Digital amplitude modulation transmitter with pulse width modulating RF drive

• US 7,369,819 B2
• Filed: 04/14/2005
• Issued: 05/06/2008
• Est. Priority Date: 04/14/2005
• Status: Active Grant

• Current Assignee: GatesAir Incorporated (Groupe Sipromad SA)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Luu, Ky Thoai
• Primary Examiner(s): NGUYEN, SIMON
• Application Number:
  US11/105,692
• Publication Number:
  US 20060252388A1
• Time in Patent Office: 1,118 Days
• Field of Search: 455108-109, 455/127.1, 455/127.3, 455/107, 455/116, 375300-301, 330/51, 330/200, 330/10, 330/136
• US Class Current: 455/91
• CPC Class Codes: H03C 1/00 Amplitude modulation H03C5/00, H03C7/00 take precedence
• CPC Class Codes: H03C 1/36 by means of semiconductor device having at least three electrodes H03C1/34, H03C1/50, H03C1/52, H03C1/62 take precedence
• CPC Class Codes: H03C 1/62 Modulators in which amplitude of carrier component in output is dependent upon strength of modulating signal, e.g. no carrier output when no modulating signal is present H03C1/28 - H03C1/34, H03C1/46, H03C1/48 take precedence
• CPC Class Codes: H04B 1/04 Circuits

Abstract

A digital amplitude modulation (AM) transmitter with pulse width modulating RF drive is presented. A plurality of RF amplifiers, each, when turned on, amplifies an applied RF drive signal by the same amount to provide a unit step RF output. An encoder supplies turn-on signals to turn on a number of the RF amplifiers wherein the number varies as a function of the value of an applied audio signal. The width of the unit step RF output is varied as a function of the number of the RF amplifiers that are turned on.

Claims

1. A digital amplitude modulation (AM) transmitter with pulse width modulating RF drive, comprising:

a plurality of RE amplifiers, each when turned on amplifying an applied RF drive signal by the same amount to provide a unit step RF output pulse of a fixed magnitude;

an encoder for supplying turn-on signals to turn on a number of said RF amplifiers wherein said number varies as a function of the value of an applied audio signal; and

pulse width driver means to vary the pulse width of each said unit step RF output pulse as a function of the number of said RF amplifiers that are turned on.

2. A transmitter as set forth in claim 1 wherein the width of each said unit step output pulse is inversely proportional to the number of said RF amplifiers that are turned on.

3. A transmitter as set forth in claim 1 wherein said means to vary include circuitry for varying the width of each said RF output pulse.

4. A transmitter as set forth in claim 3 wherein said circuitry varies the width of each said RF output pulse inversely proportional to the number of said RF amplifiers that are turned on.

5. A transmitter as set forth in claim 3 wherein said circuitry includes means for determining the number of power amplifiers to turn on.

6. A transmitter as set forth in claim 5 wherein the width of each said unit step output pulse is inversely proportional to the number of said RF amplifiers that are turned on.

7. A transmitter as set forth in claim 6 wherein said circuitry varies the width of each said unit step output pulse inversely proportional to the number of said RF amplifiers that are turned on.