Self centering frequency multiplier

• US 5,903,196 A
• Filed: 04/07/1997
• Issued: 05/11/1999
• Est. Priority Date: 04/07/1997
• Status: Expired due to Term

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Gonzalez, Armando J., Salvi, Raul, Ponce, Ramon
• Primary Examiner(s): KINKEAD, ARNOLD M
• Application Number:
  US08/835,372
• Time in Patent Office: 764 Days
• Field of Search: 331/76, 331/53, 331/1 A, 331/16, 327/105, 327/107, 327/116, 327/119, 327/156, 375/376, 455/323, 455/76, 455/260, 455/261, 455/313, 455/319
• US Class Current: 331/16
• CPC Class Codes: H03B 19/14 by means of a semiconductor device
• CPC Class Codes: H03J 7/08 using varactors, i.e. voltage variable reactive diodes H03J7/06 takes precedence
• CPC Class Codes: H03L 2207/10 Indirect frequency synthesis using a frequency multiplier in the phase-locked loop or in the reference signal path
• CPC Class Codes: H03L 7/0805 the loop being adapted to provide an additional control signal for use outside the loop
• CPC Class Codes: H03L 7/18 using a frequency divider or counter in the loop H03L7/20, H03L7/22 take precedence

Abstract

A frequency multiplier (120) having a tunable resonant circuit (122), is anticipated for use with a frequency synthesizer (100) having a Voltage Controlled Oscillator (110). The VCO control line (116) voltage establishes the VCO (110) fundamental frequency (ƒ_o) as well as the resonant circuit (122) center frequency, such that the resonant circuit (122) frequency response will track a desired harmonic component within the multiplier output (130) even as the VCO control line (116) voltage and the fundamental frequency (ƒ_o) change in response to control line variation.

Claims

1. A self centering frequency multiplier circuit comprising:

a voltage controlled oscillator (VCO) for receiving a control signal and providing a frequency output in response thereto;

a multiplier circuit, coupled to the VCO, for receiving the frequency output and providing a product signal in response thereto, said product signal having a fundamental frequency and a plurality of harmonic components; and

a resonant circuit, coupled to the multiplier circuit and having a voltage variable reactance stage, for receiving the control signal and altering a reactance of the voltage variable reactance stage in response to the control signal amplitude, to establish a frequency response for the resonant circuit that selects a desired harmonic frequency component from among the plurality of harmonic components.

2. The circuit of claim 1 further comprising an isolation circuit, coupled to the VCO and the multiplier, for receiving the control signal and feeding the control signal forward to the voltage variable reactance stage of the resonant circuit.

3. The circuit of claim 1 wherein the resonant circuit provides a high impedance response at the desired harmonic frequency.

4. The circuit of claim 1 wherein the resonant circuit provides a low impedance response at the fundamental frequency.

5. The circuit of claim 1 wherein the resonant circuit frequency response tracks the VCO output.

6. A communications device having a frequency synthesizer, said frequency synthesizer comprising:

a voltage controlled oscillator (VCO) for receiving a control signal and providing a frequency output in response thereto;

a multiplier circuit, coupled to the VCO for receiving the frequency output and providing a product signal in response thereto, said product signal having a fundamental frequency and a plurality of harmonic components;

a resonant circuit, coupled to the multiplier circuit, and having a variable reactance stage for receiving the control signal and altering a reactance of the variable reactance stage in response to control signal amplitude, to establish a response for the resonant circuit that tracks a response for desired harmonic within the product signal; and

an isolation circuit, coupled to the resonant circuit and the VCO, for receiving the control signal and feeding the control signal forward to the voltage variable reactance stage.