Harmonic radar is a kind of radar that uses the higher-order harmonics reflected by the target for nonlinear target detection. Eavesdropping equipment usually has non-linear devices, so harmonic radar can be used in the field of anti-investigation to detect voice recorders and eavesdroppers. In this paper, a kind of harmonic radar based on dual-transmitter and dual-receiver is designed to meet the needs of anti-investigation of eavesdropping equipment, and three kinds of electronic targets such as recording pen are tested and verified. The verification results show that the device can detect nonlinear electronic targets well.
A novel wired and wireless hybrid access system based on self-homodyne and heterodyne technology is presented in this paper. With the 16 Quadrature Amplitude Modulation(16QAM) and optimized self-homodyne mechanism, the system achieves 224Gbit/s wired access. Through optical heterodyne technology, the 30GHz wireless covering is implemented. The performance of the system is further improved by using the Pre-Compensation module and Post-Compensation module. Self-homodyne system improves the Optical Signal Noise Ratio(OSNR) threshold by 1.7 dB compared to the conventional coherent system, while reducing the system device requirements. The adoption of the Pre-Compensation module will save 1.7dB of OSNR tolerance even further. DSP modules of low computational complexity suitable for self-homodyne system and heterodyne system are redesigned.
In order to meet the needs of nonlinear target long-range detection, a pair of transmitting and receiving helical antenna for high-power hand-held harmonic radar are described in this paper. The operating frequency of the transmitting antenna is 3.0 GHz and the operating frequency of the receiving antenna is 6.0 GHz and 9.0 GHz. Simulated results show that both two antennas are left-handed circular polarized. The transmitting antenna has an overall impedance bandwidth (VSWR ≤ 2) from 2.6 GHz to 3.7 (24.7%), and an axial ratio (AR) bandwidth (AR ≤ 3 dB) from 2.9 GHz to 3.45 GHz (16.2%). The receiving antenna has an overall impedance bandwidth (VSWR ≤ 2) from 5.8 GHz to 10.5 GHz and an axial ratio (AR) bandwidth (AR ≤ 3 dB) from 5.8 GHz to 10.5 GHz (16.2%) for 2nd and 3rd harmonic. Maximum gain of 9 dBic for transmitting antenna and 10.7 dBic for receiving antenna are obtained as well.
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