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Browse Prior Art Database

LOW NOISE VOLTAGE CONTROLLED OSCILLATOR (VCO) WITH CHIP COIL

IP.com Disclosure Number: IPCOM000009692D
Original Publication Date: 2000-Jan-01
Included in the Prior Art Database: 2002-Sep-11
Document File: 2 page(s) / 76K

Publishing Venue

Motorola

Related People

Winfried Festag: AUTHOR

Abstract

The proposal relates to an improved VCO cir- cuit operating, for example, in the ultra high fre- quency (UHF) band. Such VCOs are used in radios where certain operating parameters are required (e.g., maximum phase noise -124 dBc in 1 Hz, fre- quency offset 25 kHz, temperature +"C...+8O"C). Further, the VCO has to follow the trend to rninia- turization and cost reduction.

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Technical MO7VROLA @ Developments

LOW NOISE VOLTAGE CONTROLLED OSCILLATOR (VCO) WITH CHIP COIL

by Winfried Festag

INTRODUCTION

  The proposal relates to an improved VCO cir- cuit operating, for example, in the ultra high fre- quency (UHF) band. Such VCOs are used in radios where certain operating parameters are required
(e.g., maximum phase noise -124 dBc in 1 Hz, fre- quency offset 25 kHz, temperature +"C...+8O"C). Further, the VCO has to follow the trend to rninia- turization and cost reduction.

SOLUTION

  The figure illustrates a VCO circuit in a Colpitts arrangement with coil L4 serially coupled to varac- tor diode VI (common kathode type) where the fre- quency is controlled by a tuning voltage. Diode Vl is known from applications in the lower, FM radio frequency band and has, preferably, a square charac- teristic. Optionally, the tuning range can be modi- tied also by capacitor Cl (by default a short path for high frequency signals) and coils Ll and L2 (both by default working as RF chokes).

  The serial connection of Vl and L4 provides that the effective, frequency determining inductance of this tank circuit is smaller than the rated induc- tance of IA (e.g., 23 nH, frequency range 480.. ,510 MHz).

  This features allow to implement IA by a sur- face mounted coil with an electrical quality Q as low as 70 for the circuit illustrated and meeting the above mentioned phase noise performance. This combines the advantages of small external dimen- sions (e.g., EIA size 12...