Miroslav Samardzija

Single-Layer Waveguide Feed for Uniform Plane TEM-Wave in Oversized-Rectangular Waveguide With Hard-Surface Sidewalls

A new single-layer waveguide feed is presented for excitation of the dominant quasi-TEM mode in oversized-rectangular waveguide with hard-surface sidewalls. Coupling windows are cut on the narrow wall of the waveguide feed and are cascaded on the same layer as the oversized waveguide. The feed is compact in terms of the length compared to the conventional hard horns and inhomogenious transformers. This type of waveguide feed is useful for the uniform feeding of the oversized-rectangular waveguide slot-array antenna with installed hard-surface sidewalls. Excitation of the uniform plane wave in 4lambda0 wide waveguide is confirmed by the measurements on 12 GHz band model. The ripple in amplitude is less than 3 dB and in phase less than 15deg. The uniformity of the field distribution is preserved along the direction of the wave propagation. Presented waveguide feed has the 3-dB beamwidth of 12.5deg which is 4.5deg narrower than the one of the conventional waveguide feed. The bandwidth is 16.7% in terms of reflection less than -10 dB for the overall feeding structure

Dominant quasi-TEM mode generator for thin oversized dielectric coated rectangular waveguide

In this paper a feed circuit is proposed for oversized dielectric-coated rectangular waveguide. Feasible simulation results show the excitation of the dominant mode with an amplitude ripple less than 3 dB in oversized waveguide. Input reflection at the design frequency is suppressed to -30 dB. The bandwidth is about 7% in terms of reflection less than -20 dB.

Scattering analysis of H-plane T-junction between fully dielectric-filled rectangular waveguide and partially dielectric-filled parallel-plate

A power divider presented in this paper can be used as a key component in a feeding structure for partially dielectric-filled parallel-plate slot-arrays. Power divider can be cascaded in series in order to feed parallel-plates. Each power diver can be tuned for desired power division and minimum input reflection by coupling window and inductive post respectively. By introducing partially dielectric-filled parallel-plates in stead of fully filled ones, lower equivalent dielectric constant is expected. Such lower equivalent dielectric constant provides simultaneously three important benefits: reduction of dielectric-loss, bandwidth enhancement and slow wave factor.

Terminating Junctions in Single Layer Feed-waveguide for Excitation of the Dominant Quasi TEM-wave in Oversized-rectangular Waveguide

This paper proposes a single-layer feed waveguide with dielectric-filled matching junctions to excite a dominant quasi-TEM mode in oversized-rectangular waveguide with hard-surface sidewalls. Two coupling junctions in cascade with matching L-terminating junctions have been manufactured and the excitation of a dominant quasi-TEM mode was confirmed by both far- and near-field measurements at 12 GHz. The ripple in amplitude was less than 3 dB and in phase less than 15 deg. The bandwidth is 2.2% in terms of reflection less than -10 dB for the overall feeding structure

T-junction array to feed partially dielectric-filled oversized rectangular waveguide

A waveguide feed is designed to feed partially dielectric-filled oversized rectangular waveguide. Waveguide feed is arranged as twelve in-series cascade of power dividers and two matching junctions. The matching junctions phase transmission control ranges form −110 deg. to −230 deg. The overall reflection at the design frequency is below −10 dB. A frequency shift of 430 MHz is observed where the reflection is below −21 dB. The dielectric constant used is relatively low resulting in amplitude and phase ripple of −11 dB and 30 deg. respectively. In order to confirm the operability of waveguide feed, radiating slots will be designed on the upper plate of oversized waveguide. The measured results will be presented and evaluated.

Corrugations for suppressing undesired wave propagation in the transverse direction in a 45° linearly polarized 76 GHz parallel-plate waveguide two-dimensional slot-array

A novel mechanism based on corrugations is proposed to control undesired oblique wave propagation inside a parallel plate waveguide existing in the presence of 45° polarized radiating slots. The improvement in the near-field aperture distribution is demonstrated experimentally by aperture field measurement in a new slot array antenna incorporating these corrugations. Only marginal directivity improvement is observed and the measured gain is lower than in the original antenna (without corrugations) due to larger dissipative loss in the structure. However, it is argued that the proposed corrugated structure has the potential to improve the overall 2D slot array antenna performance after further optimization.