WO2011020399A1

WO2011020399A1 - Radio frequency circuit structure for realizing function of converting dual-frequency global positioning system (gps) satellite signal into baseband signal

Info

Publication number: WO2011020399A1
Application number: PCT/CN2010/075471
Authority: WO
Inventors: 王永泉
Original assignee: 上海华测导航技术有限公司
Priority date: 2009-08-18
Filing date: 2010-07-27
Publication date: 2011-02-24
Also published as: CN101629996A

Abstract

A radio frequency circuit structure for realizing the function of converting dual-frequency Global Positioning System (GPS) satellite signal into baseband signal includes: an antenna receiving functional module, a signal dividing functional module for dividing the GPS signal received from the antenna receiving functional module into L1 frequency band and L2 frequency band, a circuit for generating 1743MHz, 1059MHz and 336MHz local oscillation signals and a 25MHz clock signal, a processing circuit for down-converting the GPS signal into an intermediate frequency signal and a circuit for obtaining I-channel and Q-channel digital signals by quadrature demodulating, filtering and Analog/digital (A/D) converting the intermediate frequency signal. The difference between the first-order local oscillation signal frequency of L1 and the L1 frequency band of the GPS satellite signal is positive, but the difference between the first-order local oscillation signal frequency of L2 and the L2 frequency band of the GPS satellite signal is negative, and the first-order local oscillation signal of L1 and the first-order local oscillation signal of L2 are respectively generated by different frequency synthesizers. The radio frequency circuit structure not only solves the problem of the mutual crosstalk among channel signals, but also enhances the signal to noise ration (SNR) of the system. The circuit structure is simple and practical, and has stable and reliable performance and wider application range.

Description

RF circuit structure for realizing dual-frequency GPS satellite signal conversion to baseband signal function

The invention relates to the field of GPS navigation positioning and measurement, in particular to the technical field of dual-frequency GPS satellite signal receiving and processing device, and specifically relates to a radio frequency circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal. Background technique

GPS (Global Positioning System) is a global navigation and positioning system that uses satellite transmitting signals to receive signals from the receivers on the Earth's surface or adjacent to the ground to measure the position and time of the objects. The GPS satellite signal is synthesized by a typical code division multiple access (CDMA) modulation technique, and the complete signal mainly includes three components such as a carrier, a pseudo random code and a data code. The signal carrier is in the L-band, and the frequencies of the two carriers are denoted as Ll (1575.42MHz) and L2 (1227.6MHz), respectively. Each satellite transmits broadcast ranging codes and navigation data on these two frequencies, but the ranging codes used are different from those used by other satellites. The latest and subsequent GPS satellites will also transmit these signals on carrier L5 (1176.45 MHz), but since the invention only covers the signals of the L1 and L2 channels, it is not discussed here. Navigation data is provided to the receiver to determine the position of the satellite as it is transmitted, and the ranging code enables the user receiver to determine the transmission delay of the signal to determine the distance from the satellite to the user. Therefore, GPS receivers are vital user equipment.

At present, the practical application of the GPS receiver circuit is generally composed of an antenna unit, a radio frequency unit, a GPS baseband digital signal processing unit, and the like. The role of the radio unit is to filter the GPS satellite signals of the L1 channel and the L2 channel from the ambient noise and provide appropriate gain to meet the requirements of the subsequent baseband digital signal processing unit. In theory, we can filter out the GPS satellite signals of the required channels directly in the L-band, and then zoom in and then digitally sample them. However, since the loaded quality factor of the bandpass filter is proportional to the center frequency, the higher the center frequency, the higher the quality factor of the required filter, given the constant signal bandwidth. As shown in the following formula (1):

Where / _e is the center frequency of the bandpass filter, 3^ _{3; 3⁄4} is the 3dB bandwidth of the bandpass filter.

The center frequency of the two carriers of the GPS signal is very high and the channel bandwidth is about 20 MHz. To filter out the required channel directly, a filter with a very large Q value is needed, and the current technical level is difficult to meet this index. In addition, due to the problems of gain, accuracy and stability of the high-frequency circuit, it is unrealistic to directly demodulate the GPS satellite signal in the high-frequency range. Therefore, the usual method is to downconvert the high frequency GPS satellite signal using a mixer. This can greatly reduce the technical requirements of the filter and avoid the difficulties encountered in high-frequency signal processing. However, the use of a mixer to convert high-frequency GPS satellite signals to lower intermediate frequency frequencies introduces image-frequency interference, and the effect of using filters on image-frequency interference depends on the image frequency. The frequency difference between the frequency and the signal frequency, or depending on the frequency of the IF frequency. If the IF frequency is high, the signal is far away from the image frequency, then the image frequency component can be greatly suppressed; conversely, if the IF frequency is lower, the signal is not far from the image frequency, and the filter filters the image frequency interference. The effect is worse. Since the channel selection is performed at the intermediate frequency, similarly, the higher intermediate frequency has higher requirements on the channel selection filter, so the image rejection and the channel selection form a contradiction, and the selection of the intermediate frequency becomes the key to the contradiction. . Two or three frequency conversions are often used in the design to achieve a better compromise.

In the prior art, there is a design scheme in which the intermediate frequency of 1400 MHz of L1 and L2 is selected as the local oscillator signal frequency of the first down-converted frequency, and L1 is down-converted to 175.42 MHz, and L2 is down-converted to 172.4 MHz. Then select 175MHz as the second down-converted local oscillator signal frequency, and quadrature demodulate the GPS signals of the L1 and L2 channels into I/Q signals. It is then converted to a digital signal that can be used for subsequent processing by an A/D converter. See Figure 1 for the generation process of the local oscillator signal.

The control signal 50 from the microprocessor causes the frequency synthesizer 52 to generate a signal 51 having a frequency of 10 MHz. The signal 51 is converted by a 2 frequency divider 53 into a signal 54 having a frequency of 5 MHz. The phase detector 55, the loop filter 56 and the voltage controlled oscillator 57 form a phase locked loop. When the loop is locked, the voltage controlled oscillator 57 outputs a first local oscillator signal 58 having a frequency of 1400 MHz. The first local oscillation signal 58 is divided by the 8-divider 59 to obtain a second local oscillation signal 63 of 175 MHz.

In this design, since the two first channels of L1 and L2 use the same first local oscillator signal 58 for the first down-conversion, inevitably causing crosstalk between the two channel signals, reducing the signal-to-noise ratio of the system. . Summary of the invention

The object of the present invention is to overcome the above shortcomings in the prior art, and to provide an inter-crosstalk problem that can effectively solve channel signals, improve the signal-to-noise ratio of the system, and have a simple circuit structure, convenient and fast use process, and stable and reliable working performance. The RF circuit structure for realizing the conversion of dual-frequency GPS satellite signals into baseband signals is widely applicable.

In order to achieve the above object, the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function of the present invention has the following structure:

The radio frequency circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function comprises an antenna receiving function module, and the main feature is that the circuit structure further comprises a signal splitting function module, a first channel signal processing function module, a second channel signal processing function module, a local oscillator signal and a clock signal generating function module, wherein the antenna receiving function module respectively performs the first channel signal processing function module and the second channel by using the signal dividing function module The signal processing function modules are connected;

The first channel signal processing function module includes a first channel signal first frequency conversion function circuit and a first channel signal demodulation processing circuit, and the signal branching function module sequentially performs first frequency conversion through the first channel signal. Functional circuit and The first channel signal demodulation processing circuit is connected to the baseband signal processing circuit;

The second channel signal processing function module includes a second channel signal first frequency conversion function circuit and a second channel signal demodulation processing circuit, and the signal branching function module sequentially performs first frequency conversion through the second channel signal. a functional circuit and a second channel signal demodulation processing circuit coupled to said baseband signal processing circuit;

The local oscillator signal and clock signal generating function module sends the generated first channel signal first-level local oscillator signal to the first channel signal primary frequency conversion function circuit, the local oscillator signal and the clock signal Generating a function module to send the generated second channel signal first-level local oscillator signal to the second channel signal primary frequency conversion function circuit, wherein the local oscillator signal and the clock signal generating function module will generate the second level The local oscillation signal is sent to the first channel signal demodulation processing circuit and the second channel signal demodulation processing circuit, respectively, and the local oscillator signal and the clock signal generation function module send the generated system clock signal to In the baseband signal processing circuit, the first channel signal first-order local oscillator signal and the second channel signal first-order local oscillator signal have different frequencies.

The center frequency of the first channel signal in the GPS satellite signal in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function is greater than the center frequency of the second channel signal in the GPS satellite signal, The first channel signal first-level local oscillator signal frequency is greater than a center frequency of the first channel signal of the GPS satellite signal, and the second channel signal first-order local oscillator signal frequency is smaller than the GPS satellite signal The center frequency of the second channel signal.

The frequency of the first-channel local oscillator signal in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function is 1743 MHz.

The frequency of the first-order local oscillator signal of the second channel signal in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function is 1059 MHz.

The local oscillator signal and the clock signal generating function module in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function includes a reference clock signal generating circuit, a first channel signal first-level local oscillator signal generating circuit, and a second channel a signal first-level local oscillator signal generating circuit, a second-level local oscillator signal generating circuit and a system clock signal generating circuit, wherein the reference clock signal generating circuit and the first channel signal first-level local oscillator signal generating circuit and the second The channel signal first-level local oscillator signal generating circuit, the second-level local oscillator signal generating circuit and the system clock signal generating circuit are connected, and the first channel signal first-level local oscillator signal generating circuit generates the generated first channel signal The local oscillator signal is sent to the first channel signal first frequency conversion function circuit, and the second channel signal first level local oscillator signal generating circuit sends the generated second channel signal first level local oscillator signal to the In the second channel signal primary frequency conversion function circuit, the second local oscillation signal generating circuit generates the generated second local oscillation signal Respectively to said first channel processing circuit and a second signal demodulation channel signal demodulation processing circuit, and the system clock signal generating circuit generates the system clock signal is supplied to the baseband signal Number processing circuit.

The first channel signal first-order local oscillator signal generating circuit in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function is a frequency synthesizing circuit.

The first channel signal first-level local oscillator signal generating circuit in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function comprises a first pre-divider, a first phase detector, a first loop filter, a first voltage controlled oscillator and a first frequency divider, wherein the first prescaler, the first phase detector, the first loop filter and the first voltage controlled oscillator are sequentially connected in series to the reference The clock signal generating circuit is coupled to the first channel signal primary frequency conversion function circuit, and the first frequency divider is connected between the first voltage controlled oscillator and the first phase detector.

The second channel signal first-order local oscillator signal generating circuit in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function is a frequency synthesizing circuit.

The second channel signal first-level local oscillator signal generating circuit in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function comprises a second pre-divider, a second phase detector, a second loop filter, a second voltage controlled oscillator and a second frequency divider, wherein the second prescaler, the second phase detector, the second loop filter and the second voltage controlled oscillator are sequentially connected in series to the reference And between the clock signal generating circuit and the second channel signal first frequency conversion function circuit, and the second frequency divider is connected between the second voltage controlled oscillator and the second phase detector.

The secondary local oscillator signal generating circuit in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function comprises a third prescaler, a third phase detector, a third loop filter, and a third voltage control An oscillator and a third frequency divider, wherein the reference clock signal generating circuit is respectively connected through the third prescaler, the third phase detector, the third loop filter and the third voltage controlled oscillator The first channel signal demodulation processing circuit and the second channel signal demodulation processing circuit, and the third frequency divider is connected across the third voltage controlled oscillator and the third phase detector between.

The system clock signal generating circuit in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function includes a comparator, and the comparator is connected between the reference clock signal generating circuit and the baseband signal processing circuit.

The reference clock signal generating circuit in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function may be a frequency synthesizing circuit including a high frequency stability temperature compensated crystal oscillator and a phase locked frequency synthesizer, The temperature-compensated crystal oscillator is respectively generated by the phase-locked frequency synthesizer and the first channel signal first-order local oscillator signal generating circuit, the second channel signal first-level local oscillator signal generating circuit, and the second-level local oscillator signal. The circuit is coupled to the system clock signal generating circuit.

The reference clock signal generating circuit in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function may also be a crystal oscillator.

The first channel signal in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function The frequency function circuit includes a first band pass filter and a first mixer, and the signal splitting function module sequentially passes the first band pass filter and the first mixer and the first channel signal The demodulation processing circuit is connected, and the first channel signal first-level local oscillator signal generating circuit sends the generated first channel signal first-order local oscillator signal to the first mixer.

The first low-noise amplifier is also connected in series between the first band pass filter and the first mixer in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function.

The first channel signal first frequency conversion function circuit in the RF circuit structure for realizing the conversion of the dual frequency GPS satellite signal into the baseband signal function further includes a second band pass filter and a first variable gain amplifier, the second band a pass filter and a first variable gain amplifier are sequentially connected in series between the first mixer and the first channel signal demodulation processing circuit, and the control input of the first variable gain amplifier The terminal is coupled to the baseband signal processing circuit.

The second channel signal first frequency conversion function circuit in the RF circuit structure for realizing the conversion of the dual frequency GPS satellite signal into the baseband signal function comprises a third band pass filter and a second mixer, wherein the signal split function module is in turn And connecting, by the third band pass filter and the second mixer, the second channel signal demodulation processing circuit, wherein the second channel signal first-level local oscillator signal generating circuit generates the generated The two-channel signal first-order local oscillator signal is sent to the second mixer.

The second low-noise amplifier is also connected in series between the third band pass filter and the second mixer in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function.

The second channel signal first frequency conversion function circuit in the RF circuit structure for realizing the conversion of the dual frequency GPS satellite signal into the baseband signal function further includes a fourth band pass filter and a second variable gain amplifier, wherein the fourth band a pass filter and a second variable gain amplifier are sequentially connected in series between the second mixer and the second channel signal demodulation processing circuit, and the control input of the second variable gain amplifier The terminal is coupled to the baseband signal processing circuit.

The first channel signal demodulation processing circuit in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function comprises a first channel signal quadrature demodulation filter circuit and a first channel signal analog-to-digital conversion circuit, The first channel signal quadrature demodulation filter circuit and the first channel signal analog to digital conversion circuit are connected in series between the first channel signal primary frequency conversion function circuit and the baseband signal processing circuit.

The first channel signal quadrature demodulation and filtering circuit in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function comprises a first signal splitting function module, a first demodulator, a second demodulator, and a first a low pass filter, a second low pass filter and a phase shifter, wherein the first signal splitting function module sequentially passes through the first demodulator and the first low pass filter and the first The channel signal analog-to-digital conversion circuit is connected, and the first signal branching function module sequentially passes through the second demodulator and the second low-pass filter to the first channel signal analog-to-digital conversion circuit. Connected, said two-stage local oscillator signal generating circuit is coupled to said first demodulator, and said two-stage local oscillator signal generating circuit passes said phase shifter and said second demodulation The devices are connected. The first channel signal analog-to-digital conversion circuit in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function includes a first analog-to-digital converter and a second analog-to-digital converter, and the first analog-to-digital converter Connected between the first low pass filter and the baseband signal processing circuit, the second analog to digital converter is connected between the second low pass filter and the baseband signal processing circuit, The system clock signal is sent to the first analog to digital converter and the second analog to digital converter as a sample clock signal.

The first signal splitting function module in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function is a power splitter.

The second channel signal demodulation processing circuit in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function comprises a second channel signal quadrature demodulation filter circuit and a second channel signal analog-to-digital conversion circuit, The second channel signal quadrature demodulation filter circuit and the second channel signal analog to digital conversion circuit are connected in series between the second channel signal primary frequency conversion function circuit and the baseband signal processing circuit.

The second channel signal quadrature demodulation and filtering circuit in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function comprises a second signal splitting function module, a third demodulator, a fourth demodulator, and a second a third low pass filter, a fourth low pass filter and a phase shifter, wherein the second signal splitting function module sequentially passes through the third demodulator and the third low pass filter and the second The channel signal analog-to-digital conversion circuit is connected, and the second signal branching function module sequentially passes through the fourth demodulator and the fourth low-pass filter and the second channel signal analog-digital conversion circuit Connecting, the second local oscillator signal generating circuit is connected to the third demodulator, and the second local oscillator signal generating circuit passes the phase shifter and the fourth demodulation The devices are connected.

The second channel signal analog-to-digital conversion circuit in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function comprises a third analog-to-digital converter and a fourth analog-to-digital converter, and the third analog-to-digital converter Connected between the third low pass filter and the baseband signal processing circuit, the fourth analog to digital converter is connected between the fourth low pass filter and the baseband signal processing circuit, The system clock signal is sent to the third analog to digital converter and the fourth analog to digital converter as a sample clock signal.

The second signal splitting function module in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function is a power splitter.

The antenna receiving function module in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function comprises an antenna unit and a signal amplifier, wherein the antenna unit is connected to the signal splitting function module by the signal amplifier .

The antenna receiving function module in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function further includes a low noise preamplifier, wherein the low noise preamplifier is serially connected to the antenna unit and the signal amplifier Between.

The signal splitting function module in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function is a power splitter.

The invention realizes the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function, and generates a 25 MHz reference clock signal through the frequency synthesizer or the crystal oscillator. The first stage local oscillator signal of the first channel signal is generated by the frequency synthesizer with the reference clock signal as a reference frequency, and the corresponding frequency is 1743 MHz. The first stage local oscillator signal of the second channel signal is generated by the frequency synthesizer with the reference clock signal as a reference frequency, and the corresponding frequency is 1059 MHz. The second stage local oscillator signal is generated by the frequency synthesizer with the reference clock signal as a reference frequency, and the corresponding frequency is 336 MHz. Since the first stage local oscillator signal frequencies of the first channel signal and the second channel signal are as far apart as possible, the interference of the respective local oscillator signals with respect to the other channel is reduced. Moreover, the use of independent frequency synthesizers to generate the two local oscillator signals also reduces the mutual interference of the two channels, which not only effectively solves the crosstalk problem of the channel signals in the prior art, but also improves the signal noise of the system. ratio. The circuit structure is simple and practical, the use process is convenient and fast, the work performance is stable and reliable, and the scope of application is wide. It lays a solid foundation for further improvement and optimization of the RF circuit scheme of the dual-frequency GPS receiver that receives the GPS signal and thereby determines the position data. basis. DRAWINGS

FIG. 1 is a schematic diagram of a generating circuit of a local oscillator signal in a prior art dual-frequency GPS satellite signal converted into a baseband signal function circuit.

2 is a schematic diagram showing the overall circuit structure of a radio frequency circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to the present invention.

FIG. 3 is a schematic circuit diagram of the GPS satellite signal in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal structure, which is divided into the L1 channel and the L2 channel after being received by the antenna.

4 is a schematic diagram of a generating circuit of a local oscillator signal 1743 MHz, 1059 MHz, 336 MHz, and a clock signal 25 MHz in a radio frequency circuit structure for realizing a dual-frequency GPS satellite signal conversion to a baseband signal function.

FIG. 5 is a circuit schematic diagram of down-converting a GPS satellite signal into an intermediate frequency signal in an RF circuit structure for realizing a dual-frequency GPS satellite signal conversion to a baseband signal function.

6 is a schematic circuit diagram of an intermediate frequency signal in a radio frequency circuit structure for realizing a dual-frequency GPS satellite signal converted into a baseband signal by quadrature demodulation, filtering, and A/D conversion to obtain an I-channel and a Q-channel digital signal. detailed description

In order to more clearly understand the technical content of the present invention, the following embodiments are specifically described. Referring to FIG. 2 to FIG. 6 , the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into a baseband signal function includes an antenna receiving function module, wherein the circuit structure further includes a signal dividing function module, a channel signal processing function module, a second channel signal processing function module, a local oscillator signal and a clock signal generating function module, wherein the antenna receiving function module respectively uses the signal splitting function module and the first channel signal The processing function module is connected to the second channel signal processing function module;

The first channel signal processing function module includes a first channel signal first frequency conversion function circuit and a first channel signal demodulation processing circuit, and the signal branching function module sequentially performs first frequency conversion through the first channel signal. a functional circuit and a first channel signal demodulation processing circuit coupled to said external baseband signal processing circuit;

The center frequency of the first channel signal in the GPS satellite signal is greater than the center frequency of the second channel signal in the GPS satellite signal, and the first channel signal first-level local oscillator signal frequency is greater than the The center frequency of the first channel signal in the GPS satellite signal, and the second channel signal level one local oscillator signal frequency is less than the center frequency of the second channel signal in the GPS satellite signal.

In a specific implementation of the present invention, the first channel signal first-order local oscillator signal frequency is 1743 MHz, and the second channel signal first-order local oscillator signal frequency is 1059 MHz.

At the same time, the local oscillator signal and the clock signal generating function module in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function include a reference clock signal generating circuit, a first channel signal first-level local oscillator signal generating circuit, and a first a two-channel signal first-level local oscillator signal generating circuit, a two-stage local oscillator signal generating circuit and a system clock signal generating circuit, wherein the reference clock signal generating circuit and the first channel signal first-level local oscillator signal generating circuit respectively The second channel signal first-level local oscillator signal generating circuit, the second-level local oscillator signal generating circuit and the system clock signal generating circuit are connected, and the first channel signal first-level local oscillator signal generating circuit generates the generated first channel Signal first level local oscillator signal is sent to the said In the first channel signal first-level frequency conversion function circuit, the second channel signal first-level local oscillator signal generating circuit sends the generated second channel signal first-level local oscillator signal to the second channel signal first-level frequency conversion function In the circuit, the two-stage local oscillation signal generating circuit sends the generated two-level local oscillation signal to the first channel signal demodulation processing circuit and the second channel signal demodulation processing circuit, respectively, and The system clock signal generating circuit sends the generated system clock signal to the baseband signal processing circuit.

The first channel signal first-level local oscillator signal generating circuit is a frequency synthesizing circuit, and includes a first pre-divider

160, a first phase detector 113, a first loop filter 116, a first voltage controlled oscillator 119 and a first frequency divider 163, the first prescaler 160, the first phase detector 113, The first loop filter 116 and the first voltage controlled oscillator 119 are sequentially connected in series between the reference clock signal generating circuit and the first channel signal first frequency conversion function circuit, and the first frequency divider 163 Connected between the first voltage controlled oscillator 119 and the first phase detector 113.

The second channel signal first-level local oscillator signal generating circuit is a frequency synthesizing circuit, and includes a second pre-divider

161. The second phase detector 114, the second loop filter 117, the second voltage controlled oscillator 120, and the second frequency divider 164, the second prescaler 161, the second phase detector 114, The second loop filter 117 and the second voltage controlled oscillator 120 are sequentially connected in series between the reference clock signal generating circuit and the second channel signal first frequency conversion function circuit, and the second frequency divider 164 Connected between the second voltage controlled oscillator 120 and the second phase detector 114.

The second local oscillation signal generating circuit is a frequency synthesizing circuit, and includes a third prescaler 162, a third phase detector 115, a third loop filter 118, a third voltage controlled oscillator 121, and a third The frequency divider 165, the reference clock signal generating circuit is sequentially connected by the third prescaler 162, the third phase detector 115, the third loop filter 118 and the third voltage controlled oscillator 121, respectively. The first channel signal demodulation processing circuit and the second channel signal demodulation processing circuit, and the third frequency divider 165 is connected across the third voltage controlled oscillator 121 and the third phase detector Between the devices 115.

The system clock signal generating circuit includes a comparator 128, and the comparator 128 is connected between the reference clock signal generating circuit and the baseband signal processing circuit.

The reference clock signal generating circuit may be a frequency synthesizing circuit including a high frequency stability temperature compensated crystal oscillator and a phase locked frequency synthesizer, and the temperature compensated crystal oscillator passes through the phase locked frequency synthesizer The first channel signal first-level local oscillator signal generating circuit, the second channel signal first-level local oscillator signal generating circuit, the second-level local oscillator signal generating circuit and the system clock signal generating circuit are respectively connected.

Meanwhile, the reference clock signal generating circuit may also be a crystal oscillator.

In the RF circuit structure for realizing the function of converting the dual-frequency GPS satellite signal into the baseband signal, the first channel signal primary frequency conversion function circuit includes a first band pass filter 131 and a first mixer 135, The signal branching function module sequentially passes through the first band pass filter 131 and the first mixer 135 and the first channel signal demodulation processing circuit Connected, the first channel signal first-level local oscillator signal generating circuit sends the generated first channel signal first-level local oscillator signal to the first mixer 135.

At the same time, a first low noise amplifier 133 is further connected in series between the first band pass filter 131 and the first mixer 135. The first channel signal first frequency conversion function circuit further includes a second band. a pass filter 137 and a first variable gain amplifier 139, the second band pass filter 137 and the first variable gain amplifier 139 are sequentially connected in series to the first mixer 135 and the first Between the channel signal demodulation processing circuits, and the control input of the first variable gain amplifier 139 is coupled to the baseband signal processing circuit.

Moreover, in the RF circuit structure for realizing the function of converting the dual-frequency GPS satellite signal into the baseband signal, the second channel signal primary frequency conversion function circuit includes a third band pass filter 231 and a second mixer 235. The signal splitting function module is sequentially connected to the second channel signal demodulation processing circuit by the third band pass filter 231 and the second mixer 235, and the second channel signal is The stage local oscillation signal generating circuit sends the generated second channel signal first order local oscillation signal to the second mixer 235.

At the same time, a second low noise amplifier 233 is further connected in series between the third band pass filter 231 and the second mixer 235. The second channel signal first frequency conversion function circuit further includes a fourth band. a pass filter 237 and a second variable gain amplifier 239, the fourth band pass filter 237 and the second variable gain amplifier 239 are sequentially connected in series to the second mixer 235 and the second Between the channel signal demodulation processing circuits, and the control input of the second variable gain amplifier 239 is coupled to the baseband signal processing circuit.

In addition, in the RF circuit structure for realizing the function of converting the dual-frequency GPS satellite signal into the baseband signal, the first channel signal demodulation processing circuit includes a first channel signal quadrature demodulation filter circuit and a first channel signal. The analog-to-digital conversion circuit, the first channel signal quadrature demodulation filter circuit and the first channel signal analog-to-digital conversion circuit are connected in series between the first channel signal primary frequency conversion function circuit and the baseband signal processing circuit.

The first channel signal quadrature demodulation and filtering circuit includes a first signal splitting function module 141, a first demodulator 144, a second demodulator 145, a first low pass filter 148, and a second low a pass filter 149 and a phase shifter 126, wherein the first signal splitting function module 141 sequentially passes the first demodulator 144 and the first low pass filter 148 and the first channel signal modulus The conversion circuit is connected, and the first signal branching function module 141 is sequentially connected to the first channel signal analog-to-digital conversion circuit through the second demodulator 145 and the second low-pass filter 149. The second local oscillator signal generating circuit is connected to the first demodulator 144, and the second local oscillator signal generating circuit passes through the phase shifter 126 and the second demodulator 145. Connected.

The first channel signal analog-to-digital conversion circuit includes a first analog-to-digital converter 152 and a second analog-to-digital converter 153, and the first analog-to-digital converter 152 is coupled to the first low-pass filter 148. And the baseband signal processing circuit, the a second analog to digital converter 153 is coupled between the second low pass filter 149 and the baseband signal processing circuit, and the system clock 125 is sent to the first analog to digital converter 152 as a sample clock. The second analog to digital converter 153, and the first signal shunt function module 141 is a power splitter.

Moreover, in the RF circuit structure for realizing the function of converting the dual-frequency GPS satellite signal into the baseband signal, the second channel signal demodulation processing circuit comprises a second channel signal quadrature demodulation filter circuit and a second channel signal modulus The conversion circuit, the second channel signal quadrature demodulation filter circuit and the second channel signal analog-to-digital conversion circuit are connected in series between the second channel signal primary frequency conversion function circuit and the baseband signal processing circuit.

The second channel signal quadrature demodulation and filtering circuit includes a second signal splitting function module 241, a third demodulator 244, a fourth demodulator 245, a third low pass filter 248, and a fourth low a pass filter 249 and a phase shifter 126, the second signal splitting function module 241 sequentially passes through the third demodulator 244 and the third low pass filter 248 and the second channel signal modulus The conversion circuit is connected, and the second signal branching function module 241 is sequentially connected to the second channel signal analog-digital conversion circuit through the fourth demodulator 245 and the fourth low-pass filter 249. The second local oscillator signal generating circuit is connected to the third demodulator 244, and the second local oscillator signal generating circuit passes through the phase shifter 126 and the fourth demodulator 245. Connected.

The second channel signal analog-to-digital conversion circuit includes a third analog-to-digital converter 252 and a fourth analog-to-digital converter 253, and the third analog-to-digital converter 252 is connected to the third low-pass filter 248. And the baseband signal processing circuit, the fourth analog-to-digital converter 253 is connected between the fourth low-pass filter 249 and the baseband signal processing circuit, and the system clock signal is sent as a sample clock signal. And the third analog-to-digital converter and the fourth analog-to-digital converter, and the second signal splitting function module 241 is a power splitter.

Moreover, in the RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function, the antenna receiving function module includes the antenna unit 100 and the signal amplifier 103, and the antenna unit 100 passes through the signal amplifier 103. The signal receiving function module is further included: the antenna receiving function module further includes a low noise preamplifier 101, and the low noise preamplifier 101 is serially connected between the antenna unit 100 and the signal amplifier 103. The signal shunt function module is a power splitter 105.

In practical applications, please refer to FIG. 2, which is a schematic diagram of the overall structural scheme of the present invention.

The GPS satellite signal received by the dual-frequency antenna 1 and amplified by the amplifier 3 is divided into two signals by the power splitter 4, which are the signal 5 of the L1 channel (the center frequency is 1575.42 MHz) and the signal 6 of the L2 channel (the center frequency is 1227.6MHz). On the L1 channel, signal 5 first passes through a passive bandpass filter 8, which is filtered to obtain signal 10, which is then mixed by mixer 13 with the first stage local oscillator signal 30 of L1. The frequency of the local oscillator signal 30 is 1743 MHz. The signal 136 obtained after mixing includes an upper sideband and a lower sideband. Filtering the signal 17 obtained after mixing by the band pass filter 19, filtering out the upper side With the signal and the incoming noise signal, an intermediate frequency signal 21 with a center frequency of 167.58 MHz is obtained. We then implement a Automatic Gain Control (AGC) function with a loop that includes a variable gain amplifier 23 to ensure that the signal has sufficient dynamic range. The signal 25 amplified by the IF signal 21 via the variable gain amplifier 23 will obtain a stable signal amplitude. A signal 34 that controls the variable gain amplifier 23 to amplify the gain is from a baseband processing circuit. The intermediate frequency signal 25 of the L1 channel and the secondary local oscillator signal 32 are demodulated by the demodulator 27 to the I/Q signals II and Q1 of L1 at a frequency of 420 kHz. The signals II and Q1 are analog-to-digital converted by the A/D converter 36 to obtain a digital signal 39. It is then sent to the baseband processing circuit for further processing.

The above signal processing procedures of the L2 channel and the L1 channel are the same, but the frequencies of the points are different. The first-stage local oscillator signal 31 of L2 has a frequency of 1059 MHz; the intermediate frequency of the first mixing 22 has a center frequency of 168.6 MHz; and the demodulated I/Q signals 12 and Q2 have a frequency of 600 kHz.

A 25 MHz reference clock signal 12 is generated by a frequency synthesizer or crystal oscillator 7. The frequency synthesizer 14 produces a first stage local oscillator signal 30 (frequency of 1743 MHz) of the L1 channel with the signal 12 as the reference frequency. The frequency synthesizer 16 generates a first-stage local oscillator signal 31 (frequency of 1059 MHz) of the L2 channel with the signal 12 as a reference frequency. The frequency synthesizer 29 produces a second stage local oscillator signal 32 (frequency 336 MHz) with reference to signal 12. The first-stage local oscillator signals of the L1 channel and the L2 channel are separated as far as possible, thereby reducing the interference of the respective local oscillator signals with respect to the other channel. The use of separate frequency synthesizers to generate these two local oscillator signals also reduces mutual interference between the two channels.

Referring again to FIG. 3, a schematic diagram of a process in which a GPS satellite signal is received by an antenna and then divided into L1 and L2 channels is shown.

The main function of the antenna 100 is to receive airborne GPS satellite signals to provide a pure and complete satellite signal to the RF receiver's RF front end. The internal noise of each unit circuit in the whole system has different responses to the total noise figure after cascading, and the noise coefficient of the unit circuit with the higher number of stages has a greater influence on the total noise figure. Therefore, the total noise figure mainly depends on the noise figure of the first few stages of the unit circuit, where the thermal noise of the antenna unit has the greatest influence on the receiver performance. The GPS satellite signal received by antenna 100 is first amplified by a low noise preamplifier 101, which actually determines the final noise figure of the entire receiver. The GPS satellite signal 102 amplified by the low noise preamplifier is further passed through the signal amplifier 103 to further increase the gain. The gain provided by amplifier 103 is mainly to compensate for the insertion loss of the transmission line, the power divider and the filter, and at the same time increase the reverse isolation to ensure the dynamic range of the GPS satellite signal. The amplifier 103 outputs the GPS satellite signal 104 through the splitter 105 and splits into two signals, a signal 108 of the L1 channel (having a center frequency of 1575.42 MHz) and a signal 107 of the L2 channel (having a center frequency of 1227.6 MHz).

Referring again to Figure 4, the generation process of the local oscillator signals 1743MHz, 1059MHz, 336MHz and the clock signal 25MHz is described.

The signal 110 can be a 5 MHz or 10 MHz reference frequency signal generated by a high frequency stability temperature compensated crystal oscillator. It can also be an external 5MHz or 10MHz reference clock. The phase locked frequency synthesizer 111 multiplies the signal 110 to 25 MHz to obtain a reference clock signal 112. The phase detector 113, the loop filter 116 and the voltage controlled oscillator 119 together form a phase locked loop circuit, and adjust the frequency dividing ratio R1 of the prescaler 160 and the frequency dividing ratio N1 of the frequency divider 163 to make N1/R1 The first stage local oscillator signal 122 of L1 having a frequency of 1743 MHz can be obtained at 1743/25.

Similarly, adjusting the frequency dividing ratio R2 of the prescaler 161 and the frequency dividing ratio N2 of the frequency divider 164, so that N2/R2 is 1059/25, and obtaining the first-level local oscillator signal 123 of L2 having a frequency of 1059 MHz; The frequency dividing ratio R3 of the frequency divider 162 and the frequency dividing ratio N3 of the frequency divider 165 are such that N3/R3 is 336/25 to obtain the second-stage local oscillation signal 124 having a frequency of 336 MHz. Signal 112 is adjusted by comparator 128 to obtain a system clock 125 having a frequency of 25 MHz. Here we choose L1's first-level local oscillator signal frequency is 1743MHz, which is positive with the L1 frequency band of 1575.42MHz of GPS satellite signal; meanwhile, we also choose L2's second-level local oscillator signal frequency is 1059MHz, it and GPS The difference in the L2 band 1227.6 MHz of the satellite signal is negative. This is to keep the first-stage local oscillator signal frequencies of the L1 channel and the L2 channel as far as possible, thereby reducing the interference of the respective local oscillator signals with respect to the other channel. The use of separate phase-locked loop circuits to generate these two local oscillator signals is also intended to reduce mutual interference between the two channels.

Referring again to Figure 5, it is a schematic diagram of how to downconvert the GPS satellite signal to an intermediate frequency signal. On the L1 channel, the signal 130 first passes through a bandpass filter 131 having a center frequency of 1575.42 MHz and a bandwidth of 20 MHz. The filtered signal 132 is input to a low noise amplifier 133 for amplification. The amplified signal 134 is mixed by the mixer 135 with the first stage local oscillator signal 122 of L1. The local oscillator signal 122 has a frequency of 1743 MHz. The signal 136 obtained after mixing includes an upper sideband and a lower sideband. The mixed signal 136 is filtered by a bandpass filter 137 having a center frequency of 168.5 MHz and a bandwidth of 20 MHz, and the upper sideband signal and the leaked noise signal are filtered out to obtain an intermediate frequency signal 138 having a center frequency of 167.58 MHz. The intermediate frequency signal 138 obtained after mixing preserves the signal Doppler and PRN codes, but the carrier frequency is reduced. Finally, we use a loop that includes a variable gain amplifier 139 to implement automatic gain control (AGC) to ensure that the signal has sufficient dynamic range. The IF signal 138 amplified by the variable gain amplifier 139 will obtain a stable signal amplitude. Controlling the Variable Gain Amplifier 139 Amplifies the gain signal 181 from the baseband processing circuit.

On the L2 channel, signal 230 first passes through a bandpass filter 231 having a center frequency of 1227.6 MHz and a bandwidth of 20 MHz. The filtered signal 232 is input to the low noise amplifier 233 for amplification. The amplified signal 234 is mixed by the mixer 235 with the first stage local oscillator signal 123 of L2. The frequency of the local oscillator signal 123 is 1059 MHz. The signal 236 obtained after mixing includes an upper sideband and a lower sideband. The mixed signal 236 is filtered by a bandpass filter 237 having a center frequency of 168.5 MHz and a bandwidth of 20 MHz, and the upper sideband signal and the leaked noise signal are filtered out to obtain an intermediate frequency signal 238 having a center frequency of 168.6 MHz. The intermediate frequency signal 238 obtained after mixing preserves the signal Doppler and PRN The code, just the carrier frequency is reduced. Finally, we implement a automatic gain control (AGC) function with a loop that includes a variable gain amplifier 239 to ensure that the signal has sufficient dynamic range. The signal 240 amplified by the intermediate frequency signal 238 via the variable gain amplifier 239 will obtain a stable signal amplitude. A signal 182 that controls the variable gain amplifier 239 to amplify the gain is from a baseband processing circuit.

Referring again to FIG. 6, the process of the intermediate frequency signal is subjected to quadrature demodulation, filtering, and A/D conversion to obtain the I and Q digital signals.

The IF signal processing in the L1 band and the L2 band is the same. Here we only use the L1 band as an example for specific description. The intermediate frequency signal 140 of the L1 band is divided by the power splitter 141 into two signals 142 and 143 of the same amplitude and phase. The signal 142 and the two-stage local oscillator I signal 124 are demodulated by the demodulator 144 to the L1 I signal 146; the signal 143 and the second-order local oscillator Q signal 127 are demodulated by the demodulator 145 to the L1 Q signal 147. The second local oscillator Q signal 127 is phase shifted by the second stage local oscillator I signal 124 through the phase shifter 126. owned.

The I signal 146 is filtered by a low pass filter 148 having a bandwidth of 12.5 MHz to obtain a signal 150 having a carrier frequency of 420 kHz, and the signal 150 is analog-to-digital converted by the A/D converter 152 to obtain a digital signal 154. The Q signal 147 is filtered by a low pass filter 149 having a bandwidth of 12.5 MHz to obtain a signal 151 having a carrier frequency of 420 kHz, and the signal 151 is analog-to-digital converted by the A/D converter 153 to obtain a digital signal 155. Similarly, we can get I digital signal 254 and Q digital signal 255 in the L2 band with a carrier frequency of 600KHz. The digital signals 154, 155, 254, and 255 described above are all sent to the baseband processing circuitry for further processing.

The RF channel design of the present invention for converting a dual-frequency GPS satellite signal into a digital signal that can be used for baseband processing includes a process in which a GPS satellite signal is divided into L1 and L2 bands after being received by an antenna; including a local oscillator signal of 1743 MHz and 1059 MHz, 336MHz and clock signal 25MHz generation process; including the process of down-converting GPS satellite signals into intermediate frequency signals; including the process of intermediate frequency signals undergoing quadrature demodulation, filtering, A/D conversion to obtain I-channel and Q-channel digital signals.

The first-stage local oscillator signal frequency of L1 is 1743MHz, which is positive with the L1 frequency band of 1575.42MHz of the GPS satellite signal; the second-order local oscillator signal frequency of L2 is 1059MHz, which is the same as the GPS satellite signal L2 frequency band 1227.6MHz. The difference is negative.

In a specific embodiment of the invention, the first stage local oscillator signal of L1 (having a frequency of 1743 MHz) and the first stage local oscillator signal of L2 (having a frequency of 1059 MHz) are respectively generated by different frequency synthesizers.

Meanwhile, the bandpass filter having a center frequency of 1575.42 MHz, 1227.6 MHz, and 168.5 MHz used in the present invention may have a bandwidth of 20 MHz but not limited to 20 MHz; the low pass filter used in the present invention may have a cutoff frequency of 12.5 MHz but is not limited to 12.5. MHz. Moreover, the reference frequency used by each frequency synthesizer that generates the local oscillator signal may be 25 MHz but is not limited to 25MHz.

The above-mentioned RF circuit structure for realizing the conversion of the dual-frequency GPS satellite signal into the baseband signal function is used, and a 25 MHz reference clock signal is generated by the frequency synthesizer or the crystal oscillator. The first stage local oscillator signal of the first channel signal is generated by the frequency synthesizer with the reference clock signal as a reference frequency, and the corresponding frequency is 1743 MHz. The first stage local oscillator signal of the second channel signal is generated by the frequency synthesizer with the reference clock signal as a reference frequency, and the corresponding frequency is 1059 MHz. The second stage local oscillator signal is generated by the frequency synthesizer with the reference clock signal as a reference frequency, and the corresponding frequency is 336 MHz. Since the frequencies of the first-stage local oscillator signals of the first channel signal and the second channel signal are as far apart as possible, the interference of the respective local oscillator signals with respect to the other channel is reduced. Moreover, the use of independent frequency synthesizers to generate the two local oscillator signals also reduces the mutual interference of the two channels, which not only effectively solves the crosstalk problem of the channel signals in the prior art, but also improves the signal noise of the system. ratio. The circuit structure is simple and practical, the use process is convenient and fast, the work performance is stable and reliable, and the scope of application is wide. It lays a solid foundation for further improvement and optimization of the RF circuit scheme of the dual-frequency GPS receiver that receives the GPS signal and thereby determines the position data. basis.

In this specification, the invention has been described with reference to specific embodiments thereof. However, it will be apparent that various modifications and changes can be made without departing from the spirit and scope of the invention. Accordingly, the specification and figures are to be regarded as illustrative and not limiting.

Claims

Rights request

1. A radio frequency circuit structure for realizing a dual-frequency GPS satellite signal conversion to a baseband signal function, comprising an antenna receiving function module, wherein the circuit structure further comprises a signal splitting function module and a first channel signal processing function. a module, a second channel signal processing function module, a local oscillator signal and a clock signal generating function module, wherein the antenna receiving function module respectively performs the first channel signal processing function module and the first signal through the signal dividing function module The two channel signal processing function modules are connected;

The first channel signal processing function module includes a first channel signal first frequency conversion function circuit and a first channel signal demodulation processing circuit, and the signal branching function module sequentially performs first frequency conversion through the first channel signal. The functional circuit and the first channel signal demodulation processing circuit are connected to the baseband signal processing circuit;

2. The radio frequency circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 1, wherein a center frequency of the first channel signal in the GPS satellite signal is greater than the GPS satellite a center frequency of the second channel signal in the signal, the first channel signal first stage local oscillator signal frequency is greater than a center frequency of the first channel signal of the GPS satellite signal, and the second channel signal is The level local oscillator signal frequency is less than the center frequency of the second channel signal in the GPS satellite signal.

3. The radio frequency circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 2, wherein the first-channel signal has a first-order local oscillator signal frequency of 1743 MHz.

The radio frequency circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 2, wherein the first channel signal has a first-order local oscillator signal frequency of 1059 MHz.

5. The function of converting a dual-frequency GPS satellite signal into a baseband signal according to any one of claims 1 to 4. The RF circuit structure is characterized in that: the local oscillator signal and the clock signal generating function module include a reference clock signal generating circuit, a first channel signal first-level local oscillator signal generating circuit, and a second channel signal first-level local oscillator signal generating a circuit, a two-stage local oscillator signal generating circuit and a system clock signal generating circuit, wherein the reference clock signal generating circuit and the first channel signal first-level local oscillator signal generating circuit and the second channel signal first-level local oscillator signal respectively a generating circuit, a secondary local oscillator signal generating circuit and a system clock signal generating circuit are connected, and the first channel signal first-level local oscillator signal generating circuit sends the generated first channel signal first-level local oscillator signal to the In the first channel signal primary frequency conversion function circuit, the second channel signal first-level local oscillator signal generating circuit sends the generated second channel signal first-level local oscillator signal to the second channel signal In the step frequency conversion function circuit, the two-stage local oscillation signal generating circuit respectively sends the generated two-level local oscillation signal to the first channel Demodulating a second channel processing circuit, and signal demodulation processing circuit, and said system clock signal generating circuit generates the system clock signal to said baseband signal processing circuit.

The RF circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 5, wherein the first channel signal first-level local oscillator signal generating circuit is a frequency synthesizing circuit.

The RF circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 6, wherein the first channel signal first-level local oscillator signal generating circuit comprises a first pre-divider (160), a first phase detector (113), a first loop filter (116), a first voltage controlled oscillator (119), and a first frequency divider (163), the first prescaler The first phase detector (113), the first loop filter (116) and the first voltage controlled oscillator (119) are sequentially connected in series to the reference clock signal generating circuit and the first channel signal Between the primary frequency conversion function circuits, and the first frequency divider (163) is connected between the first voltage controlled oscillator (119) and the first phase detector (113).

The RF circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 5, wherein the second channel signal first-level local oscillator signal generating circuit is a frequency synthesizing circuit.

The RF circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 8, wherein the second channel signal first-level local oscillator signal generating circuit comprises a second pre-divider (161), a second phase detector (114), a second loop filter (117), a second voltage controlled oscillator (120), and a second frequency divider (164), the second prescaler The detector ( 161 ), the second phase detector ( 114 ), the second loop filter ( 117 ) and the second voltage controlled oscillator ( 120 ) are sequentially connected in series to the reference clock signal generating circuit and the second channel signal Between the primary frequency conversion function circuits, and the second frequency divider (164) is connected between the second voltage controlled oscillator (120) and the second phase detector (114).

The RF circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 8, wherein the second-level local oscillation signal generating circuit comprises a third pre-divider (162), a third phase detector (115), a third loop filter (118), a third voltage controlled oscillator (121), and a third frequency divider (165), wherein the reference clock signal generating circuit sequentially passes the a third prescaler (162), a third phase detector (115), and a third loop filter (118) And the third voltage controlled oscillator (121) is respectively connected to the first channel signal demodulation processing circuit and the second channel signal demodulation processing circuit, and the third frequency divider (165) is connected to the Between the third voltage controlled oscillator (121) and the third phase detector (115).

The RF circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 5, wherein the system clock signal generating circuit comprises a comparator (128), and the comparator ( 128) is connected between the reference clock signal generating circuit and the baseband signal processing circuit.

12. The radio frequency circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 5, wherein the reference clock signal generating circuit is a frequency synthesizing circuit including a high frequency stability temperature. Compensating a crystal oscillator and a phase-locked frequency synthesizer, wherein the temperature-compensated crystal oscillator is respectively coupled to the first channel signal first-order local oscillator signal generating circuit and the second channel signal by the phase-locked frequency synthesizer The stage local oscillator signal generating circuit, the second local oscillator signal generating circuit and the system clock signal generating circuit are connected.

13. The radio frequency circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 5, wherein the reference clock signal generating circuit is a crystal oscillator.

The RF circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 5, wherein the first channel signal primary frequency conversion function circuit comprises a first band pass filter (131) And a first mixer (135), said signal branching function module sequentially passing said first band pass filter (131) and said first mixer (135) with said first channel signal The demodulation processing circuit is connected, and the first channel signal first-level local oscillator signal generating circuit sends the generated first channel signal first-order local oscillator signal to the first mixer (135).

15. The radio frequency circuit structure for realizing a dual-frequency GPS satellite signal conversion to a baseband signal function according to claim 14, wherein said first band pass filter (131) and said first mixer (135) A first low noise amplifier (133) is also connected in series.

The radio frequency circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 14, wherein the first channel signal primary frequency conversion function circuit further comprises a second band pass filter And a first variable gain amplifier (139), wherein the second band pass filter (137) and the first variable gain amplifier (139) are sequentially connected in series to the first mixer (135) And the first channel signal demodulation processing circuit, and the control input of the first variable gain amplifier (139) is coupled to the baseband signal processing circuit.

The RF circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 5, wherein the second channel signal primary frequency conversion function circuit comprises a third band pass filter (231) And a second mixer (235), said signal branching function module sequentially passing said third band pass filter (231) and said second mixer (235) with said second channel signal The demodulation processing circuit is connected, and the second channel signal first-level local oscillator signal generating circuit is The generated second channel signal first order local oscillator signal is sent to the second mixer (235).

18. The radio frequency circuit structure for realizing a dual-frequency GPS satellite signal conversion to a baseband signal function according to claim 17, wherein said third band pass filter (231) and said second mixer (235) A second low noise amplifier (233) is also connected in series.

The radio frequency circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 17, wherein the second channel signal first-stage frequency conversion function circuit further comprises a fourth band-pass filter (237) and a second variable gain amplifier (239), wherein the fourth band pass filter (237) and the second variable gain amplifier (239) are sequentially connected in series to the second mixer (235) And said second channel signal demodulation processing circuit, and said control input of said second variable gain amplifier (239) is coupled to said baseband signal processing circuit.

The radio frequency circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 5, wherein the first channel signal demodulation processing circuit comprises a first channel signal quadrature demodulation filter a circuit and a first channel signal analog-to-digital conversion circuit, the first channel signal quadrature demodulation filter circuit and the first channel signal analog-to-digital conversion circuit are connected in series to the first channel signal primary frequency conversion function circuit and baseband Between signal processing circuits.

The RF circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 20, wherein the first channel signal quadrature demodulation filter circuit comprises a first signal branching function module (141), a first demodulator (144), a second demodulator (145), a first low pass filter (148), a second low pass filter (149), and a phase shifter (126). The first signal branching function module (141) is sequentially connected to the first channel signal analog-to-digital conversion circuit through the first demodulator (144) and the first low-pass filter (148). And the first signal branching function module (141) sequentially passes through the second demodulator (145) and the second low-pass filter (149) to the first channel signal analog-to-digital conversion circuit. Connected, the secondary local oscillator signal generating circuit is coupled to the first demodulator (144), and the secondary local oscillator signal generating circuit passes through the phase shifter (126) The second demodulator (145) is connected.

The RF circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 21, wherein the first channel signal analog-to-digital conversion circuit comprises a first analog-to-digital converter (152) And a second analog to digital converter (153), the first analog to digital converter (152) is coupled between the first low pass filter (148) and the baseband signal processing circuit, the second An analog to digital converter (153) is coupled between the second low pass filter (149) and the baseband signal processing circuit, and the system clock signal is sent to the first analog to digital conversion as a sample clock signal (152) and a second analog to digital converter (153).

The radio frequency circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 21, wherein the first signal branching function module (141) is a power splitter. The RF circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 5, wherein the second channel signal demodulation processing circuit comprises a second channel signal quadrature demodulation filter a circuit and a second channel signal analog-to-digital conversion circuit, wherein the second channel signal quadrature demodulation filter circuit and the second channel signal analog-to-digital conversion circuit are connected in series to the second channel signal primary frequency conversion function circuit and baseband Between signal processing circuits.

The radio frequency circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 24, wherein the second channel signal quadrature demodulation filter circuit comprises a second signal shunt function module (241), a third demodulator (244), a fourth demodulator (245), a third low pass filter (248), a fourth low pass filter (249), and a phase shifter (126). The second signal branching function module (241) is sequentially connected to the second channel signal analog-to-digital conversion circuit through the third demodulator (244) and the third low-pass filter (248). And the second signal branching function module (241) sequentially passes through the fourth demodulator (245) and the fourth low-pass filter (249) to the second channel signal analog-digital conversion circuit. Connected, the second local oscillator signal generating circuit is connected to the third demodulator (244), and the second local oscillator signal generating circuit passes through the phase shifter (126) The fourth demodulator (245) is connected.

The RF circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 24, wherein the second channel signal analog-to-digital conversion circuit comprises a third analog-to-digital converter (252) And a fourth analog to digital converter (253), the third analog to digital converter (252) is connected between the third low pass filter (248) and the baseband signal processing circuit, the fourth An analog to digital converter (253) is coupled between the fourth low pass filter (249) and the baseband signal processing circuit, and the system clock signal is sent to the third analog to digital conversion as a sample clock signal (252) and a fourth analog to digital converter (253).

27. The radio frequency circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 24, wherein the second signal shunt function module (241) is a power splitter.

The radio frequency circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to any one of claims 1 to 4, wherein the antenna receiving function module comprises an antenna unit (100) and a signal Amplifier

(103), the antenna unit (100) is connected to the signal branching function module by the signal amplifier (103).

The radio frequency circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to claim 28, wherein the antenna receiving function module further comprises a low noise preamplifier (101), A low noise preamplifier (101) is connected in series between the antenna unit (100) and the signal amplifier (103).

The RF circuit structure for realizing the function of converting a dual-frequency GPS satellite signal into a baseband signal according to any one of claims 1 to 4, wherein the signal branching function module is a power splitter (105) .