The Research And FPGA Implementation Of Cognitive Anti-jamming For Aviation Datalink

With the increasing of serious electromagnetic jamming in the modern airborne battlefield, there is a great deal of limitation for blind anti-jamming methods in aviation radio system. Recently, a novel anti-jamming technology based on cognitive radio(CR) is proposed, but the study about this anti-jamming scheme has not yet completely integrated system, and many problems need to be solved.In order to meet the requirements of the actual application and enhance the anti-jamming capability of aviation data link(ADL) in the complex electromagnetic environment, in this paper, the new strategy based simultaneous transmit and receive cognitive anti-jamming(SCAJ) is proposed, the jamming sensing and communication mode is designed, and the jamming sensing of SCAJ receiver impaired by IQ imbalance?phase noise?aperture jitter in ADC is investigated. The adaptive threshold algorithm for jamming sensing and FPGA Implementation are considered in detailed.Firstly, the transmit-sense-receive(T-S-R) mode based SCAJ strategy is proposed, and the real time anti-jamming ability can be achieved by dynamically allocating the sensing timeslot and receiving timeslot. We study the performance of jamming sensing based on energy detection(ED) under fading channels, and the system capacity of SCAJ is derived. That it is provided a theoretical basis to quantitatively evaluate the performance of SCAJ system.Secondly, we explore the problem of the image distortion impaired by IQ channel imbalance in SCAJ system. The jamming sensing of SCAJ single- and multi-channel receiver impaired by IQ imbalance is investigated, and ED based the jamming detection and false alarm probabilities in closed-form for SCAJ system are derived. Then, the image channel interference cancellation scheme is proposed to mitigate the image channel crosstalk.And then, the jamming sensing of SCAJ receiver impaired by phase noise in local oscillators(LO) is investigated under fading channel. ED based the jamming signal to noise ratio of SCAJ receiver with phase noise under different channels is analyzed, and the jamming detection and false alarm probabilities for SCAJ receiver are derived. Then, the Modified Bayesian Cra`mer Rao Bound(BCRB) for the channel and phase noise estimators are studied. Furthermore, an accurate phase noise estimation and compensation scheme can improve the jamming detection probability of SCAJ receiver and approach to the upper bound.Further, the jamming sensing of same- and different-frequency SCAJ receiver impaired by aperture jitter in ADC is investigated. ED based the jamming signal to noise ratio of SCAJ receiver under different channels is analyzed. These studies can provide the theoretical basis to analyze the performance of receiver with aperture jitter in ADC quantitatively.Finally, the adaptive threshold algorithm for jamming sensing of SCAJ is proposed, and the logic design is built on FPGA of ALTERA Corp using Vrilog HDL. FPGA implementation results show that the proposed meathod can correctly sense the jamming when the jamming signal to noise ratio is-10 dB, which enhance the system capacity and shorten the sensing time. It is significant to enhance the anti-jamming capability of ADL and achieve the full-time ? full-band and full-airspace electromagnetic jamming sensing.