Abstract-In this paper an edge coupled microstrip coupler with defected ground structure is presented. A normally 7 dB coupler designed on Alumina substrate is converted into a 3 dB coupler by cutting single rectangular slot in the ground plane encompassing the two transmission lines. Other properties of backward wave coupler remain the same, except for a tighter coupling. With this method of design optimization, it will be possible to fabricate a 3 dB coupler in compact form without strain in fabrication process. The structure is analyzed considering magnetic and electric coupling between the two transmission lines. Simulation based studies show reasonable agreement between analytical results and corresponding simulation results.

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Abstract-In this paper we propose a digital beamformer utilizing the radar integrator method of detection. In the receive mode the digitized radar returns weights are allocate on the such a way that the first pulse reflect a SUM pattern and the subsequent three pulses reflect DIFFERENCE pattern. The pulses on DIFFERENCE pattern are added to each other and the net signal subtracted from signal received in SUM pattern. This results in very narrow beam which shows narrow spatial resolution. The schematic is presented and the results are shown.

Abstract-In this paper a programmable beam-switching algorithm for planar phased array antenna is presented. Using micro-controller the planar array can be steered over 49 directions over the complete hemisphere. Each element is connected to delay lines and switching module. The bits at micro-controller output after being amplified by driver circuit are fed to the switching modules which control the insertion of fixed phase tapering. Switching is performed on a unique set of delay lines to steer the beam in particular direction in the horizon. For high frequency application PIN diode is used as switch. In total 12 bits are used to select 49 beam positions with some bit patterns being redundant.