A substrate-insensitive microstrip monopolar antenna is proposed and analyzed. The measured operational bandwidth of this antenna is 12% and this antenna has typical monopolar omnidirectional radiation patterns in the operational band. By using the hollow configuration, the efficiency and maximum gain of this antenna change little with the loss tangent of used substrates and can respectively reach 95% and 8.1 dBi when all used substrates are FR4. The proposed configuration provides a possibility to make antenna performance free from the long-lasting dependence on substrate's quality.

A new electronic system to realize time reversal (TR) of electromagnetic waves is proposed in this paper. By utilizing the dispersion compensation approach, the system mainly contains a chirped pulse generator, a wideband multiplier, and a chirped delay line (CDL). The TR transformation is achieved by dispersing the modulated chirped pulse through a single microwave CDL. The chirped electromagnetic band gap structure with a reflected group delay slope is fabricated and used to be the CDL. It has been demonstrated by experiments that TR of triangular-wave signals in the microwave regime can be obtained through the proposed system.

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Based on the equivalent dielectric model of the periodic metal wire array, the analytical expression of time reversal EM wave in the metal wire array is derived using transmission line method. Then, the influence of metal wire radius, metal wire array period and the amount of layers on time reversal EM wave focusing property is discussed within the equivalent dielectric model. This structure can be used to focus time reversal EM wave in the far field, at the same time, it provides an engineering reference for time reversal technique.