Asynchronous digital correlator and demodulators including a correlator of this type
First Claim
1. An asynchronous, digital correlator to correlate a binary reference signal (REF) with a complex signal formed by a first carrier and second carrier (I, Q), modulated by a pseudo-random function and by an M-ary orthogonal encoding, said two carriers being sampled and digitized, said correlator comprising:
- a multiplexer to transmit, alternately, a value (I) of the first carrier, and a value (Q) of the second carrier, with a period equal to half their sampling period;
a first digital filter adapted to the pseudo-random function (PN), comprising a chain of registers to store L consecutive bits of the reference signal (REF) and a chain of M correlation macro-cells receiving the sequence of multiplexed values of the first carrier and the second carrier (I and Q), each macro-cell computing the value (CPI0,..., CPI15) of a first function, called a partial correlation function, between N bits of the reference signal and N values of the first carrier (I), and then computing the value (CPQ0,..., CPQ15) of a second function, called a partial correlation function, between N bits of the reference signal and N values of the second carrier (Q), N being equal to L/M;
a second digital filter adapted to at least one of the M-ary encoding codes and having computation means to determine the value of at least one linear combination of the values of the first functions of partial correlation (CPI0,... CPI15); and
then to determine the value of a linear combination of the values of the second functions of partial correlation (CPQ0,..., CPQ15), the coefficients of the linear combination being unchanged and being equal to ±
1; and
having means to demultiplex the values of the two linear combinations (FIi, FQi), and to determine the modulus (Fi) of a vector having, as its components, the values of these two linear combinations (FIi, FQi).
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Accused Products
Abstract
A demodulator to demodulate a complex signal formed by two carriers, in quadrature, the spectrum of which is spread by a pseudo-random signal, and which are modulated by an M-ary, Walsh, code comprises:
a chain of registers to store 256 bits of a pseudo-random signal;
a multiplexer to temporally multiplex the processing of the two carriers;
a chain of correlation macro-cells having a systolic structure enabling temporal multiplexing and having intermediate outputs providing for partial correlation values on 16 chips;
a device for the computation of linear combinations of the functions of partial correlation, to compute two functions of correlation corresponding to two carriers for each M-ary code;
a demultiplexing and computation device to compute the module of the function of correlation for each of the Walsh codes which may modulate the signal to be demodulated;
a device for the selection of the greatest value of the correlation functions and for the selection of the corresponding piece of data.
173 Citations
6 Claims
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1. An asynchronous, digital correlator to correlate a binary reference signal (REF) with a complex signal formed by a first carrier and second carrier (I, Q), modulated by a pseudo-random function and by an M-ary orthogonal encoding, said two carriers being sampled and digitized, said correlator comprising:
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a multiplexer to transmit, alternately, a value (I) of the first carrier, and a value (Q) of the second carrier, with a period equal to half their sampling period; a first digital filter adapted to the pseudo-random function (PN), comprising a chain of registers to store L consecutive bits of the reference signal (REF) and a chain of M correlation macro-cells receiving the sequence of multiplexed values of the first carrier and the second carrier (I and Q), each macro-cell computing the value (CPI0,..., CPI15) of a first function, called a partial correlation function, between N bits of the reference signal and N values of the first carrier (I), and then computing the value (CPQ0,..., CPQ15) of a second function, called a partial correlation function, between N bits of the reference signal and N values of the second carrier (Q), N being equal to L/M; a second digital filter adapted to at least one of the M-ary encoding codes and having computation means to determine the value of at least one linear combination of the values of the first functions of partial correlation (CPI0,... CPI15); and
then to determine the value of a linear combination of the values of the second functions of partial correlation (CPQ0,..., CPQ15), the coefficients of the linear combination being unchanged and being equal to ±
1; and
having means to demultiplex the values of the two linear combinations (FIi, FQi), and to determine the modulus (Fi) of a vector having, as its components, the values of these two linear combinations (FIi, FQi). - View Dependent Claims (2, 3, 4, 5, 6)
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Specification