Importance

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Abstract

Digital tuning of a locally generated frequency supplied to a frequency converting mixer, a mobile radio receiver is provided with great economy of components by utilizing the sampling rate oscillator for an analog-to-digital converter provided at the output of an analog intermediate frequency amplifier of the receiver as the source of the difference frequency for a phase locked loop (PLL) for control of the phase of a local oscillator for the mixer or mixers. All frequencies used to supply local oscillations to mixers, as well as the operating frequency of the phase locked loop are integer number multiples of the sampling rate pulse generator. Some division stages have fixed dividers and others have divisors selectable by a tuning processor and in some of the divisor connections it is useful to interpose a fixed or selectable-factor multiplier. A sampling rate of 42.75 MHz is recommended and an intermediate frequency amplifier frequency which is a rational number multiple of 57 kHZ, preferably 10.6875 MHz are similarly recommended.

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First Claim