Programmable matched filter searcher for multiple pilot searching

• US 6,480,529 B1
• Filed: 12/21/1999
• Issued: 11/12/2002
• Est. Priority Date: 12/21/1999
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Patrick, Christopher, Kang, Inyup, Sih, Gilbert C., Fevrier, Ian
• Primary Examiner(s): Ghayour, Mohammad H.
• Application Number:
  US09/468,556
• Time in Patent Office: 1,057 Days
• Field of Search: 375/152, 375/143, 375/343, 375/147, 375/136
• US Class Current: 375/152
• CPC Class Codes: G06F 17/15 Correlation function computation including computation of convolution operations arithmetic circuits for sum of products per se, e.g. multiply-accumulators G06F7/5443; digital filters, e.g. FIR, IIR, adaptive filters H03H17/00
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04B 2201/70711 with modular structure

Abstract

A novel and improved method and apparatus for searching is described. This searcher combines the ability to search multiple offsets of single pilots, such as those found in the IS-95 system, with the ability to search multiple pilots, such as those found in a GPS location determination system. Both types of searching can be done in a single architecture combining the parallel computation features of a matched filter with the flexibility of allowing a variable number of coherent accumulations and a variable number of non-coherent accumulations to be performed at high speed for a wide range of search hypotheses in a resource efficient manner. This invention allows for parallel use of the matched filter structure in a time-sliced manner to search multiple windows. In addition, the searcher allows for optional independent Walsh decovering for each search window. The time-sharing approach allows for optional frequency searching of any offset.

Claims

1. A programmable matched filter searcher comprising:

a shift register, operating as a single shift register when receiving a first type of data and operating as a multiple shift registers when receiving a second type of data, the first type of data being received from a single source and the second type of data being received from a plurality of sources;

a PN generator for generating PN sequences;

a despreader for receiving the PN sequences and the data from the shift register and for producing sets of despread values, the despreader concurrently receiving multiple PN sequences while despreading the second type of data;

a first set of summers for summing the sets of despread values from the despreader, for producing a complete sum when the data from the shift register are the second type of data, and for producing a partial sum when the data from the shift register are the first type of data; and

a second set of summers for receiving the partial sum from the first set of summers and producing a complete sum when the data from the shift register are the first type of data.

2. The programmable matched filter searcher of claim 1 wherein said sets of incoming data from said plurality of sources are received from a plurality of path processors, each of said path processors comprising:

a code doppler adjust block;

a frequency rotator; and

an optional decimator.

3. A programmable matched filter searcher comprising:

a first shift register, operating as a single shift register when receiving a first type of data and operating as a multiple shift registers when receiving a second type of data, for receiving sets of incoming in-phase(I) first or second type of data from one or a plurality of sources;

a second shift register, operating as a single shift register when receiving a first type of data and operating as a multiple shift registers when receiving a second type of data, for receiving sets of incoming quadrature (Q) first or second type of data from one or a plurality of sources;

a PN generator for generating PN sequences;

a matched filter having;

a despreader for receiving said sets of I data, said sets of Q data, and said PN sequences and for producing sets of despread I values and producing sets of despread Q values, the despreader concurrently receiving multiple PN sequences and producing distinct sets of despread I and Q values when receiving second type of data from the first and second shift registers;

a first set of summers for summing the sets of despread I and Q values from the despreader, for producing complete I and Q sums when the data from the first and second shift registers are the second type of data, and for producing partial I and Q sums when the data from the first and second shift registers are the first type of data;

a second set of summers for receiving the partial sums from the first set of summers and producing complete I and Q sums when the data from the shift registers are the first type of data

an I accumulator for receiving said complete I sums and accumulating them in sets to produce a set of accumulated I sums;

a Q accumulator for receiving said complete Q sums and accumulating them in sets to produce a set of accumulated Q sums;

an energy calculator for receiving sets of accumulated I sums and sets of accumulated Q sums, squaring respective ones of sets of accumulated I sums, squaring respective ones of sets of accumulated Q sums, and summing the results of said squares of respective ones of sets of I and Q sums to produce sets of energy values; and

outputs for providing said set of accumulated I sums and said set of accumulated Q sums prior to processing in said energy calculator.

4. The programmable matched filter searcher of claim 3 further comprising an accumulator for receiving said sets of energy values and producing sets of accumulations of ones of said sets of energy values.

5. The programmable matched filter searcher of claim 4 wherein:

I and Q PN sequences are produced by said PN generator; and

said despreader performs QPSK despreading.

6. The programmable matched filter searcher of claim 4 wherein said despreader performs BPSK despreading.

7. The programmable matched filter searcher of claim 4 further comprising a multiplexor for receiving multiple PN sequences and delivering them for time-sharing of said matched filter to produce additional sets of sums based on said multiple PN sequences.

8. The programmable matched filter searcher of claim 4 further comprising:

a multiplexor for receiving one or more phase values; and

I and Q rotators for receiving outputs said I and Q loadable matched filters and rotating said outputs according to the phase output of said multiplexor, and delivering the results to said I and Q accumulators.

9. A programmable matched filter searcher comprising:

a shift register, operating as a single shift register when receiving a first type of data and operating as a multiple shift registers when receiving a second type of data, the first type of data being received from a single source and the second type of data being received from a plurality of sources;

a plurality of PN generators for generating a plurality of PN sequences;

a loadable matched filter for loading said plurality of PN sequences, despreading said sets of incoming data and summing the intermediate results; and

an accumulator for receiving said sums and accumulating them in sets to produce a set of accumulated sums.

10. The programmable matched filter searcher of claim 9 wherein said loadable matched filter is configurable to receive a single PN sequence from one of said plurality of PN generators or a plurality of PN sequences from said plurality of PN generators.

11. A method for performing programmable matched filter searching comprising the steps of:

a) storing one set of I and Q data in a shift register if the data is a first type of data and storing a plurality of sets of I and Q data in the shift register if the data is a second type of data;

b) producing one or a plurality of PN sequences;

c) despreading the data with one PN sequence if the data are of the first type to produce a set of I and Q despread values and despreading the data with plurality of PN sequences if the data are of the second type to produce sets of I and Q despread values;

d) summing results of said despread I values;

e) summing results of said despread Q values;

f) accumulating the resultant summed despread I values to produce one or a plurality of results, respectively; and

g) accumulating the resultant summed despread Q values to produce one or a plurality of results, respectively.

12. The method of claim 11 further comprising the steps of:

i) squaring the accumulated despread I values;

j) squaring the accumulated despread Q values; and

k) summing both said squares.

13. The method of claim 12 further comprising the step l) of accumulating said sum of squares.

14. The method of claim 13 further comprising the step h) of providing as outputs said plurality of accumulated summed despread I and Q values calculated in said steps f) and g) when said plurality of sets of I and Q data are stored in said step a) and alternately proceeding to perform said steps i) through l) when said one set of I and Q data is stored in step a).