Wideband in‐phase/quadrature imbalance compensation using finite impulse response filter

Abstract

The authors proposed an in-phase/quadrature (I/Q) imbalance compensation technique for wideband digital receiver applications. An I/Q channel-based receiver can double the receiver working bandwidth. However, the amplitude/phase imbalance of an imperfect hybrid coupler can generate image signals thus reducing the receiver's instantaneous dynamic range. They developed a finite impulse response filter-based technique to mitigate deleterious effects because of the amplitude/phase imbalance. Both simulations and experiments were conducted to verify validity of the developed algorithm. The simulation and experiment results show that the proposed imbalance mitigation technique can reduce image signal powers by more than 24 dB or down to noise level. A receiver system level simulation is also conducted to demonstrate the practicality of the proposed imbalance mitigation method.

Wideband receiver with I/Q channels for multiple Nyquist zone coverage

“…The author co-developed an imbalance compensation method for wideband receiver applications [18] and its working principle can be explained by Fig. 4.…”

“…By revising the matrix representation in Fig. 4 into a complex-number representation and taking the inverse digital Fourier transform on the resulting coefficients, we can derive the operation of the compensator in the time-domain, which will be in the format of a finite impulse response (FIR) filter whose representation is given in (1) [18] …”

“…By revising the matrix representation in Fig. 4 into a complex‐number representation and taking the inverse digital Fourier transform on the resulting coefficients, we can derive the operation of the compensator in the time‐domain, which will be in the format of a finite impulse response (FIR) filter whose representation is given in (1) [18] where (2 M + 1) is the tap number of the FIR filter. The larger the number M , the better performance of the imbalance compensator and the value of M will depend on coupler's mismatch profile.…”

Wideband receiver design using frequency-dependent magnitude/phase mismatch

“…However, mismatch compensation schemes developed by communication engineers either assume the magnitude/phase mismatch is a constant value [6,7] or signals of interests are confined in the same Nyquist zone [8]. Recently, the author co-developed a new magnitude/phase mismatch compensation scheme designed to compensate frequency-dependent magnitude/phase mismatch over two Nyquist zones [9]. The input and output relation of the equalizer is given in Eq.…”

“…Although the magnitude and phase imbalance is a common issue in communication systems, due to the facts that wideband receiver does not assume signal frequency and signals to be detected might have very short duration, the imbalance compensation methods developed for communication receiver are not suitable for wideband receiver [6,7,8]. Recently, the author co-developed an algorithm to compensate frequency dependent magnitude/phase mismatch for wideband receiver application [9]. With a magnitude/phase imbalance compensator, the working bandwidth of a wideband receiver can be doubled.…”