Wideband Circulators for Use at Frequencies Above 100 GHz to Beyond 350 GHz

High-performance circulators operating at frequencies in the range from 100 to 350 GHz have been developed for application in major measurement systems. These circulators have open quasi-optical structures. The magnetized plates in these devices are of nonmetallic magnetic materials which have both well-developed millimeter-wave gyrotropic properties and the magnetostatic properties of an excellent permanent magnet material. Very few commercially available magnetic materials have been found that meet both the magnetostatic and the magnetooptical selection criteria. Those few have, however, made possible the design, manufacture, and successful operation of high-performance circulators/isolators at these high operating frequencies. Several circulators/isolators of this type have been installed in major measurement systems.     

Broad-Band Isolators and Variable Attenuators for Millimeter Wavelengths

A longitudinally magnetized rod of ferrite has been used as a dielectric waveguide which provides Faraday rotation independent of frequency in the band from 50 to 60 kMc. This rotator has been incorporated into broad-band isolators with forward losses of 1 db and reverse losses greater than 30 db with return losses of approximately 20 db over the band. It has also been used in a variable attenuator with a minimum loss of 1 db and a maximum loss greater than 30 db which is essentially constant over the band. Advantages of this type of rotator at millimeter wavelengths include bandwidths in excess of 20 per cent, low field requirements (25-50 /spl oelig/), relatively large dimensions, the use of common ferrites, and the absence of conducting waveguide walls which permits rapid switching of the control field. The last feature has been utilized in an automatic power leveling system capable of removing variations of several kc frequency content from the swept output of a millimeter wave BWO.     

Microoptic grating multiplexers and optical isolators for fiber-optic communications

As new optical devices for increasing further the utility of and to expand the application of fiber-optic communications, grating multiplexers and isolators have been developed for 0.8 μm band employing microoptic approach. The development of these devices is the subject of this paper. The devices have desirable features of small size, compactness, high optical performances, and high reliability. The grating multiplexer consists of a graded-index rod, a blazed reflection grating replicated onto the graded-index rod slanting facet or a wedge facet, and an input-output fiber array. Simple calculations have been done to determine necessary element parameters for a given channel spacing. Experimental results are presented for five-channel multiplexers devised using a SELFOC^®lens. Around 3 dB insertion loss and less than -30 dB crosstalk have been obtained for about 35 nm channel spacing in overall device size of18 times 13 times 50mm. Faraday rotation optical isolators for 0.8 μm band have been miniaturized by employing an efficient paramagnetic glass Faraday rotator, a magnet with a through hole and a folded optics in the Faraday rotator. The path number in the folded optics has been optimized in terms of trading-off between the magnet size and the insertion loss. A 0.9 dB insertion loss including fiber coupling loss and 36 dB isolation have been obtained in overall device size of24 times 24.5 times 42mm. Results on the temperature and wavelength dependence of the isolation are also presented. In addition, fundamental properties of optical circulators for 0.8 μm band and optical isolators and circulators both for 1.3 μm band, developed as extended modifications of the optical isolators for 0.8 μm band, are briefly described.     

Precise Design of Millimeter Wave Quasi-Optical Faraday Rotators

A method of designing high performance millimeter wave quasi-optical Faraday rotators (QOFR) is reported in this paper. First, the dielectric and magnetic parameters for the ferrite sample are determined by fitting theoretical curves to the measured data. These fitted parameters are then used in a precise numerical model to predict the rotation angle and insertion loss of the QOFR. Finally, the parameters of the QOFR are optimized according to the requirements of devices. Examples are given showing the performance of the QOFR with an isolation better than 20 dB and an insertion loss less than 0.6 dB from 75 GHz to 95 GHz.     

毫米波扩展互作用器件

扩展互作用器件是一种采用慢波谐振系统作为高频互作用电路的真空电子器件,是目前能够在毫米波亚毫米波段提供大功率输出的重要器件之一。本文给出了目前国内外毫米波亚毫米波段扩展互作用器件（EIK和EIO）技术的发展情况,并介绍了扩展互作用器件在毫米波亚毫米波段的技术特点和最新研究趋势。     

Performance Predictions For Isolators And Differential Phase Shifters For The Near-Millimeter Wave Range

An analytical and numerical study is presented for a five region planar canonical structure modeling quasi-optical integrated surface magnetoplasmon based nonreciprocal devices for the near-millimeter wave range. The model includes a slab of a high quality semiconducting material, such as n-GaAs, magnetized parallel to its surfaces and perpendicular to the direction of propagation. The analysis performed is exact. Sample results show the possibility of acceptable performance for isolators over a bandwidth of 45 GHz in the 500-GHz range and of differential phase shifter design over a bandwidth of 65 GHz in the 380-GHz range.     

Quasi-optical ferrite devices for millimeter and submillimeter wave bands

Main features of the development of quasi-optical ferrite devices, using Faraday effect, are considered. Properties of a polarizing divider and a ferrite rotator of a polarization plane are analysed with standpoint of minimum losses. A matching method, based on an utilization of the rotator element in a form of the multilayers ferrite structure, which can be adjusted independently for right-handed and left-handed cyrcularly polarized waves, is suggested. It is shown, that this method allows to obtain a total matching in a quasi-optical transmission line. Results of an investigation of quasi-optical ferrite devices for the oversized round waveguide withH ₁₁ mode are presented.     

A new Faraday rotator using a thick Gd:YIG film grown by liquid-phase epitaxy and its applications to an optical isolator and optical switch

A new Faraday rotator using a thick garnet film grown by liquid-phase epitaxy (LPE) has been proposed and film growth technology for the rotator has been investigated. The new Faraday rotator had good features of very low cost and small size, due to high productivity of the LPE-grown film and low magnetic saturation field, respectively. By using the new Faraday rotator, an optical isolator and magnetooptic switch for single-mode fiber systems have been developed. The optical isolator featured 0.8-dB insertion loss and 25-dB isolation at 1.3-μm wavelength. The magneto-optic 1 × 2 switch was independent of light polarization and featured 1.3-1.7-dB insertion loss, -25-dB crosstalk, and 30-μs switching time at 1.3-μm wavelength. Minimum switching voltage was ±5 V. Magneto-optic devices using the new Faraday rotator is practical for use in1.2-1.7-mum wavelength fiber-optic systems, because of good optical properties, compactness, and low cost.     

A Novel Quasi-Optical Frequency Multiplier Design for Millimeter and Submillimeter Wavelengths

This paper describes a novel design for millimeter and sub-millimeter wavelength varactor frequency triplers and quadruplers. The varactor diode is coupled to the pump source via waveguide and stripline impedance matching and filtering structures. Output power at the various harmonics of the pump frequency is fed to quasi-optical filtering and tuning elements. The low-loss quasi-optical structures enable near-optimum control of the impedances seen by the varactor diode at the idler and output frequencies, resulting in efficient high-order harmonic conversion. A minimum efficiency of 4 percent with 30-mW input power has been obtained for a tripler operating between 200 and 280 GHz, with a peak efficiency of 8 percent between 250 and 280 GHz. Another tripler, designed for the 260-350-GHz band, gave a minimum conversion efficiency of 3 percent with 30-mW input power, with a peak efficiency of 5 percent at 340 GHz.     

Advanced devices and components for the millimeter and submillimeter systems

The purpose of this paper is to discuss key topics related to low-noise mixers, high efficiency multipliers, the use of quasi-optical techniques to reduce circuit losses, and the development of very high-Q devices applicable to the millimeter and submillimeter wavelengths [1]-[5]. In particular, we will describe the development of a highly reliable metalized GaAs Ta-Schottky-barrier diode with native-oxide passivation. The zero-bias cutoff frequency of these diodes is greater than 1000 GHz when measured accurately near 60 GHz with a zero-bias junction capacitance near 0.1 pF. This zero-bias cutoff frequency is approximately twice the value for a comparable nonmetallized device. Using these very high-Q devices, we have achieved RF performance that has advanced prior state of the art. In frequency multipliers, doublers (100-200 GHz), and triplers (100-300 GHz), we have realized conversion efficiencies of 12 and 2 percent, respectively. The CW output power of the doubler was 18 mW and that of the tripler 2 mW. In an image-enhanced mixer at 35 GHz with an IF of 1 GHz, we have realized conversion loss below 3 dB including 0.6-dB circuit losses, and less than 5.9-dB noise figure (SSB) including a 2-dB IF noise-figure contribution.     

（英）亚毫米波波段波束功率合成方法

对于亚毫米波或太赫兹系统而言,关键问题是功率源的输出功率非常小。 功率合成技术是增加输出功率的有效方法。 然而,在微波和毫米波段中使用的常规功率合成方法（例如电路级合成或波导内空间合成）在亚毫米波波段因损耗高及难以加工等因素而受到制约。 本文提出了一种基于准光学技术的波束功率合成方法。 它具有损耗低,合成效率高,相对容易制造的优点。本文给出了分析,仿真和实验结果,并得到高的输出合成效率。     

用于准光系统的毫米波波纹馈源的设计

介绍了可用于准光系统,工作于毫米波和亚毫米波波段的圆波纹馈源喇叭天线的设计方法,包括喇叭内壁波纹尺寸的设计,喇叭张角的选择与如何选取加工工艺等。考虑到传统加工工艺的限制,为了保证尺寸精度,尤其是喇叭内壁波纹尺寸的加工精度,采用了电镀腐蚀的加工工艺。并以中心频率为94GHz,带宽为35GHz的波纹馈源为例,对天线进行了加工和测试分析,验证了该设计方法的精确性和该加工工艺的可靠性。并将该方法推广用于从54GHz到340GHz间的若干毫米波亚毫米波段的准光系统的馈源设计和加工。     

Criteria for Designing High-Power Coupled Wave Duplexers and Isolators

This paper presents criteria for designing nonreciprocal coupled-wave devices which may be used as isolators, circulators and duplexers. An experimental model of such a device was designed and tested over a 6 per cent frequency band centered at 35 kMc, and the obtained data are in good agreement with the theory. Such devices should have numerous applications as they offer the capability of operating under extremely high power levels, and are not restricted to dominant mode operation.     

毫米波准光功率合成评述

本文对各种毫米波功率合成技术做了简单地回顾,综述了几种当前国际上开展的毫米波准光功率合成方法,最后简单地介绍了作者提出的复合式准光功率合成方法。     

Fundamental Considerations in Miuimeter and Near-Millimeter Component Design Employing Magnetoplasmons

The feasibility of using surface magnetoplasmons on semiconducting substrates to obtain circuit functions which match those of ferrite loaded devices at lower frequencies, is investigated. This article describes some initial results obtained in our study of performance characteristics using the best loss parameters available for GaAs materials. Canonical models are considered which relate directly to proposed configurations for differential phase shifters and isolators in the millimeter and near-millimeter ranges.     

Densification of Alumina Ceramics Sintered by Using Submillimeter Wave Gyrotron

The sintering of high purity alumina, by using a very high frequency in range sub-millimeter waves, is presented in this paper. The sintering was performed by using a 300 GHz material processing system. Achieving homogeneous and volumetric heating on submillimeter wave sintering was confirmed by the grain size distribution analysis. The densification curves were obtained for submillimeter wave (300 GHz), millimeter wave (28 GHz), and conventional processing. The enhancement of densification and early shrinkage were observed on submillimeter wave sintering. However, compared with millimeter wave method, the densification of sub-millimeter wave sintering is lower at all sintering temperatures. The grain coarsening was analyzed using SEM photographs of fracture surfaces. The grain sizes of submillimeter wave sintered samples were smaller than those of the millimeter wave sintered samples. The effect of cold isostatic pressing, was also evaluated on submillimeter wave sintering. It suggests that the cold isostatic pressing method is quite effective for densification of SMMW sintering alumina.     

用于高速无线通信的毫米波行波管

毫米波行波管可以为高速无线通信提供高性能与实用化的功率放大器解决方案.国外正在开展多项基于毫米波行波管的高速无线通信技术的研究,工作频率范围在71~300GHz.本文综述了国内外71~235GHz的毫米波行波管的技术发展与研制水平,并结合作者所在团队的研究成果分析了研制该类器件所需要解决的慢波结构微加工、新型慢波结构设计和宽带低损耗输能等关键技术.     

Quasi-optical antenna duplexers

The development of antenna duplexers for transceiving quasi-optical systems of millimeter and submillimeter wavelengths are considered for two groups of devices — passive and active action. Duplexers, using properties of quasi-optical hybrids, belong to the first group, and duplexers on the base of semiconductor or ferrite devices are included to the second group. Results of developments and investigations of considered devices in the millimeter wave range are presented.     

Millimetric Nonreciprocal Coupled-Slot Finline Components

Promising preliminary results are presented for isolators and a four-port circulator in novel finline structures in the frequency range 26.5-40.0 GHz. The basic configuration is a ferrite-loaded coupled-slot finline with the ferrite magnetized parallel with the direction of propagation. The nonreciprocal effects of the odd mode propagating alone and of the odd and even modes propagating are described. All structures exhibit a 20-dB isolation bandwidth greater than 3.6 GHz. It is suggested that such structures would also be suitable for higher frequencies.     

Millimeter wave components for electronically controllable antennas

Many present and future military and commercial systems operating at millimeter wave frequencies require the use of sophisticated electronically controllable antennas for maximum capability and flexibility. Electronic control of the antenna pattern is provided by electronically switchable phase control of each radiating element such as that achieved in phased array antennas or via electronically reconfigurable antenna feeds referred to as beam forming networks (BFN). Multibeam antennas provided by BFN'S can be realized using switches, variable power dividers (VPD), and phase shifters. Ferrite materials and associated application technology are being utilized to achieve these switchable RF control components at millimeter wave frequencies. The performance achievable in ferrite switchable circulators, variable power dividers and phase shifters in the frequency region from 20 to 100 GHz is discussed.