Phase-locked loop frequency synthesizer

Abstract

The invention discloses a phase-locked loop frequency synthesizer. The phase-locked loop frequency synthesizer comprises a phase frequency detector, a charge pump and an adaptive filter, a Voltage-controlled oscillator, a Frequency divider and a decoder; the phase frequency detector , a charge pump and an adaptive filter, the Voltage-controlled oscillator, the frequency dividers are sequentially connected in series to form a feedback loop; the decoder is connected between the frequency divider and the self-adaptive filter; the decoder is used for decoding the frequency division ratio of the frequency divider and providing a corresponding control signal for the adaptive filter; and the self-adaptive filter comprises a self-adaptive on-resistance network which has different resistance valuesunder the control of the control signal and can keep the loop bandwidth of the phase-locked loop frequency synthesizer constant. The phase-locked loop frequency synthesizer disclosed by the inventionrealizes that the bandwidth of the loop is not changed along with the change of the output frequency, and has better system stability and response speed.

Description

technical field [0001] The invention relates to the field of electronic technology, in particular to a phase-locked loop frequency synthesizer with a relatively large output frequency range. Background technique [0002] Phase-locked loop frequency synthesizer is a key module in wireless communication and image sensor systems. It has the characteristics of pure output signal spectrum, low implementation and application costs, and is widely used in occasions that require relatively high transmission speed. At the same time, due to the application The output frequency is constantly changing due to the different scenarios and modes, and frequency synthesis is required to respond quickly and stably to the switching of the output frequency to ensure the stable operation of the system. [0003] The output frequency of the existing phase-locked loop frequency synthesizer is different according to the actual application scenarios, and its frequency range is very large, which leads t...

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Problems solved by technology

[0003] The output frequency of the existing phase-locked loop frequency synthesizer is different according to the actual application scenarios, and its frequency range is very large, which leads to the uncertain locking time of the phase-locked loop frequency synthesizer when the frequency is switched, and cannot respond to the output frequency quickly and stably. On the other hand, due to the unknown deviation of more than 10% in the resistance value of the resistance of the filter and the like when the process is realized, it may cause the bandwidth to deviate from the value set by the chip design, and even cause The phase margin deviates too much, which affects the stability of the loop

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