Adaptive Interference Cancellation System Research Articles

Modeling and analysis for group delay mismatch effect on wideband adaptive spatial interference cancellation

The adaptive interference cancellation technique has been widely utilized in radar, GPS, data link, etc., systems to address challenges from external interference, such as co-site and hostile interference. Since the anti-jamming performance of the adaptive interference cancellation technique is sensitive to group delay mismatch between channels, the group delay mismatch becomes one of the main factors that limit the system’s anti-jamming capability. However, the traditional adaptive interference cancellation system’s mathematical model cannot quantitatively characterize the group delay mismatch effect on the wideband interference cancellation performance. In this paper, the mathematical model of the wideband adaptive spatial interference cancellation (ASIC) system is established, which considers the group delay mismatch, to quantitatively analyze the impact of group delay mismatch on the hostile interference cancellation. The mathematical model utilizes the weighted multi-tone signals to fit the wideband interference, and then, delay differences are attached to each tone signal to simulate the group delay mismatch. Then, the analytic expressions of weight and interference cancellation ratio are derived, which consider the interference bandwidth and group delay mismatch, to quantitatively analyze the group delay mismatch effect on the anti-jamming performance of the wideband ASIC system. Simulation results indicate that the theoretical analysis based on the mathematical model of wideband ASIC system are accurate, which can achieve the quantitative analysis of the group delay mismatch effect on the WIC performance.

Development of a single LMS loop three channels analog adaptive co-site interference cancelling system

Co-site interference is becoming prominent on some independent platforms (e.g., airplanes, satellites, space stations, and vessels). Although many digital multichannel cancellation algorithms have been investigated, the saturation problem of the receiver front-end caused by severe co-site interference should be addressed first with analog RF cancellation. Many studies are currently being conducted to develop an analog adaptive co-site interference cancellation system (AACICS). However, double LMS (Least Mean Square) loop in every channel raises the complexity and implemented difficulty. Above all, the interference cancellation in the scene of antenna swaying has received little attention, which severely limits the effective suppression of wideband interference. This study developed an analog 3-channel adaptive co-site wideband interference cancellation system (AACWICS-3ch) with one LMS loop in every channel and established the equivalent model of the AACWICS-3ch. The steady-state weight and interference cancellation ratio (ICR) were obtained by analyzing and solving the equivalent model. An in-depth analysis was conducted on the quantitative relationship correlations between the interference cancellation bandwidth, ICR, system gain, and antenna swing amplitude. Results reveal that AACWICS-3ch can greatly enhance the interference cancellation performance compared to 2-channel analog adaptive co-site interference cancellation system (AACICS-2ch). The maximum improved ICR is greater than 30 dB, and it overcomes the complexity of double LMS loop cancellation system with the increasing of channel. Finally, simulations and experiments validated the improvement of interference cancellation performance in AACWICS-3ch.

A novel adaptive noise canceling system for urea NQR spectrum analysis

Due to its practical ease of use and sufficiently high reliability, Nuclear Quadrupole Resonance (NQR) has largely been used in remote sensing-based detection of quadrupole nuclei, especially Nitrogen-containing materials. Since the received signal of free induction decay (FID) is inherently weak in this technique, the noise and the interference of the environment would dramatically impair the performance of the detecting systems. To handle such challenges, an adaptive noise canceling method was employed to improve the signal to noise and interference ratio (SNIR) in FID signals. FID signals, noise, and interference were received by the main antenna, while similar noise and interference would be received by the auxiliary antenna. The proposed system significantly reduced noise and interference through the digital noise and interference cancellation algorithm, pulse integration, averaging, and singular spectrum analysis (SSA). Urea powder was empirically analyzed outdoors, suggesting that the proposed adaptive noise and interference cancellation (ANIC) system, effectively suppressed noise and interference by 41.13 dB and amplified the FID signal by 53.36 dB. The strongest signal was detected at 2870.4 kHz.

A new adaptive co-site broadband interference cancellation method with auxiliary channel

With the boom of the communication systems on some independent platforms (such as satellites, space stations, airplanes, and vessels), co-site interference is becoming prominent. The adaptive interference cancellation method has been adopted to solve the co-site interference problem. But the broadband interference cancellation performance of traditional Adaptive Co-site Interference Cancellation System (ACICS) with large delay mismatching and antenna sway is relatively poor. This study put forward an Adaptive Co-site Broadband Interference Cancellation System With Two Auxiliary Channels (ACBICS-2A). The system model was established, and the steady state weights and Interference Cancellation Ratio (ICR) were deduced by solving a time-varying differential equation. The relationship of ICR, system gain, modulation factor, interference signal bandwidth and delay mismatching degree was acquired through an in-depth analysis. Compared with traditional adaptive interference cancellation system, the proposed ACBICS-2A can improve broadband interference cancellation ability remarkably with large delay mismatching and antenna sway for the effect of auxiliary channel. The maximum improved ICR is more than 25 ​dB. Finally, the theoretical and simulation results were verified by experiments.

Multichannel Adaptive Interference Cancellation for Full-Duplex High Power AM Radios

In space-limited co-located communication systems, wideband transmitters and receivers are deployed for various applications. The strong coupling between transmitters and receivers becomes a major concern. It is crucial to suppress the high power self-interference (SI) to prevent the receiver from working in the nonlinear area, or even saturating. As an effective approach to achieve this, the adaptive interference cancellation (AIC) technology is proposed in the context of a complex high power amplitude modulation radios. In this article, the system-level performance including the interference cancellation ratio requirements and the impact of the AIC on the receiving system is comprehensively studied for the first time. The operating mechanism of a single channel AIC system (AICS) and the configuration of a multichannel AICS are discussed. The performance analysis of the receiving system when implementing the AICS is performed, in terms of the noise figure and the sensitivity. By employing the proposed AICS, very limited effect is observed on the receivers, while the SI is successfully reduced with a high ICR, which fully satisfies the requirements for AM systems. The realization of the multichannel AICS as well as the measured cancellation performance are presented, verifying the proposed concept.

Broadband cancellation method in an adaptive co-site interference cancellation system

With the boom of communication systems on independent platforms (such as, airplanes and vessels), co-site interference has become prominent. Currently, extensive research has been conducted on the development of an adaptive co-site interference cancellation system (ACICS); however, the related interference cancellation bandwidth characteristics have not been adequately investigated, thereby critically restricting the further optimisation of the ACICS design. In this study, the bandwidth signal calculation formula of the ACICS interference cancellation ratio is derived, and the quantitative relationships among the interference cancellation bandwidth, interference cancellation ratio, system gain, and delay-matching degree are analysed exhaustively. The results reveal that the higher the required interference cancellation ratio, the smaller is the interference cancellation bandwidth; the interference cancellation bandwidth can be enhanced to a limited degree by increasing the system gain. Furthermore, the interference cancellation bandwidth and the delay-matching distance follow an approximately inverse relation, and the interference cancellation bandwidth can be improved by delay matching. The nearest matching method can be employed for broadband interference. Finally, the conducted simulations and experiments validate the correctness and effectiveness of the theoretical analysis.

Analysis of Three Channel SW Interference Adaptive Cancellation System

Aiming at the adjacent channel interference problem of short-wave, a model of three-way short-wave interference signals has been established. The interference cancellation of the short-wave interference signal of three adjacent channels is analyzed, and the time-domain characteristics of the adaptive interference cancellation system are simulated. The theoretical and simulation analysis of the adaptive system show that the offset of the bypass signal will be affected when the intermediate signal frequency is biased to one side because of the existence of the intermediate channel bandwidth.

Performance Analysis and Optimal Design of the Adaptive Interference Cancellation System

A time-domain model of the analog adaptive interference cancellation system (AAICS) involving both the interference and the desired signal is proposed. The stability, interference cancellation ratio, and convergence time of the AAICS are analyzed in detail. In addition, the desired signal cancellation ratio is taken into account in order to evaluate the system performance and optimize the AAICS more accurately. It is found that the parameters including the loop gain and the time constant of the negative feedback control loop need to be set reasonably so as to reduce a great distortion to the desired signal. The rules of parameter optimization are obtained for the AAICS operating in high frequency. Experiments are carried out to demonstrate the system's performance varying with parameters, and experimental results are in agreement with theoretical analysis, which is of great value for the optimization design of the AAICS.

Optimization on Tracking Performance of RLS Algorithm Using Transfer Function of Butterworth Low Pass Filter

In order to get further optimizations on tracking performance of the RLS algorithm in nonstationarity signal processing, and to simplify the variable forgetting factor updating model, a novel variable forgetting factor updating model based on Butterworth low pass filter transfer function was proposed. The relationship between the variable forgetting factor and the tracking performance of RLS algorithm was analyzed. The updating model proposed in this paper was built based on the modification of the transfer function of Butterworth low pass filter. The model function fit the theoretical variation curve of the variable forgetting factor well. It also could be adjusted by parameters of the function order and the critical point according to the different applications. In addition, the computation of the updating model was simple and convenience. The RLS algorithm with the updating model was tested in an adaptive interference cancellation system. Some conclusions were drawn from the simulation results. The optimized RLS algorithm had a better tracking performance in nonstationarity signal processing as well as small stationary errors after convergence.

Research on the Interference Cancellation Based on Adaptive Algorithms

The adaptive interference cancellation algorithms(AICA) is proposed in this paper. The Matlab simulation results of the performance of six different kinds of AICA are presented. According to the comparison of the simulation results, especially the usage of resource, convergence rate and effects of cancellation, the NLMS adaptive interference cancellation algorithm and frequency-domain block LMS algorithm are selected, which are suitable for the further design on FPGA. By simulating the functions by Modelsim, and analyzing the PSD curve and the constellation of output signals, the adaptive interference cancellation algorithm system based on frequency-domain block LMS have achieved expected effect. The frequency-domain block LMS adaptive echo interference cancellation system has better flatness on the in-band PSD curve and better convergence effect on the constellation. Therefore, frequency-domain block LMS adaptive interference cancellation algorithm is chosen as the design with high performance-price ratio. The more points there are, the more obvious advantages it will perform.

Digital and analog hybrid control in adaptive interference cancellation system

The digital proportion control is introduced to improve the performance of the analog adaptive interference cancellation system (ICS). For the high frequency parts of the signals after multiplier are not required, the sampling frequency need not satisfy the sampling theorem for high frequency. Because the sampling, calculation and output expend time in digital control, the ideal condition, delay condition and delay-wait condition are taken into account. Through analyzing the system model with three conditions, we gain the stable conditions of the system, the optimization step factors that can make the system converge fastest and the formulas of the interference cancellation ratios (ICRs). One step convergence can be accomplished under ideal condition, whereas the system can not converge in one step under delay condition and delay-wait condition. The calculation results show the convergence speed of delay-wait condition is slower than that of delay condition. The ICR is improved with the increase of the step factor which is in stable bound, but the convergence speed is decreased if the step factor exceeds the optimization step factor. In order to avoid that confine, the method of amending the steady state weight to improve the ICR is proposed. The analyses are in agreement with the computer simulations.

A Study on Digital RF Repeaters with Interference Cancellation System

In this paper, the adaptive interference cancellation system (ICS) in order to cancel the feedback signal in the wireless communication system is proposed. We cancel the interference with the attenuation signal corresponding to the feedback signal and estimate the feedback signal by using Normalized Least Mean Square (NLMS) algorithm. The proposed scheme showed a better performance of interference cancellation in the measurement results.

InGaP/GaAs HBT 공정을 이용하여 향상된 탱크 구조와 LC 필터링 기술을 적용한 차동 LC 전압 제어 발진기 설계

본 논문은 InGaP/GaAs HBT 공정을 통해 제작한 적응성궤환 잡음제거시스템용 낮은 위상잡음을 갖는 LC 차동 전압제어 발진기를 제안합니다. 전압제어 발진기는 필터링 기술을 포함한 향상된 공진 탱크 구조를 갖습니다. 비대칭 인덕터 대칭 캐패시터 구조로 제안된 전압제어 발진기의 출력 가변 범위는 207 MHz입니다. 출력 전력은 balun과 케이블 손실을 포함하여 -6.68 dBm입니다. 10 kHz, 100 kHz, 1 MHz에서의 위상잡음은 각각 -102.02, -112.04 그리고 -130.4 dBc/Hz입니다. 이 전압제어 발진기는 총 <TEX>$0.9{\times}0.9mm^2$</TEX> 면적 내에 집적화되었습니다. This paper presents the InGaP/GaAs HBT differential LC VCO with low phase noise performance for adaptive feedback interference cancellation system(AF-lCS). The VCO is verified with enhanced tank structure including filtering technique. The output tuning range for proposed VCO using asymmetric inductor and symmetric capacitors withlow pass filtering technique is 207 MHz. The output powers are -6.68 including balun and cable loss. The phase noise of this VCO at 10 kHz, 100 kHz and 1 MHz are -102.02 dBc/Hz, -112.04 dBc/Hz and -130.40 dBc/Hz. The VCO is designed within total size of <TEX>$0.9{\times}0.9mm^2$</TEX>.

Influence of nonlinear property for the microwave adaptive interference cancellation system

Several differences between the low-frequency interference cancellation model and the microwave interference cancellation model are investigated in this paper, with emphasis on their effects on the interference cancellation ratio and weight converging speed. When comparing the results of the computer imitation with measurements for a real microwave interference cancellation system, it can be seen that the nonlinear property of the microwave mixers limits the weight converging speed, the finite maximum attenuation of the microstrip balun bipolar p-i-n diode voltage-controlled attenuator limits the interference cancellation ratio, and the weights oscillate because of the mixers used in the system. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 425–428, 1999.

Influence of nonlinear property for the microwave adaptive interference cancellation system

Several differences between the low-frequency interference cancellation model and the microwave interference cancellation model are investigated in this paper, with emphasis on their effects on the interference cancellation ratio and weight converging speed. When comparing the results of the computer imitation with measurements for a real microwave interference cancellation system, it can be seen that the nonlinear property of the microwave mixers limits the weight converging speed, the finite maximum attenuation of the microstrip balun bipolar p-i-n diode voltage-controlled attenuator limits the interference cancellation ratio, and the weights oscillate because of the mixers used in the system. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 425–428, 1999.