A high‐selectivity dual‐polarization filtering antenna with metamaterial is presented in this letter. The multilayer coupled radiation structure of the antenna determines a filtering function. With the metamaterial layer designed above the antenna, a sharp roll‐off rate at high pass band edge and a better out‐of‐band rejection occurs, thus a better high selective filtering characteristic can be achieved. Simulating and measuring the antenna, the impedance bandwidth (VSWR <2) of the antenna is from 3.25 GHz to 3.85 GHz; meanwhile, the maximum gain can reach 9dBi. The gain of antenna can quickly decrease 43dBi at the high pass band edge from 3.85 GHz to 4.05 GHz and the antenna has an out‐of‐band rejection level of 27dBi from 4.05 GHz to 5 GHz. The tested results verify our designs and the antenna could be a good candidate for the 5G anti‐interference wireless terminal communication system.

A new pattern‐reconfigurable antenna with the function of 360° wide‐beam scanning and main beam direction finely‐adjustable is proposed in this letter. The antenna consists of a central feeding disc which surrounded by four snowflake radiators on the top layer of the FR4 substrate. PIN diodes are placed between the disc and each snowflake patch for realizing the wide‐angle beam steering of the antenna. By controlling the four PIN diodes on the top layer, main beam can be switched in four directions with about 90° steps in the H‐plane (17°, 106°, 197°, and 287°).The bottom layer of the substrate includes a ground plane with eight rectangular ring slots. Eight PIN diodes installed on each slot are used to further control the beam direction of the antenna. By controlling the states of the PIN diodes on the bottom layer, the main beam of the proposed antenna is capable to deflect rightward or leftward about 10° on the basis of the original four states. The simulated and measured results show that the antenna operates well at 3.64–3.88 GHz under 12 states and achieves good performance with flexible pattern reconfigurability in 12 directions. The proposed antenna could be applied in 5G wireless communication systems.

In this letter, a new integrated filtering monopole antenna with wideband harmonic suppression is presented. In the design of the proposed antenna, a compact multiple harmonic suppression low pass filter is introduced and its stopband characteristic from 5 to 20 GHz is well integrated with the common monopole antenna. The final integrated filtering antenna can work from 2.88 to 4.02 GHz, and its wideband harmonic suppression successfully achieves 5.8 times of the central working frequency. The good performances of the present filtering antenna are shown by the simulated results and measured results, which could be a good candidate for the 5G anti‐interference wireless terminal communication system.

Experimental results are in very good agreement with numerical simulations. | CONCLUSIONSA compact waveguide DC-Break operating at 18 GHz has been designed and implemented for a commissioning phase of the compact AISHa ion source at INFN-LNS.The experimental measurement confirms that the proposed structure is able to fulfill an insulation requirement of 50 kV and microwave power losses less than 0.3 dB in about 334 mm without any discharge. The modular solution and the particular shape of insulator windows provides a mechanical self-sustainability and versatility for eventual further modifications.The device is currently mounted on the DBS band microwave link of the ion source and it is allowing to keep the source operational.ACKNOWLEDGMENT

In this letter, a new wide stopband and high gain Quasi‐Yagi filtering antenna is proposed. At the beginning of feeder line in the improved Balun filtering antenna, it is integrated with the stripline low‐pass filter that contributes to wide out‐of‐band suppression. The proposed filtering antenna works from 2.25 GHz to 2.55 GHz, with a maximum gain of 8dBi at 2.5 GHz. Moreover, it possesses a faster roll‐off rate from 2.55 GHz(8 dB) to 2.8 GHz (−20 dB) and a better rejection up to 12 GHz(5 times of central frequency) outside the working band.