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FREQUENCY ACQUISITION DETECTOR AND TRANSMITTER INHIBITOR CIRCUIT

IP.com Disclosure Number: IPCOM000006293D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2001-Dec-20
Document File: 1 page(s) / 60K

Publishing Venue

Motorola

Related People

Armando J. Gonzalez: AUTHOR [+3]

Abstract

In the event of malfunction in a radio frequency phase locked loop (PLL), the radio frequency emissions created by the PLL will be uncontrolled. This uncon- trolled RF emissions could interfere with other radio frequency users anywhere in the RF spectrum. This sce- nario reveals the need for a circuit which must accom- plish two objectives. The circuit must be able to sense a PLL malfunction and respond to this PLL operating sta- tus by suppressing all radio frequency emissions.

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MOTOROLA INC. Technical Developments Volume 14 December 1991

FREQUENCY ACQUISITION DETECTOR AND TRANSMITTER

INHIBITOR CIRCUIT

by Armando J. Gonzalez, Cesar Carralero, and Jaime A. Borra

  In the event of malfunction in a radio frequency phase locked loop (PLL), the radio frequency emissions created by the PLL will be uncontrolled. This uncon- trolled RF emissions could interfere with other radio frequency users anywhere in the RF spectrum. This sce- nario reveals the need for a circuit which must accom- plish two objectives. The circuit must be able to sense a PLL malfunction and respond to this PLL operating sta- tus by suppressing all radio frequency emissions.

  A typical characteristic of a malfunctioning PLL is the generation of an output frequency outside the author- ized frequency operating range. These erroneous RF emissions usually correspond to the minimum or maxi- mum signal frequencies which can be generated by a voltage controlled oscillator (VCO). Since the output signal frequency of a VCO is controlled by the voltage present at the VCO frequency steering input (control voltage line), a PLL malfunction can be detected, ifeither maximum or minimum voltage is sensed at the VCO steering input. A critical characteristic to be considered in the design of the circuit is the degradation of spectral

purity a VCO can suffer due to the inadequate probing ofthe control voltage line.

The frequency aquisitiqn detector consists of a pair of comparator circuits. These...