Rapid local oscillator leakage calibrating device facing IQ modulator

Abstract

The invention discloses a rapid local oscillator leakage calibrating device facing an IQ modulator. A radio frequency signal source provides a local oscillator signal and a spectrum analyzer is used for measuring amplitude of the local oscillator signal output by an IQ modulator. During actual operation, the radio frequency signal output end of the a radio frequency signal source is connected to a local oscillator signal input end of the IQ modulator; and the spectrum analyzer is connected to the radio frequency signal output end of the IQ modulator. By controlling the IQ modulator, the output level of direct current bias compensation DAC of an internally arranged I path and a Q path are changed for five times, and direct current bias error compensation values of the I path and the Q path of the IQ modulator can be obtained via calculation, thereby further finishing calibration of local oscillator leakage of the IQ modulator.

Description

technical field [0001] The invention belongs to the technical field of IQ modulator calibration, and more specifically relates to a fast local oscillator leakage calibration device for IQ modulators. Background technique [0002] The IQ modulator is used to up-convert the IQ baseband signal into a radio frequency modulation signal, which is the basis of modern digital communication technology and has broad application prospects. In the actual application of the IQ modulator, the local oscillator signal is easy to pass through various factors such as circuit crosstalk, radiation, or baseband signal DC bias error. When there is no signal in the I and Q channels, the radio frequency of the IQ modulator will be caused. A weak LO frequency signal appears at the output, a phenomenon known as LO leakage. Since the leakage of the local oscillator does not carry any information, the leakage of the local oscillator will reduce the transmission efficiency of the transmitter; at the sa...

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Problems solved by technology

[0005] However, the problem with the above-mentioned IQ modulator local oscillator leakage calibration method is that the calibration time is too long. For each frequency point to be calibrated, the entire calibration process needs to continuously adjust the DC bias of the I channel and the Q channel, and use a spectrum analyzer to measure the IQ modulation The amplitude of the local oscillator leakage signal at the radio frequency output terminal of the device. In order to achieve a better calibration effect of the local oscillator leakage, the IQ modulator needs dozens or even hundreds of bias adjustments and RF signals when calibrating each local oscillator frequency point. For amplitude measurement, it takes longer to complete the calibration of all local oscillator frequency points in the whole frequency band

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