Coupling matrix synthesis of orthomode transducers

Orthomode Transducers (OMTs) are key components in dual-polarized satellite communication systems. Turnstile junction (TJ) OMTs are widely popular since their structural symmetry suppresses the undesired higher order modes, which degrade impedance matching and isolation of the OMT. Several works on TJ OMTs operating in single (or narrow) frequency band have been published. In contrast, this paper presents a modified TJ OMT designed for multiple frequency bands: Ku-Band (10.7 GHz-12.75 GHz), lower Ka-Band (19.5 GHz-20.5 GHz) and upper Ka-Band (29.2 GHz-30.2 GHz). Unlike ordinary TJ OMT, the modified OMT besides discriminating the orthogonal polarization signals, also acts as a frequency diplexer. The OMT was manufactured using cost-effective 3D metal printing. The simulated and measured S-parameters were evaluated in Ku, lower and upper Ka bands. The OMT functionality was verified through field test measurement.

Dramatic advances in millimeter and submillimeter wave receivers in recent years have resulted from the development of superconductor insulator superconductor (SIS) mixers, which now offer unsurpassed performance from 70 GHz to 1 THz. To increase the sensitivity of the receivers further at these frequencies, one needs to use dual-polarized and balanced receivers. When both the polarizations are received simultaneously, there is a square root of two improvement in the signal to noise ratio (SNR). Balanced mixers improve the sensitivity of receivers by suppressing local oscillator (LO) amplitude modulation (AM) noise and rejecting LO thermal noise. This thesis describes the design, fabrication and performance of mixers and components for low noise dual-polarized and balanced receivers at millimeter and submillimeter wavelengths both in quasi-optical and waveguide configurations. The quasi-optical receiver utilizes a novel cross-slot antenna on a silicon hyperhemispherical lens, two junction tuning circuits, niobium trilayer junctions, and an IF circuit containing a lumped element 180 degree hybrid. The antenna has four feed points, two for each polarization; and each feed point is coupled to a two-junction SIS mixer. For dual polarization operation, the mixer is mounted in such a way that a single LO can pump the junctions for both the polarizations. For the balanced receiver, the LO and the RF signals are coupled to the mixer in orthogonal polarizations using a wire-grid polarizer. For waveguide dual polarization receivers, a moderately broadband septum ortho-mode transducer (OMT) is designed and experimental results are presented at millimeter wavelengths. Broadband finline OMTs are investigated for possible use at millimeter wavelengths, and experimental results of a finline OMT is presented at X-band.

An orthomode transducer (OMT) is widely employed to launch two perpendicularly polarized waves in a waveguide for frequency reuse and for polarization diversity applications. In this paper, a circular waveguide orthomode transducer operating at W-band is designed, fabricated and tested. First, an OMT is designed by transforming a circular waveguide into a rectangular waveguide with a multi-step transformer to couple one polarization and by introducing a small longitudinal slot in the circular waveguide wall and impedance matching steps to couple the other orthogonal polarization. The designed structure is amenable to fabrication in two split blocks by precision milling operations. Next, the designed OMT is fabricated to required precision after many trials of milling operations. Tests of the fabricated OMT shows good performance: reflection coefficients of less than -20㏈ at all ports, insertion loss of less than 0.5㏈ and isolation of 30㏈.

This paper describes the turnstile junction-based OMT(Ortho-mode Transducer). It is usually well-known that turnstile junctions have symmetry structure of waveguide so the higher order modes, which occur inside the waveguide, can be easily cancelled. Because of this structure, the turnstile junction-based OMTs have high isolation and low return loss characteristics in broadband and are good for easy realization of dual polarization. The designed OMT has the application of radar seeker and operates in W-band(94GHz). The OMT design and electrical verification are performed through commercially available full-EM software.

A wideband septum-based orthomode transducer (OMT) is designed to characterize and measure dual circularly polarized 5G communication systems. The OMT is designed for the n260 (37–40 GHz) and n259 (39.5-43.5 GHz) bands. The fabricated OMT has 20% fractional bandwidth (36–44 GHz) with a measured return loss and isolation better than 18 dB. The OMT achieves a simulated cross polarization discrimination (XPD) and axial ratio (AR) of 42.5 dB and 0.45 dB respectively. Good agreement between simulations and measurements is obtained.

ABSTRACTA smooth taper double-ridge waveguide orthomode transducer (OMT) has been designed for the new 100 GHz band receiver system on the Nobeyama Radio Observatory (NRO) 45-m radio telescope. The OMT consists of a smooth taper double-ridge waveguide followed by a Bøifot type junction with a main arm and two side arms. The main arm output is a smoothed tapered transformer followed by an E-plane bend and an oval waveguide. This design facilitates the fabrication of the OMT using split blocks machined on a CNC (computer numerical control) machine. The OMT shows a return loss of better than 18 dB, a polarization isolation of better than 28 dB, and an insertion loss of less than 0.5 dB across the 74–116 GHz, and also demonstrated the excellent performance on the NRO 45-m radio telescope.

This paper presents a novel orthomode-transducer (OMT) architecture,which is particularly suitable for correlation receivers at millimeter waves. By exploiting an on-axis reverse-coupling structure, a compact OMT configuration is obtained, which provides high levels of channel equalization. The Ka-band prototypes exhibit very good electric performances in terms of isolation, cross-polarization, return loss, and channel equalization.

A three-dimensional (3-D) substrate integration method by using both the planar dimensions and the vertical dimensions in multilayered substrates for millimeter-wave devices and circuits design is presented in this article. The vertical substrate-integrated groove gap waveguide (SIGGW) is studied first, whose multilayered geometry without metal contact between stacked substrates and wide operating band supporting the single quasi-TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode with stable propagation features enables it to be a promising vertical waveguide structure with ease of realization. By simultaneously utilizing the vertical and planar SIGGWs, a fully 3-D substrate-integrated orthomode transducer (OMT) consisting of E-plane power dividers, U-shaped connections, and a turnstile junction that are difficult to fulfill in previous works is successfully implemented in the Ka-band. Its compact geometry and significantly performance improvement demonstrate the merits of the proposed method. After that, the OMT is used for feeding a dual-polarized pyramidal horn antenna also with a 3-D substrate-integrated configuration. The overall multilayered antenna module with experimentally confirmed wide bandwidths, high isolations, and stable radiation patterns can still be fabricated conveniently by employing the standard single-layered printed circuit board (PCB) facilities. Taking the advantages of the flexible design freedom and satisfying operating characteristics, the presented design method and devices are valuable to advanced millimeter-wave applications.

For the need of polarization multiplexing, an asymmetric orthomode transducer (OMT) working at 260~325 GHz is demonstrated in this paper. Since the reflection efficient bandwidth of directed port is commonly wider than that of side port in the previous designs, the coupling aperture corresponding to side port is enlarged, which optimizes the performance of the side port and reduces difficulty of high frequency processing while deteriorate directed port a little due to higher discontinuity. Then the first two high-order-modes introduced by discontinuity and asymmetry is investigated. To achieve a better polarization isolation, the size of the common port is reduced, which decreases the cross-polarization component introduced by structural design and fabrication errors with the help of the suppression of the highorder-modes. As a result, the bandwidth and polarization isolation are increased. The return loss is less than -15db and the polarization isolation is better than -50db in the working frequency.

In this article, an innovative approach for characterization of one dimensional photonic band gap (PBG) structures comprised of subwavelength dipole elements is presented.Through an efficient S- to T-parameters conversion technique, polarization sensitivity of the subwavelength cell element was exploited to propose a novel combination of elements which allows achieving PBGs with simultaneous frequency and polarization selectivity. The proposed approach demonstrated that dispersion characteristics of each orthogonal polarization can be independently adjusted with dipole elements parallel to that same polarization. The structure has potential application in orthomode transducer and generally whenever the polarization of the incoming signal is to be used as a means of separating it from another signal in the same frequency band that is of orthogonal polarization. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:611–615, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27378

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>

The prototype cartridges for ALMA Band-1 receivers have been developed, based on the key components developed in ALMA Band-1 consortium laboratories. The prototype cartridges for each receiver consist of two parts, cold cartridge assembly and warm cartridge assembly. The cold cartridge assembly (CCA) consists of horn antenna, orthomode transducer and a pair of 35-52 GHz cold low-noise amplifiers, the amplified signals of both polarizations are transmitted to warm cartridge assembly by long waveguide sections. In warm cartridge assembly (WCA), two major modules incorporated, down-converter assembly including warm low-noise amplifier, high-pass filter, mixer and 4-12 GHz IF amplifier, and local oscillator based on a 31-40 GHz YIG-tunes oscillator. The frequency range is based on the upper sideband scheme. Based on the measured performance of the key components, the expected noise performance of the receiver will be 26-33K.

The MARS (Matrix Radiometric System) project is described. The instrument is intended to be used as a possible radiometric support to the ‘Cosmological Gene’ project. MARS is planned to be installed in the focal line of the RATAN-600 radio telescope. An input signal of two orthogonal linear polarizations is transferred via orthomode transducers, 128 units in line, to 256 radiometric modules. Each module of the system is an independent noise-added, gain-balanced straight-amplifier radiometer. The first prototype models of the radiometric module and of the noise generator unit design and test results are presented. MMICs and KEMT chip transistors as active components were applied. For one radiometric unit, 210 K noise temperature, 65 dB gain and 6 GHz bandwidth at 30 GHz centre frequency were measured.

Since the Federal Communication Committee has announced a range of frequencies from 3.10GHz to 10.60GHz constituting a bandwidth of 7.5GHz, Ultra wideband technology (UWB) is move ahead quickly as a high data rate technology for wireless communication. The effect of combining different geometrical patches derived from a basic rectangular patch antenna for wireless communications, GPS technology, satellite communication and air-craft applications are presented here. The antenna proposed is designed in FR-4 substrate which has 1.6 mm thick and permittivity of 4.4. The size of the substrate is 37.9mm × 47.63mm × 1.6mm. The antennas are simulated with ANSYS HFSS, the 3D electromagnetic (EM) simulation tool for radio frequency and fast electronic components. The impact on return loss and band width as a result of imperfections on patch can be observed from the obtained results. Introducing slots, defects on ground plane, making irregularities on patch shapes causes a wide variation in antenna parameters. It is clear that an increase in band width and reduction in return loss is obtained by combining the different shaped geometrical patches.

In this paper, we present the modeling and experimental validation of an efficient, compact, and high-isolation waveguide duplexer operating at 225 GHz. While duplexers based on ferrite circulators are key components of many monostatic radar systems, at W-band frequencies and above the performance of waveguide circulators rapidly deteriorates. The design presented here uses a ferrite-free duplexing concept based on transmitting and receiving in orthogonal circular polarizations. The circular polarization is efficiently generated in waveguide using a septum orthomode transducer polarizer, leading to a compact device with a single horn antenna. The complete duplexer is designed using efficient numerical algorithms, resulting in a fabricated device with a measured 10% fractional bandwidth, a return loss better than 20 dB, isolation of 30 dB, and insertion loss below 1 dB.