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Automatic Frequency Correction of Voltage Controlled Oscillator.

IP.com Disclosure Number: IPCOM000007115D
Publication Date: 2002-Feb-26
Document File: 1 page(s) / 74K

Publishing Venue

The IP.com Prior Art Database

Abstract

ID401177

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ID401177

Automatic Frequency Correction of Voltage Controlled Oscillator

A VCO has a bank of capacitors any of which may be selected by a

control process to adjust the VCO frequency. The control process

commences with Counter 2 reset to 000000, all of the capacitors in circuit,

and therefore with the VCO switched to the bottom of its switching frequency

range (thereby avoiding the need for Counter 1 to count at a rate higher than

the wanted VCO frequency divided by the divider ratio), but with the tuning

voltage set to the middle of the tuning range. The frequency of the VCO is

measured by counting in Counter 1 the divided output of the VCO over a

known period derived from a Reference Frequency. The result of this count is

compared with the value that would be expected if the VCO were operating at

the required frequency. If the VCO is not operating at the required frequency,

a pulse is generated which increments Counter 2. Counter 2 switches the

capacitor bank thereby incrementing the VCO frequency. The process of

measurement and incrementing is repeated until the required VCO frequency

is reached. For single-band operation the target counter value used when

measuring the VCO frequency may be fixed, or for multi-band operation, the

target counter value may be programmable.

/co

Frequency

Divider

b3 b2

Counter 2

bl bo

ck

24.5 MHz

Frequency

Count

Pulse

Generator

Reference

Frequency

stop

Reference

Divider

Disclosed anonymously