Dielectric slab Rotman lens

A new form of a Rotman lens has been proposed for applications above 10 GHz, such as a collision avoidance radar. The proposed lens can be described as a dielectric slab fed by slot lines. The new form is expected to show lower loss and lower mutual coupling than the conventional Rotman lenses at higher frequency than 10 GHz. The prototype was implemented with nine beam ports and nine array ports. The measurements show that the mutual coupling can be lowered at higher frequency, and that the efficiency of the dielectric slab lens of about 30% can be obtained. We conclude that the dielectric lens is comparable to the conducting plate lens even though a spillover loss is presumed at frequency of the implementation.     

A 20 GHz Steerable Array Antenna Using 3-bit Dielectric Slab Phase Shifters on a Coplanar Waveguide

A simple steerable array antenna is designed and developed using a movable dielectric phase shifter. The change of effective dielectric constant at different dielectric slab positions on a coplanar waveguide is used as the phase shifter. The impedance matching and desired phase shift conditions are satisfied at two slab heights, and the reflection is designed to be minimized at these slab positions. The low-loss dielectric material is used as the dielectric slab and is placed close to a coplanar transmission line with airgap. The 4times4 steerable array antenna with the phase shifters is designed and fabricated at 20 GHz. The H-plane radiation patterns are measured at different phase shift positions and compared with the expected results     

Flat spectral response arrayed-waveguide grating multiplexer withparabolic waveguide horns

An eight-channel flat spectral response arrayed-waveguide grating multiplexer with parabolic waveguide horns has been fabricated on a planar lightwave circuit (PLC). A double-peaked intensity distribution is formed at the slab interface by the parabolic waveguide horn. A 1 dB bandwidth of 98 GHz, 3 dB bandwidth of 124 GHz and 20 dB bandwidth of 196 GHz are obtained for 200 GHz channel spacing. The crosstalk to neighbouring channels is less than -27 dB and the on-chip insertion losses range from 6.1 to 6.4 dB, respectively     

Dielectric Slab Rotman Lens for Microwave/Millimeter-Wave Applications

A new form of a Rotman lens is proposed for microwave/millimeter-wave applications such as a collision-avoidance radar. The proposed lens can be described as a dielectric slab fed by slot lines. The new form is expected to show lower loss and lower mutual coupling than the conventional Rotman lenses fabricated with conducting plates at millimeter-wave frequency. Taking the field distribution inside the dielectric slab into account, the$ TE_0$mode was chosen to excite the dielectric slab lens. The dielectric Rotman lens consists of a dielectric slab, tapered slot structure, and the transitions between the antipodal slots and microstrip lines for subminiature A connectors. The conventional design equations have been modified for use in designing the dielectric slab Rotman lens with a high dielectric material. A prototype was implemented with nine beam ports and nine array ports. Measurements from 10 to 20 GHz show that mutual coupling can be lowered at higher frequency. The obtained efficiency of the dielectric slab lens system is approximately 30%. The efficiency of the lens is comparable to that of the conducting plate lenses even though there is a spillover loss from the dielectric slab.     

Tunable millimetre-wave ferrite bandpass filter with reduced biasing field

A magnetodynamic resonance mode in a partially metallised ferrite slab is proposed for use as an electronically tunable bandpass filter for the frequency range from 30 to 40 GHz. Unloaded Q-factors of greater 100 (350) and an insertion loss of less than 3 dB at 40 GHz have been observed.     

Transverse slot antenna array in the broad wall of a rectangular waveguide partially filled with a dielectric slab

A compact and wide-band transverse slot antenna array in the broad wall of a rectangular waveguide partially filled with an H-plane -dielectric slab is presented in this paper. By partially filling an H-plane dielectric slab in the waveguide, the inter-element spacing between slots is reduced to be about 0.8 free-space wavelengths to avoid grating lobes. In addition, the partially filled material provides extra flexibility to adjust the slot impedance as desired within a relatively wide frequency range. A new feeding network is designed for this antenna array, which can prevent the shift in the pointing angle of the array's main radiation beam with the change of frequency. Experimental data for a 2/spl times/4 antenna array operating at X-band show that stable radiation pattern over a wide frequency range can be obtained. The measured gain is 16.9 dB at 10 GHz and the fluctuation is less than 2 dB over a frequency band of 1.5 GHz. The slot array's 10-dB return loss bandwidth is 13% and the cross-polarization level is better than -25 dB.     

Tunable bandpass microwave filters based on defect commandable photonic bandgap waveguides

A new type of tunable filter based on a commandable defect in the bandgap of a periodic CPW structure is proposed. The defect level is tuned either mechanically by adding a covering slab over the device or electrically by polarising diodes located at the defect. The validity of this concept is experimentally demonstrated at 4 GHz. This kind of filter is well suited for applications in the 10 to 60 GHz frequency range.     

Experimental analysis of metal coated dielectric waveguides

This paper concerns the experimental characteristics of metal coated dielectric waveguides with a rectangular surface corrugation. Waveguide are designed to operate at a second Bragg frequency of 90 GHz. The period, height and the duty cycle of a rectangular grating were calculated using the chosen frequency. A metallic layer of aluminum is sputtered on one side of the slab waveguide. The purpose of the metallic layer is to simulate a layer of high density plasma on the surface of the waveguide similar to that obtained by optical excitation of semiconductor structures. Experiments were performed to examine the far field radiation pattern, attenuation constant and the dispersion relation. Due to the presence of the plasma layer there will be an angular shift in the far field radiation pattern. We have observed angular shifts of about 20? in the radiation pattern of the waveguide before and after coating. Measurements are made in the frequency range of 88–95 GHz. This waveguide structure can be used to design an electronically steerable antenna and an electronic phase shifter operating in the millimeter-wave frequency band.     

Experimental studies of magnetically scannable leaky-wave antennashaving a corrugated ferrite slab/dielectric layer structure

The radiation characteristics of a magnetically scannable leaky-wave antenna using a corrugated ferrite slab supported by a Teflon waveguide have been demonstrated experimentally. A corrugated polycrystalline yttrium iron garnet (YIG) slab having the dimensions 150.0 mm×15.0 mm×10 mm has been fabricated. The corrugation depth, corrugation spacing, and number of corrugations are 150.0 μm, 2.0 mm, and 55.0, respectively. Experiments have been carried out in the millimeter-wave frequency range from 40.0 to 50.0 GHz. The main beam direction of the leaky wave shifts continuously about 41.0° at the operating frequency 46.8 GHz by altering the DC magnetic field up to 1.4 T. It is found that the corresponding half-power beamwidth varies from 3.2° to 3.6° and a maximum scanning rate is 1.0°/0.02 T. Experimental results are compared with theory based on the dispersion relation of the ferrite slab/dielectric layer structure     

First attempts at modelling earth-to-space radio propagation using SIRIO measurements in the 11 and 18 GHz bands

A bi-dimensional statistical model for earth-to-space radio links, characterized by effective rain rates and rain path lengths is proposed. These parameters refer to an equivalent homogeneous slab of rain having depth and rain rate such as to produce similar values of measured attenuations. Input data for the present study were attenuation data at 11.6 GHz (absolute and differential over a 520 MHz band) and 17 GHz, collected by the Sirio satellite: these data were found to be jointly log-normally distributed as were the effective rain rate and path length. A straightforward application of the model is the extrapolation of attenuation statistics to higher frequencies: the effectiveness of the method, when applied to 11.6 GHz data is tested against the data at 17 GHz; both the statistics and the time profiles are excellently reproduced. This suggests the use of a differential radiometer working at a relatively low frequency in order to acquire reliable higher frequency statistics and effective model parameters.     

Bragg Interaction of Electromagnetic Waves in a Ferrite Slab Periodically Loaded with Metal Strips

The waveguiding characteristics of electromagnetic TE waves in a ferrite slab periodically loaded with metal strips are investigated. Theoretical formulation by means of the spectral domain approach is employed to obtain the Brillouin diagrams of two types of volume modes and a surface mode. It is found that the nonreciprocal properties of waves depend on the metal strip profile and bias magnetic field strength. Experiments on the magnetic-field dependence of the Bragg frequency and the stop bandwidth are carried out in the millimeter-wave frequencies. Typical results obtained from a polycrystalline YIG slab with periodic gold strips deposited on one surface are stop bandwidth about 2.14 GHz, with return loss about 2 dB at the Bragg frequency of 47.5 GHz, for the bias magnetic-field strength of 5.7 kG. The Bragg frequency can be tuned over the range of 1.39 GHz by varying the bias magnetic field from 0 to 8.2 kG. Experimental results show good agreement with theoretical predictions.     

兼容4G/WiFi/WiMAX的新型宽带人工电磁媒质天线设计

设计了一款新颖的基于互补开口谐振环结构和条形缝隙的贴片天线。通过在金属贴片上蚀刻圆环形互补开口谐振环结构,并且在金属接地板上蚀刻条形缝隙完成天线的人工电磁媒质结构设计,它们和介质板共同作用将天线工作频段明显扩宽到1.7~2.98 GHz和3.99~5.34 GHz。该天线仅使用单层双面覆铜板即可完成加工,具有结构简单的特点。同时,天线的电尺寸仅有0.408λ0×0.408λ0×0.0086λ0(在天线最低工作频率1.7 GHz处),且最大增益为6.04 dBi;可以同时兼容中国的第四代(4G)移动通信的所有频段(1.88~2.66 GHz)、WiFi频段(2.4~2.484 GHz)和微波存取全球互通(WiMAX)频段(2.5~2.69 GHz)。     

GaAs-loaded metal waveguide components for high-speed low-VSWR optoelectronic millimetre-wave switching

A new approach to fast optoelectronic microwave and millimetre-wave switching is reported. The concept is based on a metal waveguide section containing a thin slab of semi-insulating GaAs. Modulation or switching is achieved by wave attenuation across a laser-induced photoconductive plasma wedge generated within the GaAs slab via edge excitation. First experimental results in the 30?35 GHz range are presented.     

Microwave thermal emission of rain

The effective medium temperature necessary for the conversion of microwave thermal emission to slant-path attenuation has been calculated for 11.8 GHz for a homogeneous slab of rain. The first results from calculations on a cylindrical model of rain at 11.8 GHz are also presented. The influence of ground reflectivity coefficient is investigated.     

Characteristics of millimeter-wave radiation in a corrugatedferrite slab structure

The characteristics of millimeter-wave radiation in a corrugated ferrite slab supported by a grounded dielectric slab are investigated both theoretically and experimentally. Theoretical analysis is performed by the perturbation theory combined with multiple space scales for the transverse electric mode. A pair of amplitude transport equations are derived, and the characteristics of the leaky wave are explained in terms of the radiation angle and the radiation efficiency. Experiments were carried out using a layered structure composed of a corrugated polycrystalline yttrium iron garnet slab and a Teflon slab in the frequency range from 40 to 50 GHz. The experimental results are compared with the theory     

Partially Dielectric-Slab-Filled Waveguide Phase Shifter

An equivalent circuit of a waveguide junction between two asymmetrically filled waveguides is obtained. This equivalent circuit is applied to the design of single-section impedance-matching transformers for a dielectric-slab-filled waveguide phase shifter. Calculation and measurement indicated that when a thin alumina slab is employed, a 360/spl deg/ phase shift can be accomplished in a section approximately 1.1 times the unloaded waveguide wavelength at 2.7 GHz, and that the VSWR between 2.7 and 3.0 GHz is kept to less than 1.15.     

Scattering parameters measurement of a nonreciprocal couplingstructure

A novel ferrite image guide was designed and tested from 26.5 to 40 GHz. The nonreciprocal structure consisted of two dielectric image guides separated by a ferrite slab. M-type hexagonal ferrite was used with its C-axis oriented parallel and perpendicular to the direction of propagation. The S-parameters of the device were measured for a nonuniform external biasing magnetic field applied parallel to the C-axis of the ferrite slab. Nonreciprocal effects were observed for all cases considered above. The results imply applications for ferrite devices operating at millimeter wavelength frequencies, such as isolators, filters, modulators, switches, phase shifters, etc     

A Quasi-Optical Method for Measuring the Complex Permittivity of Materials

A quasi-optical method for measuring the complex permittivity of materials is described. The determination is derived from measurements of the transmission of a perpendicularly polarized wave through a dielectric slab at different angles of incidence. This relatively simple method is quite sensitive. Accurate estimates of the relative permittivity and the loss tangent can be obtained by accurately measuring the frequency of the signal and by the use of large, precisely machined Fabry-Perot plates. Estimates of the standard errors in the determinations are obtained by using a bootstrap resampling technique. The measurements here are made at a frequency of 93.788 GHz at ambient temperature.     

设计小椭圆度的圆波导移相器的新方法

本文介绍设计小椭圆度的圆波导移相器的新方法。该方法在理论上虽不严格,但在工程应用上作为处理某些难解决的相移问题却是有效的。在4GHz频段500MHz带宽内,90相移量的理论值与实测值间的最大差异仅为1.4。     

Radiation of Millimeter Waves from a Leaky Dielectric Waveguide with a Light-Induced Grating Layer

A theoretical analysis is presented for the radiation characteristics of millimeter waves in a periodic dielectric waveguide having a light-induced grating layer. The waveguide is assumed to be composed of an insulator (sapphire) slab whose one surface is coated with a high-resistivity semiconductor (silicon) film. A boundary-integral-equation formulation is employed to obtain characteristic solutions of the waveguide. Numerical calculations are made at 94 GHz for both TM and TE polarizations. Estimations of the illumination power required to produce the grating are given. The waveguide presented in this paper, in conjunction with a high-power semiconductor diode laser array as a light source, may be developed to operate as an electronically beam-steerable leaky-wave antenna at millimeter-wave frequencies.