Patent Publication Number: US-2020301024-A1

Title: Circuit for a receiver rf front end and a method of same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Chinese Application number 201910214786.X entitled “CIRCUIT FOR A RECEIVER RF FRONT END AND A METHOD OF SAME,” filed on Mar. 20, 2019 by Beken Corporation, which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present application relates to a receiver&#39;s RF front end, but not exclusively, to a circuit for a receiver&#39;s RF front end and a method of the same. 
     BACKGROUND 
     Global Navigation Satellite Systems (GNSS) can provide users with accurate location, speed, and time signals, which has developed rapidly in recent years. GNSS mainly includes the United States&#39; Global Positioning System (GPS), China&#39;s Beidou System (BDS), Russia&#39;s GLONASS system and the EU&#39;s Galileo System (Galileo). 
     Due to the effect of spatial obstruction, a single GPS satellite receiver often cannot receive signals from enough satellites with good geometry, resulting in longer positioning times and poor positioning accuracy. Therefore, it may be helpful to receive GLONASS or BDS at the same time to speed up the positioning time to improve the positioning accuracy. This system is called a dual-mode satellite receiver that receives GPS+BDS or GPS+GLONASS simultaneously. 
     A RF front-end circuit is a key module in the dual-mode satellite receiver, which has a significant impact on the performance, power consumption, and cost of the entire receiver. The RF front-end circuit of a conventional dual-mode satellite receiver is generally composed of two independent RF receive paths, which has twice cost and power consumption of the single-mode receiver. In addition, the two frequency synthesizers within each RF path operate at different RF frequencies and are prone to mutual interference. 
     SUMMARY 
     According to an aspect of an embodiment of the invention, an RF front end circuit in a receiver, comprising a low noise amplifier configured to receive an RF signal from an antenna; a frequency synthesizer and divider, configured to generate a first local oscillation signal and a second local oscillation signal; a first mixer communicatively connected to the low noise amplifier and the frequency synthesizer and divider, and configured to generate a first middle frequency signal by mixing the RF signal with the first local oscillation signal; a second mixer communicatively connected to the first mixer and the frequency synthesizer and divider, and configured to generate a second middle frequency signal by mixing the first middle frequency signal with the second local oscillation signal; a first complex band path filter communicatively connected to the first mixer and configured to generate a first satellite navigation signal by filtering the first middle frequency signal to suppress signal in unwanted frequency band; a second complex band path filter communicatively connected to the second mixer and configured to generate a second satellite navigation signal by filtering the second middle frequency signal to suppress signal in unwanted frequency band, wherein the second satellite navigation signal is different from the first satellite navigation signal; a first analog to digital converter (ADC) communicatively coupled to the first complex band path filter and configured to generate a first digital satellite navigation signal by converting the first satellite navigation signal digitally; and a second analog to digital converter (ADC) communicatively coupled to the second complex band path filter and configured to generate a second digital satellite navigation signal by converting the second satellite navigation signal digitally. 
     According to another aspect of the embodiments of the invention, a method in a receiver, comprising receiving, by a low noise amplifier (LNA), an RF signal from an antenna; generating, by a frequency synthesizer and divider, a first local oscillation signal and a second local oscillation signal; generating, by a first mixer communicatively connected to the low noise amplifier and the frequency synthesizer and divider, a first middle frequency signal by mixing the RF signal with the first local oscillation signal; generating, by a second mixer communicatively connected to the first mixer and the frequency synthesizer and divider, a second middle frequency signal by mixing the first middle frequency signal with the second local oscillation signal; generating, by a first complex band path filter communicatively connected to the first mixer, a first satellite navigation signal by filtering the first middle frequency signal to suppress signal in unwanted frequency band; generating, by a second complex band path filter communicatively connected to the second mixer, a second satellite navigation signal by filtering the second middle frequency signal to suppress signal in unwanted frequency band, wherein the second satellite navigation signal is different from the first satellite navigation signal; generating, by a first analog to digital converter communicatively coupled to the first complex band path filter, a first digital satellite navigation signal by converting the first satellite navigation signal digitally; and generating, by a second analog to digital converter communicatively coupled to the second complex band path filter, a second digital satellite navigation signal by converting the second satellite navigation signal digitally. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. 
         FIG. 1  is a circuit diagram of a RF front end in a receiver according to an embodiment of the invention. 
         FIG. 2  is a circuit diagram of a RF front end in a receiver according to another embodiment of the invention. 
         FIG. 3  is a circuit diagram of a complex band path filter within the RF front end in a receiver according to an embodiment of the invention. 
         FIG. 4  is a flow chart of a method in a RF front end in a receiver according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     Various aspects and examples of the invention will now be described. The following description provides specific details for a thorough understanding and enabling description of these examples. Those skilled in the art will understand, however, that the invention may be practiced without many of these details. 
     Additionally, some well-known structures or functions may not be shown or described in detail, so as to avoid unnecessarily obscuring the relevant description. 
     The terminology used in the description presented below is intended to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific examples of the invention. Certain terms may even be emphasized below, however, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such in this Detailed Description section. 
       FIG. 1  is a circuit diagram of a RF front end circuit  100  in a receiver according to an embodiment of the invention. 
     The RF front end circuit  100  comprises a low noise amplifier (LNA)  102 , a frequency synthesizer and divider FS-DIV  104 , a first mixer  106 , a second mixer  108 , a first complex band pass filter (BPF)  110 , a second complex band pass filter (BPF)  112 , a first analog to digital converter (ADC1)  114  and a second analog to digital converter (ADC2)  116 . The LNA  102  is configured to generate an amplified RF signal A from an RF signal received from an antenna. The frequency range of the RF signals are shown as followed: 1575.42 MHz for GPS signal, 1598.0625-1609.3125 MHz for GLONASS signal and 1561.098 MHz for BDS signal. The frequency synthesizer and divider  104  is configured to generate a first local oscillation signal E and a second local oscillation signal F. The first mixer  106  is communicatively connected to the LNA  102  and the frequency synthesizer and divider FS-DIV  104 , and is configured to generate a first middle frequency signal B by mixing the amplified RF signal A with the first local oscillation signal E. The second mixer  108  is communicatively connected to the first mixer  106  and the frequency synthesizer and divider FS-DIV  104 , and configured to generate a second middle frequency signal G by mixing the first middle frequency signal B with the second local oscillation signal F. The first complex band path filter  110  is communicatively connected to the first mixer  106  and configured to generate a first satellite navigation signal C by filtering the first middle frequency signal B to suppress signal in unwanted frequency band. The second complex band path filter  112  is communicatively connected to the second mixer  108  and configured to generate a second satellite navigation signal H by filtering the second middle frequency signal G to suppress signal in unwanted frequency band. The second satellite navigation signal H is different from the first satellite navigation signal C. The first band path filter may have a pass frequency of 2.2 MHz, and the second band path filter may have a pass frequency of 11.3 MHz for GLONASS mode, or a pass frequency of 4.2 MHz for BDS mode. 
     The first analog to digital converter (ADC1)  114  is communicatively coupled to the first complex band path filter  110  and configured to generate a first digital satellite navigation signal D by converting the first satellite navigation signal C digitally. The second analog to digital converter (ADC2)  116  is communicatively coupled to the second complex band path filter  112  and configured to generate a second digital satellite navigation signal I by converting the second satellite navigation signal H digitally. 
     As further shown in  FIG. 1 , alternatively, the frequency synthesizer and divider  104  further comprises a frequency synthesizer FS  118 , a first divider  120  and a second divider  122 . The frequency synthesizer  118  is communicatively coupled to both the first divider  120  and the second divider  122 , and configured to generate and send a double-frequency signal J to both the first divider  120  and the second divider  122 . The first divider  120  is further communicatively coupled to the first mixer  106  and configured to send the first local oscillation frequency signal E to the first mixer  106  by dividing the double-frequency signal J by two. The second divider  122  is further communicatively coupled to the second mixer  108  and configured to send the second local oscillation frequency signal F to the second mixer by dividing the double-frequency signal J by a divisor. 
     Embodiment 1 
       FIG. 2  is a circuit diagram of a RF front end  200  in a receiver according to another embodiment of the invention. The RF front end  200  includes similar circuit components as the RF front end  100  shown in  FIG. 1 . The RF front end circuit  200  comprises a low noise amplifier  202 , a frequency synthesizer and divider FS-DIV  204 , a first mixer  206 , a second mixer  208 , a first complex band pass filter (BPF)  210 , a second complex band pass filter (BPF)  212 , a first analog to digital converter (ADC)  214  and a second analog to digital converter (ADC)  216 . 
     The frequency synthesizer and divider  204  is configured to generate an in-phase branch E1 of the first local oscillation signal and a quadrature branch E2 of the first local oscillation signal, and to generate an in-phase branch F1 of the second local oscillation signal and a quadrature branch F2 of the second local oscillation signal. Specifically, the frequency synthesizer and divider  204  comprises a frequency synthesizer  218 , a first divider  220  and a second divider  222 . The frequency synthesizer  218  is communicatively coupled to both the first divider  220  and the second divider  222 , and configured to generate and send a double-frequency signal J to both the first divider  220  and the second divider  222 . The double-frequency signal J may be a local oscillation signal at frequency F J =1571.328*2=3142.656 MHz. The first divider  120  is further communicatively coupled to the first mixer  106  and configured to send an in-phase branch E1 of the first middle frequency signal E and a quadrature branch E2 of the first middle frequency signal E to the first mixer  206  by dividing the double-frequency signal J by two. Therefore the in-phase branch E1 and the quadrature branch E2 of the first local oscillation signal have a frequency of F E1 =F E2 =F J /2=1571.328 MHz. The local oscillation frequency of the first local oscillation signal can be 16.368*96=1571.328 MHz with 16.368 MHz crystal oscillation, therefore the circuit can have an integer number of Phase Locked Loops (PLL). The second divider  222  is further communicatively coupled to the second mixer  208  and configured to send the second middle frequency signal F to the second mixer by dividing the double-frequency signal J by a divisor. 
     The divisor of the second divider DIV2 is configurable according to types of the first satellite navigation signal and the second satellite navigation signal. For example, if the first satellite navigation signal is Global Positioning System (GPS) L1 signal which has a frequency of 1575.42 MHz, and the second satellite navigation signal is BeiDou Navigation Satellite System B1 signal which has a frequency of 1561.1 MHz, the divisor of the second divider DIV2  222  can be chosen as  220 , if the divisor of the first divider  220  is fixed to 2. As a result, the in-phase branch F1 and the quadrature branch F2 of the second local oscillation signal F have a frequency of F F1 =F F2 =F J /220=14.2848 MHz. Note the frequency mix of the first local oscillation signal and the BDS signal (1561.098 MHz) is 10.23 MHz, and the output of the second mixed middle frequency signal ranges from 4-6 MHz which is easy to demodulate, the frequency of the second local oscillation signal F is chosen as 14.2848 MHz. Alternatively, if the first satellite navigation signal is Global Positioning System (GPS) L1 signal, and the second satellite navigation signal is Global Navigation Satellite System (GLONASS) L1 signal, the divisor of the second divider DIV2  222  can be chosen as 128, if the divisor of the first divider  220  is fixed to 2. As a result, the in-phase branch F1 and the quadrature branch F2 of the second local oscillation signal F have a frequency of F F1 =F F2 =F J /128=24.552 MHz. 
     Embodiment 2 
     In the above Embodiment 1, the circuit outputs combination of GPS L1 signal and BDS B1 signal, or the circuit outputs combination of GPS L1 signal and GLONASS L1 signal. Alternatively, in the following embodiment 2, the circuit may output combination of GPS L5 signal and BDS B2 signal, or the circuit outputs the combination of GPS L5 signal and GLONASS L2 signal. For example, the double-frequency signal J may be a local oscillation signal at frequency F J =1178.496*2=2356.992 MHz. In this case, if the first satellite navigation signal is Global Positioning System (GPS) L5 signal which has a frequency of 1176.45 MHz, and the second satellite navigation signal is BeiDou Navigation Satellite System B2 signal which has a frequency of 1246 MHz, the divisor of the second divider DIV2  222  can be chosen as 32, if the divisor of the first divider  220  is fixed to 2. As a result, the in-phase branch E1 and the quadrature branch E2 of the first local oscillation signal E have a frequency of F E1 =F E2 =F J /2=1178.496 MHz, and the in-phase branch F1 and the quadrature branch F2 of the second local oscillation signal F have a frequency of F J /32=73.656 MHz. 
     Alternatively, the double-frequency signal J may be an local oscillation signal at frequency F J =1178.496*2=2356.992 MHz. In this case, if the first satellite navigation signal is Global Positioning System (GPS) L5 signal which has a frequency of 1176.45 MHz, and the second satellite navigation signal is Global Navigation Satellite System (GLONASS) L2 signal which has a frequency of 1207.14 MHz, the divisor of the second divider DIV2  222  can be chosen as 64, if the divisor of the first divider  220  is fixed to 2. As a result, the in-phase branch E1 and the quadrature branch E2 of the first local oscillation signal E have a frequency of F E1 =F E2 =F J /2=1178.496 MHz, and the in-phase branch F1 and the quadrature branch F2 of the second local oscillation signal F have a frequency of F J /64=36.828 MHz. Note although GPS, Beidou and GLONASS global navigation satellite system signals are used as examples, those skilled in the art can understand that other navigation satellite system signals including global navigation satellite system and regional navigation satellite system, such as Galileo in Europe, NAVigation with Indian Constellation (NAVIC), or Quasi-Zenith Satellite System (QZSS) in Japan, can also be used in the embodiments. 
     Further, the first mixer  206  is further configured to generate an in-phase branch B1 of the first middle frequency signal B by mixing the RF signal A with the in-phase branch E1 of the first local oscillation signal E and a quadrature branch B2 of the first middle frequency signal B by mixing the RF signal A with the quadrature branch E2 of the first local oscillation signal E, therefore down-converting the RF signal A to the in-phase branch B1 and quadrature branch B2 of the first middle frequency signal B. In-phase branch B1 and quadrature branch B2 of the first middle frequency signal B may include GPS L1 signal and BDS B1 signal, or GPS L1 signal and GLONASS L1 signal, or GPS L5 signal and BDS B2 signal, or GPS L5 signal and GLONASS L2 signal. 
     The second mixer  208  is further configured to generate an in-phase branch G1 of the second middle frequency signal G by mixing the in-phase branch B1 of the first middle frequency signal B with the in-phase branch F1 of the second local oscillation signal F, and a quadrature branch G2 of the second middle frequency signal G by mixing the quadrature branch B2 of the first middle frequency signal B with the quadrature branch F2 of the second local oscillation signal F. Similar to the In-phase branch B1 and quadrature branch B2, In-phase branch G1 and quadrature branch G2 of the second middle frequency signal G may include GPS L1 signal and BDS B1 signal, or GPS L1 signal and GLONASS L1 signal, or GPS L5 signal and BDS B2 signal, or GPS L5 signal and GLONASS L2 signal. 
     The first complex band path filter  210  is further configured to generate an in-phase branch C1 and a quadrature branch C2 of the first satellite navigation signal C by filtering the in-phase branch B1 of the first middle frequency signal B and the quadrature branch B2 of the first middle frequency signal B to suppress signal in unwanted frequency band. For example, the first complex band path filter  210  is used to derive the GPS L1 or GPS L5 signal and suppress the other navigation signals, such as BDS B1, BDS B2, GLONASS L1, or GLONASS L2 navigation signal. Therefore, in-phase branch C1 and a quadrature branch C2 of the first satellite navigation signal C only includes GPS L1 or GPS L5, depending on the configuration of divisors of the first divider  220  and the second divider  222  in the FS-DIV  204 . 
     The second complex band path filter  212  is further configured to generate an in-phase branch H1 and a quadrature branch H2 of the second satellite navigation signal H by filtering the in-phase branch of the second middle frequency signal and the quadrature branch of the second middle frequency signal to suppress signal in unwanted frequency band. For example, the second complex band path filter  212  is used to derive the BDS B1, BDS B2, GLONASS L1, or GLONASS L2 signal and suppress the other navigation signals, such as GPS L1 or GPS L5 navigation signal. Therefore, in-phase branch H1 and a quadrature branch H2 of the second satellite navigation signal only includes BDS B1, BDS B2, GLONASS L1, or GLONASS L2 signal, depending on the configuration of divisors of the first divider  220  and the second divider  222  in the FS-DIV  204 . 
     For example, in the case that the RF front circuit  200  is used to treat GPS L1 and BDS B1 signals, the frequency of the in-phase branch C1 and a quadrature branch C2 of the first satellite navigation signal C is 4.092 MHz, and the frequency of in-phase branch H1 and a quadrature branch H2 of the second satellite navigation signal H is 4.0548 MHz. Alternatively, in the case that the RF front circuit  200  is used to treat GPS L1 and GLONASS L1 signals, the frequency of the in-phase branch C1 and a quadrature branch C2 of the first satellite navigation signal C is 4.092 MHz, and the frequency of in-phase branch H1 and a quadrature branch H2 of the second satellite navigation signal H is 6.12 MHz. Alternatively, in the case that the RF front circuit  200  is used to treat GPS L5 and BDS B2 signals, the frequency of the in-phase branch C1 and a quadrature branch C2 of the first satellite navigation signal C is 2.046 MHz, and the frequency of in-phase branch H1 and a quadrature branch H2 of the second satellite navigation signal H is 6.152 MHz. Alternatively, in the case that the RF front circuit  200  is used to treat GPS L5 and GLONASS L2 signals, the frequency of the in-phase branch C1 and a quadrature branch C2 of the first satellite navigation signal C is 2.046 MHz, and the frequency of in-phase branch H1 and a quadrature branch H2 of the second satellite navigation signal H is 8.184 MHz. Note although GPS, Beidou and GLONASS global navigation satellite system signals are used as examples, those skilled in the art can understand that other navigation satellite system signals can be used in the embodiments. 
     The following table  1  and table  2  show the frequency of the treated signals for RF front end circuit shown in  FIG. 2  that is used to treat different combinations of satellite navigation signals. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Combination of treated 
                 GPS L1 + 
                 GPS L1 + 
                   
               
               
                 signals 
                 BDS B1 
                 GLONASS L1 
                 Unit 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 GPS L1 satellite signal 
                 1575.42 
                 1575.42 
                 MHz 
               
               
                 frequency 
               
               
                 BDS B1 or GLONASS L1 
                 1561.098 
                 1602 
                 MHz 
               
               
                 satellite signal frequency 
               
               
                 First oscillation signal E1 
                 1571.328 
                 1571.328 
                 MHz 
               
               
                 and E2 frequency 
               
               
                 Second oscillation signal F1 
                 14.2848 
                 24.552 
                 MHz 
               
               
                 and F2 frequency 
               
               
                 the filtered first middle 
                 4.092 
                 4.092 
                 MHz 
               
               
                 frequency signal C1 
               
               
                 and C2 frequency 
               
               
                 the filtered second middle 
                 4.0548 
                 6.12 
                 MHz 
               
               
                 frequency signal H1 and H2 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Combination of treated 
                 GPS L5 + 
                 GPS L5 + 
                   
               
               
                 signals 
                 BDS B2 
                 GLONASS L2 
                 
                   
                 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 GPS L5 satellite signal 
                 1176.45 
                 1176.45 
                 MHz 
               
               
                 frequency 
               
               
                 BDS B2 or GLONASS L2 
                 1246 
                 1207.14 
                 MHz 
               
               
                 satellite signal frequency 
               
               
                 First oscillation signal E1 
                 1178.496 
                 1178.496 
                 MHz 
               
               
                 and E2 frequency 
               
               
                 First oscillation signal E1 
                 73.656 
                 36.828 
                 MHz 
               
               
                 and E2 frequency 
               
               
                 the filtered first middle 
                 2.046 
                 2.046 
                 MHz 
               
               
                 frequency signal C1 
               
               
                 and C2 frequency 
               
               
                 the filtered second middle 
                 6.152 
                 8.184 
                 MHz 
               
               
                 frequency signal H1 and H2 
               
               
                   
               
            
           
         
       
     
     Further, the first analog to digital converter (ADC1)  214  is communicatively coupled to the first complex band path filter  210  and configured to generate a first digital satellite navigation signal D by converting the in-phase branch C1 of the first satellite navigation signal C digitally. For example, the first ADC  214  only converts the in-phase branch C1, as the baseband demodulation only needs one branch. The second analog to digital converter (ADC2)  216  is communicatively coupled to the second complex band path filter  112  and configured to generate a second digital satellite navigation signal I by converting the second satellite navigation signal H digitally. For example, the ADC  216  only converts in-phase signal H1, as the baseband demodulation only needs one branch. 
       FIG. 3  is a circuit diagram of a complex band path filter  300  within the RF front end in a receiver according to an embodiment of the invention. 
     The first complex band path filter and the second complex band path filter each further comprises an in-phase branch filter  302  configured to filter an in-phase branch signal; a quadrature branch filter  304  configured to filter a quadrature branch signal; an in-phase branch programmable gain amplifier (I PGA)  306  communicatively connected to both the in-phase branch filter  302  and the quadrature branch filter  304  and configured to generate an in-phase branch of an amplified signal based on the in-phase branch signal and the quadrature branch signal; and a quadrature branch programmable gain amplifier (Q PGA)  308  communicatively connected to both the in-phase branch filter  302  and the quadrature branch filter  304  and configured to generate a quadrature branch of the amplified signal based on the in-phase branch signal and the quadrature branch signal. 
       FIG. 4  is a flow chart of a method  400  in a RF front end in a receiver according to an embodiment of the invention. The method  400  comprises receiving, in block  410 , by a low noise amplifier (LNA), an RF signal from an antenna; generating, in block  420  by a frequency synthesizer and divider, a first local oscillation signal and a second local oscillation signal; generating, in block  430  by a first mixer communicatively connected to the low noise amplifier and the frequency synthesizer and divider, a first middle frequency signal by mixing the RF signal with the first local oscillation signal; generating, in block  440  by a second mixer communicatively connected to the first mixer and the frequency synthesizer and divider, a second middle frequency signal by mixing the first middle frequency signal with the second local oscillation signal; generating, in block  450  by a first complex band path filter communicatively connected to the first mixer, a first satellite navigation signal by filtering the first middle frequency signal to suppress signal in unwanted frequency band; generating, in block  460  by a second complex band path filter communicatively connected to the second mixer, a second satellite navigation signal by filtering the second middle frequency signal to suppress signal in unwanted frequency band, wherein the second satellite navigation signal is different from the first satellite navigation signal; generating, in block  470  by a first analog to digital converter communicatively coupled to the first complex band path filter, a first digital satellite navigation signal by converting the first satellite navigation signal digitally; and generating in block  480 , by a second analog to digital converter communicatively coupled to the second complex band path filter, a second digital satellite navigation signal by converting the second satellite navigation signal digitally. 
     Alternatively, generating in block  420 , by the frequency synthesizer and divider, a first local oscillation signal and a second local oscillation signal is further implemented by generating an in-phase branch of the first local oscillation signal and a quadrature branch of the first local oscillation signal, and generating an in-phase branch of the second local oscillation signal and a quadrature branch of the second local oscillation signal; and generating in block  430 , by the first mixer communicatively connected to the low noise amplifier and the frequency synthesizer and divider, a first middle frequency signal by mixing the RF signal with the first middle frequency signal is further implemented by generating an in-phase branch of the first middle frequency by mixing the RF signal with the in-phase branch of the first local oscillation signal and a quadrature branch of the first middle frequency signal by mixing the RF signal with the quadrature branch of the first local oscillation signal; generating in block  440 , by the second mixer communicatively connected to the first mixer and the frequency synthesizer and divider, a second middle frequency signal by mixing the first middle frequency signal with the second local oscillation signal is further implemented by generating an in-phase branch of the second middle frequency signal by mixing the in-phase branch of the first middle frequency signal with the in-phase branch of the second local oscillation signal, and a quadrature branch of the second middle frequency signal by mixing the quadrature branch of the first middle frequency signal with the quadrature branch of the second local oscillation signal; generating in block  450 , by the first complex band path filter communicatively connected to the first mixer, a first satellite navigation signal by filtering the first middle frequency signal is further implemented by generating an in-phase branch and a quadrature branch of the first satellite navigation signal by filtering the in-phase branch of the first middle frequency signal and the quadrature branch of the first middle frequency signal to suppress signal in unwanted frequency band; and generating in block  460 , by the second complex band path filter communicatively connected to the second mixer, a second satellite navigation signal by filtering the second middle frequency signal is further implemented by generating an in-phase branch and a quadrature branch of the second satellite navigation signal by filtering the in-phase branch of the second middle frequency signal and the quadrature branch of the second middle frequency signal to suppress signal in unwanted frequency band. 
     Alternatively, wherein generating in block  450 , by a first complex band path filter communicatively connected to the first mixer, a first satellite navigation signal by filtering the first middle frequency signal and generating in block  460 , by a second complex band path filter communicatively connected to the second mixer, a second satellite navigation signal by filtering the second middle frequency signal each is further implemented by filtering, by an in-phase branch filter, an in-phase branch signal; filtering, by a quadrature branch filter, a quadrature branch signal; generating, by an in-phase branch programmable gain amplifier communicatively connected to both the in-phase branch filter and the quadrature branch filter, an in-phase branch of an amplified signal based on the in-phase branch signal and the quadrature branch signal; and generating, by a quadrature branch programmable gain amplifier communicatively connected to both the in-phase branch filter and the quadrature branch filter, a quadrature branch of the amplified signal based on the in-phase branch signal and the quadrature branch signal. 
     Alternatively, wherein the first satellite navigation signal and the second satellite navigation signal are from different navigation satellite systems. 
     Features and aspects of various embodiments may be integrated into other embodiments, and embodiments illustrated in this document may be implemented without all of the features or aspects illustrated or described. One skilled in the art will appreciate that although specific examples and embodiments of the system and methods have been described for purposes of illustration, various modifications can be made without deviating from the spirit and scope of the present invention. Moreover, features of one embodiment may be incorporated into other embodiments, even where those features are not described together in a single embodiment within the present document. Accordingly, the invention is described by the appended claims