An array of coupled nonradiative dielectric waveguide radiators

A novel antenna array that radiates a single mode of multiple coupled nonradiative dielectric (NRD) waveguides, is described. The array is fed by a single NRD waveguide, which is designed to propagate a wave with the same wave number as that of free-space. The individual radiators of the array are spaced at one free-space wavelength, but due to the narrow beamwidth of the individual radiators, grating lobes are effectively suppressed. An eight-element array is described and measurements presented, but the design method can be extended to any number of elements     

Leaky NRD guide as a feeder for microwave planar antennas

Although leaky wave antennas have been studied extensively in the literature, their practical use is still limited. This work proposes a novel and unique application of leaky NRD guides as feeding systems for microwave planar antennas and shows their substantial possibilities of practical use. At first a new leaky waveguide is introduced based on a periodic array of grooves on the upper side of the dielectric strip in the NRD guide. Then, leaky waves issuing from this configuration are used to feed a slot array cut on the upper metal plate of the NRD guide. Design examples of linearly and circularly polarized planar antennas were constructed, and their characteristics were measured at 23 GHz. The obtained results show the validity for this application of the leaky waveguide     

A Transition from Rectangular to Nonradiating Dielectric Waveguide (Short Paper)

A transition between standard X-band waveguide and non-radiating dielectric (NRD) waveguide is described. It consists of a transition from air-filled rectangular waveguide to reduced-width dielectric-filled waveguide, cascaded with a transition to NRD. Both transitions are theoretically designed to provide both mode matching as well as a low reflection coefficient. The composite transition can be used for measurements in NRD while making use of conventional waveguide test equipment.     

Noninvasive pulse modulator concept for nonradiative dielectric(NRD) waveguide

The nonradiative dielectric (NRD) waveguide has been identified as a promising candidate for use at millimetre-wave frequencies. To realise this promise NRD waveguide must support the design of the necessary active and passive components for the realisation of systems and subsystems. The authors describe the principle of a novel modulator for use with NRD waveguide and present preliminary results     

The bandwidth of single-mode operation in groove NRD waveguide

Based on analysing the dispersion characteristics of groove NRD waveguide using the eigen-weighted BIEM, the frequency bandwidth forE ₁₁ ^y single-mode operation is calculated, and the results show that the bandwidth of groove NRD waveguide is broader than that of NRD waveguide with the same principal sizes.     

Substrate integrated nonradiative dielectric waveguide

A new substrate integrated circuits (SICs) fabrication technique is proposed for realizing nonradiative dielectric (NRD) waveguide circuits. This new technique called substrate integrated NRD (SINRD) guide allows the NRD guide be integrated within a dielectric substrate by drilling a pattern of air holes. Dispersion analysis and design considerations of the new structure are discussed. A hybrid integrated scheme of planar and SINRD circuits is demonstrated for the first time with simulation and measurement results.     

Aperture coupled microstrip patch antenna fed by nonradiating dielectric waveguide

Owing to its low loss property at millimetre-wave frequencies, the nonradiating dielectric (NRD) waveguide is very attractive for use as a feed network in planar arrays. The design, fabrication and testing of a microstrip patch antenna fed by NRD guide at X-band is described. Radiation patterns are measured and presented.<>     

新型NRD波导漏波天线特性分析

本文利用多模网络理论结合模匹配技术对任意横截面NRD波导漏波天线的辐射特性作了系统的分析,这些天线可以作为低成本的实用天线应用在毫米波系统中.文中着重研究了结构参数的变化对天线辐射特性的影响.这些计算结果对这类新型漏波天线的设计和确定NRD波导作为传输结构时的制作容差有重要的指导意义.     

Analysis and measurement of NRD-guide leaky wave coupler in Ka-band

A new structure for a nonradiative dielectric (NRD) waveguide directional coupler has been developed. The structure combines two NRD guides and a dielectric slab guide in order to utilize a leakage mechanism for coupling. The coupling depends on this leaky mechanism, but not on field interactions as in a conventional proximity coupler. A theoretical formula for calculation of the decay constant is derived. The field along the NRD guide and the decay constant are measured at Ka band (35 GHz) and compared with the theoretical data. Reasonable agreement between the measured and theoretical data is found     

TLM-based modal-extraction approach for the investigation of discontinuities in the rectangular waveguide and the NRD

This paper describes the development of a rigorous transmission-line matrix-based modal-extraction approach to analyze discontinuities in guided-wave structures in general, with particular attention to the nonradiative dielectric waveguide (NRD). The motivation for this paper arose from the need to ascertain the admittance of a slot in the ground plane of an NRD without relying on experimental data. These data enabled one to design an NRD-based slot array following the methodology of Malherbe (1984), Malherbe et al. (1984), and Ghosh et al.(1997). Previous work in this area relied on placing observation points sufficiently remote from the discontinuity in order to ensure the decay of scattered evanescent modes to appreciably low levels. The method discussed here obviates this requirement and allows the evaluation of generalized scattering-matrix coefficients arbitrarily close to the discontinuity, thus significantly reducing the computational overhead. Results pertaining to discontinuities in the NRD and the rectangular waveguide have been presented and shown to give good agreement with those in the literature and with measurements. The perfectly matched layer has been used as an absorbing boundary condition in our simulations. Finally, the results have been verified using the power-conservation and Poynting's theorems.     

The characteristics of NRD waveguide gratings

The filter characteristic of NRD waveguide grating is investigated rigorously by combining network approach with mode matching theory. Numerical examples are shown and compared with experiment results.     

Analysis of slots in nonradiating dielectric waveguide using the modal expansion method

A modal expansion method is used with the reciprocity and Poynting theorems to derive the admittance of inclined slots cut in the metal wall of a nonradiating dielectric (NRD) waveguide. Theoretical values of normalised conductance and susceptance are compared with previously reported experimental results and are found to be in good agreement.<>     

New leaky-wave antenna for millimetre waves constructed from groove NRD waveguide

A new leaky-wave antenna constructed from a groove non-radiative dielectric (GNRD) waveguide is presented. The GNRD leaky-wave antenna overcomes the difficulty of assembling precisely the dielectric strip in the NRD leaky-wave antenna, and is superior to the NRD leaky-wave antenna of the same size in the radiation pattern. The propa-gation and radiation characteristics of the GNRD leaky-wave antenna are analysed by use of the transverse resonance method. The theoretical results are in good agreement with experimental data.     

Leaky wave antenna based on image NRD guide with staircase-shapeddielectric slab

A leaky wave antenna based on the use of an asymmetric image nonradiative dielectric (NRD) guide has been studied experimentally. By using a staircase-shaped image NRD guide, the gain bandwidth of the antenna becomes three times that of a leaky wave antenna using an ordinary image NRD guide. Moreover, this antenna employs a flared horn in the NRD guide which makes the H-plane beamwidth controllable     

Characteristic impedance of nonradiative dielectric waveguide and its application

In this paper a formula for determining the characteristic impedance of the nonradiative dielectric waveguide (NRD-guide) is presented. The numerical results are obtained, which are very useful for designing NRD waveguide components, such as impedance transformers, filters, branch-line hybrids, and active circuits. As a practical example for applying the formula, a 3 dB brainched NRD-guide directional coupler was designed and fabricated. The experiments show good consistency with the theory.     

A Systematic Investigation on Leaky Characteristics for NRD Guide with Arbitrary Profile of Cross-Section

The leaky characteristics of the NRD guide with arbitarary profile of cross section are systematically studied by a method which combines staircase approximation with multimode network theory and mode-matching procedure. Emphasis is laid on the investigation of the effect of the different profile dimensions on the leakage characteristics of the NRD guide. Extensive numerical results are given to establish useful guidelines for the design of some new types of NRD guide leaky wave antennas.     

The design of a slot array in nonradiating dielectric waveguide, part I: Theory

A set of theoretical design equations for a slot array fed by nonradiating dielectric (NRD) waveguide is developed. Mutual coupling between the slots cut into one of the metal walls of the waveguide is taken into consideration for a design that can have a predetermined radiation pattern. The theoretical development follows that of Elliott.     

Full-wave analysis of a nonradiative dielectric waveguide with apseudochiral Ω-slab

This paper presents a new microwave device - a non-radiative dielectric (NRD) waveguide with a dielectric pseudochiral Ω-slab - the Ω-NRD waveguide. A rigorous full-wave analysis is presented and the modal equations for the longitudinal-section magnetic (LSM) and longitudinal-section electric (LSE) modes are derived. The dispersion curves and operational diagrams for the first hybrid LSM modes are presented. The effect of the pseudochiral Ω-medium is discussed. New interesting modal features are revealed, showing that the propagation characteristics may differ considerably from the common isotropic case     

Design and fabrication of a nonradiative dielectric waveguidecirculator

A technique is described for constructing a high-performance nonradiative dielectric waveguide (NRD guide) circulator for use at 50 GHz. A mode suppressor, which serves to reduce unwanted modes to a negligible level, was devised and used to improve circulator performance significantly. A half-wavelength step transformer was installed at each port of the circulator to increase the operational bandwidth. The insertion loss of this circulator is less than 0.3 dB, and the 20-dB isolation bandwidth is about 2.6 GHz. Characteristics of the NRD guide circulator are analyzed based on an equivalent circuit representation. This analysis considerably facilitates the design procedure of the circulator     

新型毫米波Gunn振荡器

本文提出了一种新型的毫米波Gunn振荡器。在设计上利用了无辐射介质波导和谐振帽振荡器的优点。实验结果表明,这是一种很有发展前途的毫米波源。