US 5,020,076 AGranted

Hybrid modulation apparatus

AssigneeMotorola, Inc.

InventorsStephen V. Cahill, Steven F. Gillig, Thomas J. Walczak

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Abstract

A .pi./4-shift DQPSK modulator modulates a digitized voice signal and other information. An FM modulator modulates the analog voice signal and other information. The FM modulator is coupled to the quadrature mixers (109 and 110) of the .pi./4-shift DQPSK modulator. When an FM modulated signal is required, the mixers (109 and 110) are biased (114) to allow carrier feedthrough by applying a fixed, non-zero DC signal to one or both mixers (109 and 110). The carrier is then FM modulated using conventional methods such as voltage-modulation of a phase locked loop (PPL) (113). When .pi./4-shift DQPSK is to be generated, the conventional baseband I and Q vector-length signals (101 and 102) are applied to the mixers (109 and 110), and the carrier is left unmodulated by switching (115) out the input signal to the PLL (113). The PPL (113) will then generate only the carrier frequency to be mixed with the I and Q vector-length signals (101 and 102).

Claims26

Dependent claims

A hybrid modulation apparatus, with a voice signal input, having at least a digital mode and an analog mode, the apparatus comprising:

(a) differential quadrature phase shift keying (DQPSK) means, coupled to the voice signal, for generating a .pi./4-shifted DQPSK signal in the digital mode, the means comprising:
an I vector source coupled to an I vector path;
and
a Q vector source coupled to a Q vector path;
(b) first mixing means having a first input, a second input, and an output, the first input coupled to the I vector path;
(c) second mixing means having a first input, a second input, and an output, the first input coupled to the Q vector path;
(d) offset oscillator means for generating a frequency modulated signal in the analog mode and a carrier frequency in the digital mode, the means having an output coupled to the second input of the first mixing means, and a modulation input;
(e) switching means having a first input coupled to the voice signal, a second input coupled to ground potential, and an output coupled to the modulation input of the offset oscillator means, the switching means coupling the voice signal to the offset oscillator means in the analog mode and the ground potential to the offset oscillator means in the digital mode;
(f) phase shifting means having an input and an output, the input coupled to the output of the offset oscillator means and the output coupled to the second input of the second mixing means;
(g) control means coupled to the first input of the first mixing means, for enabling the analog mode;
and
(h) combining means, having an output, for combining the outputs of the first and second mixing means, the combining means output is an output of the hybrid modulation apparatus.

9 more elements

A hydrid modulation apparatus, with a voice signal input, having at least a digital mode and an analog mode, the apparatus comprising:

(a) differential quadrature phase shift keying (DQPSK) means, coupled to the voice signal, for generating a .pi./4-shifted DQPSK signal in the digital mode, the means comprising:
an I vector source coupled to an I vector path;
and
a Q vector source coupled to a Q vector path;
(b) first mixing means having a first input, a second input, and an output, the first input coupled to the I vector path;
(c) second mixing means having a first input, a second input, and an output, the first input coupled to the Q vector path;
(d) offset oscillator means for generating a frequency modulated signal in the analog mode and a carrier frequency in the digital mode, the means having an output coupled to the second input of the first mixing means, and a modulation input;
(e) switching means having a first input coupled to the voice signal, a second input coupled to ground potential, and an output coupled to the modulation input of the offset oscillator means, the switching means coupling the voice signal to the offset oscillator means in the analog mode and the ground potential to the offset oscillator means in the digital mode;
(f) phase shifting means having an output and an input, the input coupled to the output of the offset oscillator means and the output coupled to the second input of the second mixing means;
(g) control means coupled to the first input of the second mixing means, for enabling the analog mode;
and
(h) combining means, having an output, for combining the outputs of the first and second mixing means, the combining means output is an output of the hybrid modulation apparatus.

9 more elements

A hybrid modulation apparatus, with a voice signal input, having at least a digital mode and an analog mode, the apparatus comprising:

(a) differential quadrature phase shift keying (DQPSK) means, coupled to the voice signal, for generating a .pi./4-shifted DQPSK signal in the digital mode, the means comprising:
an I vector source coupled to an I vector path;
and
a Q vector source coupled to a Q vector path;
(b) first mixing means having a first input, a second input, and an output, the first input coupled to the I vector path;
(c) second mixing means having a first input, a second input, and an output, the first input coupled to the Q vector path;
and
(d) offset oscillator means for generating a frequency modulated signal in the analog mode and a carrier frequency in the digital mode, the means having an output coupled to the second input of the first mixing means, and a modulation input;
(e) switching means having a first input coupled to the voice signal, a second input coupled to ground potential, and an output coupled to the modulation input of the offset oscillator means, the switching means coupling the voice signal to the offset oscillator means in the analog mode and the ground potential to the offset oscillator means in the digital mode;
(f) phase shifting means having an output and an input, the input coupled to the output of the offset oscillator means and the output coupled to the second input of the second mixing means;
(g) control means coupled to the first input of the first and the second mixing means, for enabling the analog mode;
and
(h) combining means, having an output, for combining the outputs of the first and second mixing means, the combining means output is an output of the hybrid modulation apparatus.

10 more elements

A hybrid modulation apparatus having at least a digital mode and an analog mode, comprising:

(a) differential quadrature phase shift keying (DQPSK) means for generating a .pi./4-shifted DQPSK signal in the digital mode, the means comprising:
an I vector source coupled to an I vector path;
a Q vector source coupled to a Q vector path;
(b) first mixing means having a first input, a second input, a third input, a fourth input, and an output, the first input coupled to the I vector path;
(c) second mixing means having a first input, a second input, a third input, a fourth input, and an output, the first input coupled to the Q vector path;
and
(d) offset oscillator means for generating a frequency modulated signal in the analog mode and a carrier frequency in the digital mode, the means having an output coupled to the second input of the first mixing means, and a modulation input;
(e) switching means having a first input coupled to the voice signal, a second input coupled to ground potential, and an output coupled to the modulation input of the offset oscillator means, the switching means coupling the voice signal to the offset oscillator means in the analog mode and the ground potential to the offset oscillator means in the digital mode;
(f) phase shifting means having an output and an input, the input coupled to the output of the offset oscillator means and the output coupled to the second input of the second mixing means;
(g) control means coupled to the third and fourth inputs of at least one of the mixing means, for enabling the analog mode;
and
(h) combining means, having an output, for combining the outputs of the first and second mixing means, the combining means output is an output of the hybrid modulation apparatus.

9 more elements

Dependencies are inferred from the claim text.