Fast locking frequency locking ring with automatic frequency control circuit

Abstract

A fast locking frequency locking ring with an automatic frequency control circuit comprises the automatic frequency control circuit and a frequency locking loop. The frequency locking loop comprises an amplifier, a first switch, a second switch, a voltage-controlled oscillator, a buffer, a frequency divider N and a frequency and voltage converter. The automatic frequency control circuit comprises a voltage comparator and a logic control circuit. At the beginning, the logic control circuit outputs an enabling signal to control the first switch to be turned off and the second switch to be turned on, the circuit is in the open loop state, the frequency locking ring carries out rough frequency selecting, increase and decrease of the number of logic output control words are controlled according to the output m of the voltage comparator to select an appropriate sub-band, the frequency locking ring carries out fine frequency selecting, the logical control circuit outputs the enabling signal to control the first switch to be turned on and the second switch to be turned off, the circuit is in the closed loop state, the frequency locking loop finishes the target frequency locking according to a signal input into the amplifier, and the fast locking frequency locking ring has the advantage of being fast in locking due to the work mode.

Description

technical field [0001] The invention relates to a frequency-locked loop, in particular to a fast-locked frequency-locked loop with an automatic frequency control circuit. Background technique [0002] Compared with the phase-locked loop PLL, the frequency-locked loop FLL has the characteristics of fast locking time. It is generally used in occasions with strict requirements on the locking time. The output range of the frequency-locked loop is determined by the tuning range of the voltage-controlled oscillator VCO. For broadband voltage-controlled oscillators, the tuning range generally reaches more than 50%. If a single tuning curve is used to achieve such a wide tuning range, the tuning gain Kvco is too large, which will cause serious AM-PM conversion and deteriorate the phase. noise performance. Therefore, a wideband oscillator generally adopts a switch selection method to divide a wideband tuning range into several narrowband tuning ranges, and ensure that adjacent volta...

AI Technical Summary

Problems solved by technology

[0005] Purpose of the invention: In view of the above-mentioned prior art, provide a fast locking frequency-locked loop with an automatic frequency control circuit, which can solve the problem of long locking time of the entire loop in the frequency-locked loop

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