A single-layered radial line slot antenna (RLSA) is proposed for a direct broadcast from a satellite (DBS) subscriber antenna. It utilizes a radially outward-traveling wave and the aperture field is intolerably tapered if the uniform slots are used. Two novel techniques are applied. First, the slot design for uniform aperture field distribution is introduced. Second, the radial line is terminated by a matching spiral, in place of a dummy load. It suppresses reflection and radiates all the residual power in circular polarization. For a model antenna of 600-mm diameter, the efficiency of 65% is observed. >

A slot design for uniform aperture field distribution in single-layered radial line slot antennas

The authors propose the design of one radial line slot antenna with two simultaneous beams, one broadside beam and one conical beam. The antenna is a radial line slot antenna (RLSA), with the slots placed on the upper plate in concentric rings. The radiating element is a slot pair, designed for getting left hand circular polarization. The antenna has been designed to work in the range of 13.4 GHz and 14 GHz. Both beams are obtained independently through very simple excitation circuits, realized with microstrip technology. These feeding networks include a Butler Matrix Network. Comparing both radiation patterns, amplitude and phase, theta and phi angles of arrival direction can be obtained. This monopulse performance can be used to orientate the pencil beam for satellite communication antennas. Measurements for a first prototype are presented to validate the design.

Low-cost monopulse radial line slot antenna

The gap waveguide technology for millimeter waves applications has been recently presented. The new structure is made by generating a parallel plate cut-off region between an artificial magnetic conductor (AMC) and a metallic plate. Propagating waves will be only allowed to follow a metal ridge or groove surrounded by the AMC. The gap waveguide can be made of only metal and does not need any contact between the metal joints compared to standard waveguides. In this study, a study of Q-factors of resonators made in ridge and groove gap waveguides are presented. The resonators are made of copper and the AMC used is a textured surface of metallic pins. Simulated and measured unloaded Qs are presented and compared with Q of a standard rectangular waveguide. High Q-factors are measured for the prototypes presented, approaching 90-96% of the simulated values. Furthermore, it is shown how the lid of pins can easily stop the leakage loss at the joints of the circuit, which is the typical cause of reduced Q-factor of standard waveguides at high frequency.

https://publications.lib.chalmers.se/records/fulltext/182464/local_182464.pdf

Study of Q-factors of ridge and groove gap waveguide resonators

A novel planar antenna in which radiating slots are arrayed on one side of a square parallel plate waveguide and coupling slots occupy the other side is proposed. The antenna is excited via the coupling slots by a rectangular waveguide. In order to suppress unwanted reflections and to assure the purity of the transverse electromagnetic traveling-wave mode in the parallel plate waveguide, all the slots are arrayed in pairs. An X-band model antenna was fabricated, and uniform aperture illumination was demonstrated with 48% antenna efficiency. These results demonstrate the feasibility of antennas of this type. >

Waveguide-fed parallel plate slot array antenna

A design for linearly polarized radial line slot antenna (RLSA) is proposed. A novel slot arrangement is presented which couples to the rotationally symmetric guided waves to produce a uniform aperture distribution with linear polarization. Basic characteristics were measured in the 12-GHz band on a model antenna. The radiation patterns indicate a reasonable cross-polarization level more than 15 dB below the copolarization. The poor VSWR response is typical for waveguide broadside arrays. A technique to suppress this reflection is to tilt the beam from the boresight. >

A linearly polarized radial line slot antenna

Characteristics of a novel planar antenna which can radiate a circularly polarized pencil beam in x -band are presented for the application of receiving direct broadcast from a satellite. This antenna belongs to a class of slotted waveguide antennas and promising performances, especially its high efficiency, have already been predicted theoretically. The measured performance of a model antenna with a diameter of 0.6 m, is presented. Antenna gain of about 35 dBi and axial ratio of about 1 dB are realized at 12.2 GHz; the associated antenna efficiency of 57 percent is very high in comparison with that of the conventional microstrip antennas, in this range of gain.

Characteristics of a radial line slot antenna for 12 GHz band satellite TV reception

Coupling between slots and slow-wave waveguides in a radial line slot antenna (RLSA) is discussed. Field analysis of the waveguide with a surface impedance wall revealed a considerable change in the propagation constant due to coupling. Experiments were performed to confirm these results and to obtain the surface impedance for actual slots. The change in the propagation constant caused the antenna efficiency to exhibit its maxima at two separated frequencies. An efficiency of 60% and 50% was measured at 11.6 and 12.4 GHz, respectively, which confirms a theoretical prediction. This effect suggests the possibility of broadband planar antennas. >

Slot coupling in a radial line slot antenna for 12-GHz band satellite TV reception

The analysis and the design of the matching slot pair for a circularly polarized slotted waveguide array are described. The position and the size of the slots are numerically optimized to suppress reflection and to realize a desired polarization in the tilted beam direction, which contributes to the improvement of the antenna efficiency. A boundary value problem is analyzed for the matching slot pair taking the wall thickness of a waveguide into account in order to evaluate the phase of aperture fields accurately. The position and the size of the slots are determined on the basis of this analysis. The design is verified by measuring the reflection coefficient, the radiation patterns, and the axial ratio of a model slot pair. It was verified experimentally that the return loss is below -15 dB over 0.1 GHz at the 4-GHz band and the 3-dB axial ratio bandwidth is about 5% in the titled beam direction. >

A matching slot pair for a circularly-polarized slotted waveguide array

This paper presents a measurement method for determining effective conductivity of copper-clad dielectric laminate substrates in the millimeter-wave region. The conductivity is indirectly evaluated from measured resonant frequencies and unloaded Q values of a number of Whispering Gallery modes excited in a circular disk sample, which consists of a copper-clad dielectric substrate with a large diameter of 20-30 wavelengths. We can, therefore, obtain easily the frequency dependence of the effective conductivity of the sample under test in a wide range of frequency at once. Almost identical conductivity is predicted for two kinds of WG resonators (the copper-clad type and the sandwich type) with different field distribution; it is self-consistent and provides the important foundation for the method if not for the alternative method at this moment. We measure three kinds of copper foils in 55-65GHz band, where the conductivity of electrodeposited copper foil is smaller than that of rolled copper foil and shiny-both-sides copper foil. The measured conductivity for the electrodeposited copper foil decreases with an increase in the frequency. The transmission losses measured for microstrip lines which are fabricated from these substrates are accurately predicted with the conductivity evaluated by this method.

Kimio Sakurai

Papers

Characteristics of a radial line slot antenna for 12 GHz band satellite TV reception

Slot coupling in a radial line slot antenna for 12-GHz band satellite TV reception

A matching slot pair for a circularly-polarized slotted waveguide array

Evaluation of Effective Conductivity of Copper-Clad Dielectric Laminate Substrates in Millimeter-Wave Bands Using Whispering Gallery Mode Resonators

Design and Measurement of the Plate Laminated Waveguide Slot Array Antenna and Its Feasibility for Wireless Link System in the 120GHz Band