Motorola Corporation

Alan M Victor

Jaime Andres Borras

Jose I Suarez

Darrell Eugene Davis

Alfred B Wieczorek

Francis Robert Steel

Ralph T Enderby

Ruben J Gonzalez

Daniel M Smith

A multiple conversion superheterodyne receiver system includes a first frequency synthesizer capable of generating any one of a number of predetermined first local oscillator frequencies for mixing with an incoming signal to produce a first intermediate frequency. A second frequency synthesizer selectively generates any one of two local oscillator frequencies corresponding to either high side or low side injection to be mixed with first intermediate frequency producing an appropriate second intermediate frequency. A frequency selecting circuit is operatively coupled to the first and second frequency synthesizer for selecting an appropriate one of the first local oscillator frequencies to tune the receiver to a desired channel and for selecting an appropriate one of the second local oscillator frequencies for avoiding receiver self-quieting spurious responses.

Synthesized multiple conversion receiver system with provision for

A method of programming a ROM for a multiple conversion frequency synthesizer provides a mechanism for avoiding receiver self-quieting. The method includes the steps of searching for frequencies which cause potential receiver self-quieting responses and selecting a second local oscillator frequency suitable for avoiding receiver self-quieting. A single bit of a ROM is used to represent possible second local oscillator frequencies synthesized by the frequency synthesizer which provide either high-side or low-side injection to the second mixer. Finally, the method includes the step of encoding the single second local oscillator frequency determining bit of the ROM appropriately for selecting the local oscillator frequency which avoids receiver self-quieting.

Method of programming a synthesizer ROM for elimination of receiver

A sample and hold phase detector for a phase locked loop includes a digital detector for detecting the frequency and phase difference between the reference signal and the voltage controlled oscillator (VCO) signal. In a first mode of operation, the digital detector generates a first signal relating the difference in frequency and in a second mode of operation generates a second signal relating the difference in phase. A capacitor stores the first or second signal depending on the operational mode of the digital detector. The capacitor is selectively discharged in response to a discharge signal produced by the digital detector when either the VCO frequency is higher than the reference frequency or following each detection of a phase difference. A first amplifier is used to bypass a portion of the loop filter to effect rapid changes in VCO frequency in the first mode while a second amplifier couples the control voltage to the VCO via the loop filter to maintain proper VCO frequency in the second mode.

Digital and analog phase detector for a frequency synthesizer

In a frequency synthesizer phase locked loop including a reference oscillator, a variable reference divider (.div.M), a sample and hold phase detector, a loop filter, a voltage controlled oscillator and a variable divider (.div.N), a voltage converter for controlling the voltage of a control input to the voltage controlled oscillator is disclosed. In the preferred embodiment, the voltage converter has its input connected to the output of a first reference divider in the variable reference divider (.div.M) and its output connected to a control input (varactor diode) of the voltage controlled oscillator. The voltage converter clamps the divider reference signal from the first reference divider and provides a negative voltage level output to bias the varactor diode of the voltage controlled oscillator. Thus, the tuning range of the frequency synthesizer is increased.

Voltage converter for a frequency synthesizer

An improved wideband phase modulator suitable as a simple modulation interface for existing phase modulated transmitters. The disclosed modulator arrangement utilizes a high stability reference oscillator and an associated phase locked loop for optimum long term stability. Means are included for extended phase range and high fidelity of modulation irrespective of loop bandwidth. Both tone and digital modulation is accommodated.

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Cooper City, FL, United States of America

Alan M Victor