A dual-frequency continuous-wave (DF-CW) radar is a cost-effective device for multiple target tracking in indoor environments. To position the target, the traditional DF-CW radar adopts a quasi-monostatic structure to acquire the target range and direction of arrival (DOA). However, the traditional DF-CW radar usually suffers from the drawbacks of low positioning accuracy, biased target information, and severe ambiguous frequency interference. To overcome these drawbacks, the traditional DF-CW radar structure is modified, and an improved target tracking algorithm, which is based only on the range measurements, is proposed in this paper. Compared with the traditional DF-CW radar-based detection, the proposed algorithm not only can achieve higher positioning accuracy, reveal more abundant and precise target information, but also can help to suppress the ambiguous frequency interference, which is of great importance in the multiple target tracking scenarios. Besides, the proposed DF-CW radar can also effectively reduce the coupling interference, thus contributing to the improvement of the radar dynamic range. A series of experiments are conducted to demonstrate the effectiveness of the proposed algorithm, and the obtained results illustrate a better performance of the proposed algorithm compared with the traditional algorithms.

The omnidirectional transmission properties of photonic heterostructures composed of cascaded one-dimensional photonic crystals (1DPCs) with the same materials and different thickness ratios of the alternate high- and low-refractive index layers were studied theoretically. A criterion for designing omnidirectional reflectors with a maximum bandgap width is presented for heterostructures with an arbitrary number of cascaded 1DPCs. Omnidirectional reflectors based on two and three cascaded 1DPCs are designed according to the criterion.

Optical interleavers based on Michelson Gires-Tournois interferometer (MGTI) with arbitrary cascaded reflectors for symmetrical or asymmetrical periodic frequency response with arbitrary duty cycles are defined as universal MGTI optical interleaver (UMGTIOI). It can significantly enhance flexibility and applicability of optical networks. A novel and simple method based on digital signal processing is proposed for the design of UMGTIOI. Different kinds of design examples are given to confirm effectiveness of the method.

This letter proposes a Doppler through-wall radar (TWR) positioning method based on the Hough transform of the extended Bezier model. First, the Hough transform based on the extended Bezier model is used to extract the interested target components from received echoes and estimate their instantaneous frequency (IF). Next, the real-time position of the target is estimated according to the Doppler processing. To improve the adaptability of the algorithm to different target trajectories, especially to solve the problem of asymmetric curve fitting, the proposed extended Bezier model can approach the practical IF curve by dynamically adjusting two parameters, which can not only keep the relatively low computational complexity but also significantly improve the positioning accuracy. Moreover, the proposed algorithm effectively solves the problem of ``frequency ambiguity.'' The experimental results demonstrate and validate that the proposed algorithm is effective in the field of human sensing applications of Doppler radar.

In this letter, a multiperspective target tracking approach is proposed for Doppler through-wall radar (TWR). To properly identify stationary and tangentially moving targets, an expansion receiver is added to the traditional cost-effective Doppler TWR, and a data fusion process is applied to track targets. Using the expansion receiver, the information on the target is acquired from another perspective, which can help to eliminate the detection dead zone. This proposed approach can also improve estimation accuracy. As a preliminary assessment, experimental results are provided to illustrate the performance of the proposed approach.