In recent few years fractals have been employed in conjunction with antennas to develop new applications. In this work, novel fractal geometry is introduced as a miniaturized microstrip patch antenna. Compared to a square patch antenna, the antenna shows an improvement of 68% size reduction. Furthermore, by applying of a new feeding method, refereed to here as the sleeve feeding, up to 27% impedance bandwidth is achieved as shown in the experiments.

This paper presents a new wideband, low-loss and sharp rejection Band pass filter which is implemented by using broadside coupled lines and stepped-impedance open circuit stubs. It is demonstrated that using stepped impedance open stub, controllable transmission zeroes are attainable. Transmission line model for proposed structure is introduced and detailed analysis is investigated. The goals of broad pass band and sharp rejection are achieved by choosing the impedances of transmission lines properly. Designed filter operates in 2-6 GHz with low insertion loss (less than 1dB) and high rejection in out of frequency band. The theoretically predicted performance is in good agreement with experimental results.

A two-way combiner with a built-in broadside-coupled stripline coupler, for digital video broadcast transmitters at UHF frequencies is presented. The combiner exhibits more than 28dB of return losses at all ports in the entire digital television broadcast frequency band (namely 470MHz-862MHz). The isolation levels between each pair of isolated ports are more than 29dB in the above frequency band. The excellent frequency responses are obtained due to our modifications in the structure of the constituent coupled-line coupler in the form of the utilization of a multi-section broadside-coupled stripline structure and the elimination of the improper stripline bends. While the presented combiner satisfies all standard industrial requirements such as 3U (three Rack Units) distance of input ports, it shows wideband and non-resonant behavior in the frequency responses. In addition, by introducing a novel asymmetry in the structure of the intrinsic coupled-line coupler, significant reductions in the combiner size and cost are achieved.

A novel approach to ultra-wideband (UWB) antenna design is presented which is based on a general description for the geometry of monopole antennas. This general description is capable of producing almost all possible shapes for monopole antennas and it is compatible with different optimization methods. The general description is used for the optimization of rotationally-symmetric monopole antenna with finite ground plane. The optimization of antennas is performed by applying a hybrid procedure, which begins with a global search and completes with a local optimization. The optimization procedure aims at minimizing the reflection from antennas while reducing the distortion of radiated pulses. In some cases, the reduction of variations in the energy pattern is also considered. The numerical results show the reliability and effectiveness of the whole process and considerable improvement in comparison with similar antennas reported in the literature.

In this paper, a wideband coaxial power combiner with tray con guration, employing twenty 1-Watt elements mounted on antipodal nline boards, is implemented to achieve a rather high power microwave ampli er in the frequency band of 6-18 GHz. The average gain, Continuous Wave (CW) output power and Power-Added E ciency (PAE) of the combiner are measured as 17 dB, 15 Watts and 17%, respectively with ripples of less than 3 dB. In order to investigate the combining e ciency, the passive structure is fabricated and tested in the rst step. Its main components, i.e. the coaxial adapter and the antipodal nline boards, are synthesized by using Klopfenstein's optimum impedance taper, and simulated by Ansoft HFSS. Next, the active devices are added to the system. Stability, thermal management and life time issues are examined and addressed in this step. The system reliability is also demonstrated as graceful degradation due to the failure of devices.

A new type of interconnect structures called S-L-S (Signal-Load-Signal) interconnects is proposed. In these interconnect structures an extra loaded line is inserted between two signal traces. The performance of these interconnects is studied and compared for some values of the load of the loaded lines in order to get efficient and wideband interconnects.

A broadband microstrip antenna based on log periodic technique was conceived and demonstrated practically. The antenna exhibits a wideband characteristic comparing with other microstrip antennas. Over the operation frequency range, i.e.2.5-6 GHz, a 50 W input impedance has been considered.