Four state phase shift modulator, in particular for amplitude modulation of two carriers in quadrature with a large number of states

• US 4,999,590 A
• Filed: 05/15/1990
• Issued: 03/12/1991
• Est. Priority Date: 10/21/1987
• Status: Expired due to Fees

• Current Assignee: Georges Verdot
• Original Assignee: Georges Verdot
• Inventors: Verdot, Georges
• Primary Examiner(s): GRIMM, SIEGFRIED H
• Application Number:
  US07/523,842
• Time in Patent Office: 301 Days
• Field of Search: 332/9 R, 332/16 R, 332/21, 332/22, 332/23 R, 332/31 R, 332/103-105, 375/39, 375/52, 375/53, 375/54, 375/67
• US Class Current: 332/104
• CPC Class Codes: H04L 27/2057 with a separate carrier for each phase state
• CPC Class Codes: H04L 27/362 Modulation using more than one carrier, e.g. with quadrature carriers, separately amplitude modulated H04L27/366 takes precedence

Abstract

A QPSK modulator has a signal generator which generates four carrier outputs having respective phases of 0°, 90°, 180°, and 270°. A four input phase selector is connected to the four outputs of the generator, has four modulator signal inputs, and has four phase shifted carrier outputs connected to an OR gate which provides the QPSK output signal. The generator comprises a source of signals in opposite phase coupled to two frequency dividers, each divider having two outputs of opposite phase. It also has two pairs of flip-flops whose outputs form the four outputs of the generator. The signal inputs of one pair of flip-flops are connected to the outputs of the first divider. The signal inputs of the other pair of flip-flops are connected to the outputs of the second divider. Variable capacitors are provided between the clock inputs of the flip-flops and ground. A 2²ⁿ QAM modulator can be formed with n QPSK modulators whose outputs are connected to the inputs of n attenuators followed by an adder.

Claims

1. A four state phase shift modulator comprising a high frequency signal generator provided with four outputs Q5 to Q8 generating signals with four different phases, each phase shifted by 90°

respectively, a four input phase selector connected to the four outputs of the generator and having four modulating signal inputs and four phase shifted carrier outputs, the generator having a source of signals providing first and second outputs with opposing phases, two frequency dividers each having two outputs in opposing phases and each having a clock input, the clock input of the first divider being connected to the first output of the source of signals and the clock input of the second divider being connected to the second output of the source of signals, two pairs of flip-flops whose outputs make up the four outputs of the generator, the clock inputs of the first pair of flip-flops being connected to the first output of the source of signals and the clock inputs of the second pair of flip-flops being connected to the second output of the source of signals, the signal inputs of the first pair of flip-flops being connected to the outputs of the first divider and the signal inputs of the second pair of flip-flops being connected to the outputs of the second divider respectively, the four phase shifted carrier outputs being connected to the four inputs of an OR gate respectively, generating a QPSK modulation signal.

2. A modulator in accordance with claim 1, in which RC circuits with variable capacitors are connected between each clock input of the first pair of flip-flops and ground.

3. A 2²ⁿ QAM modulator comprising a plurality (n) of QPSK modulators, n attenuators, and an adder;

each of said QPSK modulators being coupled via one of said attenuators to said adder which produces a QAM output signal;

each of said attenuators providing an attenuating coefficient 6(n-1), with n varying from 1 to n; and

each of said QPSK modulators comprising;

a high frequency signal generator provided with four outputs Q5 to Q8 generating signals with four different phases, each phase being shifted by 90°

respectively, a four input phase selector connected to the four outputs of the generator and having four modulating signal inputs and four phase shifted carrier outputs, the generator having a source of signals provided first and second outputs with opposing phases, two frequency dividers each having two outputs in opposing phases and each having a clock input, the clock input of the first divider being connected to the first output of the source of signals and the clock input of the second divider being connected to the second output of the source of signals, two pairs of flip-flops whose outputs make up the four outputs of the generator, the clock inputs of the first pair of flip-flops being connected to the first output of the source of signals and the clock inputs of the second pair of flip-flops being connected to the second output of the source of signals, the signal inputs of the first pair of flip-flops being connected to the outputs of the first divider and the signal inputs of the second pair of flip-flops being connected to the outputs of the second divider respectively, the four phase shifted carrier outputs being connected to the four inputs of an OR gate respectively, generating a QPSK modulation signal.

4. A modulator in accordance with claim 3, in which RC circuits with variable capacitors are connected between each clock input of the first pair of flip-flops and ground.