# US 2010/0166121 A1 · Methods and apparatus for receiver having fast walsh transform

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- Number: US 2010/0166121 A1
- Document ID: US20100166121A1
- Status: Published application
- Kind: A1
- Application number: 12/600,729
- Filed: 2008-06-19
- Published: 2010-07-01
- Earliest claimed: 2007-06-19
- Assignees: Raytheon Company
- Inventors: Lawrence M. Kenney, JR.
- Web page: https://patentgrep.com/patent/US20100166121A1

## CPC

- H04B 1/7093: Matched filter type
- H04B 2001/70935: {using a bank of matched fileters, e.g. Fast Hadamard Transform}
- H04B: TRANSMISSION

## Abstract

Methods and apparatus for correlating a receiving signal using a Fast Walsh Transform for efficient processing. In one embodiment, a Walsh encoded signal is received and then processing using a Fast Walsh Transform to generate outputs from which a largest one of the orthogonal sequences is selected.

## Claims

### Claim 1

A method, comprising:
receiving a complex valued Walsh encoded signal in the in-phase and quadrature channels of a linear receiver processor;
performing Fast Walsh Transform processing to generate estimates of a cross correlation of the received Walsh encoded signal with Walsh sequences separately in the in-phase and quadrature channels;
combining the estimates of the in-phase and quadrature channel data using a magnitude approximation;
selecting a first one of the data words from the combined estimates having a largest magnitude;
decoding the encoded signal using the selected first one of the data words; and
outputting the decoded signal.

### Claim 2 (depends on 1)

The method according to claim 1, further including using linear representations of the transmitted chip plus received noise as the input to the Walsh Transform processing.

### Claim 3 (depends on 1)

The method according to claim 1, further including using sixteen Walsh sequences for the Fast Walsh Transform processing.

### Claim 4 (depends on 1)

The method according to claim 1, further including performing the Fast Walsh Transform processing in a pipelined configuration.

### Claim 5 (depends on 4)

The method according to claim 4, further including accepting vectors of 16 input data samples and providing related results four epochs of 16 sample epochs later.

### Claim 6 (depends on 1)

The method according to claim 1, further including acceptance of new input data samples into the Fast Walsh Transform processing pipeline every sixteen sample epochs.

### Claim 7 (depends on 1)

The method according to claim 1, wherein the magnitude approximation includes a root-sum-square approximation.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the waveform includes at least one preamble symbols and Walsh encoded data symbols.

### Claim 9 (depends on 1)

The method according to claim 1, wherein the received signal is encoded four bits at a time with a 16-bit Walsh sequence.

### Claim 10

A system, comprising:
a receiver to receive a Walsh encoded input signal;
an in-phase Fast Walsh Transform module to generate in-phase data words by performing Fast Walsh Transform processing for generating estimates of cross correlation of the received Walsh encoded input signal with Walsh sequences;
a quadrature Fast Walsh Transform module to generate quadrature data words by performing Fast Walsh Transform processing for generating estimates of cross correlation of the received Walsh encoded input signal with Walsh sequences;
a magnitude module to combine the respective in-phase data words from the in-phase module and the quadrature data words from the quadrature module for providing magnitude information for the data words; and
a selection module to select a first one of the combined in-phase and quadrature data words having a greatest magnitude.

### Claim 11 (depends on 10)

The system according to claim 10, wherein the magnitude module includes a root-sum square module.

### Claim 12 (depends on 10)

The system according to claim 10, wherein the input signal is encoded four bits at a time with a 16-bit Walsh sequence.

### Claim 13 (depends on 12)

The system according to claim 12, wherein the Fast Walsh Transform processing is performed in a data-re-ordering stage and four stages of butterfly operations.