阅读说明：本技术 中频数字下变频方法、电路、基带芯片及卫星导航接收机 (Intermediate frequency digital down-conversion method, circuit, baseband chip and satellite navigation receiver ) 是由 王东会 郑彬 向为 易文鑫 于 2020-12-22 设计创作，主要内容包括：本发明公开了一种中频数字下变频方法,包括获取输入的AD数据；进行格式变换和频点选择；进行混频和宽带滤波；进行降采样得到最终的宽带零频信号；进行窄带滤波得到最终的窄带零频信号。本发明还公开了一种包括所述中频数字下变频方法的电路。本发明还公开了一种包括所述中频数字下变频方法和电路的基带芯片。本发明还公开了一种包括所述中频数字下变频方法、电路和基带芯片的卫星导航接收机。本发明降低了资源消耗和芯片面积,提高了对射频前端的适应性和芯片设计开发测试的效率；而且本发明占用硬件资源较少、兼容性好、可靠性高且适用性好。(The invention discloses an intermediate frequency digital down-conversion method, which comprises the steps of obtaining input AD data; carrying out format conversion and frequency point selection; performing frequency mixing and broadband filtering; performing down-sampling to obtain a final broadband zero-frequency signal; and carrying out narrow-band filtering to obtain a final narrow-band zero-frequency signal. The invention also discloses a circuit comprising the intermediate frequency digital down-conversion method. The invention also discloses a baseband chip comprising the intermediate frequency digital down-conversion method and the intermediate frequency digital down-conversion circuit. The invention also discloses a satellite navigation receiver comprising the intermediate frequency digital down-conversion method, the circuit and the baseband chip. The invention reduces the resource consumption and the chip area, and improves the adaptability to the radio frequency front end and the efficiency of chip design development and test; the invention occupies less hardware resources, and has good compatibility, high reliability and good applicability.)

1. An intermediate frequency digital down-conversion method comprises the following steps:

s1, acquiring input AD data;

s2, carrying out format conversion and frequency point selection on the input AD data;

s3, mixing the data output in the step S2;

s4, performing broadband filtering on the data after frequency mixing;

s5, performing down-sampling on the data subjected to the broadband filtering to obtain a final broadband zero-frequency signal;

and S6, narrow-band filtering is carried out on the data after the down-sampling, so that a final narrow-band zero-frequency signal is obtained.

2. The if digital down-conversion method according to claim 1, wherein the format conversion and frequency point selection are performed on the input AD data in step S2, specifically, the input AD data is uniformly converted into IQ two-way 10-bit complement data according to the bit number, IQ form and coding mode of the input AD data; meanwhile, for convenience of subsequent unified processing, eight frequency point data of B1, B2, L1, L2, G1, G2, B3 and L5 are extracted from the input AD data; finally, the following rules are adopted for output setting:

if the input data is AD data input by a single I way, after format conversion and frequency point selection are carried out, the output I way data is the input I data, and the output Q data is 0;

if the input data is AD data input by IQ double paths, after format conversion and frequency point selection, the output I path data is input I data, and the output Q data is input Q data.

3. The method according to claim 2, wherein the step S3 mixes the data outputted from the step S2, specifically, the following steps are adopted for mixing:

if the input data is AD data input by a single path I, mixing by adopting the following formula:

wherein a is the satellite signal phase; b is a local oscillation phase;

if the input data is AD data input by IQ double paths, mixing is carried out by adopting the following formula:

I:cos(a-b)＝cos(a)cos(b)+sin(a)sin(b)

Q:sin(a-b)＝sin(a)cos(b)-cos(a)sin(b)

wherein a is the satellite signal phase; and b is the local oscillation phase.

4. The method according to claim 3, wherein the down-sampling of the wideband-filtered data in step S5 is performed by:

A. setting the ratio M to N of two clocks of clka and clkb; wherein clka is the sampling frequency corresponding to the AD data; clkb is the operating frequency of baseband signal processing; m and N are positive integers;

B. initializing an accumulated value to be N in a clka clock domain;

C. and accumulating and counting the accumulated value:

when the accumulated value is larger than M, generating a carry signal step, and simultaneously subtracting M from the accumulated value;

D. when the carry signal step is effective, sampling data under a clka clock domain, and resetting the carry signal step after sampling is completed;

E. continuously carrying out accumulation counting on the accumulated value;

F. repeating the steps C-E until the down-sampling is completed, thereby completing the lossless down-sampling;

G. during down-sampling, whether a broadband signal is output or not is set according to the following rules according to input data:

for signals of three frequency points of B1, G1 and G2, only narrow-band signals are output;

and outputting a broadband signal and a narrowband signal aiming at signals of five frequency points of B2, L1, L2, B3 and L5.

5. The method according to any one of claims 1 to 4, wherein the step S4 is performed by performing wideband filtering on the mixed data, specifically, performing wideband filtering on zero-frequency baseband data outputted by the mixing, so as to prevent mixing aliasing; the filter bandwidth is set to 20 MHz.

6. The intermediate frequency digital down-conversion method according to any one of claims 1 to 4, wherein in step S6, the down-sampled data is subjected to narrowband filtering, specifically, the data output by down-sampling is subjected to narrowband filtering to obtain a narrowband signal; the filter bandwidth is set to 4 MHz.

7. A circuit for realizing the intermediate frequency digital down-conversion method according to any one of claims 1 to 6, characterized by comprising a parameter configuration module, an AD data conversion module, a mixing module, a broadband filtering module, a down-sampling module and a narrow-band filtering module; the AD data conversion module, the frequency mixing module, the broadband filtering module, the down-sampling module and the narrow-band filtering module are sequentially connected in series; the output end of the parameter configuration module is simultaneously connected with the AD data conversion module, the frequency mixing module and the down-sampling module; the parameter configuration module is used for issuing control parameters to the AD data conversion module, the frequency mixing module and the down-sampling module; the AD data conversion module is used for carrying out format conversion and frequency point selection on input AD data and uploading the obtained output data to the frequency mixing module; the frequency mixing module is used for mixing frequency of received data and uploading the output after frequency mixing to the broadband filtering module; the broadband filtering module is used for carrying out broadband filtering on the received data and uploading the filtered data to the down-sampling module; the down-sampling module is used for down-sampling the received data to obtain a final broadband zero-frequency signal and uploading the down-sampled data to the narrow-band filtering module; the narrow-band filtering module is used for carrying out narrow-band filtering on the received data so as to obtain a final narrow-band zero-frequency signal.

8. A baseband chip comprising the intermediate frequency digital down-conversion method of any one of claims 1 to 6 and the circuit of claim 7.

9. A satellite navigation receiver, characterized in that it comprises the intermediate frequency digital down-conversion method of any one of claims 1 to 6, the circuit of claim 7 and the baseband chip of claim 8.

Technical Field

The invention belongs to the field of satellite navigation positioning, and particularly relates to an intermediate frequency digital down-conversion method, an intermediate frequency digital down-conversion circuit, a baseband chip and a satellite navigation receiver.

Background

With the development of economic technology and the improvement of living standard of people, the satellite navigation positioning technology is widely applied to the production and the life of people, and brings endless convenience to the production and the life of people.

Currently, there are four satellite navigation systems in the world, which are: GPS, BDS (beidou system), GLONASS and Galileo. Each system has a plurality of frequency points, each frequency point contains 1 or more signal components, and different frequency point signal components of different systems often have different parameters such as signal bandwidth. According to the parameters of signals disclosed by each large satellite navigation system at present, a baseband chip needs to be provided with 12 digital down-conversion channels to receive signals of a full constellation and a full frequency point. The 12 channels are respectively B1, B2 wide band, B2 narrow band, L1 wide band, L1 narrow band, L2 wide band, L2 narrow band, G1, G2, B3, L5 wide band and L5 narrow band. The bit number and format of AD sampling data output by the radio frequency chip are configurable parameters, and the bit number of the AD sampling data is commonly used to be 2bit, 4bit, 10bit and the like; the output form may be I branch single path or I, Q double path; the encoding may be two's complement or offset binary. The different parameters all require corresponding adjustment of the intermediate frequency digital down-conversion channel.

In the prior art, a digital down-conversion channel is independently designed for each signal of each frequency point, and the required number is 12; one of the different parameters of the AD data is often selected and not compatible with the other parameters. Therefore, the current technical scheme not only needs more hardware resources, but also has poor compatibility.

Disclosure of Invention

One of the objectives of the present invention is to provide an intermediate frequency digital down conversion method with less hardware resources, good compatibility, high reliability and good applicability.

The invention also provides a circuit for realizing the intermediate frequency digital down-conversion method.

It is a further object of the present invention to provide a baseband chip including the method and circuit for intermediate frequency digital down-conversion.

The invention also provides a satellite navigation receiver comprising the intermediate frequency digital down-conversion method, the intermediate frequency digital down-conversion circuit and the baseband chip.

The invention provides an intermediate frequency digital down-conversion method, which comprises the following steps:

s1, acquiring input AD data;

s2, carrying out format conversion and frequency point selection on the input AD data;

s3, mixing the data output in the step S2;

s4, performing broadband filtering on the data after frequency mixing;

s5, performing down-sampling on the data subjected to the broadband filtering to obtain a final broadband zero-frequency signal;

and S6, narrow-band filtering is carried out on the data after the down-sampling, so that a final narrow-band zero-frequency signal is obtained.

The step S2 of performing format conversion and frequency point selection on the input AD data, specifically, uniformly converting the input AD data into IQ two-way 10-bit complementary data according to the bit number, IQ form and encoding mode of the input AD data; meanwhile, for convenience of subsequent unified processing, eight frequency point data of B1, B2, L1, L2, G1, G2, B3 and L5 are extracted from the input AD data; finally, the following rules are adopted for output setting:

if the input data is AD data input by a single I way, after format conversion and frequency point selection are carried out, the output I way data is the input I data, and the output Q data is 0;

if the input data is AD data input by IQ double paths, after format conversion and frequency point selection, the output I path data is input I data, and the output Q data is input Q data.

In step S3, the mixing of the data output in step S2 specifically includes the following steps:

if the input data is AD data input by a single path I, mixing by adopting the following formula:

wherein a is the satellite signal phase; b is a local oscillation phase;

if the input data is AD data input by IQ double paths, mixing is carried out by adopting the following formula:

I:cos(a-b)＝cos(a)cos(b)+sin(a)sin(b)

Q:sin(a-b)＝sin(a)cos(b)-cos(a)sin(b)

wherein a is the satellite signal phase; and b is the local oscillation phase.

The step S4 of performing wideband filtering on the data after frequency mixing, specifically performing wideband filtering on zero-frequency baseband data output by frequency mixing, thereby preventing mixing aliasing; the filter bandwidth is set to 20 MHz.

The down-sampling of the data after the broadband filtering in step S5 specifically includes the following steps:

A. setting the ratio M to N of two clocks of clka and clkb; wherein clka is the sampling frequency corresponding to the AD data; clkb is the operating frequency of baseband signal processing; m and N are positive integers;

B. initializing an accumulated value to be N in a clka clock domain;

C. and accumulating and counting the accumulated value:

when the accumulated value is larger than M, generating a carry signal step, and simultaneously subtracting M from the accumulated value;

D. when the carry signal step is effective, sampling data under a clka clock domain, and resetting the carry signal step after sampling is completed;

E. continuously carrying out accumulation counting on the accumulated value;

F. repeating the steps C-E until the down-sampling is completed, thereby completing the lossless down-sampling;

G. during down-sampling, whether a broadband signal is output or not is set according to the following rules according to input data:

for signals of three frequency points of B1, G1 and G2, only narrow-band signals are output;

and outputting a broadband signal and a narrowband signal aiming at signals of five frequency points of B2, L1, L2, B3 and L5.

In step S6, performing narrow-band filtering on the down-sampled data, specifically, performing narrow-band filtering on the data output by down-sampling to obtain a narrow-band signal; the filter bandwidth is set to 4 MHz.

The invention also provides a circuit for realizing the intermediate frequency digital down-conversion method, which comprises a parameter configuration module, an AD data conversion module, a frequency mixing module, a broadband filtering module, a down-sampling module and a narrow-band filtering module; the AD data conversion module, the frequency mixing module, the broadband filtering module, the down-sampling module and the narrow-band filtering module are sequentially connected in series; the output end of the parameter configuration module is simultaneously connected with the AD data conversion module, the frequency mixing module and the down-sampling module; the parameter configuration module is used for issuing control parameters to the AD data conversion module, the frequency mixing module and the down-sampling module; the AD data conversion module is used for carrying out format conversion and frequency point selection on input AD data and uploading the obtained output data to the frequency mixing module; the frequency mixing module is used for mixing frequency of received data and uploading the output after frequency mixing to the broadband filtering module; the broadband filtering module is used for carrying out broadband filtering on the received data and uploading the filtered data to the down-sampling module; the down-sampling module is used for down-sampling the received data to obtain a final broadband zero-frequency signal and uploading the down-sampled data to the narrow-band filtering module; the narrow-band filtering module is used for carrying out narrow-band filtering on the received data so as to obtain a final narrow-band zero-frequency signal.

The invention also provides a baseband chip which comprises the intermediate frequency digital down-conversion method and the intermediate frequency digital down-conversion circuit.

The invention also provides a satellite navigation receiver which comprises the intermediate frequency digital down-conversion method, the circuit and the baseband chip.

According to the intermediate frequency digital down-conversion method, the circuit, the baseband chip and the satellite navigation receiver, the common part is extracted and designed uniformly according to the difference of different constellation and different frequency point signal parameters, the difference of AD input digit, IQ form, coding mode and the like, and the difference part is configured in a parameterized form; for different signal components of the same frequency point, the same module is shared to realize the maximum resource optimization, and the originally required 12 down-conversion channels can be reduced to 8; meanwhile, the method can adapt to AD input parameters of various forms, not only reduces resource consumption and chip area, but also greatly improves the adaptability to the radio frequency front end, brings convenience to chip testing, and greatly improves the efficiency of chip design, development and testing; the invention occupies less hardware resources, and has good compatibility, high reliability and good applicability.

Drawings

FIG. 1 is a schematic process flow diagram of the process of the present invention.

FIG. 2 is a functional block diagram of the circuit of the present invention.

Detailed Description

FIG. 1 is a schematic flow chart of the method of the present invention: the invention provides an intermediate frequency digital down-conversion method, which comprises the following steps:

s1, acquiring input AD data;

s2, carrying out format conversion and frequency point selection on the input AD data; specifically, input AD data are uniformly converted into complementary data of an IQ double-path 10bit according to the bit number, the IQ form and the coding mode of the input AD data; meanwhile, for convenience of subsequent unified processing, eight frequency point data of B1, B2, L1, L2, G1, G2, B3 and L5 are extracted from the input AD data; finally, the following rules are adopted for output setting:

if the input data is AD data input by a single I way, after format conversion and frequency point selection are carried out, the output I way data is the input I data, and the output Q data is 0;

if the input data is AD data input by IQ double paths, after format conversion and frequency point selection are carried out, the output I path data is input I data, and the output Q data is input Q data;

s3, mixing the data output in the step S2; specifically, the following steps are adopted for mixing:

if the input data is AD data input by a single path I, mixing by adopting the following formula:

wherein a is the satellite signal phase; b is a local oscillation phase;

after the signals pass through the broadband filtering module, sum frequency components are filtered, difference frequency components are reserved, and I, Q branch signals are obtained as follows:

I:cos(a-b)＝2*cos(a)cos(b)

Q:sin(a-b)＝-2cos(a)sin(b)

if the input data is AD data input by IQ double paths, mixing is carried out by adopting the following formula:

I:cos(a-b)＝cos(a)cos(b)+sin(a)sin(b)

Q:sin(a-b)＝sin(a)cos(b)-cos(a)sin(b)

wherein a is the satellite signal phase; b is a local oscillation phase;

s4, performing broadband filtering on the data after frequency mixing; specifically, broadband filtering is carried out on zero-frequency baseband data output by frequency mixing, so that frequency mixing aliasing is prevented; the filter bandwidth is set to 20 MHz;

s5, performing down-sampling on the data subjected to the broadband filtering to obtain a final broadband zero-frequency signal; specifically, the following steps are adopted for down-sampling:

A. setting the ratio M to N of two clocks of clka and clkb; wherein clka is the sampling frequency corresponding to the AD data; clkb is the operating frequency of baseband signal processing; m and N are positive integers;

B. initializing an accumulated value to be N in a clka clock domain;

C. and accumulating and counting the accumulated value:

when the accumulated value is larger than M, generating a carry signal step, and simultaneously subtracting M from the accumulated value;

D. when the carry signal step is effective, sampling data under a clka clock domain, and resetting the carry signal step after sampling is completed;

E. continuously carrying out accumulation counting on the accumulated value;

F. repeating the steps C-E until the down-sampling is completed, thereby completing the lossless down-sampling;

G. during down-sampling, whether a broadband signal is output or not is set according to the following rules according to input data:

for signals of three frequency points of B1, G1 and G2, only narrow-band signals are output;

aiming at signals of five frequency points of B2, L1, L2, B3 and L5, outputting broadband signals and narrowband signals;

s6, narrow-band filtering is carried out on the data after the down-sampling, and therefore a final narrow-band zero-frequency signal is obtained; specifically, narrow-band filtering is carried out on data output by down sampling to obtain a narrow-band signal; the filter bandwidth is set to 4 MHz.

FIG. 2 shows a functional block diagram of the circuit of the present invention: the circuit for realizing the intermediate frequency digital down-conversion method comprises a parameter configuration module, an AD data conversion module, a frequency mixing module, a broadband filtering module, a down-sampling module and a narrow-band filtering module; the AD data conversion module, the frequency mixing module, the broadband filtering module, the down-sampling module and the narrow-band filtering module are sequentially connected in series; the output end of the parameter configuration module is simultaneously connected with the AD data conversion module, the frequency mixing module and the down-sampling module; the parameter configuration module is used for issuing control parameters to the AD data conversion module, the frequency mixing module and the down-sampling module; the AD data conversion module is used for carrying out format conversion and frequency point selection on input AD data and uploading the obtained output data to the frequency mixing module; the frequency mixing module is used for mixing frequency of received data and uploading the output after frequency mixing to the broadband filtering module; the broadband filtering module is used for carrying out broadband filtering on the received data and uploading the filtered data to the down-sampling module; the down-sampling module is used for down-sampling the received data to obtain a final broadband zero-frequency signal and uploading the down-sampled data to the narrow-band filtering module; the narrow-band filtering module is used for carrying out narrow-band filtering on the received data so as to obtain a final narrow-band zero-frequency signal.

In addition, the invention also provides a baseband chip, which comprises the intermediate frequency digital down-conversion method and the intermediate frequency digital down-conversion circuit; the chip adopts the intermediate frequency digital down-conversion method for down-conversion, and comprises a circuit for realizing the down-conversion method.

The invention also provides a satellite navigation receiver which comprises the intermediate frequency digital down-conversion method, the circuit and the baseband chip.