Digital demodulator arrangement for quadrature signals

Claim 1

A radio receiver having a first signal path in which a signal is mixed with a local oscillator frequency running at the main transmission frequency and then filtered to give a first mixed signal defined as an in-phase signal (I), a second signal path in which the received signal is mixed with the local oscillator frequency but with a relative phase shift and then filtered to give a second mixed signal defined as a quadrature signal (Q), characterised in that each signal path includes analogue-to-digital conversion means whereby the I and Q signals are converted into pulse density modulated (PDM) digital data streams respectively, the receiver also including a logic means to which the outputs of the PDM streams are applied, whereby the logic means output is a demodulation of the digital signals.

Claim 5

A method of demodulating quadrature signals formed in a zero I.F. or direct conversion radio receiver characterised in that the quadrature signals are each analogue-to-digital converted into respective pulse density modulated digital data streams, the data streams being applied to a logic means arranged to process the signals according to a predetermined table of input logic conditions.

Claim 6

A method of demodulating quadrature signals formed in a zero I.F. or direct conversion radio receiver characterised in that the quadrature signals are each analogue-to-digital converted into respective pulse density modulated digital data streams, the data streams being applied to a logic means arranged to process the signals according to a predetermined table of input logic conditions.