CN112731454B - Intermediate frequency digital down-conversion method, circuit, baseband chip and satellite navigation receiver - Google Patents
Intermediate frequency digital down-conversion method, circuit, baseband chip and satellite navigation receiver Download PDFInfo
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- CN112731454B CN112731454B CN202011531045.3A CN202011531045A CN112731454B CN 112731454 B CN112731454 B CN 112731454B CN 202011531045 A CN202011531045 A CN 202011531045A CN 112731454 B CN112731454 B CN 112731454B
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- 238000006243 chemical reaction Methods 0.000 title claims abstract description 62
- 238000000034 method Methods 0.000 title claims abstract description 37
- 238000001914 filtration Methods 0.000 claims abstract description 52
- 238000005070 sampling Methods 0.000 claims description 13
- 238000012545 processing Methods 0.000 claims description 6
- 230000000295 complement effect Effects 0.000 claims description 4
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/35—Constructional details or hardware or software details of the signal processing chain
- G01S19/37—Hardware or software details of the signal processing chain
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/42—Determining position
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D7/00—Transference of modulation from one carrier to another, e.g. frequency-changing
- H03D7/16—Multiple-frequency-changing
Abstract
The invention discloses an intermediate frequency digital down-conversion method, which comprises the steps of obtaining input AD data; performing format conversion and frequency point selection; mixing and broadband filtering are carried out; downsampling 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 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.
Description
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 living of people, and brings endless convenience to the production and living of people.
Currently, four large satellite navigation systems exist in the world, which are respectively: 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 parameters such as different signal bandwidths and the like are often different among the signal components of different frequency points of different systems. According to the parameters of the public signals of each large satellite navigation system at present, a baseband chip is required to be provided with 12 digital down-conversion channels so as to realize the signal reception of all constellation and all frequency points. The 12 channels are B1, B2 broadband, B2 narrowband, L1 broadband, L1 narrowband, L2 broadband, L2 narrowband, G1, G2, B3, L5 broadband and L5 narrowband respectively. The number and format of AD sampling data bits output by the radio frequency chip are configurable parameters, and the number of the AD sampling data bits is commonly 2 bits, 4 bits, 10 bits and the like; the output may be in the form of an I branch single path or I, Q double paths; the coding mode may be a two's complement or an offset two's code. The different parameters all need to be correspondingly adjusted by the intermediate frequency digital down-conversion channel.
In the prior art, each signal of each frequency point is independently designed with a digital down-conversion channel, and the required number is 12; for different parameters of AD data, one of them is often selected, and the other parameters are not compatible. Therefore, the current technical scheme not only requires more hardware resources, but also has poor compatibility.
Disclosure of Invention
The invention aims to provide an intermediate frequency digital down-conversion method which has the advantages of less occupied hardware resources, good compatibility, high reliability and good applicability.
The second object of the present invention is to provide a circuit for implementing the intermediate frequency digital down-conversion method.
It is a further object of the present invention to provide a baseband chip comprising the intermediate frequency digital down-conversion method and circuit.
The fourth object of the present invention is to provide a satellite navigation receiver comprising the intermediate frequency digital down-conversion method, circuit and baseband chip.
The intermediate frequency digital down-conversion method provided by the invention 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, broadband filtering is carried out on the mixed data;
s5, downsampling the data after broadband filtering, so that a final broadband zero-frequency signal is obtained;
s6, carrying out narrow-band filtering on the downsampled data, so as to obtain a final narrow-band zero-frequency signal.
The step S2 of carrying out format conversion and frequency point selection on the input AD data, namely uniformly converting the input AD data into complementary data of 10 bits of an IQ double-way according to bit numbers, IQ forms and coding modes of the input AD data; meanwhile, eight frequency point data of B1, B2, L1, L2, G1, G2, B3 and L5 are extracted from the input AD data in order to facilitate subsequent unified processing; finally, the following rules are adopted for output setting:
if the input data is AD data input by a single-channel I, performing format conversion and frequency point selection, and outputting the I-channel data as the input I data and the Q-channel data as 0;
if the input data is AD data input by IQ two-way, the output I-way data is the input I data, and the output Q data is the input Q data after format conversion and frequency point selection.
The step S3 of mixing the data output in the step S2 specifically includes the following steps:
if the input data is AD data input by a single-path I, mixing is carried out by adopting the following formula:
wherein a is the satellite signal phase; b is the local oscillation phase;
if the input data is AD data input by IQ two-way, the following formula is adopted for mixing:
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 the local oscillator phase.
Step S4, performing broadband filtering on the mixed data, specifically performing broadband filtering on zero-frequency baseband data output by mixing, so as to prevent mixing aliasing; the filter bandwidth is set to 20MHz.
The step S5 of downsampling the wideband filtered data specifically includes the following steps:
A. setting the proportion M of two clocks of clka and clkb to N; wherein clka is the sampling frequency corresponding to the AD data; clkb is the working frequency of baseband signal processing; m and N are positive integers;
B. initializing an accumulated value as N under a clka clock domain;
C. accumulating and counting the accumulated value:
when the accumulated value is greater than M, generating a carry signal step, and subtracting M from the accumulated value;
D. sampling data under the clka clock domain when the carry signal step is valid, and resetting the carry signal step after sampling is completed;
E. continuously accumulating and counting the accumulated value;
F. repeating the steps C-E until the downsampling is completed, thereby completing lossless downsampling;
G. during downsampling, whether to output a broadband signal is set according to the input data by adopting the following rule:
for signals of three frequency points of B1, G1 and G2, only a narrowband signal is output;
for signals of five frequency points of B2, L1, L2, B3 and L5, a broadband signal and a narrowband signal are output.
Step S6, performing narrow-band filtering on the downsampled data, specifically performing narrow-band filtering on the downsampled data to obtain a narrow-band signal; the filter bandwidth is set to 4MHz.
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 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 downsampling module and the narrowband filtering module are sequentially connected in series; the output end of the parameter configuration module is connected with the AD data conversion module, the frequency mixing module and the downsampling module at the same time; the parameter configuration module is used for issuing control parameters to the AD data conversion module, the frequency mixing module and the downsampling module; the AD data conversion module is used for carrying out format conversion and frequency point selection on the input AD data, and uploading the obtained output data to the mixing module; the frequency mixing module is used for mixing the received data and uploading the mixed output 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 downsampling module; the downsampling module is used for downsampling the received data to obtain a final broadband zero-frequency signal, and uploading the downsampled data to the narrowband filtering module; the narrowband filtering module is used for carrying out narrowband filtering on the received data so as to obtain a final narrowband zero-frequency signal.
The invention also provides a baseband chip, which comprises the intermediate frequency digital down-conversion method and the 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, common parts are extracted to be uniformly designed according to differences of signal parameters of different frequency points of different constellations and differences of AD input bits, IQ forms, coding modes and the like, and the difference parts are configured in a parameterized form; for different signal components of the same frequency point, sharing the same module to realize maximized resource optimization, and reducing 12 down-conversion channels originally needed to 8; meanwhile, the method can adapt to AD input parameters in various different 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 test, and greatly improves the efficiency of chip design, development and test; the invention occupies less hardware resources, and has good compatibility, high reliability and good applicability.
Drawings
FIG. 1 is a schematic flow chart of the method of the present invention.
Fig. 2 is a functional block diagram of the circuit of the present invention.
Detailed Description
A schematic process flow diagram of the method of the present invention is shown in fig. 1: the intermediate frequency digital down-conversion method provided by the invention comprises the following steps:
s1, acquiring input AD data;
s2, carrying out format conversion and frequency point selection on the input AD data; according to bit number, IQ form and coding mode of the input AD data, uniformly converting the input AD data into IQ double-channel 10bit complement data; meanwhile, eight frequency point data of B1, B2, L1, L2, G1, G2, B3 and L5 are extracted from the input AD data in order to facilitate subsequent unified processing; finally, the following rules are adopted for output setting:
if the input data is AD data input by a single-channel I, performing format conversion and frequency point selection, and outputting the I-channel data as the input I data and the Q-channel data as 0;
if the input data is AD data input by IQ two-way, performing format conversion and frequency point selection, and outputting I-way data as input I data and Q-way data as input Q data;
s3, mixing the data output in the step S2; the method comprises the following steps of:
if the input data is AD data input by a single-path I, mixing is carried out by adopting the following formula:
wherein a is the satellite signal phase; b is the local oscillation phase;
after the path of signals pass through a broadband filtering module, the sum frequency component is filtered, the difference frequency component is reserved, and I, Q path of 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 two-way, the following formula is adopted for mixing:
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 the local oscillation phase;
s4, broadband filtering is carried out on the mixed data; specifically, wideband filtering is carried out on zero-frequency baseband data output by mixing, so that mixing aliasing is prevented; the filter bandwidth is set to 20MHz;
s5, downsampling the data after broadband filtering, so that a final broadband zero-frequency signal is obtained; the method specifically comprises the following steps of:
A. setting the proportion M of two clocks of clka and clkb to N; wherein clka is the sampling frequency corresponding to the AD data; clkb is the working frequency of baseband signal processing; m and N are positive integers;
B. initializing an accumulated value as N under a clka clock domain;
C. accumulating and counting the accumulated value:
when the accumulated value is greater than M, generating a carry signal step, and subtracting M from the accumulated value;
D. sampling data under the clka clock domain when the carry signal step is valid, and resetting the carry signal step after sampling is completed;
E. continuously accumulating and counting the accumulated value;
F. repeating the steps C-E until the downsampling is completed, thereby completing lossless downsampling;
G. during downsampling, whether to output a broadband signal is set according to the input data by adopting the following rule:
for signals of three frequency points of B1, G1 and G2, only a narrowband signal is output;
outputting a broadband signal and a narrowband signal aiming at signals of five frequency points of B2, L1, L2, B3 and L5;
s6, carrying out narrow-band filtering on the downsampled data, so as to obtain a final narrow-band zero-frequency signal; the method specifically comprises the steps of carrying out narrow-band filtering on data output by downsampling to obtain a narrow-band signal; the filter bandwidth is set to 4MHz.
Fig. 2 is 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 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 downsampling module and the narrowband filtering module are sequentially connected in series; the output end of the parameter configuration module is connected with the AD data conversion module, the frequency mixing module and the downsampling module at the same time; the parameter configuration module is used for issuing control parameters to the AD data conversion module, the frequency mixing module and the downsampling module; the AD data conversion module is used for carrying out format conversion and frequency point selection on the input AD data, and uploading the obtained output data to the mixing module; the frequency mixing module is used for mixing the received data and uploading the mixed output 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 downsampling module; the downsampling module is used for downsampling the received data to obtain a final broadband zero-frequency signal, and uploading the downsampled data to the narrowband filtering module; the narrowband filtering module is used for carrying out narrowband filtering on the received data so as to obtain a final narrowband zero-frequency signal.
In addition, the invention also provides a baseband chip, which comprises the intermediate frequency digital down-conversion method and the circuit; the chip adopts the intermediate frequency digital down-conversion method to carry out 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.
Claims (8)
1. An intermediate frequency digital down conversion method, comprising the steps of:
s1, acquiring input AD data;
s2, carrying out format conversion and frequency point selection on the input AD data; according to bit number, IQ form and coding mode of the input AD data, uniformly converting the input AD data into IQ double-channel 10bit complement data; meanwhile, eight frequency point data of B1, B2, L1, L2, G1, G2, B3 and L5 are extracted from the input AD data in order to facilitate subsequent unified processing; finally, the following rules are adopted for output setting:
if the input data is AD data input by a single-channel I, performing format conversion and frequency point selection, and outputting the I-channel data as the input I data and the Q-channel data as 0;
if the input data is AD data input by IQ two-way, performing format conversion and frequency point selection, and outputting I-way data as input I data and Q-way data as input Q data;
s3, mixing the data output in the step S2;
s4, broadband filtering is carried out on the mixed data;
s5, downsampling the data after broadband filtering, so that a final broadband zero-frequency signal is obtained;
s6, carrying out narrow-band filtering on the downsampled data, so as to obtain a final narrow-band zero-frequency signal.
2. The method as claimed in claim 1, wherein the step S3 of mixing the data output in the step S2 is performed by:
if the input data is AD data input by a single-path I, mixing is carried out by adopting the following formula:
wherein a is the satellite signal phase; b is the local oscillation phase;
if the input data is AD data input by IQ two-way, the following formula is adopted for mixing:
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 the local oscillator phase.
3. The method according to claim 2, wherein the step S5 of downsampling the wideband filtered data is performed by:
A. setting the proportion M of two clocks of clka and clkb to N; wherein clka is the sampling frequency corresponding to the AD data; clkb is the working frequency of baseband signal processing; m and N are positive integers;
B. initializing an accumulated value as N under a clka clock domain;
C. accumulating and counting the accumulated value:
when the accumulated value is greater than M, generating a carry signal step, and subtracting M from the accumulated value;
D. sampling data under the clka clock domain when the carry signal step is valid, and resetting the carry signal step after sampling is completed;
E. continuously accumulating and counting the accumulated value;
F. repeating the steps C-E until the downsampling is completed, thereby completing lossless downsampling;
G. during downsampling, whether to output a broadband signal is set according to the input data by adopting the following rule:
for signals of three frequency points of B1, G1 and G2, only a narrowband signal is output;
for signals of five frequency points of B2, L1, L2, B3 and L5, a broadband signal and a narrowband signal are output.
4. The method for down-conversion of intermediate frequency digital signals according to any one of claims 1 to 3, wherein the step S4 performs wideband filtering on the mixed data, specifically wideband filtering on zero-frequency baseband data outputted by the mixing, so as to prevent mixing aliasing; the filter bandwidth is set to 20MHz.
5. A method of down-converting an intermediate frequency digital signal according to any one of claims 1 to 3, wherein in step S6, the down-sampled data is subjected to narrowband filtering, specifically, the down-sampled data is subjected to narrowband filtering to obtain a narrowband signal; the filter bandwidth is set to 4MHz.
6. A circuit for implementing the intermediate frequency digital down-conversion method according to any one of claims 1 to 5, characterized by comprising a parameter configuration module, an AD data conversion module, a mixing module, a wideband filtering module, a downsampling module and a narrowband filtering module; the AD data conversion module, the frequency mixing module, the broadband filtering module, the downsampling module and the narrowband filtering module are sequentially connected in series; the output end of the parameter configuration module is connected with the AD data conversion module, the frequency mixing module and the downsampling module at the same time; the parameter configuration module is used for issuing control parameters to the AD data conversion module, the frequency mixing module and the downsampling module; the AD data conversion module is used for carrying out format conversion and frequency point selection on the input AD data, and uploading the obtained output data to the mixing module; the frequency mixing module is used for mixing the received data and uploading the mixed output 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 downsampling module; the downsampling module is used for downsampling the received data to obtain a final broadband zero-frequency signal, and uploading the downsampled data to the narrowband filtering module; the narrowband filtering module is used for carrying out narrowband filtering on the received data so as to obtain a final narrowband zero-frequency signal.
7. A baseband chip characterized by comprising the circuit of claim 6 for implementing the intermediate frequency digital down-conversion method of one of claims 1 to 5.
8. A satellite navigation receiver comprising the circuit of claim 6 for implementing the intermediate frequency digital down conversion method of one of claims 1 to 5 and the baseband chip of claim 7.
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