A Blind Calibration Model for I/Q Imbalances of Wideband Zero-IF Receivers

Abstract

Frequency-dependent I/Q imbalance and frequency-independent I/Q imbalance are the major impairments in wideband zero-IF receivers, and they both cannot be ignored. In this paper, a blind calibration model is designed for compensating these I/Q imbalances. In order to accurately estimate the imbalance parameters with low cost, a classification rule is proposed according to the frequency-domain statistical characteristics of the received signal. The calibration points in the frequency-domain are divided into two groups. Then, the amplitude imbalance and the frequency-dependent phase imbalance are derived from the group of signal points and, separately, the frequency-independent phase imbalance is calculated from the group of noise points. In the derivation of the frequency-dependent phase imbalance, a general fitting model suitable for all signal points is proposed, which does not require special calculations for either DC point or fs/2 point. Then, a finite impulse response (FIR) real-valued filter is designed to correct the impairments of received signal. The performances of the proposed calibration model are evaluated through both simulations and experiments. The simulation results show the image rejection ratio (IRR) improvement to around 35–45 dBc at high signal-to-noise ratio (SNR). Based on the mismatched data of the ADRV9009 evaluation board, the experimental results exhibit the IRR improvement of both multi-tone and wideband signals to about 30 dBc.

Widely-Linear Digital Self-Interference Cancellation in Full-Duplex USRP Transceiver

“…where G Tx 1 ( f ) and G Tx 2 ( f ) stand for the transfer functions corresponding to g Tx 1 (t) and g Tx 2 (t), respectively [30].…”

A Frequency-Domain I/Q Imbalance Calibration Algorithm for Wideband Direct Conversion Receivers Using Low-Cost Compensator

“…of factors such as analog device mismatch, I/Q imbalance (IQI) is caused, which produces undesired image interference signals and affects the demodulation performance of the baseband signal [2].…”

“…The IQI in the wideband direct conversion receiver is caused by two different sources: (1) The frequencyindependent (FI) amplitude and phase imbalances caused by the non-ideal analog quadrature mixer, (2) The frequencydependent (FD) amplitude and phase imbalances caused by the differences between the two I/Q baseband analog paths, the analog paths including low-pass filter (LPF), analog to digital converter (ADC), and other devices. Neither of these I/Q imbalances can be ignored for wideband direct conversion receivers.…”

A Compact 10–14.5 GHz Quadrature Hybrid with Digitally Reconfigurable I/Q Phase in SiGe BiCMOS Process

“…Recently, the pursuit for high throughput wireless data transmission has driven the need for wide bandwidth and high-order modulation schemes in modern communications. The quadrature technique is the best way to implement high-order quadrature amplitude modulation (QAM) scheme, where quadrature hybrid couplers have been widely used to provide signals with the desired 90-degree phase characteristics for the QAM signal generations [1][2][3][4][5][6][7][8]. The main problem of quadrature circuits is the I/Q mismatch, that is, quadrature phase and differential gain errors between the in-phase (I) and quadraturephase (Q) channels.…”

“…Thus, the I/Q mismatch calibration method is necessary in high-order modulation systems. Several methods to compensate the I/Q mismatch have been reported, including compensating 90-degree phase characteristics in the digital domain [1][2][3][4], and in the analog domain [5], which need complex phase compensation circuits with increased power consumption. Thus, a compact, low-loss, and low power I/Q phase reconfiguration approach in the RF domain still needs to be explored.…”