Phase coherent TDMA quadrature receiver for multipath fading channels

Claim 2

A time division multiple access (TDMA) radio system receiver utilizing a synchronizing sequence in an assigned timeslot of message data to adapt a multi-phase demodulator to the finite impulse response of a radio channel during the assigned timeslot, characterized by: means for correlating a first phase of a received synchronizing sequence to a predetermined sequence to produce a first correlator signal; means for correlating a second phase of said received synchronizing sequence to said predetermined sequence to produce a second correlator signal; and means for demodulating received message data into at least first phase data and second phase data by correlating a first phase of received message data and a second phase of received message data with said first correlator signal and said second correlator signal and combining the resulting outputs of correlation.

Claim 3

A time division multiple access (TDMA) radio system receiver in accordance with claim 1 wherein the synchronizing sequence is further characterized by a binary phase shift keying (BPSK) signal.

Claim 4

A time division multiple access (TDMA) radio system receiver in accordance with claim 1 wherein said means for demodulating is further characterized by: first means for correlating said first phase of received message data with said first correlator signal and said second correlator signal to produce first and second weighted signals, respectively; second means for correlating said second phase of received message data with said first correlator signal and said second correlator signal to produce third and fourth weighted signals, respectively; and means for adding said first and fourth weighted signals and for subtracting said second weighted signal from said third weighted signal.

Claim 5

A time division multiple access (TDMA) radio receiver demodulator which demodulates from a radio channel a multipath-impaired quadrature phase shift keying (QPSK) data signal including a predetermined acquisition sequence and a message in a TDMA timeslot, the radio receiver demodulator characterized by: means for separating a received data signal into quadrature phase components; means for detecting the predetermined acquisition sequence from said quadrature phase components of said received data signal; means, responsive to said detected acquisition sequence, for synthesizing at least one multipath profile of the radio channel for each quadrature phase component of the received data signal; means, responsive to each multipath profile, for performing multipath correlation of the message in each quadrature phase component to produce pairs of a multipath correlated message for each quadrature phase component; and means for summing mutually exclusive pairs of said multipath correlated message.

Claim 6

A time division multiple access (TDMA) radio receiver demodulator which demodulates from a radio channel a multipath-impaired quadrature phase shift keying (QPSK) data signal including a predetermined acquisition sequence and a message in a TDMA timeslot, the radio receiver demodulator characterized by: means for separating a received data signal into quadrature phase components; means for detecting the predetermined acquisition sequence from said quadrature phase components of said received data signal; means, responsive to said detected acquisition sequence, for synthesizing at least one multipath profile of the radio channel for each quadrature phase component of the received data signal; means, responsive to each multipath profile, for performing multipath correlation of the message in each quadrature phase component to produce pairs of a multipath correlated message for each quadrature phase component; and means for summing mutually exclusive pairs of said multipath correlated message.

Claim 7

A time division multiple access (TDMA) radio receiver demodulator in accordance with claim 4 wherein the predetermined acquisition sequence is further characterized by a binary phase shift keying (BPSK) signal.

Claim 8

A digital radio receiver which receives and demodulates a time division multi-phase modulated data signal having multiple copies introduced by multipath signal interference on a radio channel, the data signal having a synchronizing signal portion and a message signal portion, the digital radio receiver characterized by: (a) means for separating a received data signal into first and second intermediate signals, each said first and second intermediate signal having a synchronizing signal portion and a message signal portion; (b) means for detecting a received synchronizing signal, further comprising: (1) means for correlating said first intermediate signal synchronizing signal portion to a predetermined signal to produce a first correlator signal, and (2) means for correlating said second intermediate signal synchronizing signal portion to said predetermined signal to produce a second correlator signal; and (c) means for demodulating a received message signal with the multiple copies compensated, further comprising: (1) means for correlating said first intermediate signal message signal portion with said first correlator signal to produce a first weighted signal, (2) means for correlating said first intermediate signal message signal portion with said second correlator signal to produce a second weighted signal, (3) means for correlating said second intermediate signal message signal portion with said first correlator signal to produce a third weighted signal, (4) means for correlating said second intermediate signal message signal portion with said second correlator signal to produce a fourth weighted signal, (5) means for adding said first weighted signal and said fourth weighted signal to produce a demodulated first phase of the multi-phase modulated signal, and (6) means for subtracting said second weighted signal from said third weighted signal to produce a demodulated second phase of the multi-phase modulated signal.

Claim 9

A digital radio receiver which receives and demodulates a time division multi-phase modulated data signal having multiple copies introduced by multipath signal interference on a radio channel, the data signal having a synchronizing signal portion and a message signal portion, the digital radio receiver characterized by: (a) means for separating a received data signal into first and second intermediate signals, each said first and second intermediate signal having a synchronizing signal portion and a message signal portion; (b) means for detecting a received synchronizing signal, further comprising: (1) means for correlating said first intermediate signal synchronizing signal portion to a predetermined signal to produce a first correlator signal, and (2) means for correlating said second intermediate signal synchronizing signal portion to said predetermined signal to produce a second correlator signal; and (c) means for demodulating a received message signal with the multiple copies compensated, further comprising: (1) means for correlating said first intermediate signal message signal portion with said first correlator signal to produce a first weighted signal, (2) means for correlating said first intermediate signal message signal portion with said second correlator signal to produce a second weighted signal, (3) means for correlating said second intermediate signal message signal portion with said first correlator signal to produce a third weighted signal, (4) means for correlating said second intermediate signal message signal portion with said second correlator signal to produce a fourth weighted signal, (5) means for adding said first weighted signal and said fourth weighted signal to produce a demodulated first phase of the multi-phase modulated signal, and (6) means for subtracting said second weighted signal from said third weighted signal to produce a demodulated second phase of the multi-phase modulated signal.

Claim 12

A method in accordance with the method of claim 7 wherein said demodulating step is further characterized by the steps of: correlating said first phase of received message data with said first correlator signal and said second correlator signal to produce first and second weighted signals, respectively; correlating said second phase of received message data with said first correlator signal and said second correlator signal to produce third and fourth weighted signals, respectively; and adding said first and fourth weighted signals and subtracting said second weighted signal from said third weighted signal.