E-plane Beamwidth Research Articles

ANALYSIS OF RADIATION CHARACTERISTICS OF A PROBE-EXCITED RECTANGULAR RING ANTENNA BY THE DYADIC GREEN'S FUNCTION APPROACH

Radiation characteristics of a probe-excited rectangular ring antenna are investigated by using the dyadic Green's function approach. The radiation characteristics, such as radiation pattern, beam-peak direction, half-power beamwidth and directivity, are analyzed. For the specified operating frequency, the ring width and ring height are selected as the same cross-sectional dimension of rectangular waveguide operated at the dominant mode. The effects of the excited probe and rectangular ring to the modal distributions are described. For the desired modal distribution, the directivity primarily depends on the ring lengths. For compact size of the proposed antenna, the ring length of 0.4λ is chosen to provide a bidirectional pattern with the calculated half-power beamwidth in E-plane and H-plane of 100 and 69 degrees respectively, and directivity of 4.43 dBi. Furthermore, the prototype antenna was fabricated and measured. The coincided results between the theory and the experiment are obtained.

Micromachined waveguide antennas for 1.6 THz

A new type of horn antenna for operation at 1.6 THz, that can be fabricated monolithically with 1/4-height micromachined waveguide, is described. Height limitations imposed by the micromachining process are overcome by removing a tapered slot in the upper surface of a scalar horn, allowing the E-plane fields to extend outside the confines of the metallic structure before radiation, with a consequent reduction in E-plane beamwidth. 1.6 THz radiation pattern measurements for different designs show that, while there is scope for further optimisation, 3 dB beamwidths of 24° and 17.5° in the E- and H-planes, respectively, can be achieved.

Ultra-wideband transmit/receive antenna pair for ground penetrating radar

Experimental results from a novel compact transmit/receive antenna pair consisting of two loss-loaded bow-tie monopole antennas are described. Instead of using a distributed resistive loading of the antenna, a broadband microwave absorber is applied as a lossy dielectric loading of the bow-tie elements. The antenna pair has a number of remarkable features. It is characterised by a high bandwidth (400-6000 MHz), a low cross-coupling, and a sharp impulse response with low reverberation. The radiation pattern maintains the same shape and orientation across the whole bandwidth, with an E-plane beamwidth ranging from 100/spl deg/ to 40/spl deg/ and a maximum antenna gain of 3.0 dBi. The input impedance is resistive, and has a value of 75 /spl Omega/ over a wide frequency range. Furthermore, the input impedance is not affected by the presence of the soil when the antenna is placed on the ground surface.