Method and apparatus for efficient correlation detection
AssigneeMotorola, Inc.
InventorsRobert K. Schweickert, Mahibur Rahman, Christopher T. Thomas, Clinton C Powell, II
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Abstract
A full serial implementation of a M-level correlation based demodulator (100) includes a two's complement, pass-through, zero-out complex conjugate multiplier element (102), a boxcar filter (104) coupled to the multiplier element, a complex magnitude approximater element (106) coupled to the boxcar filter and a maximum value and index holding element (108). The multiplier element reuses common products along an M-level of cross-correlation to reduce multiplication functions at a rate 2 times M faster than a sampling rate at an input of the demodulator.
Claims21
A serial implementation of a M-level correlation based demodulator, comprising:
- a two's complement, pass-through, zero-out complex conjugate multiplier element providing a multiplier element output;
- a boxcar filter coupled to the multiplier element output, wherein the boxcar filter comprises:
- a differentiator coupled to and receiving the multiplier element output and providing a differentiator output, and
- an integrator coupled to and receiving the differentiator output and providing a boxcar filter output;
- a complex magnitude approximater element coupled to and receiving the boxcar filter output and providing a complex magnitude approximater element output;
- and
- a maximum value and index holding element coupled to and receiving the complex magnitude approximater element output.
A serial implementation of a M-level correlation based demodulator, comprising:
- a two's complement pass-through zero-out complex conjugate multiplier element providing a multiplier element output;
- a boxcar filter coupled to the multiplier element output, wherein the boxcar filter comprises:
- a differentiator coupled to and receiving the multiplier element output and providing a differentiator output, and
- an integrator coupled to and receiving the differentiator output and providing a box car filter output;
- a complex magnitude approximater element coupled to and receiving the boxcar filter output and providing a complex magnitude approximater element output;
- and
- a symbol generator coupled to and receiving the complex magnitude approximater element output.
A serial implementation of a M-level correlation based demodulator, comprising:
- a two's complement pass-through zero-out complex conjugate multiplier element, wherein the complex conjugate multiplier element comprises a counter output which is decoded to generate a 2 bit wide Q term and also a 90 degree phase offset is created to generate a 2 bit-wide I term;
- a boxcar filter coupled to the multiplier element;
- a complex magnitude approximater element coupled to the boxcar filter;
- and
- a symbol generator.
A serial implementation of a M-level correlation based demodulator, comprising:
- a two's complement pass-through zero-out complex conjugate multiplier element, wherein the complex conjugate multiplier element comprises a 3 stage tapped delay line coupled to a multiplexer to reduce the current drain by reducing a number of cycles required for the plus and minus frequency shift keying deviation operations of the complex conjugate multiplier;
- a boxcar filter coupled to the multiplier element;
- a complex magnitude approximater element coupled to the boxcar filter;
- and
- a symbol generator.
A serial implementation of a M-level correlation based demodulator, comprising:
- a complex conjugate multiplier element providing a multiplier element output;
- a boxcar filter coupled to the multiplier element output, wherein the boxcar filter comprises:
- a differentiator coupled to the multiplier element output for receiving an input and providing a differentiator output, and
- an integrator coupled to and receiving the differentiator output and for providing a boxcar filter output;
- a complex magnitude approximater element coupled to and receiving the boxcar filter output and for providing a complex magnitude approximater element output;
- and
- a symbol generator coupled to and receiving the complex magnitude approximater element output.
A serial implementation of a M-level correlation based demodulator, comprising:
- a complex conjugate multiplier element providing a multiplier element output;
- a boxcar filter coupled to the multiplier element output, wherein the boxcar filter comprises:
- a differentiator coupled to and receiving the multiplier element output and providing a differentiator output, and
- an integrator coupled to and receiving the differentiator output and providing a boxcar filter output;
- a complex magnitude approximater element coupled to and receiving the boxcar filter output wherein the approximater element approximates a complex magnitude of I and Q signals without multiplication elements and without square root elements to provide a complex magnitude approximater element output;
- and
- a maximum value and index holding element coupled to and receiving the complex magnitude approximater element output.
A serial implementation of a multiplierless M-level correlation based demodulator, comprising:
- a complex conjugate element providing a complex conjugate element output;
- a boxcar filter coupled to the complex conjugate element output, wherein the boxcar filter comprises:
- a differentiator coupled to and receiving the complex conjugate element output and providing a differentiator output, and
- an integrator coupled to and receiving the differentiator output and providing a boxcar filter output;
- a complex magnitude approximater element coupled to and receiving the boxcar filter output and providing a complex magnitude approximater element output;
- and
- a symbol generator coupled to and receiving the complex magnitude approximater output.
A method of performing correlation detection of M-level frequency shift keyed signals I and Q in a serial fashion, comprising the steps of:
- multiplying I and Q by the complex conjugate of an apriori known signal to provide a multiplied signal for each pair of I and Q samples at a rate of 2M faster than a sampling rate at a demodulator input;
- integrate the multiplied signal over a desired integration window L to provide an integrated signal for each pair of I and Q samples at a rate of 2M by:
- differentiating the multiplied signal to provide a differentiated multiplied signal, and
- integrating the differentiated multiplied signal to provide the integrated signal;
- compute the magnitude of the integrated signal for each pair of I and Q samples at a rate of M time faster than the sampling rate;
- and
- select as a detected symbol, a symbol corresponding to the integrated signal having the highest magnitude at each sampling instance at a rate M times faster than the sampling rate.
Dependencies are inferred from the claim text.