A compact slot-coupled endfire radiation antenna based on a tapering spoof surface plasmon polaritons (SSPPs) structure with high efficiency is proposed in this paper. A narrow slot balun is designed to feed the SSPPs structure rather than to work as the primary radiator. Simulated results show that the odd SPP mode is successfully excited on the tapering SSPPs structure, which contributes to the endfire radiation. Due to the high confinement of SSPPs, the proposed antenna shows low RCS within the frequency band of 1.5 GHz-4 GHz and 5.6 GHz-8 GHz. A prototype is fabricated and tested. Simulated and measured results show good agreement that the proposed antenna can provide stable endfire radiation patterns within the frequency band of 2 GHz-3.4 GHz. The maximum gain reaches 8 dBi, and the average efficiency over this bandwidth is 80%. The high-efficiency endfire SSPPs antenna with balanced broad band and high gain has a promising application in communication systems and integrated circuits.

Abstract-A distinctive connection method in cascaded RF/MW active device system achieving both stability and low gain loss is presented. Unlike traditional methods (isolator and attenuator), the proposed solution introduces an appropriate length of transmission line to change the input impedance at the out-band instable frequency point and uses a narrow-band termination to absorb the instable power without deteriorating in-band signal. Moreover, the reason that instability often occurs in the cascaded system is analysed with S-parameters, and it turns out to be a kind of out-band instability. The solution is verified by an adjustable circuit example whose insertion loss is below 0.3 dB.

Abstract-Two improved circularly polarized microstrip planar antennas operating in 5 GHz-6 GHz are proposed in this paper. The Swastika slot and a circular feeding line are introduced into Ant.2 which exhibits wide impedance bandwidth and AR bandwidth during simulation and measurement than a basic truncated edge CP microstrip antenna. In further studies, a center circular slot is introduced into Ant.3, and the experimental results show a wider impedance bandwidth and AR bandwidth with high gain.