On-line rapid automatic frequency calibration circuit for frequency synthesizer and method thereof

Abstract

The invention discloses an on-line rapid automatic frequency calibration circuit for frequency synthesizer and a method thereof. The automatic frequency calibration circuit mainly comprises a rapid charge and discharge circuit (21), a comparator circuit (22) and a digital logic processing circuit. The calibration method in the invention adopts closed loop calibration. The main thinking is taking capacitance array as expansion of variable capacitance and imitating establishment process of phase-locked loop only with variable capacitance and without capacitance array to integrate automatic frequency calibration process and the phase-locked loop establishment process as one body. According to the invention, calibration time of frequency synthesizer is reduced, thus output frequency of the frequency synthesizer can be switched rapidly.

Description

technical field [0001] The invention belongs to the field of electronic technology, and is specifically applicable but not limited to a fast frequency calibration method and circuit of a frequency synthesizer in a radio frequency transceiver. Background technique [0002] At present, in wireless transceivers, frequency synthesizers are used to generate programmable and precise oscillation signals, such as figure 1 As shown, it generally consists of a reference oscillator 11, a frequency and phase detector 12, a charge pump 13, a loop filter 14, a voltage-controlled oscillator 15 and a frequency divider 16. A frequency synthesizer capable of generating fractional frequency division ratios typically also includes a sigma-delta modulator 17 . The output frequency range of the frequency synthesizer 29 depends on the output frequency range of the voltage-controlled oscillator 15. In order to obtain lower phase noise, the voltage-controlled oscillator is generally realized by an ...

AI Technical Summary

Problems solved by technology

[0010] With the continuous development of technology, people have higher and higher requirements for wireless communication. For example, it is required that the same transceiver can meet different communication standards and cover multiple frequency bands. Wide frequency band not only increases the complexity of the circuit, but also makes it more difficult to improve the noise. It also makes the calibration time of the frequency synthesizer longer, which is difficult to meet the requirements of some communication standards using traditional automatic frequency calibration techniques

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