Mismatch calibrating device for I and Q channel signals of orthogonal down-conversion receiver

Abstract

The invention discloses a mismatch calibrating device for I and Q channel signals of an orthogonal down-conversion receiver, which belongs to the technical field of frequency conversion receiver calibration. The device comprises two calibrating modules with same structures of an I channel and a Q channel, wherein each calibrating module comprises twelve MOS (Metal Oxide Semiconductor) transistors M1-M12, two load resistors R11 and R12, three adjustable resistors Rsp1, Rsp2 and Rsg and seven bias current sources I1-I7. The phase mismatch of I and Q channel signals of the orthogonal down-conversion receiver can be calibrated by adjusting resistance values of the first adjustable resistor Rsp1 and the second adjustable resistor Rsp2; and the amplitude mismatch of the I and Q channel signals of the orthogonal down-conversion receiver can be calibrated by adjusting a resistance value of the third adjustable resistor Rsg. The calibrating device improves the capability for inhibiting an image signal of the frequency conversion receiver and reduces the error rate of the receiver. A calibrating method is simple.

Description

technical field [0001] The invention belongs to the technical field of frequency conversion receiver calibration, and in particular relates to a device for calibrating the mismatch of I and Q channel signals of a quadrature down conversion receiver. Background technique [0002] In modern wireless receivers, low-IF structure and zero-IF structure are widely used. The RF signal undergoes quadrature down-conversion to generate two channel signals of in-phase I and quadrature Q. After subsequent signal processing, the signal at the image frequency of the receiver is eliminated, thereby saving The image rejection filter before the down conversion is removed. Due to the amplitude and phase mismatch of the I and Q two-way channel signals, the subsequent signal processing circuit cannot completely suppress the image signal at this time, and the useful signal will still be interfered by the image signal, resulting in an increase in the bit error rate and degrading the performance of...

AI Technical Summary

Problems solved by technology

Due to the amplitude and phase mismatch of the I and Q two-way channel signals, the subsequent signal processing circuit cannot completely suppress the image signal at this time, and the useful signal will still be interfered by the image signal, resulting in an increase in the bit error rate and reducing the performance of the receiver

For low-IF receivers, since the IF frequency is not zero, the image signal and the useful signal are not in the same channel, their energy is unpredictable, and the energy of the image signal may be 50-70dB higher than the useful signal; for a zero-IF receiver, the image signal It is the useful signal itself, they have the same energy, the receiver has slightly lower requirements for image rejection than the low-IF receiver, but the high-performance zero-IF receiver still needs an image rejection rate of more than 25dB

Images