i/q Mismatch Compensation Circuit for Low IF Receiver

Abstract

The invention discloses an I / Q mismatch compensation circuit of a low-intermediate frequency receiver. The I / Q mismatch compensation circuit is used for performing I / Q mismatch compensation on a first signal from an I channel or a second signal from a Q channel and comprises a mismatch detection module, a compensation value update module and a mismatch compensation module, wherein the mismatch compensation module receives the first signal, the second signal and output of the compensation value update module and outputs the compensated first signal and / or the second signal, the mismatch detection module receives the first signal and the second signal and outputs amplitude mismatch and phase mismatch, and the compensation value update module updates an amplitude and phase mismatch corrected value according to the amplitude mismatch and the phase mismatch. The I / Q mismatch compensation circuit of the low-intermediate frequency receiver compensates I / Q mismatch in a digital domain and is simple in principle and high in transferability. When the I / Q mismatch changes suddenly, the I / Q mismatch compensation circuit can obtain a stable compensation value in two update periods, react quickly and have flexible function expansion.

Description

technical field [0001] The invention relates to a compensation circuit, in particular to an I / Q mismatch compensation circuit of a low intermediate frequency receiver. Background technique [0002] In recent years, based on the use of quadrature down-conversion structure, low-IF receivers have been widely used. Low-IF receivers have the advantages of superheterodyne receivers and zero-IF receivers, that is, small DC offset interference, 1 / f noise The effect of interference is small, but there is a problem of image signal interference in low-IF receivers. The signal received by the antenna is turned into two signals in phase and quadrature after a quadrature down-conversion by the mixer. However, since the local oscillator cannot accurately generate signals with a 90° phase difference, the amplifier and the complex filter itself in the post-mixing stage The structural asymmetry of the I / Q circuit will also cause the amplitude and phase mismatch of the I / Q channels. Therefore...

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Problems solved by technology

This invention has high correction accuracy and high integration, but it cannot correct the amplitude mismatch. Moreover, as the range of phase mismatch that needs to be corrected increases, the scale of the circuit will also increase.

[0006] The widely used solution is to eliminate in the digital domain, using ADC and DSP to use a variety of baseband processing algorithms to eliminate in the digital domain. This design can simultaneously eliminate the mismatch caused by the asymmetry of the complex filter and amplifier, but due to the High image rejection ratio requires high-precision ADC and high-speed DSP, which is at the cost of cost and power consumption

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