A Phase Locked Loop Frequency Synthesizer

Abstract

The invention discloses a phase locking loop frequency synthesizer. The phase locking loop frequency synthesizer comprises a frequency synthesis unit, a radio frequency switch, a phase frequency detector, a first loop filter, a voltage controlled oscillator, a preparatory frequency divider, a direct digital frequency synthesizer and a second loop filter, wherein an input end of the frequency synthesis unit is used to receive a first level reference frequency, the frequency synthesis unit performs synthesis treatment on the first level reference frequency and outputs frequencies, the number of the output frequencies is i, the radio frequency switch arbitrarily selects a frequency from the i frequencies, which is not in a multiple relationship with an output frequency, and uses the selected frequency as a second level reference frequency, the phase frequency detector performs phase comparison on the second level reference frequency and a feedback frequency after smoothing, and outputs phase detection voltage according to a comparison result, the first loop filter performs filtering processing on the phase detection voltage and outputs error voltage, the voltage controlled oscillator converts the error voltage into the output frequency, and the direct digital frequency synthesizer is used to perform fractional frequency division processing on another frequency output by the preparatory frequency divider and then output the feedback frequency. The phase locking loop frequency synthesizer uses switching of a plurality of reference sources, and can effectively restrain a stray phenomenon.

Description

technical field [0001] The invention belongs to the field of radio technology, and in particular relates to a phase-locked loop frequency synthesizer. Background technique [0002] In modern electronic equipment and electronic systems, frequency synthesis technology has become an indispensable key technology and has been widely used in various fields. To this day, in order to meet different application requirements, various new frequency synthesis schemes are still emerging continuously. [0003] As a key technology capable of generating high-quality sine waves, frequency synthesis technology has been widely used in electronic measurement systems and electronic equipment. In the receiver, the frequency source designed using frequency synthesis technology is used as a local oscillator, and the carrier signal is mixed and down-converted to a baseband signal; in the transmitter, the frequency source is also used as a local oscillator, and the baseband signal is mixed and up-co...

AI Technical Summary

Problems solved by technology

[0014] Aiming at the defects of the prior art, the purpose of the present invention is to provide a phase-locked loop frequency synthesizer, which aims to solve the problem that the prior art cannot avoid the spurious problem that the output frequency of the phase-locked loop is near the integer multiple of the reference frequency

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