A new monolithic transmit-receive GaAs FET switch has been developed, named the FET series-shunt connected TR switch and capable of switching high rf transmitting power. Both insertion loss and isolation limitations of this type TR switch have been analyzed using the switching cutoff frequency of the control FET, and the formula for calculating the rated power is provided. A unique feature of this switch is that the power handling of the switch is not limited by the FET gate break-down voltage but is limited by the saturation current, so higher handling power capability is available by using FETs with a larger gate periphery. A design example of the TR switch at a rated power of 8 W in the transmit mode as well as the results of an X band switch are presented.

In this paper, authors propose a linear array antenna using two bifilar helical antenna elements placed along the helix axis to reduce beam direction movement according to frequency change. The beam direction movement of this proposed array antenna is smaller than that of a conventional bifilar helical antenna. Also, the gain of this proposed array antenna is higher than that of the conventional helical antenna for a cross point angle of radiation patterns at the different transmit and receive(Tx and Rx) frequencies. The conventional helical antenna is suitable for vehicle antennas in mobile satellite communication systems such as the MSAT system because it owns circularly polarized omni-directional radiation pattern and its thin pole form. However, this antenna has a disadvantage that the beam direction in an elevation plane moves according to frequency change. In the proposed array antenna, the beam direction movement is about 9 smaller than that of the conventional bifilar helical antenna on condition that antenna total length is 4.83 λ0, antenna diameter is 0.12 λ0, and frequency change is from 0.957f0 to 1.043f0(f0 is center frequency and λ0 is free space wavelength at f0). Also, the Tx and Rx gains of this proposed array antenna at the cross point angle between Tx and Rx beams are about 2 dB higher than that of the conventional bifilar helical antenna on the same condition.

This paper presents a configuration of circularly polarized annular-ring microstrip antenna (ARMSA) and its design method to obtain high gain and low axial ratio including the analysis of finite ground plane effect using G.T.D. for personal satellite communication use. The ARMSA excited at TM21 mode through co-planar branch-line hybrid coupler for circular polarization produces a conical pattern which has high gain in low elevation angle. The relation of gain and axial ratio versus the dielectric constant of substrate are shown and the existence of the dielectric constant which satisfies two requirements, that is, high gain and low axial ratio are clarified. For car-top application, experimental results in the L-band showed satisfactory characteristics for vehicle antenna.

This letter describes a high power monolithic GaAs FET transmit-receive switch (TR switch) with two FETs. Both FETs operate in the same states, low impedance state in transmitting and high in receiving, so rf voltage imposed on FET is low both in transmitting and receiving. The developed TR switch can handle more than 12 W peak power at X-band frequencies.