Accession Number : ADD006844

Title :   Means for Reducing Spurious Frequencies in a Direct Frequency Synthesizer.

Descriptive Note : Patent,

Corporate Author : DEPARTMENT OF THE AIR FORCE WASHINGTON DC

Personal Author(s) : Harrison,Earnest R , Jr

Report Date : 22 Jan 1980

Pagination or Media Count : 5

Abstract : Spurious frequencies are eliminated in a direct frequency synthesizer by means of a feed forward correction circuit. The improved direct frequency synthesizer of the invention includes a series adder, clocked register, a D/A converter and a phase corrector. The adder is inputted by a digital control increment and the output of the register. The system clock frequency is divided down by a smoothing counter that in part controls the phase of the output signal. Spurious frequencies are manifested by overflow of the register. The register overflow is converted to an analog signal by the D/A converter. The system output is provided by a voltage controlled oscillator that is controlled by an amplifier which is responsive to both the smoothing counter output and the analog output of the D/A converter. Additionally, the D/A converter is sampled twice for every cycle of output frequency, resulting in a doubling of the output frequency for a given D/A converter. (Author)

Descriptors :   *Patents, *Frequency synthesizers, Registers(Circuits), Clocks, Analog to digital converters, Frequency dividers, Phase locked systems, Sampling, Frequency multipliers, Noise reduction, Circuit analysis, Spurious effects

Subject Categories : Electrical and Electronic Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE