Frequency synthesizer based on digital temperature compensation circuit

Abstract

The invention discloses a frequency synthesizer based on a digital temperature compensation circuit. The circuit comprises a phase frequency detector, a charge pump, a loop filter, a voltage-controlled oscillator, a driver, a frequency divider and a temperature compensation circuit, the phase difference between the reference clock frequency Fref and the frequency division clock output by the frequency divider is identified by the phase frequency detector; the charge pump converts the phase difference into a corresponding current; the current passes through a loop filter to obtain a corresponding control voltage Vtune for controlling the frequency of the voltage-controlled oscillator; wherein an output signal of the voltage-controlled oscillator passes through the driver circuit to serve assystem output and is also sent to the frequency divider to form a negative feedback loop, and the temperature compensation circuit further comprises a temperature compensation varactor, a resistancevoltage division network, a comparator, a digital circuit, a digital-to-analog converter and a low-pass filter.

Description

technical field [0001] The invention belongs to the technical field of integrated circuits, and in particular relates to a frequency synthesizer based on a digital temperature compensation circuit. Background technique [0002] The tuning gain of a VCO in a frequency synthesizer affects its own phase noise. The larger the tuning gain, the larger the phase noise. A broadband frequency synthesizer requires a voltage-controlled oscillator with a wide frequency coverage. If the broadband voltage-controlled oscillator still uses a tuning curve (also called a "subband"), it will produce a large Tuning the gain will inevitably degrade the phase noise performance. A common practice at present is to use a digitally controlled switched capacitor array in a voltage-controlled oscillator to divide one tuning curve into multiple tuning curves to reduce the tuning gain. This effectively improves the phase noise performance while covering a wide frequency range. [0003] After the freq...

AI Technical Summary

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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