Method and apparatus for generating combination output for acquisition by coherently combining correlation outputs of multiple channels
A multi-hypothesis combination circuit includes a coherent combination circuit and a selection circuit. The coherent combination circuit generates a plurality of coherent combination outputs by performing coherent combination according to a plurality of correlation outputs and a plurality of sign sequences, wherein the plurality of correlation outputs correspond to a plurality of channels, respectively, and each of the plurality of coherent combination outputs is derived from the plurality of correlation outputs and one of 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.
1 . A multi-hypothesis combination circuit comprising:
a coherent combination circuit, arranged to generate a plurality of coherent combination outputs by performing coherent combination according to a plurality of correlation outputs and a plurality of sign sequences, wherein the plurality of correlation outputs correspond to a plurality of channels, respectively, and each of the plurality of coherent combination outputs is derived from the plurality of correlation outputs and one of the plurality of sign sequences; and
a selection circuit, arranged to generate and output a combination output of the multi-hypothesis combination circuit according to the plurality of coherent combination outputs.
2 . The multi-hypothesis combination circuit of claim 1 , wherein the selection circuit comprises:
a hypothesis metric value computation circuit, arranged to generate a plurality of hypothesis metric values of the plurality of coherent combination outputs, respectively; and
a maximum value selection circuit, arranged to select and output a maximum value among the plurality of hypothesis metric values as the combination output of the multi-hypothesis combination circuit.
3 . The multi-hypothesis combination circuit of claim 2 , wherein each of the plurality of hypothesis metric values is an absolute value.
4 . The multi-hypothesis combination circuit of claim 1 , wherein the multi-hypothesis combination circuit is a part of a global navigation satellite system (GNSS) receiver.
5 . The multi-hypothesis combination circuit of claim 4 , wherein the plurality of channels comprises at least one data channel and at least one pilot channel.
6 . The multi-hypothesis combination circuit of claim 5 , wherein the multi-hypothesis combination circuit receives a correlation output of a data channel and a correlation output of a pilot channel, and further comprises:
a multiplier circuit, arranged to multiply the correlation output of the pilot channel by √{square root over (− 1 )} to generate a multiplication result; and
a multiplexer circuit, arranged to select and output one of the multiplication result and the correlation output of the pilot channel as one of the plurality of correlation outputs according to a phase difference between the data channel and the pilot channel.
7 . The multi-hypothesis combination circuit of claim 5 , wherein each of the plurality of channels uses a secondary code as one 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 at an 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 at an 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 at an L6 band.
11 . A multi-hypothesis combination method comprising:
generating, by a coherent combination circuit, a plurality of coherent combination outputs by performing coherent combination according to a plurality of correlation outputs and a plurality of sign sequences, wherein the plurality of correlation outputs correspond to a plurality of channels, respectively, and each of the plurality of coherent combination outputs is derived from the plurality of correlation outputs and one of the plurality of sign sequences; and
generating and outputting a combination output according to the plurality of coherent combination outputs.
12 . The multi-hypothesis combination method of claim 11 , wherein generating and outputting the combination output according to the plurality of coherent combination outputs comprises:
generating a plurality of hypothesis metric values of the plurality of coherent combination outputs, respectively; and
selecting and outputting a maximum value among the plurality of hypothesis metric values as the combination output.
13 . The multi-hypothesis combination method of claim 12 , wherein each of the plurality of hypothesis metric values is an absolute value.
14 . The multi-hypothesis combination method of claim 11 , wherein the multi-hypothesis combination method is employed by a global navigation satellite system (GNSS) receiver.
15 . The multi-hypothesis combination method of claim 14 , wherein the plurality of channels comprises at least one data channel and at least one pilot channel.
16 . The multi-hypothesis combination method of claim 15 , further comprising:
receiving a correlation output of a data channel and a correlation output of a pilot channel;
multiplying the correlation output of the pilot channel by √{square root over (− 1 )} to generate a multiplication result; and
selecting and outputting one of the multiplication result and the correlation output of the pilot channel as one of the plurality of correlation outputs according to a phase difference between the data channel and the pilot channel.
17 . The multi-hypothesis combination method of claim 15 , wherein each of the plurality of channels uses a secondary code as one of spreading codes.
18 . The multi-hypothesis combination method of claim 17 , wherein the at least one data channel and the at least one pilot channel are at an L1 band.
19 . The multi-hypothesis combination method of claim 17 , wherein the at least one data channel and the at least one pilot channel are at an L5 band.
20 . The multi-hypothesis combination method of claim 17 , wherein the at least one data channel and the at least one pilot channel are at an L6 band.