Browse Prior Art Database

LOW DISTORTION, WIDE BAND VOLTAGE CONTROLLED OSCILLATOR MODULATION

IP.com Disclosure Number: IPCOM000007864D
Original Publication Date: 1996-Nov-01
Included in the Prior Art Database: 2002-Apr-30
Document File: 3 page(s) / 85K

Publishing Venue

Motorola

Related People

Wayne Shepherd: AUTHOR [+3]

Abstract

EXISTING METHODS Wueless communication systems often require extremely accurate modulation methods. This cre- ates the need for a VCO with modulation sensitiv- ity flatness up to a cutoff frequency determined by the application. The method presented here of modulating VCO (Voltage Controlled Oscillator) is an inexpensive way to accomplish the above requirements.

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Page 1 of 3

8 @l-LA Technical Developments

LOW DISTORTION, WIDE BAND VOLTAGE CONTROLLED OSCILLATOR MODULATION

by Wayne Shepherd, Gus Leizerovich and Raul Salvi

lNlRODUCTlON

EXISTING METHODS

  Wueless communication systems often require extremely accurate modulation methods. This cre- ates the need for a VCO with modulation sensitiv- ity flatness up to a cutoff frequency determined by the application. The method presented here of modulating VCO (Voltage Controlled Oscillator) is an inexpensive way to accomplish the above requirements.

  Figures 1,2 and 3 illustrate existing methods of modulating a VCO. Each of them have drawbacks which make them unsuitable for high accuracy applications.

  VCO modulation in methods 1 and 2 are obtained by applying the modulation signal to the control varactor. These methods are highly noise sus ceptible and their modulation sensitivities change with the control voltage (channel changing). This is caused by the fact that Vctrl sets the operating point of the varactor.

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Fig. 1

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November1996

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Page 2 of 3

Technical Developments

Vmod

Fig. 3

  In method 3, a separate varactor is coupled to in methods 1 and 2 but to a lesser degree. the main control band changing varactor. Even
though it would seem that this method provides for SOLUTION

good isolation between varactor responses, in real- ity Cx provides a path for the high frequency com- VCO Modulation in Fig. 4 consists i...