This letter introduces a topology of a very wideband filter intended for the use in ultra-wideband 3.1-10.6 GHz applications. Basic filter configuration consists of quarter-wave short-circuited stubs and quarter-wave series transformers. To improve the out-of-band rejection, a low-pass filter is added across the symmetry plane. The proposed component is fabricated in a planar microstrip configuration; however, the topology can be easily adopted for other technologies including those based on surface micromachining. The measurements have shown an insertion loss below 0.86 dB, return loss above 14 dB, group-delay variation under 0.15 ns, and the third harmonic rejection better than 16 dB.

In this letter, we present a design method for K-band substrate-integrated waveguide (SIW) resonator filters utilizing mode. More importantly, a methodology for suppressing an unwanted higher-order mode ( ) close to the passband is demonstrated. It is shown that suppressing the unwanted mode give rise to the improved stopband performance. In addition, the resonator used in this filter design has capability of adjusting the resonant frequency, and this allows for compensating the fabrication error. Verification of the presented design method has been carried out by fabricating and measuring the filter.

A novel substrate integrated waveguide to rectangular waveguide (RWG) transition for effective power transfer is proposed. The substrate taper is inserted into a conventional height-stepped impedance transformer of the RWG region to improve transmission loss and bandwidth. The transition is designed to cover the entire K-band (18-26 GHz), showing a return loss of 20 dB. A back-to-back transition has been fabricated to verify the proposed transition. The experimental results show good agreement with the analysis. The transmission loss of the stand-alone transition is 0.22 dB at 21.7 GHz with a usable bandwidth of 36%.

This letter proposes a novel calibration method for a multiport amplifier (MPA) to achieve optimum port-to-port I. IntroductionModern satellite communication systems generally adopt various techniques to increase the flexibility of the antenna and the power allocation of their coverage [1]. To adaptively control communication traffic during the lifetime of a satellite, using an architecture based on the multiport amplifier (MPA) is an effective approach in multibeam systems. The theoretical analysis of an MPA with respect to classical power amplification architectures reflects that it has lower DC power consumption with lower saturation power amplifiers (PAs) [2].In this case, the isolation characteristic among the output ports of the MPA is important for successful operation. A fair port-to-port isolation characteristic can be achieved by Manuscript received Dec. 1, 2012; revised Feb. 2, 2013; accepted Feb. 12, 2013. Seong-Mo Moon (phone: +82 42 860 0862, smmoon@etri.re.kr), Dong-Hwan Shin (dhshin@etri.re.kr), Hong-yul Lee (hylees@etri.re.kr), Man-seok Uhm (msuhm@etri.re.kr), and In-Bok Yom (ibyom@etri.re.kr) are with the Broadcasting