CN101867542B - IF processing engine, IF carrier removal method, and GNSS receiver - Google Patents

Abstract

The present invention provides an intermediate frequency processing engine, an intermediate frequency carrier removal method, and a GNSS receiver. The intermediate frequency processing engine is used in a GNSS receiver, and includes: a local oscillator unit, which generates multiple carriers with different frequencies; an intermediate frequency down-converter, which mixes multiple intermediate frequency signals with the carrier generated by the local oscillator unit to generate multiple signal segments from which the intermediate frequency carrier has been removed; a time division multiplexing controller, which schedules each mixing operation of the intermediate frequency down-converter; and a buffer, which stores the signal segments from which the intermediate frequency carrier has been removed generated by the intermediate frequency down-converter. The intermediate frequency processing engine, intermediate frequency carrier removal method, and GNSS receiver provided by the present invention can remove multiple intermediate frequency carriers with different frequencies from an intermediate frequency signal by allowing spread spectrum signals with different carrier frequencies to share one intermediate frequency processing engine.

Description

IF processing engine, IF carrier removal method, and GNSS receiver

technical field

The present invention relates to an intermediate frequency processing engine, an intermediate frequency carrier removal method, and a Global Navigation Satellite System (Global Navigation Satellite System, hereinafter referred to as GNSS) receiver, and in particular to a plurality of spread spectrum signals with different carrier frequencies (spreadspectrumsignal ), an intermediate frequency (intermediate frequency, hereinafter referred to as IF) processing engine (processing engine) shared by ), an IF carrier removal method for removing multiple IF carriers with different frequencies in an IF signal, and a GNSS receiver using the IF processing engine.

Background technique

At present, there are many available GNSS, including: Global Positioning System (Global Positioning System, hereinafter referred to as GPS), Galileo (Galileo) system and Global Navigation Satellite System (GLObalNAvigationSatellite System, hereinafter referred to as GLONASS). GPS uses code division multiple access (Code Division Multiple Access, hereinafter referred to as CDMA). That is, in GPS, satellites are distinguished from each other by modulating signals of respective satellites with different PRN codes (pseudo-random noise code, pseudo-random code). GLONASS uses frequency division multiple access (Frequency Division Multiple Access, hereinafter referred to as FDMA). That is, in GLONASS, satellites are distinguished from each other by using different carrier frequencies. Table 1 shows the GLONASS carrier frequencies in the L1 and L2 subbands.

channel number Nominal value of frequency in L1 sub-band (unit: MHz) channel number Nominal value of frequency in L2 sub-band (unit: MHz) 13 1609.3125 13 1251.6875 12 1608.75 12 1251.25 11 1608.1875 11 1250.8125 10 1607.625 10 1250.375 09 1607.0625 09 1249.9375 08 1606.5 08 1249.5 07 1605.9375 07 1249.0625 06 1605.375 06 1248.625 05 1604.8125 05 1248.1875 04 1604.25 04 1247.75 03 1603.6875 03 1247.3125

channel number Nominal value of frequency in L1 sub-band (unit: MHz) channel number Nominal value of frequency in L2 sub-band (unit: MHz) 02 1603.125 02 1246.875 01 1602.5625 01 1246.4375 00 1602.0 00 1246.0 -01 1601.4375 -01 1245.5625 -02 1600.8750 -02 1245.1250 -03 1600.3125 -03 1244.6875 -04 1599.7500 -04 1244.2500 -05 1599.1875 -05 1243.8125 -06 1598.6250 -06 1243.3750 -07 1598.0625 -07 1242.9375

Table 1

Figure 1 is a schematic diagram of the basic structure of a modern GNSS receiver 100 according to the prior art. The receiver 100 includes: an antenna 101, a radio frequency (radiofrequency, hereinafter referred to as RF) front end (frontend) 112, an IF down-converter (down-converter) 123, a local oscillator 128, a correlator engine (correlator engine) 130, and a correlator memory 135 , a local code generator 147, and a processor 150. The receiver 100 receives satellite signals in the RF frequency band via an antenna 101 . The received RF signal is down-converted to an IF signal in the RF front end 112 and amplified. The IF signal is passed to the IF downconverter 123 . The IF down-converter 123 down-converts the IF signal to a baseband signal by using the IF carrier provided by the local oscillator 128 . The baseband signal is transmitted to the correlator engine 130 for correlation with the code provided by the local code generator 147 . Correlation results are stored in correlator memory 135 for accumulation. The processor 150 processes the correlation results and/or accumulation of correlation results to generate position-velocity-time (position-velocity-time, hereinafter referred to as PVT) information. In this structure, the IF carrier frequency can only be a fixed value. However, in practice, spread spectrum signals from different satellites (eg, the satellites in GLONASS described above) or different GNSS systems may use different carriers. That is, the carrier frequencies of the received spread spectrum signals are different. Therefore, existing receivers (eg, GLONASS receivers) use multiple IF carrier removal modules to improve satellite search and tracking efficiency. Each of the plurality of IF carrier removal modules is for a specific carrier frequency.

Contents of the invention

In order to solve the above technical problems, the present invention provides an IF processing engine, an IF carrier removal method and a GNSS receiver.

The invention provides an IF processing engine for a GNSS receiver, comprising: a local oscillator unit, which generates multiple carriers with different frequencies; an IF down-converter, which respectively combines multiple IF signals with those generated by the local oscillator unit carrier mixing to generate multiple signal segments with the IF carrier removed; a time division multiplexing controller to schedule the individual mixing operations of the IF downconverter; and a buffer to store the IF downconverter generated IF removed The signal segment of the IF carrier.

The present invention also provides an IF carrier removal method for a GNSS receiver to remove multiple IF carriers with different frequencies from an IF signal. The IF carrier removal method includes: generating multiple carriers with different frequencies; Based on time division multiplexing scheduling, respectively mixing the carrier and the IF signal to generate a signal segment with the IF carrier removed; and storing the signal segment with the IF carrier removed.

The present invention also provides a GNSS receiver, comprising: an RF front end, which down-converts the RF signal into an IF signal; an IF processing engine, which provides multiple carriers with different frequencies, and converts the IF signal by using the carrier in time division multiplexing scheduling. The signal is down-converted to a baseband signal; and a correlator engine correlates the baseband signal with the code to generate a plurality of correlation results.

The IF processing engine, IF carrier removal method and GNSS receiver provided by the present invention can remove multiple intermediate frequency carriers with different frequencies from the intermediate frequency signal by making spread spectrum signals with different carrier frequencies share one intermediate frequency processing engine.

Description of drawings

Fig. 1 is a schematic schematic diagram of the basic structure of a modern GNSS receiver according to the prior art.

FIG. 2 is a schematic diagram of a GNSS receiver according to a first embodiment of the present invention.

FIG. 3 is a schematic diagram of an IF processing engine according to an embodiment of the present invention.

Figure 4A is a schematic diagram of a generic NCO according to an embodiment of the invention.

FIG. 4B is a schematic diagram of the simulated waveform and the real mapping table of the NCO according to an embodiment of the present invention.

Fig. 5 is a schematic diagram of a TDM scheduling mechanism according to an embodiment of the present invention.

FIG. 6 is a schematic diagram of an IF processing engine according to another embodiment of the present invention.

FIG. 7 is a schematic diagram of an IF processing engine according to another embodiment of the present invention.

FIG. 8 is a schematic diagram of an IF processing engine according to another embodiment of the present invention.

FIG. 9 is a flowchart of a method for removing multiple IF carriers with different frequencies from multiple IF signals in a GNSS receiver according to an embodiment of the present invention.

detailed description

Certain terms are used throughout the specification and claims to refer to particular elements. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same element. The specification and claims do not use the difference in name as a way to distinguish components, but use the difference in function of components as a criterion for distinguishing. "Includes" mentioned throughout the specification and claims is an open-ended term, so it should be interpreted as "including but not limited to". In addition, the term "coupled" herein includes any direct and indirect means of electrical connection. Therefore, if it is described that the first device is coupled to the second device, it means that the first device may be directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices or connection means.

FIG. 2 is a schematic diagram of a GNSS receiver 200 according to a first embodiment of the present invention. The basic structure of the receiver 200 is similar to that of the receiver 100 shown in FIG. 1, and elements with the same names have similar functions, so descriptions of these elements are omitted here. The main difference between the receiver 200 and the receiver 100 is that the receiver 200 has an IF processing engine 220 for converting IF signals with different carrier frequencies from the RF front-end 212 into baseband signals.

FIG. 3 is a schematic diagram of an IF processing engine 220 according to an embodiment of the present invention. In this embodiment, the IF processing engine 220 includes: an IF down-converter 223, a multiplexer (multiplexer) 224, a time division multiplex (timedivision multiplex, hereinafter referred to as TDM) controller 225, a local oscillator unit (composed of multiple local oscillators) device 228), and buffer 229. Wherein, each local oscillator 228 can be simply implemented by a numerically controlled oscillator (NCO for short). For example, it can be seen from FIG. 3 that the local oscillator unit of the IF processing engine 220 includes three local oscillators 228 . Each local oscillator 228 generates a different carrier, that is, generates a plurality of carriers with different frequencies. Multiple carriers are scheduled to be sequentially transmitted to IF downconverter 223 through multiplexer 224 , which is controlled by TDM controller 225 . Correspondingly, the IF down-converter 223 down-converts the received IF signal in TDM mode (TDMmanner). The result of the down conversion is stored in buffer 229 .

FIG. 4A is a schematic diagram of the basic structure of a general NCO 28 according to an embodiment of the present invention. FIG. 4B is a schematic diagram of a simulated waveform (waveform) and a real mapping table (mappingtruetable) of the NCO 28 according to an embodiment of the present invention. Each of the local oscillators 228 described in the embodiments of the present invention can be realized by an NCO28. Any other suitable oscillator may also be used in the present invention. The NCO 28 includes: an adder 281 , a holding register (holding register) 283 , a cosine mapping unit (COS map unit, hereinafter referred to as the COS mapping unit) 285 , and a sine mapping unit (SIN map unit, hereinafter referred to as the SIN mapping unit) 287 . The clock clkfs is fed to the holding register 283 to determine the frequency of the NCO 28 . The adder 281 performs phase accumulation according to the clock rate of the clock clkfs. The accumulation result (ie, NCO phase) is fed back for the next accumulation. The accumulated output is transmitted to the COS mapping unit 285 or the SIN mapping unit 287 for performing a look-up table (LUT) operation, thereby outputting a simulated cosine wave or sine wave. By controlling the accumulation step in adder 281, the output frequency can be adjusted. Figure 4B shows a simple example of simulated waveforms and real mapping tables used in LUT operation.

For example, in the embodiment shown in FIG. 3 , the IF processing engine 220 includes three local oscillators 228 . Fig. 5 is a schematic diagram of a TDM scheduling mechanism according to an embodiment of the present invention. The top row in FIG. 5 represents the time slot (timeslot) scheduling of the multiplexer 224 controlled by the TDM controller 225 , that is, TDM scheduling. The second row represents the received IF signal. The third row represents multiple carriers LO ₀ , LO ₁ , LO ₂ generated by multiple local oscillators 228 respectively. The bottom row in FIG. 5 shows the spread spectrum signal (IFremoved spread spectrum signal) stored in the buffer 229 with the IF carrier removed. As shown in Figure 5, the time slots are allocated as IF ₀ , IF ₁ , IF ₂ . For time t=i, in time slot IF ₀ , carrier LO ₀ is mixed with IF signal i to produce segment SSS _i,0 of the spread spectrum signal from which the IF carrier has been removed; in time slot IF ₁ , carrier LO ₁ is mixed with IF signal i to generate segment SSS _i,1 of the spread spectrum signal with IF carrier removed; in time slot IF ₂ , carrier LO ₂ is mixed with IF signal i to generate IF carrier removed The segment SSS _{i, 2} of the spread spectrum signal; for time t=i+1, t=i+2..., the scheduling method is the same as above.

In this embodiment, each block in the IF processing engine 220 operates at three times the frequency of the IF signal. That is, in FIG. 2 , the IF processing engine 220 operates at three times the sampling rate of the RF front end 212 . Three samples of each sinusoidal waveform having different frequencies are mixed with data samples of the received IF signal during one sampling period. After mixing, the spread spectrum signal from which the IF carrier has been removed is stored in buffer 229 (as shown in FIG. 3 ), and then passed to modules that will perform subsequent processing, such as correlator engine 230 and processing device 250.

FIG. 6 is a schematic diagram of an IF processing engine 620 according to another embodiment of the present invention. The IF processing engine 620 in this embodiment includes: an IF down-converter 623 , a TDM controller 625 , a phase latch 626 , a local oscillator 628 , and a buffer 629 . It can be seen from FIG. 6 that the local oscillator unit of the IF processing engine 620 only includes a single local oscillator 628 . The local oscillator 628 is implemented by an NCO. Since the state of the NCO can be easily stored by latching the accumulation result (i.e., the NCO phase), multiple NCOs used in the embodiment shown in FIG. substitute. The phase latch 626 controlled by the TDM controller 625 latches the NCO phase of each carrier, so a single local oscillator 628 can generate multiple carriers with different frequencies in TDM mode.

FIG. 7 is a schematic diagram of an IF processing engine 720 according to another embodiment of the present invention. The IF processing engine 720 is similar to the IF processing engine 220 shown in FIG. 3 , and elements with the same names have similar functions, so descriptions of these elements are omitted here. The difference between the IF processing engine 720 and the IF processing engine 220 is that the IF processing engine 720 further includes: a digital filter bank (digital filter bank) 726, wherein the digital filter bank 726 includes a plurality of digital filters. A plurality of digital filters (not shown) in the digital filter bank 726 are used to respectively filter out the noise of the baseband signal (ie, the spread spectrum signal from which the IF carrier has been removed), so as to improve the signal performance. Wherein, the baseband signal is obtained by down-converting different IF signals through the IF down-converter 723 .

Since different IF signals with different carrier frequencies are downconverted to the same baseband, only one digital filter can be used. FIG. 8 is a schematic diagram of an IF processing engine 820 according to another embodiment of the present invention. The IF processing engine 820 is similar to the IF processing engine 720 shown in FIG. 7 . The only difference between the two is that the IF processing engine 820 uses a single digital filter 826 to filter out noise for each spread spectrum signal processed by the IF down-converter 823 with the IF carrier removed. In this embodiment, the function of the filter is related to its past state, so it is necessary to latch the state of the filter for each spread spectrum signal from which the IF carrier has been removed. Therefore, state latch 827 is used to latch the state of the filter for each spread spectrum signal from which the IF carrier has been removed.

Although the structure of the IF processing engine 720 and 820 shown in FIGS. 7 and 8 is similar to that of the IF processing engine 220 shown in FIG. A digital filter with state latch) can also be added to the structure of the IF processing engine 620 shown in FIG. 6 .

FIG. 9 is a flowchart of a method for removing multiple IF carriers with different frequencies from multiple IF signals in a GNSS receiver according to an embodiment of the present invention. As shown in FIG. 9, the method includes: generating a plurality of different carriers (that is, a plurality of carriers with different frequencies) (step S910); based on TDM scheduling, mixing each carrier with each IF signal to generate The signal segment with the IF carrier removed (step S920); and storing the signal segment with the IF carrier removed in a buffer (step 930). As described above, the spread spectrum signal from which the IF carrier has been removed is stored in a buffer to be passed to modules for subsequent processing, eg, a correlator engine and a processor, for further use.

Although the present invention has been disclosed above with specific implementations, it is not intended to limit the present invention. Any skilled person in the art can make some changes without departing from the scope of the present invention. Therefore, the protection scope of the present invention should be as follows: The scope defined by the claims shall prevail.

Claims (20)

1. an intermediate frequency process engine, for GNSS receiver, described intermediate frequency process engine comprises:

Local oscillator unit, produces multiple carrier waves with different frequency;

Multiplexer, connects described local oscillator unit and a time division multiplexing controller respectively, under the control of described time division multiplexing controller, once transmits in the described carrier wave of described local oscillator unit;

Intermediate frequency down converter, respectively by the described carrier frequency mixing that multiple intermediate-freuqncy signal and described local oscillator unit produce, produces multiple signal segment having removed intermediate frequency carrier;

Described time division multiplexing controller, each mixing operation of execution cost intermediate frequency down converter; And

Buffer, stores the described signal segment having removed intermediate frequency carrier that described intermediate frequency down converter produces.

2. intermediate frequency process engine according to claim 1, is characterized in that, described local oscillator unit comprises: multiple local oscillator, and each in described local oscillator produces one in described carrier wave.

3. intermediate frequency process engine according to claim 2, is characterized in that, each in described local oscillator is realized by digital controlled oscillator.

4. intermediate frequency process engine according to claim 1, is characterized in that, described local oscillator unit comprises single local oscillator.

5. intermediate frequency process engine according to claim 4, it is characterized in that, described single local oscillator is realized by digital controlled oscillator, wherein, described digital controlled oscillator, by accumulating multiple digital controlled oscillator phase place in different steps, produces the described carrier wave with different frequency.

6. intermediate frequency process engine according to claim 5, is characterized in that, comprise further: phase latch, latches the described digital controlled oscillator phase place accumulated.

7. intermediate frequency process engine according to claim 1, is characterized in that, comprise further: digital filter unit, the described noise having removed the signal segment of intermediate frequency carrier that intermediate frequency down converter described in filtering produces.

8. intermediate frequency process engine according to claim 7, it is characterized in that, described digital filter unit is realized by the digital filter bank comprising multiple digital filter, wherein, each in described digital filter is transferred in described buffer for the signal segment having removed intermediate frequency carrier described in only allowing and stores, wherein, the described signal segment having removed intermediate frequency carrier is by by described carrier wave and described intermediate-freuqncy signal mixing, down-conversion gets.

9. intermediate frequency process engine according to claim 7, it is characterized in that, described digital filter unit comprises: single digital filter, and described intermediate frequency process engine comprises further: status latch, latch the state of described single digital filter, store to make the signal segment having removed intermediate frequency carrier described in described single digital filter permission be transferred in described buffer, wherein, the described signal segment having removed intermediate frequency carrier is by by described carrier wave and described intermediate-freuqncy signal mixing, down-conversion gets respectively.

10. a GNSS receiver, comprises:

Radio-frequency front-end, down-converts to intermediate-freuqncy signal by radiofrequency signal;

Intermediate frequency process engine, receives and described in down-conversion, intermediate-freuqncy signal is baseband signal, and comprises;

Local oscillator unit, produces multiple carrier waves with different frequency;

Multiplexer, connects described local oscillator unit and time division multiplexing controller respectively, under the control of described time division multiplexing controller, once transmits in the described carrier wave of described local oscillator unit;

Intermediate frequency down converter, respectively by the described carrier frequency mixing that described intermediate-freuqncy signal and described local oscillator unit produce, produces multiple signal segment having removed intermediate frequency carrier;

Described time division multiplexing controller, each mixing operation of execution cost intermediate frequency down converter; And

Buffer, stores the described signal segment having removed intermediate frequency carrier that described intermediate frequency down converter produces; And

Correlator engine, carries out related operation by the code that described baseband signal and local code generator provide, to produce multiple correlated results.

11. GNSS receiver according to claim 10, is characterized in that, the operating rate of described intermediate frequency process engine is many times of radio-frequency front-end operating rate.

12. GNSS receiver according to claim 10, is characterized in that, described local oscillator unit comprises: multiple local oscillator, and each in described local oscillator produces one in described carrier wave.

13. GNSS receiver according to claim 12, is characterized in that, each in described local oscillator is realized by digital controlled oscillator.

14. GNSS receiver according to claim 10, is characterized in that, described local oscillator unit comprises single local oscillator.

15. GNSS receiver according to claim 14, it is characterized in that, described single local oscillator is realized by digital controlled oscillator, wherein, described digital controlled oscillator, by accumulating multiple digital controlled oscillator phase place in different step, produces the described carrier wave with different frequency.

16. GNSS receiver according to claim 15, is characterized in that, comprise further: phase latch, latch the described digital controlled oscillator phase place accumulated.

17. GNSS receiver according to claim 11, is characterized in that, comprise further: digital filter unit, the described noise having removed the signal segment of intermediate frequency carrier that intermediate frequency down converter described in filtering produces.

18. GNSS receiver according to claim 17, it is characterized in that, described digital filter unit is realized by the digital filter bank comprising multiple digital filter, wherein, each in described digital filter is transferred in described buffer for the signal segment having removed intermediate frequency carrier described in only allowing and stores, wherein, the described signal segment having removed intermediate frequency carrier is by by described carrier wave and described intermediate-freuqncy signal mixing, down-conversion gets.

19. GNSS receiver according to claim 17, it is characterized in that, described digital filter unit comprises: single digital filter, and described intermediate frequency process engine comprises further: status latch, latch the state of described single digital filter, store to make the signal segment having removed intermediate frequency carrier described in described single digital filter permission be transferred in described buffer, wherein, the described signal segment having removed intermediate frequency carrier is by by described carrier wave and described intermediate-freuqncy signal mixing, down-conversion gets respectively.

20. 1 kinds of intermediate frequency carrier removing methods, for GNSS receiver, multiple intermediate frequency carrier in intermediate-freuqncy signal with different frequency removed, described intermediate frequency carrier removing method comprises:

Produce multiple carrier waves with different frequency;

Based on time division multiplexing dispatching, control one that once transmits in described carrier wave;

Based on time division multiplexing dispatching, respectively by described carrier wave and described intermediate-freuqncy signal mixing, to produce the signal segment removing intermediate frequency carrier; And

The signal segment of intermediate frequency carrier has been removed described in storage.