A phase-locked loop frequency modulation circuit capable of continuous modulation

Abstract

The invention relates to a phase-locked loop frequency modulation circuit capable of realizing continuous modulation. It includes a controlled unit, a control unit, a detection unit and a mode switching unit; the control unit is used to control the controlled unit to be in a normal working state, and to detect through the detection unit, if the The controlled unit is in a normal working state, and the detection unit will notify the mode switching unit to perform corresponding mode switching, change the attributes of the control unit, and reduce the overlap between the control interval and the input signal spectrum interval of the controlled unit; The controlled unit is a voltage-controlled oscillator, the input signal of the controlled unit is a baseband signal, the control unit is a phase-locked loop, and the detection unit is a lock detection unit or a delay unit. The invention can be used in various radio frequency transceivers to realize carrier frequency modulation, and has the advantages of simple structure, low power consumption, no carrier frequency drift and the like.

Description

technical field [0001] The invention relates to a phase-locked loop frequency modulation circuit capable of realizing continuous modulation. Background technique [0002] The current RF frequency modulation circuits can be roughly divided into three categories: [0003] 1. Direct frequency conversion architecture (such as figure 1 As shown), it is composed of a phase-locked loop, a voltage-controlled oscillator, a mixer, a filter and other devices. Its working principle is that the phase-locked loop and the voltage-controlled oscillator generate a stable and accurate RF carrier signal; The baseband signal generates the final radio frequency modulation signal after frequency conversion by the mixer and filtering by the filter. The direct frequency conversion structure can realize any mode of radio frequency modulation including frequency modulation, but because it needs to use devices such as radio frequency mixers and radio frequency filters, the disadvantages are high pow...

AI Technical Summary

Problems solved by technology

Its advantages are simple structure and low power consumption; however, since the phase-locked loop and the voltage-controlled oscillator are in an open-loop working state during modulation, the center frequency of the radio frequency modulation signal is easily affected by the outside world and the frequency point drifts, and it must be switched after a period of modulation. Closed loop back for frequency calibration, so continuous modulation is not possible

[0006] It can be seen from the above analysis that the third frequency modulation circuit structure - phase-locked loop open-loop modulation - has the advantages of simple structure and low power consumption, but its disadvantage is that due to open-loop operation, there is frequency point drift, which cannot Achieving Continuous Modulation

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