Frequency synthesizer based on switched capacitor array temperature compensation circuit

Abstract

The invention discloses a frequency synthesizer based on a switched capacitor array temperature compensation circuit. The circuit comprises a phase frequency detector, a charge pump, a loop filter, avoltage-controlled oscillator, a driver, a frequency divider and an automatic frequency calibration digital circuit and a temperature compensation circuit, the phase frequency detector identifies thephase difference between the reference clock frequency and the frequency division clock output by the frequency divider; the charge pump converts the phase difference into a corresponding current, thecurrent passes through the loop filter to obtain a corresponding control voltage for controlling the frequency of an output signal of the voltage-controlled oscillator, and the output signal of the voltage-controlled oscillator also passes through the driver to serve as an output signal and is sent to the frequency divider to form a negative feedback loop; the automatic frequency calibration digital circuit is used for selecting an appropriate sub-band for the voltage-controlled oscillator and outputting a sub-band control signal; and the temperature compensation circuit is used for adjustingthe temperature compensation switched capacitor array through the comparator and the digital circuit according to the output signal of the loop filter so as to adjust the output signal of the voltage-controlled oscillator.

Description

Technical field [0001] The invention belongs to the technical field of integrated circuits, and specifically relates to a frequency synthesizer based on a temperature compensation circuit of a switched capacitor array. Background technique [0002] The tuning gain of the VCO in the frequency synthesizer will affect its own phase noise. The greater the tuning gain, the greater the phase noise. A wide-band frequency synthesizer needs a voltage-controlled oscillator with a wide frequency coverage. If the wide-band voltage-controlled oscillator still uses a tuning curve (the tuning curve can also be called a "subband"), it will produce extremes A large tuning gain is bound to deteriorate the phase noise performance. The current common practice is to use a digitally controlled switched capacitor array in the voltage-controlled oscillator to divide a tuning curve into multiple tuning curves to reduce the tuning gain. This can effectively improve the phase noise performance while cov...

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Problems solved by technology

But the disadvantage of this method is that the phase noise performance deteriorates due to the increased tuning gain

In addition, the control voltage of the voltage-controlled oscillator is generally at an intermediate value after locking. At this time, the linearity of the control voltage is the best. As the temperature changes, the control voltage will change, and the closer to the limit value, the better the linearity Difference

And the additional phase noise introduced by the nonlinearity will also degrade the performance of the frequency synthesizer

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