Special vestigial sideband signal for use in communication systems

• US 4,660,222 A
• Filed: 01/27/1984
• Issued: 04/21/1987
• Est. Priority Date: 01/27/1984
• Status: Expired due to Fees

• Current Assignee: Alpha Omega Engineering, Inc.
• Original Assignee: Alpha Omega Engineering, Inc.
• Inventors: Smith, Stephen F.
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Telesz, Jr., Andrew J.
• Application Number:
  US06/574,388
• Time in Patent Office: 1,180 Days
• Field of Search: 455/109, 455/46, 455/47, 332/44, 332/45
• US Class Current: 455/109
• CPC Class Codes: H03C 1/52 Modulators in which carrier or one sideband is wholly or partially suppressed H03C1/28 - H03C1/34, H03C1/46, H03C1/48 take precedence

Abstract

Several forms of a novel amplitude-modulated (AM) signal format are disclosed. Circuits of several types for generating the desired special vestigial-sideband (SVSB) AM waveforms are discussed. The principal form of the SVSB modulation provides for a reduction in transmitted signal bandwidth compared with standard double-sideband techniques plus very linear amplitude characteristics with simple synchronous detectors. Circuits according to the invention may also include means for dynamically varying signal bandwidth to accommodate special applications.

Claims

1. A circuit for generating a vestigial-sideband waveform having enhanced bandwidth and amplitude characteristics and comprising:

(a) a first signal source for generating a baseband signal which may include a d.c. component;

(b) a second signal source for generating a carrier signal;

(c) a signal modulating or multiplying device for receiving the baseband signal from the first source and the carrier signal from the second source and electronically multiplying the carrier signal by the baseband signal to produce a double-sideband AM signal with an appropriate carrier component or suppressed carrier, depending on the presence of a d.c. component in the baseband signal;

(d) signal converting means for accepting the double-sideband AM signal, with or without a carrier component, and processing it to produce a vestigial-sideband output signal, having an instantaneous bandwidth intermediate to that of a corresponding double-sideband signal which would be produced by said baseband signal and that of a corresponding single-sideband signal which would be produced by said baseband signal, which vestigial-sideband output signal can be detected without distortion by conventional double-sideband receiving equipment employing synchronous or "product" detectors as if the vestigial-sideband signal were a conventional double-sideband signal with an appropriate carrier component, and which possesses no amplitude peaks substantially in excess of those of the corresponding double-sideband signal regardless of the original baseband modulating signal.

2. A method for generating a vestigial-sideband waveform having enhanced bandwidth and amplitude characteristics and comprising:

(a) generating from a first signal source a baseband signal which may include a d.c. component;

(b) generating from a second signal source a carrier signal;

(c) receiving the baseband signal from the first source and the carrier signal from the second source and electronically multiplying the carrier signal by the baseband signal to produce a double-sideband AM signal with an appropriate carrier component or suppressed carrier, depending on the presence of a d.c. component in the baseband signal;

(d) converting the double-sideband AM signal, with or without a carrier component, and processing it to produce a vestigial-sideband output signal, said vestigial-sideband output signal having an instantaneous bandwidth intermediate to that of the corresponding double-sideband signal which would be produced by the same baseband signal and that of the corresponding single-sideband signal which would be produced by the same baseband signal, which can be detected without distortion by conventional double-sideband receiving equipment employing synchronous or product detectors as if the vestigial-sideband signal were a conventional double-sideband signal with an appropriate carrier component, and which possesses no amplitude peaks substantially in excess of those of the corresponding double-sideband signal regardless of the original baseband modulating signal.