Phase-locked loop frequency modulation circuit capable of achieving continuous modulation

Abstract

The invention relates to a phase-locked loop frequency modulation circuit capable of achieving continuous modulation. The circuit comprises a controlled unit, a control unit, a detection unit, and a mode switching unit. The control unit is used for controlling the controlled unit to be at a normally working state, and the detection unit is used for detection. If the controlled unit is at the normally working state, the detection unit will remind the mode switching unit of carrying out the corresponding mode switching, thereby changing the property of the control unit, and reducing the overlapping of a control section with an input signal frequency spectrum section of the controlled unit. The controlled unit is a voltage-controlled oscillator, and an input signal of the controlled unit is a baseband signal. The control unit is a phase-locked loop, and the detection unit is a locked detection unit or delay unit. The circuit can be used in various types of radio frequency transceivers, achieves the modulation of carrier frequency, is simple in structure, is low in power consumption, and has no carrier frequency drift.

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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