US 4,149,121 AGranted

Four phase to two phase correlator

AssigneeNCR Corporation

InventorsRobert S. Gordy, David E. Sanders, Ramon P. Chambers

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Abstract

A four phase to two phase correlator is incorporated within the demodulator section of a spread spectrum modem to process a received RF signal modulated by a transmitted PN code and a digital data signal. The correlator includes a first modulator for combining the channel 1 and channel 2 R code signals with the received RF input signal to generate a first channel 1 RF signal and a first channel 2 RF signal. The first channel 1 RF signal is modulated by the transmitted PN code signal, the channel 1 R code signal and the digital data signal. The first channel 2 RF signal is modulated by the transmitted PN code signal, the channel 2 R code signal and the digital data signal. A second modulator combines the channel 1 and channel 2 PN code signals and the channel 1 and channel 2 R code signals with a first unmodulated RF signal to generate a second channel 1 RF signal which is modulated by the channel 1 PN code signal and by the channel 1 R code signal, and a second channel 2 RF signal which is modulated by the channel 2 PN code signal by the channel 2 R code signal. A third modulator combines both channels of the first and second RF signals to generate a third RF signal which is modulated only by the digital data signal.

Claims14

Dependent claims

A four phase to two phase correlator for processing a received RF signal modulated by a transmitted PN code and a digital data signal, said correlator being adaptable for use within a modem having means for generating a channel 1 PN code signal, a channel 1 R code signal, a channel 2 PN code signal, and a channel 2 R code signal, said modem also including means for generating first and second unmodulated RF signals, said correlator comprising in combination:

(a) first modulator means connected to receive said RF signal, and to receive said channel 1 and channel 2 R code signals, for modulating said received RF signal with said channel 1 R code signal and with said channel 2 R code signal to generate a first channel 1 RF signal and a first channel 2 RF signal respectively, the first channel 1 RF signal being modulated by the transmitted PN code signal, the channel 1 R code signal and the digital data signal, and the first channel 2 RF signal being modulated by the transmitted PN code signal, the channel 2 R code signal and the digital data signal;
(b) second modulator means connected to receive said channel 1 and channel 2 R code signals, said first unmodulated RF signal, and to receive said channel 1 and channel 2 PN code signals, said second modulator means modulating said first unmodulated RF signal to generate a second channel 1 RF signal modulated by the channel 1 PN code signal and by the channel 1 R code signal and a second channel 2 RF signal modulated by the channel 2 PN code signal and by the channel 2 R code signal;
and
(c) third modulator means connected to said first and second modulator means to receive said first and second channel 1 RF signals and said first and second channel 2 RF signals for combining said signals to generate a third RF signal modulated only by the digital data signal.

1 more element

A four phase to two phase correlator for use in the demodulator section of a modem for processing a received spread spectrum RF signal, said modem including means for generating channel 1 and channel 2 PN code signals, channel 1 and channel 2 R code signals, and first and second unmodulated RF signals, said correlator comprising:

(a) means for modulating said first unmodulated RF signal with said channel 1 R code signal to produce a channel 1 R code modulated RF signal;
(b) means for modulating said first unmodulated RF signal with said channel 2 R code signal to produce a channel 2 R code modulated RF signal;
(c) power divider means connected to receive said spread spectrum RF signal and to divide said signal into first and second component signals;
(d) means connected to receive said first component signal and to receive said channel 1 R code modulated RF signal to mix said signals and produce a first channel 1 RF signal;
(e) means connected to receive said second component signal and said channel 2 R code modulated RF signal to produce a first channel 2 RF signal;
(f) a first digital mixer means connected to receive said channel 1 PN and channel 1 R code signals to produce a channel 1 PN plus R code signal;
(g) a second digital mixer means connected to receive said channel 2 R code and channel 2 PN code signals to produce a channel 2 PN plus R code signal;
(h) means connected to receive said channel 1 PN plus R code signal and to receive said second unmodulated RF signal to produce a second channel 1 RF signal;
(i) means connected to receive said channel 2 PN plus R code signal and said second unmodulated RF signal to produce a second channel 2 RF signal;
(j) mixer means connected to receive said first channel 1 RF signal and said second channel 1 RF signal to produce a first mixer output signal;
(k) mixer means connected to receive said first channel 2 RF signal and said second channel 2 RF signal and produce a second mixer output signal;
(l) power combiner means connected to receive said first and second mixer output signals;
and
(m) band pass filter means connected to receive an output signal from said power combiner means, said filter having a center pass frequency different than the frequencies of said first and second unmodulated RF signals and different than the center frequency of said spread spectrum RF signal.

11 more elements

Dependencies are inferred from the claim text.