A survey of ATL-compatible radiometer antennas

A survey was made of antennas suitable for remote sensing of the earth's surface, in particular the world ocean, by means of microwave radiometers operating in the 1 to 26 GHz frequency region and carried on board the shuttle-launched advanced technology laboratory. Array antennas are found to be unattractive and unsuited to the task. Reflectors, including Cassegrain and offset types, as well as horn-reflectors are possible candidates but all have shortcomings which impair the accuracy of measurement. Horns of the corrugated type have excellent electrical characteristics. Although they are physically very large and will require development of suitable deployment mechanisms, they appear to be valid candidates for the task. The evolution of the periscope antenna is outlined, and it is shown to possess nearly ideal electrical characteristics for the intended application. Its only shortcoming is that the feed horn creates aperture blocking; there is no blocking due to struts or any other source. The periscope antenna is recommended for ATL radiometry

Enabling Ridge Waveguide Technology for Wideband Millimeter-Wave Decoys

Emerging high power millimeter wave applications such as RF decoy repeaters require transmission line technologies operating over a wide bandwidth with the ability to carry hundreds of watts of continuous wave (CW) power. To develop such repeaters an enabling technology for integration of components such as dual-polarized antennas, filters, couplers, bends, and twists is needed. This thesis presents the analysis, design, and measurements of novel passive components for such repeaters in V- and W- bands. At these high frequencies, traditional techniques of design and fabrication are challenging due to small size, losses, and wide bandwidth.A high-power capable wideband 45 ‒ 110 GHz double-ridge waveguide (WRD45110) transmission line with low loss, low dispersion, and high theoretical power-handling is demonstrated first. Then, utilizing the designed cross-section a suite of passive waveguide components required for a typical decoy repeater system such as straight transmission lines, E- and H- plane bends, 90&deg; twists, and termination loads are developed. A quad-ridge horn antenna with consistent broadside gain and stable E- and H- plane radiation patterns over the desired frequency band is also demonstrated. All components are carefully designed across different physics-based domains (RF, thermal, air-breakdown, etc.) and fabricated with either a direct metal laser sintering (DMLS) 3D printing or a conventional CNC machining with special care taken to allow for easy interconnecting.The design of a dual polarized high power capable system over 45 ‒ 110 GHz band is also presented. To combine two polarizations into the same radiating aperture, an Orthomode Transducer (OMT) based upon WRD45110 is developed. In order to fabricate this prototype through DMLS process, this OMT is devised with all the guidelines of 3D metal printing.Also, in system level, a preliminary system integration of a decoy repeater is discussed. To enhance the isolation between the TX and RX antennas in a decoy repeater, reactive impedance surfaces (RIS) with 1D RIS (corrugations), and 2D RIS (mushroom structure) are designed and built. In addition, a switched-beam phased array system that uses a perforated gradient index flat lens for beam scanning in &plusmn;30&deg; elevation and 0&deg; ‒ 360&deg; azimuth is demonstrated over the entire 45 ‒ 110 GHz frequency range.</p

Modern corrugated horn antennas

La presente tesis doctoral ha tenido como propósito sentar las bases de diseño de las antenas corrugadas de última generación que se vienen desarrollando desde 1995 en el seno del Grupo de Antenas de la Universidad Pública de Navarra. Este tipo de antenas, ahora mundialmente conocidas como antenas corrugadas Gaussianas o más recientemente con el término “corrugated GPHA’s” donde el término GPHA hace referencia a las siglas en inglés “Gaussian Profiled Horn Antennas” que significa Antenas de Bocina de Perfil Gaussiano; son en la actualidad la mejor solución posible para conseguir patrones de radiación de muy altas prestaciones. Concretamente, las antenas corrugadas de perfil gaussiano superan al resto de antenas de bocina corrugadas en dos aspectos: - Es posible diseñar antenas con lóbulos laterales muchísimo más bajos que con cualquier otro tipo de perfil corrugado. - Son, en general, más cortas que el resto de antenas corrugadas debido a que sus prestaciones son mejores. Por todo ello, actualmente son la opción elegida por multitud de grupos de investigación a nivel mundial para realizar las antenas de bocina corrugadas que requieren sus proyectos. Antenas de este tipo ya han sido embarcadas en satélites como Hispasat 1C e Hispasat 1D, van a ser utilizadas para el instrumento aerotransportado de la ESA llamado Marschals, serán utilizadas en el futuro satélite Planck de la ESA y actualmente una nueva versión muy prometedora esta siendo comercializada por la empresa inglesa Flann Microwave, Ltd.This Ph. D. manuscript has the main purpose of summarizing the design techniques of the new technology corrugated horn antennas developed since 1995 in the Antenna Group of the Public University of Navarra. This type of world-wide accepted antennas, known as corrugated Gaussian Profiled Horn Antennas, (GPHA’s); are now-a-days the best possible solution to obtain radiation patterns of very high restrictive requirements. Corrugated GPHA’s are better than the rest of corrugated horn antennas in two particular aspects: - They present much lower sidelobes than any other corrugated profile - They are usually shorter than the rest of corrugated profiles because their performance qualities are superior. Therefore, this antennas are usually the preferred choice of many research groups around the world to develop corrugated horns for their research projects. Antennas of this type are at present on board of Hispasat 1C and Hispasat 1D satellites, are going to be used in the ESA funded Marschals airborne system, will be used in a near future in the ESA’s Planck satellite and now-a-days a new version of a corrugated GPHA is being commercialised by the British company Flann Microwave, Ltd

Electromagnetic and Quasi-Optical Analysis of Cavity Coupled Bolometers for Far-Infrared and Terahertz Receivers

The primary concern of this thesis is the development of theoretical and computational techniques for the modelling of cavity coupled bolometric detectors for future millimetre wave and terahertz astronomical receivers. Hypersensitive bolometer based receivers will be required to answer current open questions in astronomy concerning star and planetary formation, solar system physics as well as galaxy evolution and interaction. As part of the work for this thesis, fast and efficient Python code, GAMMA (Generalised Absorber Mode Matching Analysis), was developed and applied to existing and proposed future systems. One of the main goals of GAMMA was to analyse the performance of the proposed multimode pixel for the SAFARI instrument on the next generation SPICA terahertz space telescope. The pixels contain a free space gap between the horn and the cavity. The array of detectors will lie on a chip with an array of horns feeding them from the frontside and an array of backshort cavities behind them. The beam patterns for a SAFARI-like pixel were computed, using a direct calculation of the power absorbed by the bolometer in free space. This shows how the formalism can be used to directly calculate the power absorbed by a detector in a realistic terahertz receiver system. The impact of the various potential manufacturing tolerance levels for the feed horn on the predictions of the beam on the sky were also analysed for a millimetre-wave system. The specific example considered was the new 4 mm receiver on the Onsala Space Observatory 20 m millimetre-wave telescope. Mode matching, Gaussian Beam Mode Analysis and Physical Optics were used to determine the behaviour of the optical relay system. GAMMA was also applied to the multimode 857 and 545 GHz ESA Planck HFI channels. Agreement between previous predictions and both laboratory and in-flight measurements reported in literature was improved on

Antenna Design for 5G and Beyond

With the rapid evolution of the wireless communications, fifth-generation (5G) communication has received much attention from both academia and industry, with many reported efforts and research outputs and significant improvements in different aspects, such as data rate speed and resolution, mobility, latency, etc. In some countries, the commercialization of 5G communication has already started as well as initial research of beyond technologies such as 6G.MIMO technology with multiple antennas is a promising technology to obtain the requirements of 5G/6G communications. It can significantly enhance the system capacity and resist multipath fading, and has become a hot spot in the field of wireless communications. This technology is a key component and probably the most established to truly reach the promised transfer data rates of future communication systems. In MIMO systems, multiple antennas are deployed at both the transmitter and receiver sides. The greater number of antennas can make the system more resistant to intentional jamming and interference. Massive MIMO with an especially high number of antennas can reduce energy consumption by targeting signals to individual users utilizing beamforming.Apart from sub-6 GHz frequency bands, 5G/6G devices are also expected to cover millimeter-wave (mmWave) and terahertz (THz) spectra. However, moving to higher bands will bring new challenges and will certainly require careful consideration of the antenna design for smart devices. Compact antennas arranged as conformal, planar, and linear arrays can be employed at different portions of base stations and user equipment to form phased arrays with high gain and directional radiation beams. The objective of this Special Issue is to cover all aspects of antenna designs used in existing or future wireless communication systems. The aim is to highlight recent advances, current trends, and possible future developments of 5G/6G antennas

Simultaneous Transmit and Receive (Star) Antennas for Geo-Satellites and Shared-Antenna Platforms

This thesis presents the analysis, design, and experimental characterization of antenna systems considered for shipborne, airborne, and space platforms. These antennas are innovated to enable Simultaneous Transmit and Receive (STAR) at same time and polarization, either at the same, or duplex frequencies. In airborne and shipborne platforms, developed antenna architectures may enhance the capabilities of modern electronic warfare systems by enabling concurrent electronic attack and electronic support operations. In space, and more precisely at geostationary orbit, designed antennas aim to decrease the complexity of conventional phased array systems, thereby increasing their capabilities and attractiveness. All antennas researched are first designed as a standalone radiator, then as entity of a platform having multiple different antennas.An ultrawideband, lossless cavity-backed Vivaldi antenna array for flush-mounting applications is first investigated. Eigen-mode analysis is used to analyze antenna-cavity interaction and to show that the entire structure may resonate within the band of interest resulting in a significant degradation of antenna performance. A simple approach based on connecting the array’s edge elements in E-plane to the cavity walls is proposed to eliminate the deleterious impact of these cavity resonances. The designed antenna is a 3 × 4 array with 3 elements in E-plane and 4 elements in H-plane, fabricated using stacked all-metal printed circuit board technique. Scan performance of the proposed cavity-backed antenna is investigated in two principal planes and is shown to have similar performance compared to its free-standing counterpart. A simplified version of this single-polarized antenna, when used for broadside only applications is developed. This antenna, excited with a single coaxial feed is shown to have a smaller aperture than the 3 × 4 array. Isolations between two of these antennas when mounted on a compact shared-antenna platform are investigated through computation and experiments.To extend the capability of systems relying on these designed antennas, frequency reuse is enabled through dual-polarized functionality. A dual-polarized, flush mounted, Vivaldi antenna, directly integrated with an all-metal cavity is introduced as an alternative to coax-fed quad-ridge horns. An approach based on shaping the side walls of the cavity is used to eliminate the occurrence of resonances. The proposed dual-polarized resonant-free antenna has two orthogonal 2 × 1 arrays with two elements in the E-plane, one element in the H-plane. It is fed using two 2-way power dividers that can be easily designed to maintain low amplitude and phase imbalances. The antenna is fabricated as a single piece and experimentally shows a monotonic gain increase with low cross-polarization over 4:1 bandwidth.Phased array antennas operating at geostationary orbit are required to scan within Earth’s field of view, without any grating lobe appearance. For dual-polarized applications, this requirement has limited the widespread and attractiveness of these systems at frequencies such as X-band. The narrow 150 MHz guard range between transmit and receive bands, leads to impractical diplexers in conventional dual-polarized systems. This research introduces a dual-polarized subarray architecture for X-band phased array systems which enables high isolation between closely separated TX and RX bands. The proposed approach either eliminates the need for diplexers, or significantly decreases their required complexity

High Gain Broadband mm-Wave Antenna Arrays for Short-range Wireless Communication Systems

Recently, the ever-increasing demand for fifth-generation (5G) wireless applications has turned millimeter-wave (mm-wave) multi-beam array antenna into quite a promising research direction. Besides offering a remarkable bandwidth for high-speed wireless connectivity, the short wavelengths (1 to 10 mm) of mm-wave signals makes the size of the antenna array with beamforming network (BFN) compatible with a transceiver front-end. The high losses associated with mm-wave wireless links and systems considered the foremost challenge and may restrict the wireless communication range. Therefore, a wideband substrate integrated waveguide (SIW)-based antenna with high gain and beam scanning capabilities would be a solution for these challenges, as it can increase the coverage area of mm-wave wireless systems and mitigate the multipath interference to achieve a high signal to noise (S/N) ratio, and thereby fulfill the link budget requirements. This thesis focuses on the analysis and design of single- and multi-beam mm-wave antenna arrays based on SIW technology to fulfill the growing demand for wideband high-gain planar antenna arrays with beam steering capability at V-band. A tapered slot antenna (TSA) and cavity-backed patch antenna are used as the main radiators in these systems to achieve high-gain and high efficiency over a wide range of operating frequencies. Accordingly, numerous design challenges and BFN-related issues have been addressed in this work. Firstly, an antipodal Fermi tapered slot antenna (AFTSA) with sine-shaped corrugations is proposed at V-band. The antenna provides a flat measured gain of 20 dB with a return loss better than 22 dB. In addition, A broadband double-layer SIW-to-slotline transition is proposed to feed a planar linearly tapered slot antenna (PLTSA) covering the band 46-72 GHz. This new feeding technique, which addresses the bandwidth limits of regular microstrip-to-slotline transitions and avoids the bond wires and air bridges, is utilized to feed a 1x4 SIW-based PLTSA array. Secondly, a new cavity-backed aperture-coupled patch antenna with overlapped 1-dB gain and impedance bandwidth of 43.4 % (56-87 GHz) for |S11| < -10 dB and an average gain of 8.2 dBi is designed. A detailed operating principle is presented. Based on the proposed element, an SIW based 1x8 array is constructed, whose beam-shape is synthesized by amplitude tapering according to Taylor distribution to reduce the sidelobe level. Moreover, a four-layered 4x4 cavity-backed antenna array with a low-loss full-corporate SIW feed network is implemented for gain and aperture efficiency enhancement. The measured results exhibited a bandwidth of 38.4 % (55.2-81.4 GHz) for |S11| < -10 dB and a gain of 20.5 dBi. A single-layer right-angle transition between SIW and air-filled WR15 waveguide along with an equivalent circuit model is introduced and used to measure the performance of both proposed linear and planar arrays. Thirdly, two 1-D scanning multi-beam array designs based on SIW technology, at 60 GHz, have been presented. The first design is a compact multi-beam scanning 4x4 slot antenna array with broadside radiation. The BFN is implemented using a dual-layer 4x4 Butler matrix, where the 450 and 00 phase shifters are designed on a separate layer with different permittivity, resulting in a significant size reduction compared to a conventional single layer. A detailed theoretical analysis, principle of operation and the circuit-model of the proposed phase shifter have been discussed, showing less desperation characteristics compared to ordinary phase shifters. The measured results show an azimuthal coverage of 1210. The second design is a wideband high gain multi-beam tapered slot antenna array with end-fire radiation. An SIW Butler matrix with a modified hybrid crossover is used as a BFN. The fabricated prototype exhibits a field of view of 970 in the azimuthal plane, with measured gain ranges from 12.7 to 15.6 dBi. Lastly, a novel three-layered SIW-fed cavity-backed linearly polarized (LP) patch antenna element is presented, covering a bandwidth of 36.2 % (53-76.4 GHz) with a flat gain ranging from 7.6 to 8.2 dBi. A compact two-layered beam forming network is designed with a size reduction of 28 % compared to a standard one-layered BFN without affecting its s-parameters. The results show that the impedance bandwidth is 31.1 % (51.5-70.5 GHz) for |S11|<-16 dB with an average insertion loss of 1.3 dB. The proposed antenna element and BFN are employed to form a compact 2x2 multibeam array at 60 GHz for 2-D scanning applications. The array shows a bandwidth better than 27 % with a radiation gain of up to 12.4 dBi and radiation efficiency of 80%. The multi-beam array features four tilted beams at 330 from a boresight direction with 450, 1350, 2250 and 3150 in azimuth directions, i.e., on e beam in each quadrant