A leaky-wave antenna in nonradiative dielectric waveguide

A leaky-wave mechanism in a nonradiative dielectric (NRD) waveguide is described. The antenna used in the analysis consists of a long slot in one ground plane of the NRD guide; the currents present in the side walls cause the slot to radiate as a traveling-wave antenna. The antenna was designed to operate at 9.5 GHz to reduce the costs involved in working at high frequencies. The analysis of the slot follows the procedure outlined by L.O. Goldstone and A.A. Oliner (1959). A simple expression for the amount of coupling from the guide is derived under certain assumption made because information on the reactances necessary to model the slot is not as yet available. The theoretical coupling values verified by measurement and the design, construction, and performance of both leaky-wave antennas are described     

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.     

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.     

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     

Analysis of the mono-groove NRD waveguide and antenna

In this paper, an improved structure of symmetric groove nonradiative dielectric (GNRD) guide, the mono groove NRD (MGNRD) guide is presented, which keeps the similar performances of the symmetric groove structure, but is more easy to fabricate in millimeter waveband. The dispersion characteristics of the MGNRD is analysed using the transverse resonance method, then a MGNRD leaky-wave antenna is constructed, calculated and tested. The theoretical and experimental data are agreement with each other, and shows a attractive prospect for application.     

Leaky NRD guide fed microwave planar antenna

A novel and unique application of leaky waveguides as feeding systems for microwave planar antennas is presented. A new leaky nonradiative dielectric (NRD) guide based on a grating structure is proposed, and a planar array slot antenna using this leaky waveguide is constructed and measured at 23 GHz.<>     

A new type of millimeter wave-integrated directional couplers

In this paper a new type of millimeter wave integrated directional coupler is proposed. The coupling mechanism on the narrow wall of waveguide consists of a series of bilateral E-plane slots deposited on a dielectric substrate by photo-etching technique. The modified generalized transmission parameters considering the thickness effects of the strips and higher order mode interactions at the step discontinuities in the coupling region are used in optimizing program. The calculated performance of a 3-dB 12-slot directional coupler at Ka-band is given. A prototype Ka-band coupler has been tested. The measured results agree with the theoretical prediction satisfactorily.     

Analysis and Design of Bridged NRD-Guide Coupler for Millimeter-Wave Applications

A new nonradiative-dielectric (NRD)-guide directional coupler using two NRD waveguides interconnected with a bridge is proposed and demonstrated. Propagation constants of the bridged NRD-guide couplers are investigated with an electric-field integral-equation method, and modeling results show that there is a maximum of coupling coefficient when the thickness of the bridge is made around 0.68 of the plate separation. In this case, the coupling length is reduced approximately 60% and the bandwidth under the tolerance limits of$pm$0.5 dB of deviation for 3-dB coupling is nearly doubled with reference to its conventional counterparts. The use of a bridge not only improves the mechanical stability, but also makes the coupler performance reproducible. Experimental prototypes are fabricated with two 90$^circ$elbow bends that are used for the arms and the bridge-connected coupler section is terminated at both ends by tapered half-circle sections. A calibration procedure is used to remove mismatch effects between the NRD-guide and the rectangular waveguide in the measured results. Advantages of the new coupler as a passive component are shown for millimeter-wave integrated circuits.     

A New Leaky Waveguide for Millimeter Waves Using Nonradiative Dielectric (NRD) Waveguide-Part II: Comparison with Experiments

Accurate measurements were taken of the leakage constant of a leaky-wave structure based on nonradiative dielectric (NRD) waveguide in order to verify the theory derived in the companion paper, part I. Although the structure is intended for millimeter-wave use, measurements were made on a model scaled to X band (lambda = 3 cm) to improve the accuracy of the experimental results. The measurements were taken by probing the electric near field strength along the longitudinal direction. Comparisons with accurate theoretical data are presented for different frequencies and geometrical parameters, and very good agreement is found between the measurements and the theory.     

Analysis of Transmission Characteristics for NRD/Microstrip Line Hybrid Integrated LSE and LSM-Mode Baluns*

The NRD/microstrip line hybrid integration structure shows good behavior for millimeter wave applications. This paper applies the integral equations method to analyze the transmission characteristics of the NRD/microstrip line hybrid integrated baluns coupling through slot and operating in LSE or LSM modes. To apply this method, a new Greens’ function of microstrip line is presented and the slot coupling problems between NRD guide and microstrip line and the practical LSE and LSM-mode baluns are analyzed respectively. The availability of the present approach is validated by rather good agreement between the theoretical results and the experiment data given in the literature.     

Numerical and experimental analysis of nonradiative dielectric guide modulator and mixer at Ka band

This letter describes the numerical analysis of an on/off modulator and a single-ended mixer in nonradiative dielectric (NRD) guide configuration at Ka band. Currently, only experimental results are available for such structures. A shunt mounted diode switch in NRD guide configuration is analyzed using the finite element method (FEM) in conjunction with linear circuit simulation. A novel mixer is similarly analyzed using FEM and harmonic balance analysis. The results obtained from numerical analysis are compared with measured results. It is demonstrated that some counter-intuitive experimental results can be explained through numerical analysis.     

Analysis of coupled inset dielectric guide structure

The propagation and coupling characteristics of the inset dielectric guide coupler are theoretically considered in this paper. Rigorous solutions for the dispersion relation and the coupling coefficient are presented in a rapidly convergent series. Numerical computations illustrate the behaviors of dispersion, coupling, and field distribution in terms of frequency and coupler geometry     

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     

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.     

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.<>     

A quasi-TEM design method for 3 dB hybrid couplers using asemi-reentrant coupling section

An effective quasi-TEM design method for 3-db hybrid couplers using a semi-reentrant coupling section is presented. The analysis is based on the use of the rectangular boundary division method for solving the boundary value problem, including thick-strip conductors in an inhomogeneous medium. A trial design of a microstrip 3-dB coupler using substrates of low dielectric constant has been carried out by adding a sequential optimisation algorithm to the analysis method. Measured parameters of the designed 3-dB hybrid coupler are compared with the theoretical ones     

An NRD-fed dielectric rod antenna for the short millimeter wave band

A simple E-plane tapered rectangular dielectric rod fed by NRD guide is used as a millimeter wave antenna. This class of aerial features attractive radiation patterns with relatively low sidelobes and moderate gain. The measured results show that such an antenna and mounting structure can be exploited as effective radiating element in the short millimeter wave frequency band.     

An NRD fed dielectric rod antenna for the short millimeter wave band

A simple E-plane tapered rectangular dielectric rod fed by NRD guide is used as a millimeter wave antenna. This class of aerial features attractive radiation patterns with relatively low sidelobes and moderate gain. The measured results show that such an antenna and mounting structure can be exploited as effective radiating element in the short millimeter wave frequency band.     

Propagation Characteristics of a Novel NRD Guide with Double-Layer LHM Slab

A new waveguiding structure based on NRD (Nonradiative Dielectric) guide with a double-layer LHM (Left Hand Material) slab is carefully investigated. Rigorous multi-mode network treatment combining with mode matching method is carried out to analyze the propagation characteristics of the structure. Theoretical analysis results reveal that depending on the choice of permittivity and permeability of the two dielectric slabs, the guiding structure is of series distinct and interesting properties, such as anomalous dispersion, opposite polarization modes coupling, and the existence of complex mode. Besides, the new configuration can also be used as a leaky wave antenna working in the dominant or the first higher order mode. All these particular features create various applications in electromagnetic engineering.     

S波段小型Lange耦合器的应用设计

Lange耦合器在雷达设备中应用广泛,雷达技术的飞速发展对Lange耦合器的体积质量提出了非常苛刻的要求。通过Ansoft Designer仿真发现在设计中使用高介电常数的介质,使耦合器的中心频率适当偏离实际工作频率,改变耦合段结构,都可以既不影响耦合器性能又明显地减小Lange耦合器的尺寸。实际制作了两种S波段的薄膜工艺小型Lange耦合器,尺寸分别为2.25mm×11.9mm2、.25mm×8.9mm,其中尺寸较小的耦合器中心频率与实际工作频率相比较高。两种耦合器的实测结果表明,所设计的耦合器一方面在尺寸上达到了小型化的目的,另一方面性能完全满足实际工程应用的需要。