The groove-guide oscillator

The groove guide, a low-loss waveguide consists of two separate parallel plates whose separation distance can be adjusted, thereby affecting the frequency of operation of the guide itself. The standing waves in a groove guide along the direction of propagation are commonly obtained by either total reflection at both ends or by forming a closed loop. A negative resistance has to be implemented to induce oscillations of the groove guide resonator. It is desirable to induce oscillations directly inside the groove region therefore the negative resistance must be placed inside the groove. A Gunn element was selected to provide this negative resistance. A standard heterodyne system may be realized in order to use the groove-guide oscillator for distance or permittivity measurements. The groove-guide oscillator works as an active sensor in the X-band. The accuracy with which the resonant frequency is determined depends on the bias stability of the Gunn element, the phase noise of the local oscillator, and the error of the frequency counter.Scientific and Technological Research Council of Turkey (grant no.106E100

Switchless bidirectional amplifier for wireless communication systems

A bidirectional amplifier working at 2.4 GHz is presented in this article. The presented amplifier is able to amplify two signals simultaneously. This, since commonly used radio frequency switches are replaced by circulators. The amplifier is designed on a single small-sized printed circuit board. First, the new amplifier circuit is proposed and characterized. Then, its advantages and design problems are analyzed. Finally, design instructions are setup in order to obtain a good performance of the switchless amplifier within the frequency band of interest.TÜBİTA

Millimeter waveband semi-symmetrical groove guide resonators

As an alternative to the classical waveguides, such as the H-waveguide and the rectangular waveguide, the groove waveguide has been used at millimetre wavelengths for the last couple of decades. Most of these properties are attributed to the open sides of the guide, which reduce the wall losses. This article describes a semisymmetrical groove guide resonator that is designed and analyzed analytically, numerically, and experimentally. The numerical simulations are performed via a powerful time-domain simulator based on the finite-difference, time-domain (FDTD) method. Both Cartesian- and cylindrical-coordinate FDTD packages are developed and used for the simulations. The purpose in using cylindrical-coordinate FDTD is to calibrate Cartesian-coordinate FDTD and to see the error introduced due to discretization. A measurement setup with an adjustable support platform in the frequency range of 20-40 GHz is used in the experiments.IEEE Microwave Theory and Techniques Societ