A novel broadband microstrip to waveguide transition is proposed in this paper. A microstrip circuit is inserted into a waveguide along the axis of the broadside wall, and the referred waveguide is WR-90 standardized rectangular waveguide. The microstrip circuit consists of a pair of symmetric step-like patches, a microstrip probe, and a metal ground plane. The transition has a smaller size as it is end-inserted. Meanwhile, the traditionally stepped metal ridge in the waveguide is replaced with bistratal symmetric patches, integrated design of patches, and microstrip probe. Therefore, the welding loss and structural instability have been avoided. Complementary split ring resonators are loaded in the patches to broaden the bandwidth and increase efficiency. Measured results show that the proposed microstrip to waveguide transition achieves a −15 dB return loss with the bandwidth of 8.65-12.33 GHz, and its insertion loss is better 0.5 dB over the band of 8.13-12.13 GHz. Furthermore, this design features lightweight, low cost, and simple processing methods. INDEX TERMS Microstrip to waveguide transition, complementary split ring resonators (CSRRs), end-inserted transition.

A novel wideband dual-polarized antenna with load of a disk is presented in this letter. The antenna is composed of two cross magneto-electric dipole antennas vertically fixed on an aluminum plate as ground plane, which are excited by two similar Γ-shaped coaxial feeder. Furthermore, in order to further broaden the impedance bandwidth, a disc-shaped resonator is loaded on the front end of the dipole. And a metal barrel reflector is loaded around the antenna to further improve the antenna's radiation characteristics. Measured results show that the proposed antenna achieves a 10 dB with bandwidth of 1.2-2.4 GHz, and its port isolation is higher than 28 dB. Moreover, stable radiation pattern with a peak gain of 7.7-9.2 dB is obtained within that band.

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