engleski

Push-Pull Oscillating Antenna with Circular Polarization

New design of a circularly polarized microstrip patch antenna excited with a push-pull transistor oscillator is presented. At the outputs of the push-pull oscillator the signals have 180&ordm ; ; ; ; phase shift. In order to obtain circular polarization the microstrip patch is excited in two points with signals having 90&ordm ; ; ; ; phase shift. To convert the 180&ordm ; ; ; ; phase shift between the oscillator outputs to the required 90&ordm ; ; ; ; phase shift at the patch excitation points a quarter-wavelength long microstrip line is used. The oscillator and the line are integrated in an opening in the patch in order to maintain small dimensions. The antenna prototype is manufactured and its characteristics are experimentally investigated. Frequency tuning is obtained by changing the dc bias voltage. The antenna radiates left-handed circularly polarized wave. The spectrum is clean and no spurious compo-nents are observed. The radiation pattern is not disturbed by the modifications in the patch and by the active circuitry.

microstrip antenna; active integrated antenna; push-pull oscillator; circular polarization

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