Abstract:
A diplexer, for coupling a first radio frequency (RF) signal corresponding to a first carrier frequency and a second RF signal corresponding to a second carrier frequency is disclosed. The diplexer includes a first port arranged to couple the first RF signal; a second port arranged to couple the second RF signal; a third port capable of connecting an antenna; a first impedance unit coupled to the first port and the third port; and a second impedance unit coupled to the second port and the third port; wherein the first port, the second port and the third port are coupled to a direct current (DC) ground; wherein the first impedance unit is arranged to provide an first open-circuit impedance against the second RF signal, and the second impedance unit is arranged to provide a second open-circuit impedance against the first RF signal.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/767,284 filed on Feb. 21, 2013 and entitled “Balun-Filtering Diplexer”, the contents of which are incorporated herein in their entirety. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to a diplexer and transceiver thereof, and more particularly, to a diplexer and transceiver with ports coupled to a direct current (DC) ground for enhancing electro-static discharge (ESD) protection ability. 
         [0003]    As technology advances, the processes of integrated circuit (IC) become advanced, and various kinds of electronic circuits can be integrated/formed in a single chip. When the electronic circuits of an IC operate under two or more frequencies, a transmitting/receiving (T/R) switch or a diplexer is required for separating signals with different frequencies. When the diplexer is adopted, the manufacture cost of the diplexer can be reduced if the diplexer is implemented in an independent die via an integrated passive device (IPD) process. Since the die implemented by the IPD process does not have any active component, input/output pins of the die may be easily damaged due to the electro-static discharge (ESD) when manufacturing, packing, or testing the integrated circuit. Thus, how to choose the structure of the diplexer for reducing the effect of the ESD becomes an important issue to be discussed. 
       SUMMARY 
       [0004]    In order to solve the above problem, the present invention provides a diplexer and transceiver with ports coupled to a direct current (DC) ground, respectively. 
         [0005]    The present invention discloses a diplexer, for coupling a first radio frequency (RF) signal corresponding to a first carrier frequency and a second RF signal corresponding to a second carrier frequency. The diplexer comprises a first port arranged to couple the first RF signal; a second port arranged to couple the second RF signal; a third port capable of connecting an antenna; a first impedance unit coupled to the first port and the third port; and a second impedance unit coupled to the second port and the third port; wherein the first port, the second port and the third port are coupled to a direct current (DC) ground; wherein the first impedance unit is arranged to provide an first open-circuit impedance against the second RF signal, and the second impedance unit is arranged to provide a second open-circuit impedance against the first RF signal. 
         [0006]    The present invention further discloses a transceiver of a wireless communication device, for coupling a first radio frequency (RF) signal corresponding to a first carrier frequency and a second RF signal corresponding to a second carrier frequency. The transceiver comprises a first signal processing unit, for processing the first RF signal; a second signal processing unit, for processing the second RF signal; a diplexer, comprising a first port arranged to couple the first RF signal; a second port arranged to couple the second RF signal; a third port capable of connecting an antenna; a first impedance unit coupled to the first port and the third port; and a second impedance unit coupled to the second port and the third port; wherein the first port, the second port and the third port are coupled to a DC ground; wherein the first impedance unit is arranged to provide an first open-circuit impedance against the second RF signal and the second impedance is arranged to provide a second open-circuit impedance against the first RF signal. 
         [0007]    The present invention further discloses a diplexer for transmitting at least one radio frequency (RF) signal and each RF signal corresponding to a carrier frequency. The diplexer comprises at least one input port arranged to couple at least one RF signal; at least one output port, each output port is capable of connecting an antenna; and at least one impedance unit coupled between a first input port of the at least one input port and a first output port of the at least one output port; wherein each input port and output port are coupled to a DC ground; wherein the at lease one impedance unit performs is arranged to provide a short-circuit impedance against one of the at least one RF signal. 
         [0008]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic diagram of a transceiver according to an example of the present invention. 
           [0010]      FIG. 2  is a schematic diagram of a diplexer according to an example of the present invention. 
           [0011]      FIG. 3  is a schematic diagram of another diplexer according to an example of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Please refer to  FIG. 1 , which is a schematic diagram of a transceiver  10  according to an example of the present invention. The transceiver  10  is utilized in a wireless communication device (e.g. a wireless router, a wireless network accessing device, a wireless network card and wireless communication device) for coupling a radio frequency (RF) signal RFS 1  corresponding to a carrier frequency CF 1  and a RF signal RFS 2  corresponding to a carrier frequency CF 2 . As shown in  FIG. 1 , the transceiver  10  comprises signal processing units  100 ,  102  and a diplexer  104 . The signal processing units  100 ,  102  are coupled to ports POR 1 , POR 2  of the diplexer  104 , respectively, for performing relative signal processes (e.g. demodulation and modulation) of the RF signals RFS 1 , RFS 2 . The diplexer  104  comprises the ports POR 1 -POR 3  and impedance units IMU 1 , IMU 2 . The diplexer  104  is utilized for transmitting the RF signals RFS 1 , RFS 2  to the port POR 3 , respectively, and separating a RF signal RF 3  received by the port POR 3  to obtain parts of the RF signals RFS 1 , RFS 2 . In the diplexer  104 , each of the ports POR 1 -POR 3  is coupled to a direct-current (DC) ground through at least one inductor, which means that if charges of a DC current feed to the ports POR 1 -POR 3 , the charges are conducted to the ground, directly. In other words, if charges of the electro-static discharge (ESD) feed to the ports POR 1 -POR 3 , the charges are conducted to the DC ground immediately. The transceiver  10  can be avoided being damaged by the ESD, therefore. 
         [0013]    In detail, the impedance unit IMU 1  comprises inductors L 1 , L 2  and capacitors C 1 -C 4 . The inductors L 1 , L 2  and the capacitors C 1 -C 3  form a low pass filter, which is arranged to provide an open-circuit impedance (i.e. performs as open-circuit) against the RF signal RFS 2  with the carrier frequency CF 2 . The impedance unit IMU 2  comprises inductors L 3 -L 5  and capacitors C 5 -C 7 . The inductor L 3  and the capacitor C 5 , the inductor L 4  and the capacitor C 6 , and the inductor L 5  and the capacitor C 7  form parallel inductor-capacitor resonant circuits PICR 1 -PICR 3 , respectively. The parallel inductor-capacitor resonant circuit PICR 1  is magnetically connected to the parallel inductor-capacitor resonant circuit PICR 2 , and the parallel inductor-capacitor resonant circuit PICR 2  is magnetically connected to the parallel inductor-capacitor resonant circuit PICR 3 . In such a condition, the parallel inductor-capacitor resonant circuits PICR 1 -PICR 3  form a trisection filter (i.e. a band-pass filter), which is arranged to provide an open-circuit impedance against the RF signal RFS 1  with the carrier frequency CF 1 . That is, the trisection filter including the parallel inductor-capacitor resonant circuits PICR 1 -PICR 3  only allows the RF signal RFS 2  to pass and performs as open circuit for the RF signal RFS 1  (i.e. the RF signal RFS 1  is rejected by the trisection filter). 
         [0014]    The port POR 1  is arranged to couple the RF signal RFS 1  generated by the signal processing unit  100  and couple the DC ground through the inductors L 1 , L 2 . Similarly, the port POR 2  is arranged to couple the RF signal RFS 2  generated by the signal processing unit  102  and couple the DC ground through the inductor L 3 . The port POR 3  of the diplexer  104  is arranged to couple the DC ground through the inductor L 5  and may couple an antenna (not shown in  FIG. 1 ) for receiving the RF signal RFS 3  and transmitting the RF signals RFS 1 , RFS 2  (or a mixed signal of the RF signals RFS 1 , RFS 2 ). Please note that, the RF signals RFS 1  and RFS 2  have different carrier frequencies (i.e. the carrier frequency CF 1  does not equal the carrier frequency CF 2 ), resulting different transmitting paths. In this embodiment, the part corresponding to the carrier frequency CF 1  in a RF signal passes through the impedance unit IMU 1  but is rejected by the impedance unit IMU 2 , and the part corresponding to the carrier frequency CF 2  in a RF signal passes through the impedance unit IMU 2  but is rejected by the impedance unit IMU 1 . In other words, the part of RF signal RFS 1  in the RF signal RFS 3  is transmitted to the port POR 1  and is not received by the port POR 2 . The part of RF signal RFS 2  in the RF signal RFS 3  is transmitted to the port POR 2  and is not received by the port POR 1 . Moreover, the RF signal RFS 1  generated by the signal processing unit  100  is transmitted to the port POR 3  and does not feed to the port POR 2 . The RF signal RFS 2  generated by the signal processing unit  102  is transmitted to the port POR 3  and does not feed to the port POR 1 . In short, via the impedance units IMU 1  and IMU 2 , the RF signals RFS 1  and RFS 2  can be transmitted and received appropriately. Further, the components of the diplexer  104  (e.g. the capacitors C 1 -C 7 ) can be prevented from being damaged by the ESD via the paths from ports POR 1 -POR 3  to the DC ground. The ESD protection ability of the diplexer  104  is significantly enhanced therefore. 
         [0015]    The following descriptions narrate the operations of the transceiver  10  when the transceiver  10  operates in a receiving link as an example. First, the RF signal RFS 3  comprising a part of RF signal RFS 1  and a part of RF signal RFS 2  is received by the antenna and is transmitted to the port POR 3 . Since the impedance unit IMU 1  provides the open-circuit impedance against the RF signal RFS 2 , the part of the RF signal RFS 2  cannot pass through the impedance unit IMU 1 , and only the part of the RF signal RFS 1  can be transmitted to the port POR 1 . Similarly, since the impedance unit IMU 2  provides the open-circuit impedance against the RF signal RFS 1 , the part of the RF signal RFS 1  cannot pass through the impedance unit IMU 2  and only the part of the RF signal RFS 2  can be transmitted to the port POR 2 . In other words, the part of the RF signal RFS 1  and the part of the RF signal RFS 2  in the RF signal RFS 3  are transmitted to the ports POR 1  and POR 2 , respectively, after passing through the diplexer  104 . 
         [0016]    The following descriptions narrate the operations of the transceiver when the transceiver  10  operates in a transmitting link as an example. When the RF signal RFS 1  is generated by the signal processing unit  100  and passes through the impedance unit IMU 1 , the RF signal RFS 1  is only transmitted to the port POR 3  due to the open-circuit impedance provided by the impedance unit IMU 2  against the RF signal RFS 1 . Similarly, when the RF signal RFS 2  is generated by the signal processing unit  102  and passes through the impedance unit IMU 2 , the RF signal RFS 2  is only transmitted to the port POR 3  due to the open-circuit impedance provided by the impedance unit IMU 1  against the RF signal RFS 2 . In such a condition, the RF signals RFS 1  and RFS 2  can be transmitted to the port POR 3  without interfering each other. 
         [0017]    Please refer to  FIG. 2 , which is a schematic diagram of a diplexer  20  according to an example of the present invention. The diplexer  20  is similar to the diplexer  104  shown in  FIG. 1 , and thus the components and signals with similar functions in the diplexers  20  and  104  are denoted by the same symbols. Different from the diplexer  104  shown in  FIG. 1 , the impedance unit IMU 1  of the diplexer  20  is realized by an inductor L 6  and a capacitor C 8 , and the impedance unit IMU 2  of the diplexer  20  is realized by inductors L 7 -L 10  and capacitors C 9 -C 12 . The inductor L 6  and the capacitor C 8  of the impedance unit IMU 1  are arranged to form a parallel inductor-capacitor resonant circuit PICR 4  and the transfer function of which is a notch filtering function (i.e. the parallel inductor-capacitor resonant circuit PICR 4  is a notch filter). The parallel inductor-capacitor resonant circuit PICR 4  is arranged to provide the open-circuit impedance against the RF signal RFS 2  with the carrier frequency CF 2 . Similarly, the inductor L 7  and the capacitor C 9  of the impedance unit IMU 2  are arranged to form a parallel inductor-capacitor resonant circuit PICR 5  and the transfer function of which is the notch filtering function. The parallel inductor-capacitor resonant circuit PICR 5  is arranged to provide the open-circuit impedance against the RF signal RFS 1  with the carrier frequency CF 1 . Further, the impedance unit IMU 2  comprises parallel inductor-capacitor resonant circuits PICR 6 -PICR 8  formed by the inductors L 8 -L 10  and the capacitors C 10 -C 12 , respectively. The parallel inductor-capacitor resonant circuits PICR 6 -PICR 8  are magnetically connected to each other. In such a condition, the parallel inductor-capacitor resonant circuits PICR 6 -PICR 8  are provided with a band-pass transfer function and a balanced-unbalance (BALUN) function. The out-of-band signal of the RF signal RFS 2  received by the port POR 2  can be further eliminated, therefore. Noticeably, the implement method of impedance unit IMU 2  of the diplexer  20  can be various, and is not limited herein. For example, the impedance unit IMU 2  of the diplexer  20  can be implemented as the impedance unit IMU 2  of the diplexer  104  shown in  FIG. 1 , which equips with band-pass transfer function. The detailed operations of the diplexer  20  can be referring to the above, and are not narrated herein for brevity. As a result, via the impedance units IMU 1  and IMU 2 , the RF signals RFS 1  and RFS 2  can be transmitted and received appropriately. 
         [0018]    Please note that, each port of the ports POR 1 -POR 3  of the diplexer  20  is coupled to the DC ground through at least one inductor. As shown in  FIG. 2 , the port POR 1  is coupled to the DC ground through the inductors L 6 -L 8 , the port POR 2  is coupled to the DC ground thought the inductor L 10  and the port POR 3  is coupled to the DC ground through the inductors L 7 , L 8 . In such a condition, the charges of the DC current (e.g. the charges generated by the ESD), generated at the ports of the diplexer and the transceiver, are conducted to the ground directly. The components of the diplexer  104  (e.g. the capacitors C 8 -C 12 ) can be prevented from being damaged by the ESD via the paths from ports POR 1 -POR 3  to the DC ground, and the ESD protection ability of the diplexer  20  is significantly enhanced, therefore. 
         [0019]    Noticeably, each port of the diplexer shown in the above examples is coupled to the ground through at least one inductor. The charges of the DC current generated at the ports of the diplexer and the transceiver can be conducted to the ground immediately. The components of the diplexer shown in the above examples can be prevented from being damaged due to the ESD, therefore. According to different applications and design concepts, those with ordinary skill in the art may observe appropriate alternations and modifications. For example, the ports of the diplexer of the present invention are not limited to 3. As long as the RF signals of the diplexer can be appropriately transmitted and received without interfering to each other (e.g. a signal processing unit transmits/receives the RF signal with a specific carrier frequency), the ports of the diplexer can be increased according to different applications. 
         [0020]    Please refer to  FIG. 3 , which is a schematic diagram of the diplexer  30  according to an example of the present invention. The diplexer  30  is similar to the diplexer  104  shown in  FIG. 1 , thus the components and the signals with similar functions in the diplexers  30  and  104  are denoted by the same symbols. As shown in  FIG. 3 , the diplexer  30  further comprises a port POR 4  coupled to the inductor L 3  and the capacitor C 5 . The signals received by the ports POR 2  and the port POR 4  are a differential pair of the RF signal RFS 2 . When the charges of the DC current are generated at the port POR 2  or at the port POR 4 , the voltage across the capacitor C 5  is 0 since the charges are conducted to both sides of the capacitor C 5  immediately. In such a condition, the capacitor C 5  can also be prevented from being damaged by the charges of the DC current after adding the port POR 4 . The ESD protection ability of the diplexer  30  is enhanced, therefore. The detailed operations of the diplexer  30  can be referring to the above, and are not narrated herein for brevity. 
         [0021]    Please note that, the impedance unit IMU 2  of the diplexer  30  can be modified according to different applications and design concepts. For example, the impedance unit IMU 2  of the diplexer  30  can be implemented as the impedance unit IMU 2  of the diplexer  104  shown in  FIG. 1  by changing the ends of the capacitor C 5  and the inductor L 3  coupled to the ground to be coupled to the port POR 4  (i.e. the differential port of the port POR 2 ). In other words, the impedance unit IMU 2  of the diplexer  30  is not required to equip with the BALUN function. 
         [0022]    To sum up, through connecting each port of the diplexer shown in the above examples to the DC ground via at least one inductor, the components of the diplexer shown in the above examples can be prevented from being damaged by the ESD. The ESD protection ability of the diplexer and the transceiver thereof can be significantly enhanced, therefore. 
         [0023]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.