WHAT IS CLAIMED IS:

1. A demodulator for a quadrature partial response (QPR) signal of the form M_{;}(t) * sin(ω_{c}t) + M_{q}(t) * cos(ω_{c}t), where Mj(t) and M_{q}(t) are encoded partial response information modulations of the inphase and quadrature phases of a carrier of frequency (ω_{c}t), said demodulator comprising:

means for decoding a data clock from the QPR signal and for generating a recovered data clock signal;

means for generating a demodulating carrier of frequency (ω_{c}t) with inphase and quadrature phases coherent with the QPR signal carrier;

first means for mixing the QPR signal with the inphase phase of said demodulating carrier, said first mixing means generating a cunent as a function of time including the component Mj(t);

means for determining whether M_{;}(t) is positive or negative at a sampling time determined by said recovered data clock signal;

means for generating a digital output depending upon the sign determination of M;(t) where said digital output is one state if Mj(t) is positive and the other state if negative;

means for subtracting an amount of cunent equivalent to the previous state of said digital output generating means from the output of said first mixing means;

second means for mixing the QPR signal with the quadrature phase of said demodulating carrier, said second mixing means generating a cunent as a function of time including the component M_{q}(t);

means for determining whether M_{q}(t) is positive or negative at a sampling time determined by said recovered data clock signal;

means for generating a digital output depending upon the sign determination of M_{q}(t) where said digital output is one state if M_{q}(t) is positive and the other state if negative; and

means for subtracting an amount of cunent equivalent to the previous state of said digital output generating means from the output of said second mixing means.

2. A QPR demodulator as set forth in Claim 1 wherein said first mixing means generates a cunent including a first component signal including M_{;}(t) and

SUBSTITUTE SHEET cos(2ω-t) and wherein said second mixing means generates a cunent including a second component signal including M_{q}(t) and cos(2ω_{c}t) which further includes:

means for filtering M;(t) from said first component signal; and

means for filtering M_{q}(t) from said second component signal.

3. A QPR demodulator as set forth in Claim 2 wherein:

said means for filtering said first component signal includes a cunent to voltage converter; and

said means for filtering said second component signal includes a cunent to voltage converter.

4. A QPR demodulator as set forth in Claim 3 wherein:

said first digital output generating means includes an analog to digital converter for converting the analog voltage level of Mj(t) to a first digital signal having two logic states; and

said second digital output generating means includes an analog to digital converter for converting the analog voltage level of M_{q}(t) to a second digital signal having two logic states.

5. A QPR demodulator as set forth in Claim 4 wherein:

said first subtracting means further includes means for converting said first digital signal to an analog cunent signal having two cunent levels conesponding to the states of the digital signal; and

said second subtracting means further includes means for converting said second digital signal to an analog cunent signal having two cunent levels conesponding to the states of the digital signal.

6. A QPR demodulator as set forth in Claim 5 wherein said first subtracting means further comprises:

a cunent source adapted to supplying a cunent level +i to a cunent combination node;

a cunent source adapted to subtract a cunent level -2i from said combination node; and

means for switching, coupled between said combination node and said cunent sink, having a control terminal coupled to said first digital signal, said switching means coupling said cunent sink to said combination node for one state of the first digital signal and decoupling said cunent sink from said combination node for the other state of the first digital signal, whereby a cunent level of -Hi is supplied to said combination node for one state of said first digital signal and a cunent level of -i is subtracted from said combination node for the other state of said first digital signal.

7. A QPR demodulator as set forth in Claim 5 wherein said second subtracting means further comprises:

a cunent source adapted to supply a cunent -Hi to a combination node;

a cunent source adapted to subtract a cunent level -2i from said the combination node; and

means for switching, coupled between said combination node and said cunent sink, having a control terminal coupled to said second digital signal, said switching means coupling said cunent sink to said combination node for one state of the second digital signal and decoupling said cunent sink from said combination node for the other state of the second digital signal, whereby a cunent level of -Hi is supplied to said combination node for one state of said second digital signal and a cunent level of -i is subtracted from said combination node for the other state of said second digital signal.

8. A QPR demodulator as set forth in Claim 3 wherein said cunent to voltage converter comprises;

an impedance coupled between a voltage source and said cunent combination node; and

a voltage to voltage converter having a relatively high input impedance which is coupled to said node.

9. A QPR demodulator as set forth in Claim 8 wherein said voltage to voltage converter includes:

an NPN transistor configured as an emitter follower having its base coupled to the combination node and its emitter coupled to ground through an emitter impedance, wherein said voltage signal is output from the junction between the emitter terminal of said transistor and said emitter impedance.