Enlarging or reducing the antenna beam width of antennas can improve the positioning capability of detection systems. A miniaturized and easily fabricated ultra-wideband (UWB) antenna system for long-distance electromagnetic detection is proposed in this article. Two ultra-wideband Vivaldi antennae were designed. One was the transmitting antenna with a beam width of 90° or above, the other was a narrow beam antenna array with beam width less than 10°, as a receiving antenna. Both proposed antennae feature broadside gain diagrams with stable radiation patterns and wideband impedance matching in the frequency range between 2.5 GHz and 4 GHz. After detecting their frequency and time-domain behaviors, the detection system can achieve measurements covering a radius of 30 m.

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For the coexistence of SUT (System Under Test) radiative emission signal and ambient interference signal, the amplitude of SUT signal will be submerged by the amplitude of interference signal, so it is difficult to accurately measure the amplitude of SUT signal. In this paper, a two-level nested array is used as the receiving array antenna, and the mixed matrix estimation method based on Blind Source Separation (BSS) is used to separate the coherent groups of the signal. Then the Sparse Reconstruction method is used for the DOA (Degree Of Arrival) estimation of each coherent group of the signal. After the DOA information of each signal is obtained, beamforming method is used to form beams of the main channel and auxiliary channel. The beam of the main channel outputs without distortion in the direction of the SUT signal and forms zero traps in the direction of the coherent signals, while the beam of the auxiliary channel forms zero traps in both the direction of the SUT signal and the direction of the coherent signal. The data received by the array are respectively multiplied by the weights of the main channel and auxiliary channel to obtain the output signals of the two channels. The output signals of the two channels are respectively fed into the Adaptive Noise Cancellation (ANC) system, and the ANC method is used to suppress the ambient interference signals and restore the SUT signal. Simulation and experiment results show that this method can accurately estimate DOA of radiation emission signals, effectively suppress ambient signals and restore the signal of SUT in field measurement of radiation emission.