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This paper presents a novel orthomode transducer (OMT) with the dimension of WR-10 waveguide. The internal structure of the OMT is in the shape of Y so we named it a Y-junction OMT, it contain one square waveguide port with the dimension 2.54mm x 2.54mm and two WR-10 rectangular waveguide ports with the dimension of 1.27mm x 2.54mm. The operating frequency band of OMT is 70-95GHz ( more than 30% bandwidth) with simulated insertion loss <-0.3dB and cross polarization better than -40dB throughout the band for both TE10 and TE01 modes.Index Terms -Orthomde Transducer (OMT), WR-10 waveguide, Square to rectangular waveguide transition, Wideband performance.

An ultrawideband (UWB) pentagonal circular fractal antenna with notched band is proposed in this article. The antenna is excited using CPW‐feed. The notched band from 5.15 to 5.85 GHz is achieved to avoid interference with the WLAN systems using ring resonator slot on feedline. The experimental result exihibits the UWB from 2.5 to 15.0 GHz except the notched band. A parametric study of antenna has been carried out with respect to length and width of the rectangular ring resonator to adjust the notched band and center frequency. The measured radiation pattern of this antenna is omnidirectional in H‐plane and bidirectional in E‐plane. This antenna is useful for UWB communication system, medical imaging, and vehicular radar. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:430–434, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27316

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This article presents the methodology to design a single-fed circularly-polarized antenna with low front-to-back ratio (FBR). A circular-patch (CPatch) antenna has been incorporated within the rectangular-cavity, made of, substrate integrated waveguide (SIW). The size of the CPatch and the SIW cavity has been chosen appropriately, in a manner, that the both resonators dominant mode coincide. This arrangement has been adopted to realize the basic radiating unit with no surface-wave and the significantly lower FBR. The circularly polarization has been excited through shorting the periphery of CPatch radiator to the “one of the two metallic grounds” of this SIW cavity. The patch periphery has been shorted from two distinct points, separated by the quarter wavelength—Over center frequency of working band. The antenna has been designed and manufactured over Rogers RT/Duroid 5880 substrate with dielectric constant (εr) of 2.2, loss-tangent (tan δ, at 10 GHz) of 0.0009, and substrate height of 0.508 mm. Southwest® end launcher (SEL) along with SIW-to-GCPW (Grounded Co-Planar Waveguide) transition has been used here to facilitate the measurement of antenna’s electrical and the radiation performance. The designed antenna’s impedance bandwidth and the 3 dB axial-ratio (AR) bandwidth is 9.5% and the 2.3%, respectively. It’s simulated and the measured peak gain, within working frequency band, is higher than 8.5dBic. The proposed antenna’s FBR is antenna is significantly lower than the conventional circularly-polarized antennas. Through comparative study, with work in open literature, it has been demonstrated that the designed antenna, based on proposed method, can a potential candidate for applicable in satellite and in the other spaceborne communication system’s module—At ground and in the space station.