Corrugated horns are the feed of choice at millimeter and submillimeter wavelengths for quasi-optical systems in applications, which require high beam quality and low cross polarization over wide bandwidths, such as radio astronomy. However, this kind of feeds is difficult to manufacture at terahertz frequencies due to technological limits. Using the heritage established during Atacama Large Millimeter/Submillimeter Array band 10 (0.79–0.95 THz) production, some prototype corrugated horns for the 1.25–1.57 THz band have been designed and fabricated by direct machining. Two different kinds of corrugated horns with similar performance have been considered: long conical-profile corrugated horns and shorter profiled corrugated horns. A new modeling method has been proposed to obtain the quasi-optical parameters of the resulting horns and realize frequency independent quasi-optical designs. Patterns of the fabricated corrugated horns have been measured and results agree well with simulations. To the best of our knowledge, this is the first time corrugated horns have been successfully fabricated by direct machining for use up to 1.57 THz.

Terahertz Corrugated Horns (1.25${\hbox{--}}$ 1.57 THz): Design, Gaussian Modeling, and Measurements

A combined rigorous method is presented for the analysis of horn antennas with arbitrary cross section and general outer surface. The horn taper is described by the mode-matching (MM) method where the cross-section eigenvalue problem is solved by a two-dimensional (2-D) finite element (FE) technique. For the exterior horn surface including the radiating aperture, the application of the Kirchhoff-Huygens principle yields two expressions for the admittance matrix which are based on the electric (EFIE) and the magnetic (MFIE) field integral equation, respectively. The equations are solved numerically by the method of moments (MoM). For the preferred EFIE formulation, the eigenvectors of the last waveguide taper section and RWG functions for triangular patches are utilized as basis-functions for the magnetic or electric surface current densities, respectively. The presented method is verified by available reference values or measurements for a waveguide radiator with a peripheral choke, a conical and a rectangular horn. Its flexibility is demonstrated at the example of a conical ridged waveguide horn.

Rigorous combined mode-matching integral equation analysis of horn antennas with arbitrary cross section

We describe the optical design and optimisation of the Low Frequency Instrument (LFI), one of two instruments onboard the Planck satellite, which will survey the cosmic microwave background with unprecedented accuracy. The LFI covers the 30–70 GHz frequency range with an array of cryogenic radiometers. Stringent optical requirements on angular resolution, sidelobes, main beam symmetry, polarization purity, and feed orientation have been achieved. The optimisation process was carried out by assuming an ideal telescope according to the Planck design and by using both physical optics and multi-reflector geometrical theory of diffraction. This extensive study led to the flight design of the feed horns, their characteristics, arrangement, and orientation, while taking into account the opto-mechanical constraints imposed by complex interfaces in the Planck focal surface.

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Planck pre-launch status: Low Frequency Instrument optics

An innovative kind of corrugated horn antenna is proposed within this letter, the profile of the horn is based on the combination of horizontal and vertical corrugations. The main advantage of these profiles is the possibility of combining high-gain with short profiles, meanwhile keeping the main performances of the conventional corrugated horns. Besides, this horn results in an easier manufacture process due to their smaller size and eliminates the difficulties to manufacture the deep lambda/2 corrugations at the throat of classical profiles. An example of a horn with 24 dB gain, -35 dB maximum crosspolar, and sidelobe levels and 20% bandwidth has been designed, fabricated and characterized. These horns are a very promising alternative for future earth and space applications

Innovative High-Gain Corrugated Horn Antenna Combining Horizontal and Vertical Corrugations

In this article, a structure and design procedure of a novel compact dual-polarized corrugated horn antenna with high gain and a stable phase center for satellite communication is presented. The antenna incorporates an ortho-mode transducer (OMT), a mode converter, and a corrugated structure. The compact OMT section is designed to be fed by standard WR-75 waveguides. The proposed compact design utilizes only ten corrugated slots to yield a symmetric radiation pattern. The antenna impedance bandwidth (VSWR < 1.5) is 10.2 to 15 GHz. Furthermore, the antenna exhibits 14–17 dBi gain, a constant 30° half-power beamwidth (HPBW) radiation pattern, and less than 9 mm phase center variation over the operating frequency range. The aperture diameter is 7 cm and the total antenna length is 15 cm. Due to the aforementioned features, the proposed antenna is suitable as the feed reflector for both uplink and downlink satellite communications. The design is numerically and experimentally validated.

Compact Dual-Polarized Corrugated Horn Antenna for Satellite Communications

The design principles used to realize smoothly profiled corrugated horns are described. The smooth profiling causes power to be converted to higher order HE/sub 12/ modes which radiate to produce high sidelobes in the copolarization patterns. A computer-aided spherical modal-matching technique is used to study the higher-order mode conversion. The results show good agreement with measurements. A profiled horn using a series of discrete conical sections is proposed to eliminate most of the mode conversion. A horn designed in this way is presented and shown to possess improved performance characteristics in comparison to a smoothly profiled design. >

J. Xiang

Papers

Design of profiled corrugated horns

Sub-microscale precision repeatability position measurement using integrated polar microstructure and feature extraction method