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Image frequency detection method

A detection method and mirror frequency technology, applied in transmission monitoring, electrical components, transmission systems, etc., can solve problems such as high cost, error, and large volume, and achieve the effect of low cost and simple structure

Inactive Publication Date: 2014-05-14
中国兵器工业第二〇六研究所
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] To bring errors to the final frequency measurement, the broadband image frequency rejection mixer can provide about 20dB image frequency rejection and is bulky and costly

Method used

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  • Image frequency detection method

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Embodiment Construction

[0017] Now in conjunction with embodiment, accompanying drawing, the present invention will be further described:

[0018] see figure 1 , the present invention is realized by the following hardware: a microwave mixer, an intermediate frequency amplifier, a local oscillator, a filter, and a frequency measurement module. Microwave input frequency f to be detected IN Change between 6.200MHz and 6.600MHz, variable local oscillator f O From low to high in steps of 0.2MHz (f O Change between 6165MHz and 6565MHz), microwave input frequency f IN with variable local oscillator f O Frequency mixing, use a 35MHz bandpass filter (bandwidth 6MHz) to filter the mixed signal to obtain the intermediate frequency f IF . In variable local oscillator f O During the change process, the intermediate frequency f IF When it is a detectable signal, the local oscillator f O Stop the change, and test the f at this time in the frequency measurement module IF Frequency value; assuming that the ...

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Abstract

The invention relates to an image frequency detection method, which is characterized by comprising the following steps of: mixing microwave input frequency fIN and variable local frequency fO; filtering a signal in a mixing process in the step 1 by using a 35M band-pass filter, and when intermediate frequency fIF is detected in the filtered signal, stopping the variation of the variable local frequency fO with a local frequency value fOI, varying the variable local frequency fO into fOL=fOI-2fIF, and continuing mixing the fOL serving as a variable local frequency value and the microwave input frequency fIN; filtering the signal in the mixing process by using the 35M band-pass filter, and if the intermediate frequency fIF cannot be detected, determining that the microwave input frequency fIN free from the interference of image frequency is equal to the summation of fO and fIF; and if the intermediate frequency fIF can be detected, determining that the microwave input frequency fIN free from the interference of the image frequency is equal to a difference between fO and fIF. The method has the characteristics of simple structure, low cost and no use of an image frequency suppression mixer.

Description

technical field [0001] The invention relates to a mirror frequency detection method, relates to a microwave input frequency detection method free from mirror frequency interference, and is a mirror frequency detection method in a search type superheterodyne frequency measurement receiver. Background technique [0002] The search type superheterodyne frequency measurement receiver realizes frequency search by changing the local oscillator frequency, and performs frequency measurement when the beat between the local oscillator frequency and the received signal is equal to the receiver intermediate frequency frequency. The frequency measurement result is: [0003] f IN = f O +f IF [0004] Due to the input signal f IN The frequency and arrival time are unpredictable and the search mode of the local oscillator makes the input frequency f IN mirror frequency f IN -2f IF It may also fall within the IF band of the receiver, causing image frequency interference. The real inp...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04B17/00
Inventor 王涛
Owner 中国兵器工业第二〇六研究所