Multi-hypothesis combining circuit and multi-hypothesis combining method

Abstract

The invention provides a multi-hypothesis combining circuit. The multi-hypothesis combining circuit comprises a coherent combining circuit and a selecting circuit. The coherent combination circuit performs coherent combination according to a plurality of correlation operation outputs and a plurality of sign sequences so as to generate a plurality of coherent combination outputs, and the plurality of correlation operation outputs respectively correspond to a plurality of channels. And each coherent combination output in the plurality of coherent combination outputs is obtained from the plurality of correlation operation outputs and a sign sequence in the plurality of sign sequences. The selection circuit generates and outputs a combination output of the multi-hypothesis combination circuit according to the plurality of coherent combination outputs.

Description

TECHNICAL FIELD

[0001] The present invention relates to acquisition methods, and in particular to a method and apparatus for coherent combining of correlation outputs from multiple channels to produce a combined output for acquisition. BACKGROUND

[0002] Global navigation satellite systems (GNSS) are often described as "invisible utilities" that provide two basic services - time and position - accurately, reliably and inexpensively, and thus many aspects of the modern world depend on them. Each satellite of a GNSS is equipped with a high-precision atomic clock. When four or more satellites are in view, a GNSS receiver can measure the distance to each satellite by estimating the signal propagation time delay from each satellite to the receiver, and from these measurements, a GNSS-enabled device can derive its own position and synchronize to the precise GNSS system time.

[0003] GNSS satellite signals are modulated with pseudo random noise (PRN) codes, which are random sequences of 0s and Is. Each satellite transmits a unique PRN code, so GNSS receivers can identify any satellite by its unique PRN code. The unique PRN code is continuously repeated, and GNSS receivers can use a local copy of the unique PRN code to perform correlation operations with the received satellite signals to acquire the satellite. Increasing demand for location, navigation, and positioning services is driving the development of new GNSS specifications that will employ new signals and new modulations, such as data (i.e., navigation information) and pilot transmitted over different channels, and primary and secondary codes used as multiple spreading codes for a channel. However, during acquisition, GNSS receivers need to identify a satellite without any knowledge of the synchronization information (including secondary codes), so GNSS receivers need to perform a large number of computations to find correlation peaks in the acquisition space (defined by chip phase, Doppler frequency offset, and PRN code) to acquire a satellite. Therefore, there is a need for an innovative acquisition method that can exploit the correlation outputs of multiple channels to improve sensitivity. SUMMARY

[0004] One of the objects of the present application is to provide a method and apparatus for coherent combining of correlation outputs of multiple channels to produce a combined output for acquisition.

[0005] In one embodiment of the present application, a multiple hypothesis combining circuit is disclosed. The multiple hypothesis combining circuit includes a coherent combining circuit and a selection circuit. The coherent combining circuit is configured to coherently combine a plurality of correlation outputs and a plurality of sign sequences to produce a plurality of coherent combining outputs, wherein the plurality of correlation outputs respectively correspond to a plurality of channels, and each coherent combining output of the plurality of coherent combining outputs is derived from the plurality of correlation outputs and a sign sequence of the plurality of sign sequences. The selection circuit is configured to produce and output a combined output of the multiple hypothesis combining circuit based on the plurality of coherent combining outputs.

[0006] In one embodiment of the present application, a multi-hypothesis combining method is disclosed. The multi-hypothesis combining method comprises: performing coherent combining according to a plurality of correlation outputs and a plurality of sign sequences to generate a plurality of coherent combining outputs, wherein the plurality of correlation outputs respectively correspond to a plurality of channels, and each of the plurality of coherent combining outputs is derived from the plurality of correlation outputs and a sign sequence of the plurality of sign sequences; and generating and outputting a combining output according to the plurality of coherent combining outputs.

[0007] Compared to non-coherent combining (e.g., sum of absolute values of a plurality of complex correlation outputs or sum of squared absolute values of a plurality of complex correlation outputs) with non-coherent loss, the multi-hypothesis combiner design proposed in the present application can have higher sensitivity during acquisition with coherent combining (e.g., sum of a plurality of complex correlation outputs). In addition, the multi-hypothesis combiner design proposed in the present application is suitable for various global navigation satellite systems and can be used to coherently combine correlation outputs of any number of channels (e.g., 2 channels, 3 channels, or 4 channels). BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a block diagram of a multi-hypothesis combining circuit of an embodiment of the present application.

[0009] Figure 2 is a schematic diagram of a global navigation satellite system receiver using the multi-hypothesis combiner design proposed in the present application for acquisition.

[0010] Figure 3 is a schematic diagram of an implementation of a multi-hypothesis combining circuit of an embodiment of the present application.

[0011] Figure 4 is a schematic diagram of an E5a in-phase channel (data channel) format.

[0012] Figure 5 is a schematic diagram of an E5b in-phase channel (data channel) format.

[0013] Figure 6 is a schematic diagram of an E5a / E5b quadrature channel (pilot channel) format.

[0014] SYMBOL DESCRIPTION

[0015] 100, 204, 300: multi-hypothesis combining circuit

[0016] 102, 302: coherent combining circuit

[0017] 104, 304: selection circuit

[0018] 202_1, 202_2, 202_3, 202_4: correlator circuits

[0019] 206: non-coherent summation circuit

[0020] 306, 310: multiplier circuits

[0021] 308, 312: multi-tasker circuits

[0022] 314: hypothesis metric calculation circuit

[0023] 316: maximum value selection circuit

[0024] COR, , out_E5aI, out_E5aQ, out_E5bI, out_E5bQ: correlation operation outputs

[0025] : coherent combination output

[0026] combine_out: combination output

[0027] : maximum value

[0028] Different_Phase: phase difference DETAILED DESCRIPTION

[0029] Certain terms are used throughout the description and claims to refer to particular components. One skilled in the art will understand that the functions of these components can be combined or divided among several components. In addition, terms can be interchanged among the components. For example, "including" and "comprising" are used interchangeably. Furthermore, the term "coupled" and "coupling" are intended to mean either an indirect or direct electrical connection. Thus, if a first device couples to a second device, that connection can be through some other intermediate device (indirect), or that connection can directly connect the first device the second device (direct). Also, some of the components in the description and in the claims are optional unless otherwise explicitly recited.

[0030] Figure 1 is a block diagram of a multi-hypothesis combination circuit of an embodiment of the present application. The multi-hypothesis combination circuit 100 includes a coherent combination circuit 102 and a selection circuit 104. The coherent combination circuit 102 is configured to combine a plurality of correlation operation outputs , …, ( ) and a plurality of sign sequences , …, ) to produce a plurality of coherent combining outputs , …, The different sign sequences , …, correspond to different hypotheses, respectively. Each sign sequence ) comprises N sign values , …, , where , …, The correlation outputs , …, correspond to a plurality of channels, respectively. Each coherent combining output , …, is derived from a correlation output and a sign sequence , …, , for example, The selection circuit 104 is configured to generate and output a combining output combine_out of the multiple-hypothesis combiner 100 based on the coherent combining outputs , …,

[0031] For example, but not limited to, the multiple-hypothesis combiner 100 can be used in a GNSS receiver, however, this is only as an example and not as a limitation of the present application, in fact, any application using the multiple-hypothesis combiner design proposed by the present application falls within the scope of the present application.

[0032] Figure 2 is a schematic diagram of a GNSS receiver using the multiple-hypothesis combiner design proposed by the present application for acquisition. For better understanding of the technical features of the present application, the following assumes that the multiple-hypothesis combiner design proposed by the present application is applied to acquisition of Galileo E5 signals (including E5a signals and E5b signals). The E5a signal is transmitted through an E5a I-channel (which is a data channel) and an E5a Q-channel (which is a pilot channel). Similarly, the E5b signal is transmitted through an E5b I-channel (which is a data channel) and an E5b Q-channel (which is a pilot channel). As​​​Figure 2 As shown, the GNSS receiver includes four correlator circuits (labeled as "Corr 1", "Corr 2", "Corr 3" and "Corr 4") 202_1, 202_2, 202_3, 202_4, a multi-hypothesis combining circuit (labeled as "Multi-Hypothesis Comb") 204, and a non-coherent summation circuit (labeled as "Non-Coherent Summation") 206. The correlator circuit 202_1 receives an E5a baseband signal (in particular, an E5a-I baseband received signal), and performs correlation computation based on a local replica (primary code) of E5a-I with the E5a baseband signal to generate a correlation output out_E5al. The correlator circuit 202_2 receives an E5a baseband signal (in particular, an E5a-Q baseband received signal), and performs correlation computation based on a local replica (primary code) of E5a-Q with the E5a baseband signal to generate a correlation output out_E5aQ. The correlator circuit 202_3 receives an E5b baseband signal (in particular, an E5b-I baseband received signal), and performs correlation computation based on a local replica (primary code) of E5b-I with the E5b baseband signal to generate a correlation output out_E5bl. The correlator circuit 202_4 receives an E5b baseband signal (in particular, an E5b-Q baseband received signal), and performs correlation computation based on a local replica (primary code) of E5b-Q with the E5b baseband signal to generate a correlation output out_E5bQ.

[0033] The multi-hypothesis combining circuit 204 can be implemented based on the architecture of the multi-hypothesis combining circuit 100 as shown. The correlation outputs Figure 1 The correlation outputs The correlation outputs out_E5al, out_E5aQ, out_E5bl, out_E5bQ generated from the correlator circuits 202_1-202_4 can be used to obtain the correlation outputs

[0034] ​​​​​​​​The combined output `combine_out` generated by the multi-hypothesis combining circuit 204 can be the absolute value (or amplitude / norm) of the coherent combined output (which is a complex number), and can be further provided to the subsequent incoherent summing circuit 206 for incoherent integration. For example, a GNSS receiver can obtain one combined output `combine_out(k)` in each relevant computation unit time (e.g., 1 millisecond). Depending on the sensitivity requirements, the GNSS receiver can use the incoherent summing circuit 206 to accumulate K combined outputs `combine_out(k)` (i.e., ...). Since the focus of this invention is on the multi-hypothesis combination circuit 204, the operating principle of the incoherent summing circuit 206 is omitted here for the sake of simplicity. Further details regarding the multi-hypothesis combination circuit 204 will be explained below with reference to the drawings.

[0035] Figure 3 This is a schematic diagram illustrating the implementation of the multi-hypothesis combination circuit according to an embodiment of the present invention. Figure 2 The multi-hypothesis combination circuit 204 shown can utilize Figure 3 The multi-hypothesis combination circuit 300 shown is used for implementation. The implementation of the multi-hypothesis combination circuit 300 is at least partially based on Figure 1 The architecture of the multi-hypothesis combined circuit 100 is shown. (As shown...) Figure 3 As shown, the multi-hypothesis combination circuit 300 includes a coherent combination circuit 302 and a selection circuit 304, and also includes multiple multiplier circuits 306 and 310 and multiple multiplexer circuits 308 and 312. It should be noted that the multi-hypothesis combination circuit 300 can be modified appropriately to meet the requirements of different GNSS systems. For example, based on actual design considerations and / or actual GNSS system requirements, the multiplier circuits 306 and 310 and the multiplexer circuits 308 and 312 can be omitted. Furthermore, the number of related computation outputs used by the multi-hypothesis combination circuit 300 can be adjusted based on actual design considerations and / or actual GNSS system requirements.

[0036] Regarding the capture of the Galileo E5 signal in this embodiment, the correlation operation output out1 received by the coherent coupling circuit 302 is the same as the correlation operation output out_E5aI (that is, out1 = out_E5aI), and the correlation operation output out2 received by the coherent coupling circuit 302 is set to... The correlation operation output out3 received by the coherent coupling circuit 302 is directly set by the correlation operation output out_E5bI (i.e., out3 = out_E5bI), and the correlation operation output out4 received by the coherent coupling circuit 302 is set to... The multiplier circuit 306 is used to output the correlation operations of the pilot channel (i.e., the E5a quadrature channel). Multiply To produce the result of the multiplication operation. The multiplier circuit 310 is used to output the correlation operations of the pilot channel (i.e., the E5b quadrature channel). Multiply To produce the result of the multiplication operation. The multiplexer circuit 308 is used to select and output the multiplication result based on the phase difference Different_Phase between the data channel (i.e., the E5a coherent channel) and the pilot channel (i.e., the E5a quadrature channel). Related operation output One of them. The multiplexer circuit 312 is used to select and output the multiplication result based on the phase difference Different_Phase between the data channel (i.e., the E5b coherent channel) and the pilot channel (i.e., the E5b quadrature channel). Related operation output One of them. According to the Galileo E5 specification, there is a 90-degree phase difference between the data channel and the pilot channel. Therefore, the multiplexer circuit 308 will output the multiplication result under the control of Different_Phase=1. And the multitasking circuit 312, under the control of Different_Phase=1, will output the multiplication result. .

[0037] It is important to note that Figure 1 The multi-hypothesis combiner design proposed in this invention can be applied to more than one GNSS system. In some embodiments of this invention, the multi-hypothesis combiner design can be used to acquire Galileo E1 signals (including E1B and E1C signals). The E1B signal is used for data (navigation information) transmission and is transmitted through a data channel. The E1C signal is used for guidance transmission and is transmitted through a guidance channel. Since the data channel and the guidance channel are in phase, the multiplexer circuit (e.g., 308 or 312) outputs the correlation operation output of the guidance channel under the control of Different_Phase=0.

[0038] In this embodiment, the multi-hypothesis combiner is designed for Galileo E5 signal acquisition. The coherent combining circuit 302 produces multiple coherent combining outputs based on correlation operations ~ and different sign sequences (i.e., different hypotheses) . The satellite data is transmitted using a binary phase shift keying (BPSK) modulation scheme, so for BPSK modulation, the logical value "0" of the data, primary code and secondary code is converted to "+1", and for BPSK modulation, the logical value "1" of the data, primary code and secondary code is converted to "-1". The sign sequences test all possible data bits {+1, -1} and secondary code chips {+1, -1} of a primary code sequence (e.g., 10230 chips per millisecond) transmission. Figure 4 is a schematic diagram of the E5a in-phase channel (data channel) format, where a primary code (10230 chips) * data bit (+1 or -1) * secondary code (+1 or -1) is transmitted per millisecond. Figure 5 is a schematic diagram of the E5b in-phase channel (data channel) format, where a primary code (10230 chips) * data bit (+1 or -1) * secondary code (+1 or -1) is transmitted per millisecond. Figure 6 is a schematic diagram of the E5a / E5b quadrature channel (pilot channel) format, where a primary code (10230 chips) * secondary code (+1 or -1) is transmitted per millisecond.

[0039] Note that each correlation operation output ~ is based on a correlation operation of the primary code (10230 chips) per millisecond. For the E5a / E5b in-phase channel (data channel) signal, the actual data bit and secondary code during acquisition are unknown, so all possible values of data bit * secondary code {+1, -1} can be tested. Similarly, for the E5a / E5b quadrature channel (pilot channel) signal, the actual secondary code during acquisition is unknown, so all possible values of secondary code {+1, -1} can be tested.

[0040] For the correlation operation output of the E5a in-phase channel (data channel), the primary code * data bit * secondary code transmitted per millisecond can be or For the correlation operation output of the E5a quadrature channel (pilot channel), the primary code * secondary code transmitted per millisecond can be or (-1). For the correlation operation output of the E5b co-channel (data channel) , the primary code * data bit * secondary code transmitted within one millisecond can be or . For the correlation operation output of the E5b orthogonal channel (pilot channel) , the primary code * secondary code transmitted within one millisecond can be or . Therefore, the coherent combining circuit 302 is used to generate a plurality of coherent combining outputs , wherein and , .

[0041] In this embodiment, the selection circuit 304 includes a hypothesis metric value calculation circuit 314 and a maximum value selection circuit (labeled as "MAX") 316. The hypothesis metric value calculation circuit 314 is used to calculate the absolute value (or amplitude / norm) of the coherent combining output as the hypothesis metric value. Since , each hypothesis (sign sequence) has two possibilities, and the coherent combining circuit 302 only selects one of them for testing. The setting of the hypothesis (sign sequence) is shown in the following table.

[0042] Table 1

[0043]

[0044] Consider the case of combining 4 channels, where =(1,1,1,1), =(1,1,1,-1), =(1,1,-1,1), =(1,1,-1,-1), =(1,-1,1,1), =(1,-1,1,-1), =(1,-1,-1,1), and =(1,-1,-1,-1). As shown in Figure 4 , 8 coherent combining outputs can be generated by coherent combining, which are , , , , , , , Since those skilled in the art can easily understand the coherent combination outputs generated by using other settings of , , further description is omitted here for the sake of brevity.

[0045] For the embodiment shown in Figure 3 , all the relevant operation outputs ~ are combined coherently to improve sensitivity, however, this is only an example and not a limitation of the present application. In alternative designs, only two or three of the four relevant operation outputs ~ may be combined coherently to improve sensitivity. The same design concept can also be applied to other GNSS systems using multiple channels for data transmission and guidance transmission.

[0046] Consider the case of 3-channel combination, where =(1,1,1), =(1,1,-1), =(1,-1,1), and =(1,-1,-1). Four coherent combination outputs can be generated by coherent combination, respectively , , , . Since those skilled in the art can easily understand the coherent combination outputs generated by using other settings of ~ , further description is omitted here for the sake of brevity.

[0047] Consider the case of 2-channel combination, where =(1,1), and =(1,-1). Two coherent combination outputs can be generated by coherent combination, respectively , . Since those skilled in the art can easily understand the coherent combination outputs generated by using other settings of and , further description is omitted here for the sake of brevity.

[0048] Assuming that the metric value calculation circuit 314 is used to generate a plurality of coherent combination outputs (e.g. , , , , , , , ​​​a plurality of hypothesis metric values , , , , , , In this embodiment, the hypothesis metric value calculation circuit 314 calculates the absolute value (or amplitude / norm) of the coherent combining output (which is a complex number) as the hypothesis metric value of the coherent combining output. After generating the hypothesis metric value , the maximum value selection circuit 316 selects and outputs the maximum value from the hypothesis metric values as the combining output combine_out of the multiple hypothesis combiner 300 (i.e., , , , , , , , ).

[0049] Compared to non-coherent combining (e.g., the sum of the absolute values of a plurality of complex correlation operation outputs or the sum of the square of the absolute values of a plurality of complex correlation operation outputs) with non-coherent loss, the multiple hypothesis combiner design proposed in this disclosure can have higher sensitivity during acquisition with coherent combining (e.g., the sum of a plurality of complex correlation operation outputs). In addition, the multiple hypothesis combiner design proposed in this disclosure is applicable to various GNSS systems and can be used to coherently combine the correlation operation outputs of any number of channels (e.g., 2 channels, 3 channels, or 4 channels).

[0050] In some embodiments of this disclosure, the different channels include at least one data channel and at least one pilot channel on the Ll band, and each of these channels uses a primary code and a secondary code as a plurality of spreading codes. For example, the multiple hypothesis combiner design proposed in this disclosure is used to acquire Galileo ElB and ElC signals (2 channels).

[0051] In some embodiments of the application, the different channels include at least one data channel and at least one pilot channel on the L5 band, and each of these channels uses a primary code and a secondary code as a plurality of spreading codes. For example, a multi-hypothesis combiner design is presented in the application to acquire global positioning system (GPS) L5-I and L5-Q signals (2 channels). As another example, a multi-hypothesis combiner design is presented in the application to acquire Beidou B2a-I, B2a-Q, and B2b-I signals (3 channels), or a subset of Beidou B2a-I, B2a-Q, and B2b-I signals (2 channels). As another example, a multi-hypothesis combiner design is presented in the application to acquire Galileo E5a-I, E5a-Q, E5b-I, and E5b-Q signals (4 channels), or a subset of Galileo E5a-I, E5a-Q, E5b-I, and E5b-Q signals (2 channels or 3 channels).

[0052] In some embodiments of the application, the different channels include at least one data channel and at least one pilot channel on the L6 band, and each of these channels uses a primary code and a secondary code as a plurality of spreading codes. For example, a multi-hypothesis combiner design is presented in the application to acquire Galileo E6B and E6C signals (2 channels).

[0053] The above description is only the preferred embodiment of the application, any equivalent changes and modifications made within the scope of the application should be covered by the application.

Claims

1. A multi-hypothesis combination circuit, comprising: A coherent combining circuit is used to coherently combine multiple correlation operation outputs and multiple positive / negative sequence sequences to generate multiple coherently combined outputs, wherein the multiple correlation operation outputs correspond to multiple channels, and each of the multiple coherently combined outputs is derived from the multiple correlation operation outputs and the positive / negative sequence among the multiple positive / negative sequence sequences; and A circuit is selected to generate and output the combined output of the multiple hypothetical combined circuits based on the multiple coherent combined outputs.

2. The multi-hypothesis combination circuit as described in claim 1, wherein the selection circuit comprises: Assuming a metric calculation circuit is used to generate multiple hypothetical metric values ​​from the multiple coherently combined outputs; and A maximum value selection circuit is used to select and output the maximum value among the plurality of hypothetical metric values ​​as the combined output of the plurality of hypothetical combination circuit.

3. The multi-hypothesis combination circuit as described in claim 2, wherein each of the plurality of hypothesis metrics is an absolute value.

4. The multi-hypothesis combination circuit as claimed in claim 1, wherein the multi-hypothesis combination circuit is part of a global satellite navigation system receiver.

5. The multi-hypothesis combination circuit of claim 4, wherein the plurality of channels includes at least one data channel and at least one boot channel.

6. The multi-hypothesis combination circuit as described in claim 5, wherein the multi-hypothesis combination circuit receives the correlation operation output of the data channel and the correlation operation output of the pilot channel, and further comprises: A multiplier circuit is used to multiply the correlation operation output of the pilot channel by j to produce a multiplier output; and A multiplexer circuit is used to select and output one of the correlation operation outputs of the multiplier and the guidance channel as the correlation operation output among the plurality of correlation operation outputs, based on the phase difference between the data channel and the guidance channel.

7. The multi-hypothesis combination circuit of claim 5, wherein each of the plurality of channels uses a subcode as a spreading code among the plurality of spreading codes.

8. The multi-hypothesis combination circuit of claim 7, wherein the at least one data channel and the at least one pilot channel are both located in the L1 band.

9. The multi-hypothesis combination circuit of claim 7, wherein the at least one data channel and the at least one pilot channel are both located in the L5 band.

10. The multi-hypothesis combination circuit of claim 7, wherein the at least one data channel and the at least one pilot channel are both located in the L6 frequency band.

11. A multi-hypothesis combination method, comprising: Coherent combination is performed based on multiple correlation operation outputs and multiple positive and negative sign sequences to generate multiple coherently combined outputs, wherein the multiple correlation operation outputs correspond to multiple channels, and each of the multiple coherently combined outputs is derived from the multiple correlation operation outputs and the positive and negative sign sequence among the multiple positive and negative sign sequences; and A combined output is generated and output based on the multiple coherent combined outputs.

12. The multi-hypothesis combining method of claim 11, wherein the step of generating and outputting the combining output based on the plurality of coherent combining outputs comprises: Each of the multiple hypothetical metrics generated from the multiple coherently combined outputs; and The maximum value among the plurality of hypothetical metrics is selected and output as the combined output.

13. The multiple hypothesis combining method of claim 12, wherein each of the plurality of hypothesis measures is an absolute value.

14. The multiple hypothesis combining method as described in claim 11, wherein the multiple hypothesis combining method uses a global satellite navigation system receiver.

15. The multiple hypothesis combination method of claim 14, wherein the plurality of channels comprises at least one data channel and at least one boot channel.

16. The multiple hypothesis combining method as described in claim 15, further comprising: The related operation outputs of the received data channel and the related operation outputs of the pilot channel; Multiply the relevant operation output of the guiding channel by j to generate a multiplier output; and Based on the phase difference between the data channel and the pilot channel, one of the correlation operation outputs of the multiplier and the pilot channel is selected and output as the correlation operation output among the plurality of correlation operation outputs.

17. The multiple hypothesis combination method of claim 15, wherein each of the plurality of channels uses a subcode as a spreading code among the plurality of spreading codes.

18. The multiple hypothesis combination method of claim 17, wherein the at least one data channel and the at least one pilot channel are both located in the L1 band.

19. The multiple hypothesis combination method as described in claim 17, wherein both the at least one data channel and the at least one pilot channel are located in the L5 frequency band.

20. The multiple hypothesis combination method of claim 17, wherein the at least one data channel and the at least one pilot channel are both located in the L6 frequency band.

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