Hybrid modulation apparatus

• US 5,020,076 A
• Filed: 05/21/1990
• Issued: 05/28/1991
• Est. Priority Date: 05/21/1990
• Status: Expired due to Term

• Current Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Walczak, Thomas J., Gillig, Steven F., Cahill, Stephen V.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Chin, Stephen
• Application Number:
  US07/526,156
• Time in Patent Office: 372 Days
• Field of Search: 375/5, 375/44, 375/45, 375/39, 375/52, 375/104, 375/56, 455/218, 455/38, 332/100, 332/117, 332/125, 332/103, 379/93, 379/98, 340/825.44, 340/825.48
• US Class Current: 375/216
• CPC Class Codes: H04B 14/006 Angle modulation
• CPC Class Codes: H04L 27/2075 in which the data are represented by the change in carrier phase

Abstract

A π/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 π/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 π/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).

Claims

1. 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 π

/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.

2. The apparatus of claim 1 wherein the control means is a DC offset.

3. The apparatus of claim 1 wherein the control means is an offset current.

4. The apparatus of claim 1 wherein the phase shifting means is a 90°

phase shifter.

5. The apparatus of claim 1 wherein the I vector path contains at least one filter and a digital to analog converter.

6. The apparatus of claim 1 wherein the Q vector path contains at least one filter and a digital to analog converter.

7. 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 π

/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.

8. The apparatus of claim 7 wherein the control means is a DC offset.

9. The apparatus of claim 7 wherein the control means is an offset current.

10. The apparatus of claim 7 wherein the phase shifting means is a 90°

phase shifter.

11. The apparatus of claim 7 wherein the I vector path contains at least one filter and a digital to analog converter.

12. The apparatus of claim 7 wherein the Q vector path contains at least one filter and a digital to analog converter.

13. 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 π

/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.

14. The apparatus of claim 13 wherein the control means is an I and Q vector table that is input to the I and Q vector paths.

15. The apparatus of claim 13 wherein the control means is a DC offset.

16. The apparatus of claim 13 wherein the control means is an offset current.

17. The apparatus of claim 13 wherein the I vector path contains at least one filter and a digital to analog converter.

18. The apparatus of claim 13 wherein the Q vector path contains at least one filter and a digital to analog converter.

19. The apparatus of claim 13 wherein the phase shifting means is a 90°

phase shifter.

20. 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 π

/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.

21. The apparatus of claim 20 wherein the I vector path contains at least one filter and a digital to analog converter.

22. The apparatus of claim 20 wherein the Q vector path contains at least one filter and a digital to analog converter.

23. The apparatus of claim 20 wherein the phase shifting means is a 90°

phase shifter.

24. The apparatus of claim 20 wherein the control means is a DC offset.

25. A communications apparatus, comprising:

(a) receiving means; and

(b) transmitting means, comprising;

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

differential quadrature phase shift keying (DQPSK) means, coupled to the voice signal, for generating a π

/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;

first mixing means having a first input, a second input, and an output, the first input coupled to the I vector path;

second mixing means having a first input, a second input, and an output, the first input coupled to the Q vector path;

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;

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;

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;

control means coupled to the first input of the first mixing means, for enabling the analog mode; and

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.

26. A hybrid modulation apparatus, with a voice signal input, having at least two modes of operation, the apparatus comprising:

(a) first modulation means having an I source coupled to an I vector path, and a Q 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 a first mode and a carrier frequency in a second 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 first mode and the ground potential to the offset oscillator means in the second 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.