Interference cancellation holds great promising to suppress the non-cooperative interference. However, it is usually difficult to obtain an ideal copy of the non-cooperative interference since its statistical characteristics are unknown. A novel adaptive antenna array based non-cooperative co-channel interference cancellation system for ultrashort wave (USW) radios is proposed in this paper. By adopting the auxiliary antenna array, the designed system realizes blind interference extraction from the received mixed signal based on the constrained maximum variance criterion. Then, the extracted interference is assigned as the reference signal to realize interference cancellation of the received signal in the reference antenna channel. Meanwhile, the non-ideality characteristics including nonlinearity and IQ imbalance in the receiver chain are taken into account. A widely linear least mean square (WLLMS) model based on Volterra series is introduced in the cancellation process. As a blind method, no extra reference signal and specified array structure are required in this proposed system. Simulation and experimental results validate the effectiveness of the proposed scheme, which implies comparatively strong practicality in non-cooperative co-channel interference cancellation for USW radios in engineering.

The interference cancellation ratio (ICR) is a key performance indicator of digital-to-analog hybrid radio frequency (RF) interference cancellation systems. Aiming at the low convergence speed of a digital-to-analog hybrid RF interference cancellation system based on a multi-tap structure (MDARFICS), a novel, fast, and robust variable-step-size least-mean-square (LMS) algorithm based on an improved hyperbolic tangent function (IHVSS-LMS) is proposed. The IHVSS-LMS algorithm adopts an improved hyperbolic tangent function and uses adjustable parameters and the iteration number to jointly adjust the step size, which improves the convergence speed and reduces the computational complexity. Moreover, by using the prior information of the input signal, the non-linear relationship between the step size and the input signal power is established, which enhances the robustness and the ability to suppress interference with mutable power. The IHVSS-LMS algorithm is applied to the MDARFICS. Through theoretical derivation, the convergence speed and the steady-state expressions of the interference cancellation ratio of the MDARFICS are obtained. The simulation results show that under the conditions of high and low signal-to-noise ratio (SNR), the robustness, convergence speed, and steady-state error performance of the IHVSS-LMS algorithm are better than the existing variable-step-size algorithm. The experimental results show that using the IHVSS-LMS algorithm, the MDARFICS can not only effectively accelerate the convergence speed by at least three times but can also improve the ICR by more than 3 dB.

The remote sensing satellite is developing toward high resolution, large data capacity, and fast transmission rate. The ground receiver is correspondingly required to have the high parallel to improve real-time reception and processing capabilities. In the frequency domain, the parallel processing of multiple subbands is achieved by dividing broadband into narrow bands. However, narrow-band subbands are reconstructed into broadband signals, which can lead to cross-subband distortion. It will affect the accuracy of high-resolution remote sensing images. In this article, the subband division and reconstruction framework is proposed by combining the analog filter with the digital filter. The phase calibration methods and digital filter optimization are proposed to improve the amplitude and phase consistency of the reconstructed signal. The simulation results show that the proposed amplitude consistency optimization method effectively reduces the reconstruction error within 0.001 dB. The proposed phase calibration method effectively reduces the bit error rate of the reconstructed signal. The maximum deviation is no more than 0.1%. Experiments have shown that the optimization method can reduce the distortion error of high-resolution remote sensing images.

Self-interference stemming from transmission power leakage to the receiver deteriorates the performance of linear frequency modulated continuous wave (LFMCW) radar. Therefore, how to increase the isolation between the transmitting and receiving antennas becomes a major problem for the improvement of LFMCW radar. In this paper, we adopt a microwave adaptive interference cancellation system based on down-conversion, and propose to use a phase shifter to offset the phase shift caused by the circuit delay and components in the down-conversion circuit, thereby improving the self-interference cancellation ratio. Experiments are conducted to evaluate our methods. The results show that, compared with the traditional delay-based compensation method, our phase-offset based method can increase the interference cancellation ratio (ICR) by 15dB under the condition of wired interference coupling and 10dB under the wireless coupling condition.

!Adaptive interference cancellation is an effective means to fulfill the anti-interference requirements of communication systems. The radio frequency (RF) front-end gain plays a crucial role since it determines the communication sensitivity and anti-interference performance, especially in the presence of both high-power interference signals and weak communication signals. In this paper, the influence of the RF front-end gain on communication sensitivity as well as Interference cancellation ratio (ICR) are thoroughly analyzed. Thereinafter, we derive the mathematical model of the RF front-end gain constrains taking communication sensitivity, ICR requirement and analog-to-digital converter quantization accuracy into consideration. Based on the upper and lower boundary region of gain, we propose the gain design criterion for adaptive interference cancellation in communication systems. Extensive simulations demonstrate that: 1) the ICR performance improves with the increase of RF front-end gain when lower than the gain obtained from upper boundary region, and is saturated afterward; 2) the gain obtained from lower boundary region analysis can ensure the communication sensitivity. Experimental results verify that the gain design criterion ensures the communication sensitivity and satisfies the requirements of anti-interference performance under high-power interference signals.