High-resolution and low-spurious-frequency synthesizer of UHF (Ultrahigh Frequency) frequency band

Abstract

The invention relates to a frequency synthesizer, in particular to a high-resolution and low-spurious-frequency synthesizer of a UHF (Ultrahigh Frequency) frequency band, comprising a phase detector, a phase-locked loop, a DDS frequency synthesizer and a quadrature mixer, wherein the phase-locked loop comprises a low-pass filter and a voltage controlled oscillator; the DDS frequency synthesizer is a double-frequency output DDS frequency synthesizer; the phase detector is used for receiving reference signals and dividing the signals, the low-pass filter is connected with the phase detector to supply voltage control signals, a voltage control oscillator is connected with the low-pass filter to supply output signals, the quadrature mixer is coupled among the voltage control oscillator, the DDS frequency synthesizer and the phase detector, and the DDS frequency synthesizer is connected between a reference signal and the quadrature mixer. The frequency synthesizer greatly increases the frequency resolution (0.0024Hz), inhibits stray, reduces the stabilization time and can especially obtain the same high-resolution frequency signals in arbitrary frequency bands.

Description

technical field [0001] The invention relates to a frequency synthesizer, in particular to a high-resolution and low spurious frequency synthesizer used in the UHF frequency band of terrestrial television broadcasting. Background technique [0002] Frequency synthesizers in electronic systems are used to generate any range of frequencies from a single fixed time reference or oscillator. Many existing radio devices, mobile phones, mobile receivers, high-energy accelerators, radio and television transmission systems, etc., are equipped with frequency synthesizers. The national standard of the UHF frequency band has higher requirements for the frequency synthesizer of terrestrial TV broadcasting than the frequency synthesizer of the ordinary communication system: according to the national standard, the frequency resolution in the UHF frequency band (470MHz-860MHz) is below 1Hz; its characteristics are high bandwidth, high resolution, low phase noise. Therefore, the frequency s...

AI Technical Summary

Problems solved by technology

The disadvantage of the analog quadrature mixer is that it needs to suppress the sideband and carrier leakage, and the sideband and carrier leakage are different for different carrier frequencies, and all need to be adjusted

If an ordinary single mixer is used in this scheme, its function is to combine the two input frequencies f 1 , f 2 The multiplication operation is performed, and the resulting frequency is f 1 , f 2 , f 1 -f 2 , f 1 + f 2 etc.; if the mixed signal f 1 2 , the frequency signal f generated at this time 2 -f 1 and f 1 + f 2 Very close, due to the limitations of the process and bandwidth of the analog bandpass filter, it is difficult to obtain the desired output frequency range, or the output frequency cannot cover the desired frequency band

On the other hand, since the DDS operating clock is inversely proportional to its frequency resolution, if the DDS operating clock is increased, its frequency resolution will decrease

At this time, more circuit links need to be introduced, making the system noise difficult to control

Images