       . 
                     
                   
                 
               
               
                 
                   ( 
                   13 
                   ) 
                 
               
             
           
         
       
     
     Accordingly, in order to receive the RF input signal S rf   _   out  from the signal port  110  during the receiving mode of the BLE TRX  100 , the capacitance C 1  of the adjustable capacitor  3024  is adjusted to be a first capacitance and the capacitance C 2  of the adjustable capacitor  1041  is adjusted to be a second capacitance to satisfy the equation (7) and the equation (11) respectively. In addition, the capacitance C gs  of the adjustable capacitor  1066  is adjusted to be a third capacitance to satisfy the equation (3). 
     On the other hand, during the transmitting mode, the field-effect transistor  1065  of the LNTA  1062  is turned off, and consequently, the LNTA  1062  may be simplified to a series RLC network (RXMN) as shown in  FIG. 5 .  FIG. 5  is a diagram illustrating an equivalent circuit  500  of the front end  200  during the transmitting mode in accordance with some embodiments. During the transmitting mode, an RF output signal S rf   _   out  is transmitted to the antenna  102  from the DPA  1082  via the matching network  104  and the signal port  112 . The gate terminal of the field-effect transistor  1051  receives a first pre-transmit signal Sp 1  while the gate terminal of the field-effect transistor  1052  receives a second pre-transmit signal Sp 2 . The drain terminal of the field-effect transistor  1051  outputs a first amplified signal Sa 1  while the drain terminal of the field-effect transistor  1052  outputs a second amplified signal Sa 2 . It is noted that, the second winding  1044  and the third winding  1045  are re-arranged to be a plurality of inductors  506 ,  508 ,  510 , and  512  as shown in  FIG. 5 . 
     The RLC network  502  comprises an inductor  5022 , an adjustable capacitor  5024 , and a resistor  5026 . The inductance of the inductor  5022  is a total inductance (i.e. L 1 +L G ) of the inductor  1063  and the inductor  1067 . The adjustable capacitor  5024  is similar to the adjustable capacitor  1066 , i.e. C gs . The resistor  5026  is similar to the resistor  1064 , i.e. r loss . During the transmitting mode, the arrangement is to alleviate the side effects of the RLC network  502  on the efficiency of the DPA  1082 . To analyze the efficiency of the DPA  1082 , the RLC network  502  is replaced with an equivalent circuit  504 . The equivalent circuit  504  comprises a capacitor  5042  with a capacitance C RX  and a resistor  5044  with a resistance R RX , wherein the capacitor  5042  is connected to the resistor  5044  in parallel. The capacitance C RX  and the resistance R RX  may be obtained by the following equations (14) and (15) respectively: 
     
       
         
           
             
               
                 
                   
                     R 
                     RX 
                   
                   = 
                   
                     
                       r 
                       loss 
                     
                     · 
                     
                       ( 
                       
                         1 
                         + 
                         
                           
                             Q 
                             RX 
                             2 
                           
                           · 
                           
                             
                               ( 
                               
                                 
                                   
                                     ω 
                                     RX 
                                   
                                   
                                     ω 
                                     0 
                                   
                                 
                                 - 
                                 
                                   
                                     ω 
                                     0 
                                   
                                   
                                     ω 
                                     RX 
                                   
                                 
                               
                               ) 
                             
                             2 
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   14 
                   ) 
                 
               
             
             
               
                 
                   
                     C 
                     RX 
                   
                   = 
                   
                     
                       C 
                       gs 
                     
                     · 
                     
                       
                         
                           Q 
                           RX 
                           2 
                         
                         · 
                         
                           ( 
                           
                             
                               
                                 ( 
                                 
                                   
                                     ω 
                                     RX 
                                   
                                   
                                     ω 
                                     0 
                                   
                                 
                                 ) 
                               
                               2 
                             
                             - 
                             1 
                           
                           ) 
                         
                       
                       
                         
                           1 
                           + 
                           
                             Q 
                             RX 
                             2 
                           
                         
                         ⁣ 
                         
                           · 
                           
                             
                               ( 
                               
                                 
                                   
                                     ω 
                                     RX 
                                   
                                   
                                     ω 
                                     0 
                                   
                                 
                                 - 
                                 
                                   
                                     ω 
                                     0 
                                   
                                   
                                     ω 
                                     RX 
                                   
                                 
                               
                               ) 
                             
                             2 
                           
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   15 
                   ) 
                 
               
             
           
         
       
     
     The parameters ω RX  and Q RX  are the resonant frequency and the quality factor of the RLC network  502 . The resonant frequency ω RX  may be expressed by the following equation (16): 
     
       
         
           
             
               
                 
                   
                     ω 
                     RX 
                   
                   = 
                   
                     1 
                     
                       
                         
                           ( 
                           
                             
                               L 
                               1 
                             
                             + 
                             
                               L 
                               G 
                             
                           
                           ) 
                         
                         ⁢ 
                         
                           C 
                           gs 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   16 
                   ) 
                 
               
             
           
         
       
     
     Due to the resistor  5044 , the power of the DPA  1082  is dissipated, and the efficiency η RX  of the DPA  1082  is scaled down by the following equation (17): 
     
       
         
           
             
               
                 
                   
                     η 
                     RX 
                   
                   = 
                   
                     
                       R 
                       RX 
                     
                     
                       
                         R 
                         L 
                       
                       + 
                       
                         R 
                         RX 
                       
                     
                   
                 
               
               
                 
                   ( 
                   17 
                   ) 
                 
               
             
           
         
       
     
     The parameter R L  (e.g. 50 ohm) is the input impedance of the antenna  102 . As a result, the side effect of the RLC network  502  on the transmitter efficiency may be minimized by having a relatively large resistance R RX . According to the equation (14), when the resonant frequency ω RX  of the RLC network  502  is pushed to a much lower or higher frequency than ω 0  via the adjustable capacitor  1066  (or  5024 ), the side effect of the RLC network  502  on the transmitter efficiency may be minimized. 
     During the transmitting mode, the highest efficiency of the DPA  1082  is achieved by adjusting the capacitance C gs  of the adjustable capacitor  1066  (or  5024 ) to its maximum value, and then the capacitances C 1  and C 2  of the adjustable capacitors  3024  and  1041 , respectively, can be tuned to satisfy the required matching network of class-E/F2 operation. According to some embodiments, class-E/F2 tuning exhibits the lowest systematic drain current. Consequently, the DPA  1082  needs a relatively smaller impedance transformation ratio for output power, which results in a lower insertion loss for its matching network and thus higher system efficiency. 
     Accordingly, in order to transmit the RF output signal S rf   _   out  to the signal port  110  from the DPA  1082  during the transmitting mode of the BLE TRX  100 , the capacitance C 1  of the adjustable capacitor  3024  is adjusted to be a fourth capacitance and the capacitance C 2  of the adjustable capacitor  1041  is adjusted to be a fifth capacitance to satisfy the required matching network of the class E/F 2  power amplifier (i.e.  1082 ). In addition, the capacitance C gs  of the adjustable capacitor  1066  is adjusted to be a sixth capacitance to achieve the highest efficiency of the DPA  1082 . 
     According to some embodiments, the fourth capacitance of the adjustable capacitor  3024  is different from the first capacitance of the adjustable capacitor  3024 . The fifth capacitance of the adjustable capacitor  1041  is different from the second capacitance of the adjustable capacitor  1041 . The sixth capacitance of the adjustable capacitor  1066  is different from the third capacitance of the adjustable capacitor  1066 . For example, the sixth capacitance of the adjustable capacitor  1066  may be greater than the third capacitance of the adjustable capacitor  1066 . 
     According to some embodiments, the field-effect transistors  1051  and/or  1052 , and/or the adjustable capacitors  3024 ,  1041 , and/or  1066  may be connected to at least one serial peripheral interface (SPI)  116 . A host  118  is arranged to generate a plurality of digital signals, e.g. four bits signal, for controlling the operation of the field-effect transistors  1051  and/or  1052 , and/or the values of the adjustable capacitors  3024 ,  1041 , and/or  1066  via the SPI  116 . 
       FIG. 6  is a diagram illustrating a return loss S 11 _ tx  at the signal port  110  of the BLE TRX  100  during the transmitting mode in accordance with some embodiments. The curve  602  shows the value of the return loss S 11 _ tx  versus the frequency band. According to some embodiments, the value of the return loss S 11 _ tx  is between −19 to −13 dB across the Industrial Scientific Medical Band (ISM band), e.g. 2400-2483.5 MHz, during the transmitting mode. 
       FIG. 7  is a diagram illustrating a return loss S 11 _ rx  at the signal port  110  of the BLE TRX  100  during the receiving mode in accordance with some embodiments. The curve  702  shows the value of the return loss S 11 _ rx  versus the frequency band. According to some embodiments, the value of the return loss S 11 _ rx  is below −15 dB across the ISM band during the receiving mode. 
     According to the embodiments, a single-chip ultra-low power TRX for IoT applications, fully compliant with the BLE standard, is demonstrated in a digital CMOS technology. Two of the objectives of the embodiments are: 1) full monolithic integration and 2) maximum power efficiency. Toward the first goal, active devices associated with a digitally controlled oscillator (DCO) and a PA are placed underneath their passive RF components to promote vertical integration of passive/active components as opposed to their almost exclusive lateral monolithic integration done conventionally. The TX and RX share a single pin or port for a direct connection to an antenna. Toward the second goal, the embodiments implement several power-saving techniques, taking advantage of the relaxed specifications defined in the standard. The TX directly modulates the DCO in an open-loop manner. The RX is a DT super heterodyne architecture performing amplification and filtering using charge sharing (CS) complex-signaling bandpass filters (BPFs). 
     According to some embodiments, a transceiving device is provided. The transceiving device comprises a signal port, a receiver, a transmitter, and a first adjustable capacitor. The signal port is arranged to relay a radio frequency (RF) input signal during a first mode, and to relay an RF output signal during a second mode different from the first mode. The receiver is coupled to the signal port. The transmitter is coupled to the signal port. The first adjustable capacitor is coupled to the signal port. The second adjustable capacitor is arranged to have a first capacitance during the first mode such that the RF input signal is received by the receiver, and the second adjustable capacitor is arranged to have a second capacitance during the second mode such that the RF output signal is transmitted to the signal port. 
     According to some embodiments, a transceiving device is provided. The transceiving device comprises a signal port, a first amplifier, a second amplifier, and a matching network. The signal port is coupled to an antenna. The first amplifier is coupled to the signal port. The second amplifier is coupled to the signal port. The matching network is coupled between the second amplifier and the signal port. The second amplifier is turned off and the first amplifier is turned on to receive a radio frequency (RF) input signal from the antenna during a first mode, and the first amplifier is turned off and the second amplifier is turned on to transmit an RF output signal to the antenna during a second mode different from the first mode. 
     According to some embodiments, a transceiving device is provided. The transceiving device comprises a signal port, a first amplifier, a second amplifier, and a matching network. The signal port is coupled to an antenna. The first amplifier is coupled to the signal port. The second amplifier is coupled to the signal port. The matching network is coupled between the second amplifier and the signal port. The second amplifier and the matching network are configured to be a resonator and the first amplifier is arranged to receive a radio frequency (RF) input signal from the antenna during a first mode, and the first amplifier is configured to be a RLC (Resistor-inductor-capacitor) network and the second amplifier is arranged to transmit an RF output signal to the antenna during a second mode different from the first mode. 
     The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.