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TWO LEVEL REGULATOR SYSTEM FOR VCOS

IP.com Disclosure Number: IPCOM000006478D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2002-Jan-08
Document File: 1 page(s) / 59K

Publishing Venue

Motorola

Related People

William O'Connor: AUTHOR [+2]

Abstract

Problem to be Solved-Most portable synthesizer designs consist of a dual VCO approach where one VCO functions as the Rx VCO and a 2nd VCO functions as the T% VCO. The purpose of utilizing two VCOs is to increase the operating frequency range of the synthesizer while maintaining a practical resonator design, a realistic Ko due, and good SBN performance. Present synthesizers use the same regulated supply for each VCO as shown: ated at a higher supply voltage than the TX VCO. For example, operation of the Rx VCO at 5.8 VDC instead of 5.0 VDC would result in approximately 2 dB improve- ment in SBN assuming the VCO tank voltage can be increased from 3 Vrms to 3.8 Vrms (ASBN = 20 log 3.813.0 = 2 dB). As a practical note, the Rx VCO SBN requirements are much higher (5-10 dB) than the TX VCO requirements.

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MOTOROLA INC. Technical Developments Volume 16 August 1992

TWO LEVEL REGULATOR SYSTEM FOR VCOS

by William O'Connor and Richard B. Meador

  Problem to be Solved-Most portable synthesizer designs consist of a dual VCO approach where one VCO functions as the Rx VCO and a 2nd VCO functions as the T% VCO. The purpose of utilizing two VCOs is to increase the operating frequency range of the synthesizer while maintaining a practical resonator design, a realistic Ko due, and good SBN performance. Present synthesizers use the same regulated supply for each VCO as shown:

ated at a higher supply voltage than the TX VCO. For example, operation of the Rx VCO at 5.8 VDC instead of 5.0 VDC would result in approximately 2 dB improve- ment in SBN assuming the VCO tank voltage can be increased from 3 Vrms to 3.8 Vrms (ASBN = 20 log
3.813.0 = 2 dB). As a practical note, the Rx VCO SBN requirements are much higher (5-10 dB) than the TX VCO requirements.

  Solution-To achieve the improvement in Rx SBN and maintain a low end-of-lie voltage for the TX VCO, the supply voltage must be programmable to 2 levels. An example for 7.5 Volt battery supply is given below:

Unrequlstd VohJe Input

REC

5.0 voc 5.0 VDC

L T

RX vco TX vc3

  Using the same supply voltage for both VCOs is undesirable for the following reason. Studies on VCOs show that SBN performance may be improved by uti- lizing a higher supply voltage. A higher supply allows larger voltage swings thereby increasing oscillator tank power (Ps...