Experimental study for optimizing self‐oscillating mixer with electromagnetically coupled antenna element

Abstract

AbstractRecently, extensive research has been carried out on active antennas using microwave transistors such as GaAs FETs for mobile communications and millimeter‐wave applications. The active antenna including a built‐in oscillator using GaAs FET devices does not require a mixer and has the advantage of reduced attenuation in transmission lines. In this paper, with a view to enhancing the output level of the IF when an active antenna is used as a self‐oscillating mixer, the addition of an electromagnetically coupled antenna such as a dipole, monopole, loop, and patch is proposed. Experimental studies are carried out on the self‐oscillating mixer with such an electromagnetically coupled element. In order to enhance the output level of the IF, conditions for optimum shapes and positions of the parasitic element are obtained. From the results of an experiment using a dipole and a loop for which the coupling of the parasitic element near the active device significantly affects the IF output level, it is confirmed that the oscillation becomes unstable if the spacing between the FET and the parasitic element is less than 3 mm. In a monopole with a structure that can increase the spacing from the active device, improvement of IF output by about 20 dB at the maximum can be obtained. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(11): 30–37, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10118