Nonradiative Dielectric Research Articles

Complete characterization of transmission losses in generalized nonradiative dielectric (NRD) waveguide

In this paper, transmission losses of the generalized nonradiative dielectric (NRD) waveguide are modeled and presented by our closed-form equations for the design of hybrid and monolithic millimeter-wave integrated circuits. This generalized structure includes our recently proposed channelized NRD-guide. Parametric effects are studied with respect to complex propagation constant and characteristic impedance, and some useful guidelines are generated for practical design considerations. Calculated results are discussed separately for the conductor and dielectric losses for the two fundamental longitudinal section electric (LSE) and longitudinal section magnetic (LSM) modes. It is found that the LSE mode may have losses, in some cases, comparable or even smaller than those of its LSM counterpart, contradicting what has usually been perceived for the conventional NRD-guide design.

Efficient analysis of microstrip-coupled nonradiative dielectric (NRD) resonators for hybrid integrated circuits

Nonradiative dielectric (NRD) resonators have been recently known as excellent stabilizing components for the design of a new class of oscillators based on hybrid integration of planar circuits and NRD-guides. However, an accurate characterization of such a component is needed in order to develop efficient computer-aided-design programs. In this paper, a hybrid planar integrated circuit comprising an NRD resonator is accurately modeled and is coupled to input and output planar microstrip circuits by means of long slots located on the top ground plane of the NRD structure. A reciprocity approach is used to solve the coupling problem between the resonator and microstrip lines. A modal expansion of the field equations has been applied to the NRD resonator in obtaining its rigorous field expressions. Finally, a transmission-line analysis is proposed for the structure, and scattering parameters have been calculated for different slot positions. Results are discussed for various parametric effects on coupling and Q-factor characteristics.

Diverging/focusing of electromagnetic waves by utilizing the curved leakywave structure: application to broad-beam antenna for radiating within specified wide-angle

A new "broad-beam antenna" for radiating electromagnetic energy in a specified wide angular region is proposed, utilizing the "curved leakywave structure". This structure consists of the leakywave structure curved physically and longitudinally into the form of an equi-angular spiral. The expression of the radiation field from this structure is given, the effects of various geometrical parameters on the radiation properties is discussed numerically for the design of the broad-beam antennas, and a simple experiment is also performed to verify the beam broadening by the proposed method. The concept in this paper may be easily applied to any leakywave structure such as a periodic dielectric antenna and a leaky nonradiative dielectric (NRD)-guide antenna for millimeter-wave application.

Characteristics and design consideration of leaky-wave NRD-guides for use as millimeter-wave antenna

Leaky-wave characteristics of a class of nonradiative dielectric (NRD)-guides with various shapes of trapezoidal cross section are systematically studied for their potential applications in low-cost millimeter-wave antennas. A numerical technique is applied to model these irregular structures. The technique is formulated by effectively combining a multimode network theory with a mode-matching method. Our emphasis in this work is on the investigation of parametric effects in connection with the trapezoidal dimensions on leakage properties of the NRD-guide. Extensive results are presented to derive some useful guidelines for the design considerations of new types of NRD-guide leaky-wave antennas.

Hybrid integrated HEMT oscillator with a multiple-ring nonradiative dielectric (NRD) resonator feedback circuit

In this paper, a novel hybrid integrated-oscillator scheme is developed for millimeter-wave sources. A nonradiative dielectric (NRD) multiple-ring resonator is used, not only as a frequency-stabilizing element, but also as a feedback circuit coupled to a planar amplifier through the input and output slots. Such a three-dimensional circuit design indicates that a strong positive feedback can be easily implemented at millimeter wave frequencies to improve characteristics of the oscillator. A field-theoretical model is derived for accurate prediction of the resonant frequency of NRD multiple-ring structures. The very satisfactory agreement observed between our measured and calculated results validates the modeling approach. Subsequently, a 23.3-GHz hybrid integrated high electron-mobility transistor (HEMT) oscillator has been designed, fabricated, and characterized with a dual-ring NRD resonator. The oscillator exhibits 7.0-dBm output power with 6.4% dc-to-RF efficiency and less than -95.7-dBc/Hz phase noise at 1-MHz offset from the carrier. The attractive electrical performance demonstrates a new approach to the design of cost-effective millimeter-wave sources by the use of an extremely low-cost and low-loss NRD material instead of an otherwise expensive conventional high permittivity (usually ceramic-material based) dielectric resonator.

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

This paper presents a new microwave device - a non-radiative dielectric (NRD) waveguide with a dielectric pseudochiral /spl Omega/-slab - the /spl Omega/-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 /spl Omega/-medium is discussed. New interesting modal features are revealed, showing that the propagation characteristics may differ considerably from the common isotropic case.

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.

Toward an optimum design of NRD-guide and microstrip-line transition for hybrid-integration technology

The newly proposed hybrid-integration technology of a nonradiative dielectric (NRD)-guide and planar structure offers an attractive alternative for designing microwave and millimeter-wave integrated circuits and systems. This paper presents an attempt with a transmission-line matrix (TLM) analysis toward accurate design and optimization of the NRD/microstrip-line transitions for the proposed scheme. Electrical performance of the transitions is studied with respect to various parametric effects such as the influence of coupling slot size, NRD and microstrip-line open-ends, as well as dielectric permittivity. Experiments with the designed transitions are made to validate our TLM analysis, as well as to demonstrate good performance. Calculated and measured results suggest that such a hybrid integration have a promising future as high-frequency building blocks.

Optical intensity modulator using inverted slot line at 60 GHz

The inverted slot line (ISL) structure which has been proposed for millimetre wave LiNbO 3 optical modulator is found to be very simple in structure, and is also capable of easily achieving a perfect velocity matching between carrier and modulating waves. This paper describes the analysis of the ISL based on the spectral domain approach and the practical development of a Mach-Zehnder Ti-diffused LiNbO 3 optical intensity modulator using the ISL at 60 GHz. To launch millimetre waves into the ISL structure two types of transitions have been developed successfully. In one type, a balun which is made from a semi-rigid coaxial cable is used to feed millimetre waves into the ISL. In another type, a non-radiative dielectric (NRD) waveguide which can provide the total integration of the modulator with millimetre wave integrated circuits is used to excite the ISL structure ensuring minimum transition losses. A modulator response of 0.17 W -1 could be obtained at 60 GHz using a Mach-Zehnder interferometer with a rather poor extinction ratio at an optical wavelength of 0.633 μm.

A model for slot-coupled nonradiative dielectric waveguide and microstrip line

The nonradiative dielectric (NRD) waveguide provides a low-loss, planar transmission medium into the millimeter-wave region of the spectrum. A number of passive and active devices utilizing this waveguide have been demonstrated in the past. Its use in hybrid designs, containing other transmission lines, can be facilitated through the introduction of appropriate transitions and interconnections. The objective of this article is to present an engineering model for one such transition, namely the NRD-to-microstrip line coupler. The two media are coupled by means of a slot-aperture in a common ground plate. The fields of the NRD waveguide are represented in a complete spectrum of modes, permitting rigorous derivation of the associated Green function. The final results are stated in the form of an equivalent circuit suitable for inclusion in CAD procedures. Envisioned applications for this component include multilevel circuits requiring connections from an NRD waveguide network to a layer containing microstrip-fed devices or radiators. Published 1997 John Wiley & Sons, Inc. Int J Microwave Millimeter-Wave CAE7: 388–396, 1997

Corporate feed in nonradiative dielectric waveguide

The development of a corporate feed for application to antennas fed from a nonradiative dielectric (NRD) waveguide is described. A feed was constructed and tested, and its performance evaluated by allowing the unterminated circuit to radiate as an antenna.

Integrated planar NRD oscillator suitable for low-cost millimeter-wave applications

A class of oscillators is proposed on the basis of a hybrid integration of planar circuits and nonradiative dielectric (NRD) guide. Compared to the existing design procedure and the conventional geometry, the novel oscillator uses an NRD resonator made of low-loss and low-permittivity material coupled to a planar oscillator through an aperture. This three-dimensional circuit design allows one to have a completely symmetrical circuit and a built-in feedback loop. A HEMT-based experimental prototype shows that the novel scheme for oscillator design is attractive for use in future low-cost millimeter-wave circuits and systems.

Comparative modal analysis of NRD parallelepiped dielectric resonators

The resonance modes of dielectric resonators having parallelepiped shape are extensively investigated in this work referring to the nonradiative dielectric (NRD) topology. Different numerical techniques, both rigorous and approximated (boundary elements, point matching, finite elements, transmission line approaches), are proposed and implemented to compute the relevant resonance spectrum as a function of the involved geometric and electromagnetic parameters. The theoretical results are discussed and compared also in connection with experimental investigations, carried out on suitable prototypes of NRD components. Qualitative and quantitative information is thus achieved to characterize with accuracy and efficiency the basic parameters (resonant frequencies, field configurations, etc.) involved in filter design and in other applications at microwaves and millimeter waves.

An integrated transition of microstrip to nonradiative dielectric waveguide for microwave and millimeter-wave circuits

Effective interconnects between two or more different waveguides are essential for using hybrid architecture of circuits as well as multipurpose instrumentation and measurements at microwave and millimeter-wave frequencies. In this paper, a new transition of microstrip line to nonradiative dielectric (NRD) guide is reported that makes it possible to design a class of compact NRD waveguide circuits directly integrated with planar-microstrip-based devices and components. A small aperture coupling theory is developed and effectively applied to model the proposed structure. It is found that theoretical results are in good agreement with experiments. The proposed transition promises to be instrumental in integrating planar microstrip devices and components with NRD guide circuits.

Coupling and quality factors in parallelepiped nonradiative dielectric resonators

In this work, the quality factors and the coupling effects have been investigated for parallelepiped dielectric resonators in nonradiative dielectric (NRD) waveguide, in order to achieve fundamental information for the design of various types of advanced filters. The unloaded quality factor has been calculated taking into account both conductor and dielectric losses through a straightforward version of the perturbation method. The electromagnetic coupling as a function of the distance between NRD guide and resonators has been evaluated through proper extensions of typical lumped equivalent circuits, thus quantifying resonance frequency shifts, external and loaded quality factors, etc.. To validate the derived theoretical models, suitable measurements of all these parameters have been performed at microwaves on X-band NRD prototypes.

Complex permittivity measurement of dielectric materials using nonradiative dielectric guide at millimeter wavelength

AbstractIn this paper, as a method for measurement of complex permittivity of millimeter‐wave dielectric materials, a transmission resonator method is proposed which is made of a dielectric resonator with both sides open placed in a nonradiative dielectric (NRD) guide. For the evaluation of the surface resistance of the conductor indispensable for measurement of the complex permittivity, a pair of TEoml mode resonators are placed coaxially and are mutually coupled. The difference of the conductor losses for the even and odd mode resonances of this resonator system is detected as the difference of the unloaded Q's so that the surface resistance is derived.The special features of the present measurement method are to evaluate the conductor surface resistance at a high sensitivity in a condition close to the resonator with both ends short‐circuited and to use a resonator with both ends open‐circuited for sample measurement because the effect of the surface resistance is small so that high accuracy is obtained as a whole. By using an NRD guide excitation method, a measurement system is realized which affects very little the unloaded Q of the resonator system and the electromagnetic field distribution.For the calculations of the complex permittivity, the eigenvalue calculation by the finite element method and the perturbation method by Kajfez are combined. For the samples with its relative permittivity of 24 and the loss tangent of 2 × 10−4, the measurement fluctuations are less than 0.005 percent for the resonant frequency and less than 1 percent for the unloaded Q. The measurement accuracy for the relative permittivity is less than 0.4 percent and that for the loss tangent is less than 3 percent.

Nonradiative dielectric‐guide FM gunn oscillator at 60‐GHz band

AbstractA nonradiative dielectric (NRD)‐guide FM Gunn oscillator with a built‐in circulator has been developed for the 60‐GHz frequency band, which has attracted considerable attention recently in Japan. In the fabrication of the 60‐GHz band NRD‐guide Gunn oscillator, a Gunn diode sealed in a specially fabricated compact package 1.2 mm in diameter has been used instead of the large‐diameter Gunn diode package commercially available. The oscillator has an output power above 130 mW, which is sufficient for practical applications.An NRD‐guide circulator also is fabricated to protect the oscillator from reflected wave. Using NiZn ferrite material, much better performance is obtained compared to conventional microstripline circulators. A frequency modulator using a beam‐lead varactor diode has also been designed and fabricated. Emphasis has been placed on structural simplicity and modulation sensitivity. Based on all these, an FM Gunn oscillator is fabricated, and for a bias voltage of 15 V applied to the varactor diode, a frequency deviation of 260 MHz is obtained. This FM Gunn oscillator with built‐in circulator can be contained in a compact housing 3 cm × 3.5 cm.

Frequency stabilization of NRD waveguide gunn oscillator at 60 GHz

AbstractFrequency stability of a 60‐GHz nonradiative dielectric (NRD) waveguide InP Gunn diode oscillator has been improved based on the phase‐locked‐loop technique. All the millimeter wave circuit elements needed, including the directional coupler, circulator, and so on, have been fabricated by using the NRD waveguide and a new approach has been introduced for harmonic mixer configuration by combining an NRD waveguide and a laterally shielded coplanar transmission line. By means of this approach, the millimeter wave circuit can be contained in a compact housing of 4 cm × 6 cm in area. The stability of the oscillation frequency of the fabricated Gunn oscillator was 2.1 × 10−10 (13 Hz/60 GHz). Further, the phase noise was kept to a small value of ‐48 dBc/Hz. The present results confirm the applicability of the NRD waveguide in the 60‐GHz band.

Resonant frequencies and quality factors in lossy NRD cylindrical resonators

In this paper the fundamental effects of losses on resonant parameters (frequencies and quality factors) are analyzed for circular-cylindrical dielectric resonators inserted between metal plates, in the configuration also called NRD (Non-Radiative Dielectric). Power dissipations are considered both in the dielectric and in the conductors. Complex resonant frequencies and closed-form expressions for the relevant quality factors are derived rigorously for arbitrary resonant modes, even without circular symmetry. Numerical results are presented and discussed, making also use of experimental data obtained by means of a suitable NRD set-up. The present analysis accurately provides the basic information for a more realistic design of up-to-date millimeter-wave frequency-selective devices in NRD circuitry.

A combined efficient approach for analysis of nonradiative dielectric (NRD) waveguide components

An efficient approach is introduced for the analysis of three-dimensional nonradiative dielectric (NRD) waveguide components including inhomogeneous dielectric and housing grooves. This technique combines effectively the method of lines with the mode-matching method based on the theoretical principle similar to that of the space-spectral domain approach (SSDA). It can be applied to determine characteristics of various waveguide components and microwave integrated circuits such as resonant frequencies and scattering parameters. The framework of this technique is demonstrated in this paper through its applications to resonator problems. Absorbing boundary conditions (ABC) with two types of difference schemes were used to simulate unbounded space. It is found that numerical results of resonant frequency for the first two fundamental modes (quasi-LSM and quasi-LSE) are in good agreement with our experiments. Numerical results are presented for both homogeneous and inhomogeneous dielectric resonators as functions of different geometric parameters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>