Double-loop frequency synthesizer and method for tuning coarse loop

Abstract

Disclosed is a double loop frequency synthesizer and method for tuning coarse adjustment loop. The said double loop frequency synthesizer comprises coarse adjustment and fine adjustment loops, wherein the coarse adjustment includes counter comparator, successive approximation register and voltage-controlled oscillator; the fine adjustment loop includes frequency divider, phase-frequency discriminator, charge pump, loop filter and voltage-controlled oscillator that are used by two loops, switch capacitors array controlled with digital signal. The inventive method comprises steps of: 1) presetting digital control signal to make the voltage-controlled oscillator output corresponding frequency; 2) counting the number of frequency cycles and judging the relationship of counting result and preset value; 3) correcting or resetting the digital control signal according to the results and changing output frequency of voltage-controlled oscillator; 4) repeating step 2) and 3) until all the digital control signal are set to the best values.

Description

technical field [0001] The present invention relates to a frequency synthesizer and a frequency tuning method, in particular to a double-loop frequency synthesizer based on a phase-locked loop and a tuning method for the coarse tuning loop of the double-loop frequency synthesizer. technical background [0002] A frequency synthesizer is a device used to generate a stable, high-precision series of frequencies. There are two common frequency synthesizers: phase-locked loop (PLL)-based frequency synthesizers and direct digital frequency synthesizers. Among them, the frequency synthesizer based on the phase-locked loop has the advantages of low cost and high performance, especially suitable for high frequency synthesis, and has been widely used in high-speed digital systems, digital mobile communication equipment and high-precision control systems to generate accurate frequency clocks signal and high frequency carrier signal. [0003] Such as figure 1 Shown is a schematic dia...

AI Technical Summary

Problems solved by technology

But when the output frequency is relatively high (such as 1GHz), the commonly used crystal oscillator cannot meet the needs

[0011] In summary, the existing dual-loop frequency synthesizer has a complex structure, and it is difficult to achieve

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