Quasioptical millimeter-wave hybrid and monolithic PIN diodeswitches

The development of a new type of quasioptical PIN diode switch is reported. The quasioptical imaging application which motivated the development of the switch is briefly described. The theory of switch operation in both its reflection and transmission modes is explained. Experimental results from measurements of both hybrid and monolithic circuits in the millimeter-wave range are presented. The hybrid version exhibits losses in the reflection mode of 1 dB or less and isolation of 20 dB or more. Performance of the monolithic version is comparable, despite a PIN diode yield of less than 80%     

An experimental investigation of high permittivity dielectric resonators for millimeter-wave microstrip components

This paper proposes a new type of high permittivity whispering gallery mode cylindrical dielectric resonators with a geometry which is very suitable for use in microstrip type integrated circuits. These “oversized” resonators, together with high Q factors and ease of fabrication, are potentially interesting for millimeter wave integrated filters and oscillators. In this paper, we report an experimental investigation of such resonators carried out in Ka band (26.5–40 GHz). Measured results including resonant frequencies and loaded quality factors will be presented. Application to millimeter wave filters will also be demonstrated.     

Analysis of optically controlled planar dielectric waveguidesoperating in the millimeter-wave band using FDTD

The finite-difference time-domain (FDTD) technique is applied to the analysis of planar dielectric waveguides controlled by means of an optical beam. This beam, with an appropriate energy, induces a nonuniform plasma in a semiconductor layer deposited on the waveguide core. The resulting effects are analyzed through the phase dispersion characteristics. Due to the complexity of the problem, the FDTD formulation does not allow the calculation of the attenuation characteristic, particularly when the plasma presents an intermediate density, which causes a strong interaction with the guided mode. The simulations shown here suggest that the light beam may have an effective control of the phase response of a single waveguide and of the coupling between two parallel coupled waveguides     

Shielded dielectric resonators

Resonances of a dielectric stub in a waveguide shield are considered as coupled modes. The transition of cavity modes to dielectric resonances and vice versa is illustrated for the TM011 modes.     

YBCO superconducting ring resonators at millimeter-wave frequencies

Superconducting microstrip ring resonators operating at 35 GHz have been fabricated from laser ablated YBa₂Cu₃O _7-x (YBCO) films on lanthanum aluminate substrates. The circuits consisted of superconducting strips over normal metal ground planes. The circuits are measured from 20 K to 90 K and with microwave input powers ranging from 0.25 mW to 10 mW. The superconducting resonators show significant improvement in Q over identical gold resonators at 20 K, but only marginal improvement at 77 K. No variation in the superconductor performance is observed with varying input power. The lowest microwave surface resistance of the superconductors at 77 K is 9 mΩ. The change in the resonant frequency with temperature is analyzed and a value for the penetration depth computed. Double resonances were observed in some superconducting ring resonators and an explanation is advanced. Factors limiting millimeter-wave high-temperature superconductor circuits are explored and potential performance levels calculated based on current reported values for high-temperature superconductor surface resistances     

Piezoelectrically tuned dielectric resonators

A simple technique for rapid tuning of a dielectric resonator using piezoelectric actuation is described. Results are presented for three dielectric resonator materials with relative permittivities of 9.5, 47 and 100 and dielectric Q-factors of 50000 (10 GHz), 9000 (5 GHz) and 16000 (3 GHz). The advantage of the proposed tuning method is that little degradation in the device Q-factor is observed even with tuning up to 2%     

Generalized multilayer anisotropic dielectric resonators

Modeling of the generalized multilayer cylindrical anisotropic dielectric loaded resonator by a rigorous mode-matching method is presented in this paper. Eigenmodes of the multilayer two parallel-plate waveguides are obtained. By cascading the radial discontinuities of the structure, resonant frequency, field distribution, unloaded Q, and the frequency sensitivity of the resonator are obtained. The method can be used to analyze and design resonators and filters of multilayer structure. The computed results are compared with measured results and with experimental data, and shown to be in good agreement     

Increased dielectric quality factor in planar resonators byselective dielectric removal

A means for increasing the effective dielectric quality factor by selective removal of dielectric from a microstrip resonator is discussed. Methods for determining the impedance and effective dielectric constant are included. The reduction in loss compared with an equivalent microstrip resonator is presented     

Optical control of millimeter-wave propagation in dielectric waveguides

We have demonstrated a new method for controlling millimeter-wave propagation in semiconductor waveguides-optical control. Phase shifts as high as 300°/cm at 94 GHz were observed accompanied by less than 1 dB insertion loss. A theoretical model has been developed to account in detail for the observed behavior. Extension of this technique to ultra-fast switching and gating of millimeter-wave signals is also described. Millimeter-wave pulsewidths as short as 1 ns and variable to tens of nanoseconds can readily be obtained.     

A millimeter-wave six-port reflectometer using dielectric waveguide

A six-port reflectometer circuit that is particularly suited to dielectric-type waveguides is described. Its scattering matrix is derived, allowing for flexibility in design. A phase-shifting network is incorporated in the circuit, and it is shown that a quadrature hybrid can be configured for this purpose. The reflectometer was implemented in a dielectric waveguide for W-band (75 GHz-110 GHz) operation, and measurements are presented     

A millimeter-wave omnidirectional dielectric rod metallic gratingantenna

A new millimeter-wave omnidirectional dielectric rod metallic grating antenna is investigated theoretically and experimentally, in this paper. The radiation characteristics of the antenna are carefully investigated by a rigorous formulation for the TE₀₁-mode and TM₀₁-mode excitation in the Ka-band frequency range. Based on the analysis, an omnidirectional antenna excited by the TE₀₁ mode is designed and measured. The measured results are compared with theoretical predictions and good agreement is found. Extensive numerical results are given to establish some useful guidelines for the design of the omnidirectional antenna     

A millimeter-wave omnidirectional circular dielectric rod gratingantenna

A millimetre-wave omnidirectional circular dielectric rod grating antenna is investigated theoretically and experimentally. As an eigenvalue problem, the antenna is analyzed with the rigorous mode matching method. The radiation characteristics of the antenna are calculated and measured in the Ka-band frequency range. A comparison between the experimental results and the theoretical predictions is made and good agreement is found. The practicality of the omnidirectional antenna and the effectiveness of the theory are thus justified     

Direct coupling between two dielectric resonators

The letter deals with a new method of calculation of direct coupling between two dielectric resonators. This method could be used for the design of microwave integrated filters. Comparison between calculated and measured values of this coupling shows good agreement.     

Numerical study of axisymmetric dielectric resonators

In this paper, we present an effective approach to study the behavior of axisymmetric dielectric resonators. This approach is based on the finite-difference time-domain method and two accompanying techniques in order to increase the accuracy and decrease the computational cost. These two techniques are the fast-Fourier-transform approach and the Pade method. This method is used to obtain the resonant frequencies and quality factors for several resonators. Comparisons are made to show the utility of the method     

Dual-mode filters with conductor-loaded dielectric resonators

In this paper, a new class of dual-mode microwave filters is presented. These devices use conductor-loaded dielectric resonators with unloaded Q-factors of 2000-8000 achievable in half the physical size of TEM filters and with good spurious performance. The basic properties of this resonator have been examined with the aid of a finite-element field-analysis package. Fundamental design rules for bandpass filters have been developed. A design example of a transmit filter for a ground-signal-metal cellular-radio base station is demonstrated     

Sensitivity of dielectric resonators to environmental conditions

The effects of the variation of different physical parameters in a simple, shielded dielectric resonator structure is studied. The study uses an approximate analytical expression for the resonance frequency stability of dielectric resonators. The results are of special importance in applications where the dielectric resonators are subjected to varying environmental conditions.     

Theory of Fabry-Perot resonators with dielectric medium

A Fabry-Perot resonator filled with a dielectric slab is investigated using the Vainshtein method. Simple and explicit formulas are obtained for the diffraction loss, phase shift, and field distributions for both strip and circular mirrors. It is found that the presence of the dielectric reduces the diffraction loss, and causes mode confinement to certain degrees.     

A temperature-stable bandpass filter using dielectric resonators

A microstrip bandpass filter has been built with dielectric resonators made of a temperature-compensated material. Its unloaded Q at X band is calculated to be greater than 1200, a four-fold improvement upon conventional printed-on devices. With additional temperature compensation, a temperature coefficient less than 5 ppm/°C is shown to be feasible.     

Resonant frequency analysis of dielectric ring resonators

The mode-matching technique is applied to guided and continuous spectra to derive the resonant frequencies of the high-order azimuthal modes of dielectric ring resonators. The numerical results of this field theory analysis are in close agreement with the measurements in the X-band     

Temperature-stable low-loss microwave filters using dielectric resonators

Recently developed high-permittivity low-loss temperature-stable dielectric materials have been used as resonators in microwave filters. The resulting low-loss filters possess extremely good temperature stability. Proper design and the use of metal-screw mode suppressors have eliminated the further problem in dielectric-resonator filters of spurious modes just above the passband.