Multimode Horn Research Articles

Synthesis of Broadband, Oversized, Multimode Horn With Frequency-Invariant Radiation Patterns

Synthesis of Broadband, Oversized, Multimode Horn With Frequency-Invariant Radiation Patterns

A grating lobe suppression method for displaced subarrays using genetic algorithm

The large-element-spacing array is often used to reduce the channels and costs of the phased array. However, it will form grating lobes (GLs) in the visible space, which decrease the performance. The displaced subarray technique has strong GL suppression ability and simple engineering implementation, but its design process is very complex. This paper presents a new parameter design method of variable subarray gaps. The gaps between subarray are optimised using genetic algorithm, and the levels of GL and quantisation lobe (QL) can be minimised simultaneously. This method sets the normalised values of gaps and the maximum gap as optimisation variables, which greatly improves the convergence speed and has strong global optimisation. In addition, a new segmented multimode horn is proposed as the array element. Its influence on GL suppression is also considered in the optimisation process. This method is used to design a prototype with 52 subarrays. The measured results show that the GL level is below −15.9 dB and the QL level is below −24 dB from 16 to 19 GHz, which are in good agreement with the simulation results. It shows that this method has a strong ability to suppress GL and QL levels for wideband applications.

Analysis of multi-mode waveguide cavities containing free space gaps for use in future far-infrared telescopes

In order to investigate the formation and evolution of galaxies, stars and planetary systems, it is necessary to carry out astronomical observations in the far-infrared portion of the electromagnetic spectrum. Missions such as the Herschel Space Observatory (European Space Agency) have already completed observations in this region with great success. Proposed high resolution spectrometer instruments such as SAFARI (a joined European/Japanese (ESA/JAXA) proposal as part of the SPICA mission), aim to build upon the work of previous missions by carrying out observations in the 1.5–10 THz band with unprecedented levels of sensitivity. Spica (SPace Infrared telescope for Cosmology and Astrophysics) is currently a candidate mission as part of ESA’s Cosmic Vision 2015–2025.Future far-IR missions must realise higher levels of sensitivity, limited only by the cosmic microwave background. One solution in achieving these sensitivity goals is to use waveguide coupled Transition Edge Sensor (TES) detectors, arranged in a densely packed focal plane. Additionally, multi-mode pixels can be used in order to maximise the optical throughput and coupling while still defining a definite beam shape. For the SAFARI instrument multimoded horns coupling into integrating waveguide cavities that house the TES detectors and associated absorbing layer are envisioned. This represents a significant technological challenge in terms of accurate manufacture tolerances relative to the short wavelength, however in the case of the SAFARI instrument pixel much work has already been carried out, with prototype pixels having undergone extensive testing at SRON (Space Research Organisation of the Netherlands) Groningen. In order to fully characterise the experimental results, it is necessary also to carry out comprehensive electromagnetic modelling of these structures which is also computationally intensive and requires novel approaches. These waveguide structures (horn and cavity) are typically electrically large however, and so analysis techniques using commercial finite element software prove inefficient (particularly as the structures are multimoded).The mode-matching technique with new analytical features offer a computationally efficient and reliable alternative to full electromagnetic solvers, and in this paper we outline the additions to this technique that were necessary in order to allow typical SAFARI far-infrared pixels to be modeled, including the complete optical coupling calculation of the measurement test setup at SRON and the inclusion of the free space gap within the horn antenna and the integrating cavity. Optical coupling efficiencies simulated using this developed technique show excellent agreement with the experimental measurements.

A frequency domain multiplexing system to readout the TES bolometers on the LSPE/SWIPE experiment

LSPE/SWIPE is a balloon-borne experiment aimed at measuring the B-mode polarization of the cosmic microwave background (CMB) exploiting the reionization peak at ℓ < 10 , with the primary target of improving the tensor-to-scalar ratio limit down to r = 0 . 03 at 99.7% confidence level. SWIPE will use 326 spider-web Ti/Au transition-edge sensor (TES) bolometers , realized at INFN Genova, hosted on two focal planes cooled down at 300 mK and readout by superconducting quantum interference devices (SQUIDs), with multi-mode horns to couple the instrument’s optical stages to the detectors. We present our design and demonstration of a 16-channel frequency domain multiplexing (FDM) system to readout SWIPE’s TES bolometers.

Antenna Design by Means of the Fruit Fly Optimization Algorithm

In this work a heuristic optimization algorithm known as the Fruit fly Optimization Algorithm is applied to antenna design problems. The original formulation of the algorithm is presented and it is adapted to array factor and horn antenna optimization problems. Specifically, it is applied to the array factor synthesis of uniformly-fed, non-equispaced arrays and to the profile optimization of multimode horn antennas. Several numerical examples are presented and the obtained results are compared with those provided by a deterministic optimization based on a simplex method and another well-known heuristic approach, the Genetic Algorithm.

Terahertz High-Gain Offset Reflector Antennas Using SiC and CFRP Material

Two high-gain terahertz (THz) offset reflector antennas are proposed. The silicon carbide material and thermally stable carbon fiber-reinforced plastic are selected as reflectors for high specific stiffness and low thermal expansion coefficient which are helpful for space use. Dual polarization is achieved by introducing a wire-grid polarizer which can separate the two THz polarization waves provided by multimode horns fabricated in electroforming technology. Furthermore, three-coordinate test system and theodolites are employed to detect the surface error of dishes and alignment of antenna subsystem. The physical optics analysis based on the measured reflector surface data is introduced referring to the large aperture antenna patterns by virtue of its accuracy and high efficiency. The results of this novel method are compared to that of the near-field test. Measurements show that the sidelobe levels (SLLs) of the single polarization silicon-based reflector are below −32 dB while the gain is 55.3 dB at 330 GHz, and the dual polarization carbon fiber-reinforced plastic reflector antenna suppresses the SLLs to −28 and −29 dB in two principal planes while the gain is 57.2 dB at the same frequency, respectively. The good performances of the proposed antennas indicate the potential for the application of space THz radiometer.

Synthesis and analysis of multi‐mode profile horn using mode matching technique and evolutionary algorithm

This study presents the design and analysis of linear as well as cubic spline interpolated profiled smooth-wall multimode horn using mode matching (MM) technique along with genetic algorithm (GA) and particle swarm optimisation (PSO). To apply the MM technique, the smooth profile conical geometry is assumed to consist of cascaded sections of large number of small symmetrical radial steps. Scattering matrix for each section has been calculated using MM technique and over all scattering matrix of the cascaded junctions has been calculated using generalised scattering matrix technique. The radiation pattern has been calculated using hybrid boundary contour mode matching technique. Optimisation of the linear/spline profile horn has been carried out using GA as well as PSO. Detailed modal analysis along with the convergence of the present technique for the smooth profile structure has also been carried out. A spline profile multimode horn working at 89 GHz has been designed and developed. The present analysis has been verified with the measured results. There is a very good agreement between theoretical and measured results.

A W-Band Radiometer with the Offset Parabolic Antenna for Radiometric Measurements

This paper deals with the development of a W-band noise-adding radiometer which combines the millimeter-wave (MMW) radiometric measurements with a high-resolution imager. The offset parabolic antenna is presented to achieve an accurate measurement and a high resolution. To reduce the cross-polarization level of the antenna, a multimode feed horn with a multistep structure is proposed to match the focal region fields of the reflector. It has advantages over the corrugated horns in lower mass and easier manufacturing. In addition, due to an unavoidable settling time for the noise-adding radiometer output signal passing through the low-pass filter, a theoretical criterion for the optimum duty cycle determination to reject extraneous contributions from the transient is proposed in this paper. The appropriate duty cycle threshold is 0.33 for the developed W-band radiometer. Also, a geometric correction method is presented to correct the obtained passive image suffering from a distortion for a better image interpretation. Preliminary experimental results are given to illustrate and verify the presented techniques.

A distributed-absorber cold-electron bolometer single pixel at 95 GHz

We describe a Frequency Selective Surface (FSS) based distributed-absorber Cold-Electron Bolometer (CEB) pixel at 95 GHz integrated in a multi-moded horn. The FSS provides a resonant interaction with incident mm and sub-mm radiation and defines the bandwidth of the array while the horn provides the matching of the beam to the telescope optics. CEB detectors with matched impedance are integrated within the periodic elements of the FSS and generate a voltage response proportional to the incident optical power in the bandwidth of the FSS. A prototype pixel was designed, fabricated, and characterized at a temperature of 280 mK. We present optical response to blackbody radiation and fit it to the CEB model. For an absorbed power of 50 pW, we estimate an optical responsivity of 1.2 × 108 V/W and a readout dominated Noise Equivalent Power (NEP) of 1.8 × 10−15 W Hz−1/2. A measured bandwidth of 9 GHz of this detector array confirms the frequency selective nature. This prototype represents a possible solution as a detector for the 95 GHz channel of the SWIPE instrument on the LSPE balloon-borne telescope. This kind of FSS based mm-wave architecture can be easily scaled to other frequency ranges and used on any other balloon-borne telescope focal planes.

Water‐loaded metal diagonal horn applicator for hyperthermia

This study presents the design of water-loaded metal diagonal horn antenna at 2450 MHz along with simulation and experimental studies of specific absorption rate (SAR) and temperature distributions in a bio-medium (muscle) in direct contact with the water-loaded antenna for hyperthermia application. The metal diagonal horn is a multimode horn antenna, with identical aperture field distribution in the E- and H-planes. The SAR distribution in a phantom muscle in direct contact with water-loaded horn antenna measured at 2450 MHz is nearly in agreement with the corresponding simulated distribution. The simulation results for SAR distribution owing to diagonal horn are also compared with those owing to square aperture horn/box horn, of same aperture cross-section/broader dimension as the diagonal horn at 2450 MHz. The results indicate that the diagonal horn provides higher penetration depth/better transverse resolution over square aperture horn/box horn. In addition, the proposed diagonal horn provides circularly symmetric effective field size. Finally, thermal simulation results are also provided for the proposed applicator, which is in direct contact with a realistic model of muscle medium without and with small spherical as well as oval-shaped tumours of different dielectric properties embedded within the muscle medium.

Optical modeling techniques for multimode horn-coupled power detectors for submillimeter and far-infrared astronomy

An important class of detectors for the submillimeter and far-infrared uses a multimode horn to couple incident radiation into an absorbing film made from a thin conductor. We consider how to model the full, partially coherent, optical behavior of these multimode detectors using extensions of mode-matching techniques. We validate modeling the absorber as a resistive sheet, and demonstrate the equivalence of mode-matching and Green's function methods for calculating the scattering matrix representation of the film. Finally, we show how the scattering matrix of the film can be cascaded with those of the other components, as determined by mode matching, so as to calculate the overall optical response of the detector. Simulations are presented of the optical behavior of a square absorbing film in a circular waveguide.

A compact radiation system for L band magnetically insulated transmission line oscillator

A compact radiation system for L band magnetically insulated transmission line oscillator (MILO) is present. It consists of a coaxial TEM-TE11 mode converter and a coaxial multimode horn antenna. Some metal plates are inserted into the coaxial waveguide to divide it into several sectoral waveguides with different phase propagation constants to compose a coaxial TE11 mode. Then some of the sectoral waveguides are folded up to reduce the length of the mode converter. Multimode horn antenna is adopted to enhance aperture efficiency and power handling capability of the radiation antenna. A radiation system for a 1.58 GHz MILO device is designed with a length of 33 cm and an aperture radius of 20 cm. The gain is 15.8 dBi and aperture efficiency is 86.8 %. Both low power and high power microwave experiment is carried out to test the radiation character. The experiment test results agree well with computer simulation.

Development of Advanced Design Software for Complex Multimode Antenna Feeding Systems

Ka-band multiple-beam spacecraft antennas (MBA) are a key technological challenge in the design of broadband communication-satellite systems. Due to the very narrow beamwidth of multiple-beam spacecraft antennas, beam pointing is a critical issue, since even very small pointing errors can seriously affect the antenna's performance. Consequently, many of these communications antennas require closed-loop tracking. While full-wave design tools for multimode waveguide components have been well established since the mid-1990s, there was a perceived lack of similarly powerful design tools for multimode horn radiators. In order to close this technological gap, the European Space Agency (ESA) proposed a sponsored research effort, focusing on the development of multimode horn design software. The project was executed by a team consisting of MDA Satellite Systems, Canada, and Mician GmbH, Germany. While the software-requirements specification and its validation was the primary responsibility of MDA, Mician was responsible for the software implementation. This paper summarizes the work performed under this project, and also provides examples of complex multimode feed designs for multiple-beam spacecraft-antenna applications.

Ultrasensitive TES Bolometers for Space-Based FIR Astronomy

Results of study optical performance of single pixel transition edge sensor (TES) bolometer presented at wavelength band 30-60 μm are presented. FIR radiation is coupled into a multimode horn with entrance aperture of 450 μm, length 4.5 mm and exit aperture of 45 μm , which feeds a metal integrating cavity containing the detector. The radiation band is defined by a pair of lowpass and highpass mesh filters in front of the horn. Here we present measurements of optical noise equivalent power (NEP), optical efficiency, dynamic range and time constant. The results show that measured TES detectors are close to meeting the requirement of the “Band S” of SAFARI FTS imaging instrument on the SPICA mission.

Compact dual-band axially corrugated profiled horn for prime-focus reflector antenna

This paper reports a new compact dual-band axially corrugated profiled horn feed (DBCPH) for prime-focus reflector antenna at C-band (uplink and downlink frequency bands with bandwidth ratio of 1.6). DBPCH consists of one sinusoid profiled section and two internal axial corrugations (internal short-circuited ring slots), for obtaining a multimode horn feed. Such a blended structure is optimized over the specified frequency bands (3.68–3.70 and 5.865–5.915 GHz) to achieve various performance objectives (such as compactness, return loss, polarization purity, etc.). Measured and predicted results show that DBCPH provides better return loss &gt;18.6 dB, low cross-polarization (better than −32 dB), and adequate edge taper at ±48° (8.5–11.7 dB) along with compact size (1.3λ aperture diameter and 0.88λ length at lower frequency). The horn would be used as a feed element for front-fed prime-focus reflector for pencil beam spacecraft antenna application.

Multi-mode horn design and beam characteristics for the Planck satellite

The ESA Planck satellite has begun studying the anisotropies of the cosmic microwave background radiation over the whole sky with unprecedented sensitivity and high angular resolution. The High Frequency Instrument, HFI, on Planck is observing simultaneously in six bands in the range 100 GHz to 857 GHz. The inclusion of non-CMB bands allows for robust removal of foreground sources from the data. This paper is concerned with the design, modeling and predicted performances of the two highest frequency channels centered on 545 GHz and 857 GHz, which use specialized multi-mode feedhorns, and are dedicated to observing these foregrounds. Multi-mode systems have the advantage of increasing the throughput, and thus sensitivity, of the detection assembly when diffraction limited resolution is not required. The horns are configured in a back-to-back setup which transmits the signal through filters to a detector horn. The modeling of the broadband beam patterns on the sky is shown to require careful analysis. Simulations of the complex interactions of the horns is computationally challenging when the detector horn in the relay system is included. The paper describes the approach to modeling these high frequency channels and discusses how the optical requirements on the horn designs are met in terms of spillover, edge taper, illumination of the telescope aperture and beam patterns on the sky.

Compact Multimode Horn with Coaxial Corrugation for Circular Coverage

For achieving low cross-polarization component in addition to circular-coverage pattern in compact structure, this paper proposes a novel multimode horn with arbitrary coaxial-corrugation configuration which plays two roles of mode converters and chokes. The proposed horn can be designed by iteration of non-linear optimization procedure based on generalized scattering matrices pre-calculated by the mode-matching technique. We show a compact horn with four coaxial corrugations for shaping circular-coverage beam over frequency range of bandwidth 20%. The effectiveness of the designed horn is discussed by evaluating VSWR and radiation characteristics in X-band numerically and experimentally.

Low-Sidelobe Multimode Horn Design for Circular Coverage Based on Quadratic Programming Approach

To obtain a broad circular-coverage beam with low sidelobe, this paper proposes optimization design based on the quadratic programming approach for circular horns. The desired excitation coefficients of higher-order modes are pre-determined and also evaluated by calculating universal radiation patterns. We show a design example of a multimode horn which has circular-coverage beam with low sidelobe level of about-30dB. The effectiveness of the designed horn is discussed by evaluating VSWR and radiation characteristics in X-band numerically and experimentally.

Multimode adaptive signal processing: a new approach to GMTI radar

We show how a single reflector antenna with a multimode feed horn can be used in a ground moving target indication (GMTI) radar. In particular, we demonstrate the simultaneous detection and estimation of angular location of a ground moving target via adaptive cancellation of ground clutter

Multimode horn with optimum gain within circular area

AbstractIn this paper, a multimode horn efficiently illuminating the entire circular area is proposed. In comparison with the conventional dual mode horn with a pencil beam, the minimum gain within the covered area is higher by more than 1 dB. In the horn design, the mode excitation coefficients are derived from the universal pattern maximizing the gain in an arbitrary direction. By comparing this result with the optimum gain derived from the quadratic programming method, the effect of beam shaping is evaluated. The validity of the present method is verified by numerical analysis and by the measured radiation pattern of a curved flare multimode horn fabricated for trial in the X band. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(2): 12–21, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20246