Quad-ridged Waveguide Research Articles

Dual-Polarized Inverted Quad-Ridged Flared Horn Antenna With One-Decade Bandwidth for OTA Testing

This letter presents a dual-polarization inverted quad-ridged flared horn antenna with an extremely wideband of more than one decade in the range of 2–20 GHz. The modes of the inverted quad-ridged waveguide are analyzed first. A cross-shaped inverted ridge, with low TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode cutoff frequency and a tip significantly higher than the horn aperture, is proposed. The inner surface of the horn wall is based on a composite curve flare rate. It is optimized to cooperate with the inverted ridge. Furthermore, the polytetrafluoroethylene back cavity replaces metal back cavity to suppress the high- order mode in the back cavity. The measured isolation between the two orthogonal linearly-polarized ports is nearly 45 dB and the reflection coefficient is less than –15 dB over the entire working frequency band.

Development of wideband orthomode transducers for FAST cryogenic receiver system

This paper describes the design, construction, and performance of the wideband orthomode transducers (OMTs) for the L- (1.2–1.8 GHz), the S- (2–3 GHz) and the P- (0.56–1.12 GHz) band receiver systems of the Five-hundred-meter Aperture Spherical radio Telescope (FAST). These OMTs operate at the cryogenic temperature of 70K to reduce their thermal noise contribution to the receiver chains. The development on the FAST L- and S-band quad-ridged waveguide (QRWG) OMTs is carried out based on the theoretical mode analysis. In view of the miniaturization of FAST cryogenic receiver system at P-band, a novel wideband compact bowtie dipole OMT is designed with an octave bandwidth as well as a length of only quarter wavelength. The proposed L-, S- and P-band OMTs are designed and optimized by using Ansys High Frequency Structure Simulator (HFSS), and then manufactured, tested at room temperature. Measurement of FAST cryogenic receiver system noise is also performed with the L-, S- and P-band OMTs installed. The measured results fully comply with the design specifications.

Wideband orthomode transducer for the Square Kilometre Array band4 single pixel feed

The design of a compact wideband orthomode transducer (OMT) for band4 single pixel feed of the Square Kilometre Array (SKA) dish is presented. The geometry of the proposed OMT is based on circular quad-ridged waveguide to obtain wideband characteristics, which consists of a coaxial to quad-ridged waveguide transition and a circular to quad-ridged waveguide tapered transition. By adopting circular quad-ridged waveguide and high-order cosine taper for the ridges, the length of OMT is compact and the levels of higher-order modes generated at the circular waveguide aperture are lower. To verify the OMT performance, a prototype is manufactured and tested using a vector network analyzer. The measured results agree very well with the calculated ones across the frequency range 2.8-5.18 GHz. The tested reflection coefficients are less than –19 dB, the insertion losses are less than 0.25 dB for both polarization channels, and the isolation between two output ports is better than 37.7 dB. It is confirmed that the designed OMT can be satisfied with the requirement of the SKA band4 feed system.

An optimized quad-ridged horn antenna with pyramidal sidewalls

The wideband gain and voltage standing wave ratio (VSWR) performance of quad-ridged horn antennas in general are restricted due to the excitation of higher order modes in the coaxial to quad-ridged waveguide transition. This results in large gain variations vs. frequency and break-up of the radiation patterns at higher frequencies. In this paper, a quad-ridged horn antenna is presented with optimized radiation characteristics and VSWR performance. The performance of the antenna was optimized by separating the antenna into two subsections, viz. a coaxial to quad-ridged waveguide transition section and a flared quad-ridged horn section. The performance of each section was optimized individually using a numerical solver – CST Microwave Studio. Three possible configuration of the coaxial to quad-ridged waveguide transition section were considered and optimized. Four configurations for the flared quad-ridged horn section were also investigated. The best performing configuration from each one of the two sections were combined to yield the final design of the optimized quad-ridged horn antenna. The numerical performance of the quad-ridged horn antenna was validated through measurements, performed in a compact antenna test range. The optimized antenna has a 12.5:1 frequency bandwidth from 0.8 to 10 GHz. Over this frequency range, the antenna has a VSWR performance typically better than 2.5:1, stable boresight gain and radiation patterns for both ports with more than 30 dB isolation between the two ports.

Broadband offset quad-ridged waveguide orthomode transducer

The design and measurement of an offset quad-ridge waveguide orthomode transducer (OMT) are presented. The transducer comprises two orthogonal ridges inserted in a square waveguide, with one ridge offset in the propagation direction to greatly increase the singlemode operating bandwidth of the structure. Measurements of an OMT designed to operate across the 2.4–4 GHz band show a return loss of better than −20 dB for both polarisations and cross-coupling levels of below −40 dB over most of the required band.

A wide-bandwidth coupler for a free-electron-maser amplifier

The coupler described in this paper is designed to separate the hot electron beam and the high-power microwave signal in a free-electron-maser amplifier. This coupler has been designed, built, and tested and is intended for operation across the 8-18 GHz frequency band. It consists of an arc of quadridged waveguide with the electron beam entering between ridges. The RF performance was found to be critically dependent on the radius and length of the arc. The measured return loss is better than -30 dB across the band with an insertion loss of less than 0.1 dB.

A wideband orthogonal-mode junction using a junction of a quad-ridged coaxial waveguide and four ridged sectoral waveguides

A wideband orthogonal-mode junction (OMJ) using a quad-ridged circular coaxial waveguide and four single-ridged sectoral waveguides is described. The new structure is used for extracting a wide lower band signal from a coaxial dual-band feed. Theoretical results show that the broadband incoming signal in the quad-ridged coaxial waveguide can be coupled to four single-ridged sectoral waveguides with low reflection. The new structure transforms a complex system to a simple single-ridged sectoral waveguide where multi-band separation can be accomplished by a number of means. The transformation eliminates the interference among the excitation sources and enables the accurate mathematical modeling of the complete system possible.

Wide-band orthomode transducers

A summary of the results of a mainly experimental investigation into the development of wideband orthomode transducers (OMTs) is presented. It is shown that satisfactory performance for many applications is possible over bandwidths in excess of 2:1. The wideband return loss and cross-polarization behavior are given where the OMT used is measured in conjunction with a wideband corrugated horn. Two types of OMT are considered: one based on a finline technique and the other on a quad-ridged waveguide geometry. Overall, the latter design gives superior performance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Ridged waveguide phased array elements

The mutual coupling solution of dual and quad ridged waveguide is described for an infinite array environment. The method of analysis is the numerical solution of integral equations for both the eigen solution and the boundary matching problem. In addition to numerical results, comparison of theory with waveguide simulator measurements is also given.