A compact square microstrip antenna with four slits and a pair of truncated corner for circular polarization is proposed. Theoretical modal for an antenna is developed using modal cavity model and result are validated with MOM‐based simulator and earlier reported experimental results. A good agreement between the simulated, theoretical model and measured results is obtained. The proposed antenna shows about 39% reduction in antenna size as compared with the conventional circular polarized antenna. Antenna shows consistent return loss and radiation pattern for entire frequency range. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:897–900, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26746

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An inductor-less tunable Colpitts oscillator using second generation current controlled current conveyor (CCCII) is implemented. The circuit uses a CCCII and three grounded capacitors. The passive inductor has been replaced by an active inductor [14] connected to the ground. Thus the absence of external resistor and an inductor in the circuit makes it more complacent for IC Design. The frequency of oscillation can easily be electronically adjusted. The PSPICE simulation results have been deduced. The theoretical results are verified with the parameters of BJT PR100N (PNP) and NR100N (NPN) using PSPICE simulation tool.

A new technique for designing the active microstrip antenna for circular polarization is presented. The circular polarization is achieved by four slits and a pair of truncated corner and the operating frequency is electronically controlled by the bias voltage of varactor diodes. Theoretical modal for an antenna is developed using modal expansion cavity model and circuit theory concept. The results are validated with MoM-based simulator and experimental results. A good agreement between the simulated, calculated, and experimental results is obtained. The tuning range is found to be 40.24% and shows about 71% reduction in antenna size as compare to the conventional circular polarized antenna.

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