Magic Tee Research Articles

Design of the Monopulse Feeding Network for a Slotted Waveguide Array on an Annular Disk

Design of a monopulse feeding network including a compact power distribution network and a monopulse comparator for a dual polarization slotted waveguide array fabricated on an annular disk is presented in this paper. As the slotted waveguide array is arranged on an annular disk, the feeding network is more complicated than that of a regular array such as a rectangular array. The design details of some key waveguide components, such as the compact assembly of H-plane T-junctions and E-plane elbows used to connect power distribution networks and radiation waveguides, are provided. Quasiplanar magic tees are designed and used to construct the compact sum and difference comparator. The antenna system contains two comparators, which are used to generate sum and difference beams for horizontal polarization and vertical polarization, respectively. Finally, the monopulse slotted waveguide array antenna is divided into two modules, a comparator module and an antenna module (including power distribution network), and fabricated with the layered processing and bonding process. The comparator module is measured using a network analyzer to verify its amplitude-frequency characteristics and phase-frequency characteristics. Screwing the comparator module and the antenna module together, a monopulse slotted waveguide array antenna is obtained, and the sum beam and difference beam characteristics of the antenna are measured in a microwave chamber and presented.

Voltage-Controlled Polarization at 0.1 THz Based on Phase-Tuned Coupled Oscillation via a Magic Tee

We propose a technique to implement voltage-controlled polarization at 0.1 THz using a pair of phase-tuned Gunn diode oscillators coupled through a WR10 magic tee hybrid coupler. By finely tuning the free-running oscillation frequency with bias voltage, we can control the phase difference between the two coupled oscillators. Since the two output ports of the hybrid coupler correspond to the sum and difference of the signals from the two coupled oscillators, the power ratio between the two output ports can be adjusted arbitrarily by tuning their phase difference. Thus, by connecting a pair of orthogonal horn antennas to the output ports, an arbitrary polarization ratio can be obtained. The maximum polarization ratio observed in this study is 31.8 dB. To fully switch the polarization between the vertical and horizontal directions, a frequency shift of 26.6 MHz (0.03%) at around 94.3 GHz is involved when changing the bias voltage of one of the two oscillators. This frequency shift could be compensated by carefully controlling the bias voltages of the two oscillators simultaneously. The proposed approach enables fully electrical control of the polarization of subterahertz waves using a waveguide platform, which will be of importance for a variety of applications in sensing and communication.

The BINGO project

Context.The measurement of diffuse 21-cm radiation from the hyperfine transition of neutral hydrogen (H Isignal) in different redshifts is an important tool for modern cosmology. However, detecting this faint signal with non-cryogenic receivers in single-dish telescopes is a challenging task. The BINGO (Baryon Acoustic Oscillations from Integrated Neutral Gas Observations) radio telescope is an instrument designed to detect baryonic acoustic oscillations (BAOs) in the cosmological H Isignal, in the redshift interval 0.127 ≤ z ≤ 0.449.Aims.This paper describes the BINGO radio telescope, including the current status of the optics, receiver, observational strategy, calibration, and the site.Methods.BINGO has been carefully designed to minimize systematics, being a transit instrument with no moving dishes and 28 horns operating in the frequency range 980 ≤ ν ≤ 1260 MHz. Comprehensive laboratory tests were conducted for many of the BINGO subsystems and the prototypes of the receiver chain, horn, polarizer, magic tees, and transitions have been successfully tested between 2018–2020. The survey was designed to cover ∼13% of the sky, with the primary mirror pointing at declinationδ = −15°. The telescope will see an instantaneous declination strip of 14.75°.Results.The results of the prototype tests closely meet those obtained during the modeling process, suggesting BINGO will perform according to our expectations. After one year of observations with a 60% duty cycle and 28 horns, BINGO should achieve an expected sensitivity of 102 μK per 9.33 MHz frequency channel, one polarization, and be able to measure the H Ipower spectrum in a competitive time frame.

A Compact Wideband Planar Magic Tee for Monopulse Antenna Array Applications

This letter presents a compact, wideband, planar, E-arm folded magic tee at $Ku$ -band for monopulse slotted waveguide antenna array applications. A novel impedance matching structure, an L-shaped septum, is implemented at the magic tee junction, which results in wide impedance bandwidth at all ports. The height of this septum is the same as that of the waveguide height, which allows the design to be very compact. An impedance bandwidth of 22% is achieved for a return loss of 20 dB. The magic tee is manufactured using a high-precision electric discharge machining (EDM) process and followed by the integration of subparts using silver epoxy bonding. Simulation and measured results are compared. Measured amplitude balance of < 0.1 dB, phase balance of <2°, and isolation of better than −35 dB have been achieved. The proposed design is a good technique for the design of broadband, miniaturized monopulse comparators for monopulse antenna array applications.

Ridged Waveguide Magic Tees Based on 3-D Printing Technology

In this article, full-metal ridged waveguide magic tees are designed and fabricated based on 3-D printing technology. Two kinds of prototypes with different structures and performances are proposed and compared. First, a wideband design based on double-ridged waveguide (DRWG) transmission lines was proposed, and it achieved a measured operational bandwidth of 27%. However, this component has to be split into two parts that are printed separately and then assembled together by screws because the overhang structure cannot satisfy the 3-D printing rules. To overcome this problem, a novel magic tee based on pyramidal ridged waveguide (PRWG) is proposed. In spite of a narrower bandwidth of 8.6%, this design requires a simpler fabrication method and has a lower profile. To the best of our knowledge, the PRWG prototype is the first full-metal magic tee that is fabricated as a whole part without involving any assembling or tuning and, thus, saves processing time and manual work.

Review of Substrate Integrated Waveguide Circuits for Beam-Forming Networks Working in X-Band

A review of substrate integrated waveguide (SIW) components designed for the use in beam-forming networks working in X-Band is presented. The proposed devices are four-port and six-port couplers and magic tees for the network. The devices take full advantage of the use of SIW technology in order to reduce size, weight, and cost. The design processes of all devices are exposed, and the experimental results of prototypes show the feasibility of these solutions.

Additive Manufacturing of Complex Millimeter-Wave Waveguides Structures Using Digital Light Processing

Additive manufacturing technology has enabled the manufacturing of complex structures, especially those with intricate internal features. This paper proposes a method for building complex-structured millimeter-wave waveguides using a strategy that combines digital light processing 3-D printing technology, a curved corner design, an off-axis print angle of 45°, and a robust postmetallization process. To demonstrate the capability of this combined-strategy method, a traditional magic tee prototype and an adapted inherently matched magic tee prototype are fabricated for use in the W-band. The measured performance of the fabricated inherently matched magic tee demonstrates return loss better than 13.5 dB, isolation coefficients higher than 15.7 dB, insertion losses smaller than 1.3 dB, and a magnitude imbalance of less than 1.3 dB across 80-105 GHz. The 3-D printed magic tee has a comparable performance to a W-band CNC-machined magic tee but weighs 77.5% less than the metallic one.

Design of Simple and Double Ridge Waveguide T-Coupler for Space Domain

The T-Coupler or the magic tee (or magic T or hybrid tee) is a hybrid or 3 dB coupler used in microwave systems. It is an alternative to the rat-race coupler. In contrast to the rat-race, the three-dimensional structure of the magic tee makes it less readily constructed in planar technologies such as micro strip or strip line. The magic tee was originally developed in World War II, and first published by W. A. Tyrell of Bell Labs in a 1947 IRE paper. Robert L. Kyhl and Bob Dicke independently created magic tees around the same time. This paper illustrates simple and double ridge waveguide T-coupler. The relationships between the scattering variables in this sort of network are fixed by the unitary condition. Such a network has the properties that it is a matched device with one adjacent port decoupled from any incident port. The object of this paper is to present some results of simulation on the coupling and directivity of double ridge cross-waveguide couplers in a field ridge waveguide. This results are obtain by Ansoft HFSS using the Finite Element Method (FEM) calculations and the Genetic Algorithms method, and which show good performance.

$4\times4$ -Element Cavity Slot Antenna Differentially-Fed by Odd Mode Ridge Gap Waveguide

A differential feeding for a cavity slot antenna is presented. The proposed feeding is based on a simple mechanism rather than the traditional complex networks that suffer from high losses. It is based on exciting the first higher order mode (TE10) of the ridge gap waveguide (RGW) by enlarging the ridge width. This enlargement would excite some undesired even modes that are suppressed by inserting a vertical perfectly electric conducting (PEC) wall in the middle of the waveguide based on the concept of magic tee operation. The proposed 4 × 4 cavity slot antenna is implemented using substrate integrated waveguide (SIW) technology. Two horizontal slots on the top of proposed wide RGW, representing the differential feeding approach, are implemented to feed the cavity slot antenna. The slots couple the fields with same amplitudes and 1800 phase difference to the cavity. The electric fields of the two coupling slots have odd symmetry in the x-axis, and subsequently, uniform electric field distribution of the TE440 mode of a cavity can be excited. The 4/4 radiating slots are etched on the top of the cavity in a specific distribution to ensure having in-phase fields for broadside radiation with low-cross-polarization levels. The measurement and simulation results of the proposed cavity slot antenna are in a good agreement. The obtained results confirm that the proposed antenna achieves a relative bandwidth of 7.1% for -10-dB return loss, a gain of about 16.5 dBi, and a side lobe level about -17 dB in E-plane and -13.8 dB in H-plane. Moreover, the proposed antenna provides low cross-polarization levels (-35 dB in E-plane and -27 dB in H-plane) within the operating frequency band of 32.5 to 34.9 GHz. With this achieved low profile, high gain, and high efficiency of the proposed cavity slot antenna, it may have a great potential for millimeter-wave (MMW) applications.

Compact monopulse sum‐difference comparator based on double‐layer substrateintegrated waveguide

A monopulse sum-difference comparator based on double-layer substrate integrated waveguide (SIW) for X-band applications is investigated and experimentally validated. A 90° 3-dB directional coupler with a double-stepped coupling slot in the common broad side between a pair of folded parallel SIWs and an equal-length unequal-width 90° phase shifter are adopted to form a magic tee. The four magic tees are elegantly interconnected to design a highly compact comparator. Experimental results show the bandwidth (reflection coefficient < −10 dB) of the comparator can achieve 10% with an operating frequency range of 9.5–10.5 GHz, in which the output amplitude and phase imbalance are within 0.75 dB and 14° (RMS), respectively. The insertion losses are about 1.5–2.5 dB and the isolations between the three channels are all better than 20 dB. In particular, the double-layer configuration of the comparator network reduces the occupied area with the potential for high integration and makes it to be a good candidate for miniaturised and compact monopulse antenna systems.

Design of the 3.7 GHz, 500 kW CW circulator for the LHCD system of the SST-1 tokamak

Circulators are used in high power microwave systems to protect the vacuum source against reflection. The Lower Hybrid Current Drive (LHCD) system of SST-1 tokamak commissioned at IPR, Gandhinagar in India comprises of four high power circulators to protect klystrons (supplying 500kW CW each at 3.7GHz) which power the system. This paper presents the design of a Differential Phase Shift Circulator (DPSC) capable of handling 500kW CW power at 3.7GHz so that four circulators can be used to protect the four available klystrons. As the DPSC is composed by three main components, viz., magic tee, ferrite phase shifter and 3dB hybrid coupler, the designing of each of the proposed components is described. The design of these components is carried out factoring various multiphysics aspects of RF, heating due to high CW power and magnetic field requirement of the ferrite phase shifter. The primary objective of this paper is to present the complete RF, magnetic and thermal design of a high CW power circulator. All the simulations have been carried out in COMSOL Multiphysics. The designed circulator exhibits an insertion loss of 0.13dB with a worst case VSWR of 1.08:1. The total length of the circulator is 3m.

A Broadband Passive Monopulse Comparator MMIC

A broadband monopulse comparator MMIC (Monolithic Microwave Integrated Circuit) based on GaAs process is presented in this Letter. The comparator network constructed by three magic tees and one lumped power divider is proposed for one sum channel and two delta channels. The measurement results show that very wide frequency band from 15 to 30 GHz (66.7% relatively frequency bandwidth) with less than 2.5-dB loss can be achieved for the sum channel. And the null depth is more than 22 dB in 15–27GHz and 17 dB in 27–30 GHz for two delta channels. The total chip size is 3.4 mm 3.4 mm ( $0.26\lambda _{0}~0.26\lambda _{0}$ at the center frequency of 22.5 GHz).

Planar Magic-Tee Using Substrate Integrated Waveguide Based on Mode-Conversion Technique

In this letter we present a planar magic-tee using mode-conversion technique. The device is fabricated using substrate integrated waveguide (SIW) technology. Using the presented design approach, it is possible to develop a planar magic tee without the need for multi-variable optimization. In this letter we use intrinsic odd symmetry of $TE_{20}$ mode field of rectangular waveguide to generate two out-of-phase $TE_{10}$ modes in the outputs. Purity of $TE_{20}$ mode in the waveguide guarantees low phase and amplitude imbalance of output signals. To investigate phase and amplitude imbalance of output signals, we define the ratio of residual $TE_{10}$ to $TE_{20}$ as a figure of merit (F.O.M). To improve the performance of design, here a filtering section with good rejection for $TE_{10}$ mode and low insertion loss for $TE_{20}$ mode is used to improve performance. Finally, measured data are presented for the fabricated prototype, which shows less than 1 $^{\circ}$ phase imbalance and operation bandwidth between 10.75 to 11.4 GHz.

A NOVEL KA-BAND SOLID-STATE POWER COMBINING AMPLIFIER

This paper presents a high-e-ciency Ka-band solid-state power combining amplifler on the basis of a novel waveguide magic tee. By employing 16 low-power amplifler modules and compact waveguide power combining network with a low loss microstrip-to-waveguide transition, the output loss of the combining circuit is minimized, so a high combining e-ciency larger than 85% from 34 to 36GHz is obtained. Modular architecture is adopted in the combiner design. The single amplifler, bias circuit and heat sink are all fabricated separately, which add great ∞exibility to the system. Modular ampliflers can be premade and reserved in case any malfunctioning amplifler needs to be replaced. In addition, the improved power combining amplifler has the advantages of low loss, high isolation, compact structure, excellent heat-sink, etc.

A novel hybrid planar SIW magic tee and monopulse antenna

AbstractIn this article, a novel planar substrate integrated waveguide (SIW) magic Tee is proposed, and the magic Tee is implemented in a monopulse antenna design. Although the E arm is lain down, the magic Tee is of good performance. The magic Tee is used in a monopulse SIW slot array, and the beam pattern is measured. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 686–689, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24990

Resonant frequency-tunable microwave compressors

The development of resonant microwave compressors that can be tuned in the working frequency band comparable with the band of a single-mode waveguide is theoretically analyzed. The variants of the multifrequency (broadband) compressors with (i) a 3D storage cavity and an energy-output element based on the waveguide tee and (ii) a symmetric storage system and an energy-input-output element based on the magic tee are considered. The conditions for the creation and the possible characteristics of microwave compressors with discrete sets of working frequencies and quasi-continuous and continuous frequency bands are determined. The prototypes of tunable microwave compressors of the 3-cm-wavelength range are experimentally studied.

PLANAR EIGHT PORT WAVEGUIDE MONO-PULSE COMPARATOR

This paper suggests a new method for the designing of planar eight port waveguide mono-pulse comparator. Planar eight port waveguide mono-pulse comparator acts as a four-way in-phase power divider in a transmitting mode and as a mono-pulse sum and difierence combining hybrid in the receiving mode. The short-slot directional coupler is converted to an equivalent magic tee by adding dielectric- slab-fllled waveguide phase shifter. Four magic tees are connected appropriately using H-plane bends to form a compact planar eight port waveguide mono-pulse comparator. Simulation results with Ansoft HFSS software are presented, which show good performance.

A COMPACT H-PLANE MAGIC TEE DESIGNED AT W BAND

Magic tee is a widely used component in microwave systems; the four arms of a conventional magic tee direct at four different directions,which occupy much space and give inconveniences to the assemblage of a system. In this paper,a waveguide narrow-wall slot directional coupler and an E-plane dielectric loaded waveguide phase shifter are used to make up of a magic tee with four arms in the same H-plane. The narrow-wall slot directional coupler is analyzed with mode matching method and optimized with simulated annealing method,and the dielectric loaded waveguide phase shifter is designed with edge based finite element method. Numerical results of the magic tee are presented,which show that the performance of the designed magic tee is good.

A Compact Monopulse Radial Line Slot Array Antenna at Millimeter Wavelengths

This paper describes the design and performance of a radial line slot array antenna (RLSA) which generates sum or difference far field patterns. The antenna consists of rectangular waveguide to radial line transition, radial line and slot arrays etched on the upper plate of the radial line. A novel rectangular waveguide to radial line transition is designed to build up the dominate TEM mode in radial line to excite the slot arrays which are arranged in concentric rings on the upper plate of the radial line. The antenna radiates linear polarization at Ka band. Monopulse operation is obtained by a sum and difference network which is a compact eight-port comparator consisting of coplanar magic tees. The sum and difference network is waveguide structure whose loss is less than that of microstrip structure at millimeter wave lengths. The monopulse performances can be used in monopulse tracking and anti-collision application etc. Genetic algorithm (GA) is applied to optimize the parameters of the transition and antenna to obtain good performances.

A RIGOROUS ANALYSIS AND EXPERIMENTAL RESEARCHES OF WAVEGUIDE MAGIC TEE AT W BAND

Abstract—A waveguide magic tee at W band is analyzed exactly and developed. The analysis approach is a combination of the mode expansion method and finite element method, which is based on the weak form of Helmholtz equation. Mode expansion instead of PML (Perfectly Matched Layers) is used to truncate the computing space of finite element. A magic tee at W band (75∼110 GHz) with the structure, which is easy for manufacture, is developed. Calculated results are presented and compared to those in experiments. Agreement has been observed. A sensitivity analysis is carried out, which shows the influence of the tolerance of manufacture on the performance of the magic tee. And the power carrying capacity of the designed magic tee is also evaluated.