Low-loss Microwave Research Articles

Microwave Air Strip Transmission Line forS-Band

A low-loss microwave shielded air strip transmission line has been fabricated using a dielectric material Tellite and 3 cm waveguide as a substitute for waveguides in the 5-Band 10 cm region. This has made it possible to use strip line transmission for long distances, such as used in marine radars. It has the added advantage of reduced cost and size over waveguides normally used in 10 cm region.

Bubble materials—composition, growth and evaluation

The development of materials for magnetic bubble domain applications and of the techniques for their preparation has been rapid and has achieved considerable success. In this review an attempt has been made to cover some of the important aspects of this complex field. Starting with the compositions used and the reasons for their selection, the methods of preparation are described with particular reference to the process of liquid-phase epitaxy. This is the currently preferred process for the preparation of high quality magnetic layers.For bubble applications the optimization of the magnetic properties and device parameters is also complex. Some discussion of the requirements and of the techniques used for property evaluation is given.The main emphasis is necessarily on the magnetic garnets, which have specific and unique properties for applications as low-loss microwave materials as well as being the best media so far discovered for bubble domain generation and manipulation.

A New BaO‐TiO2 Compound with Temperature‐Stable High Permittivity and Low Microwave Loss

The dielectric properties of ceramics in the TiO2‐rich region of the BaO‐TiO2 system were investigated. In the composition range between BaTi4O9 and TiO2, another compound, Ba2Ti9O20, can be obtained when calcining and sintering conditions are controlled carefully. When dense and single‐phase, this ceramic has excellent dielectric and physical properties. At 4 GHz, the dielectric K= 39.8, Q= 8000, and τK (temperature coefficient of dielectric constant) =−24 ± 2 ppm/°C.

High‐Permittivity Temperature‐Stable Ceramic Dielectrics with Low Microwave Loss

The compounds SrZrO3 and CaZrO3 combine high permittivity with low loss and positive temperature coefficient of permittivity. Temperature‐stable materials were produced by forming solid solutions between these zirconates and zirconates or titanates having negative coefficients. The properties of temperature‐stable compositions in the systems Ca(Zr,Ti)O3 and (Ba,Sr)(Zr,Ti)O3 were investigated. At 4 GHz the relative permittivities were from 29 to 35 and the loss tangents from 3 to 11×10−4. Both permittivity and microwave loss increased as the principal alkaline‐earth ion was changed from Ca to Sr to Ba, but the higher losses could be reduced by adding ∼1 mol% Nb or Ta. Dense fine‐grained ceramics with the properties required for microwave applications were prepared.

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.

Low Insertion Loss Microwave Ultrasonic Delay Device Using a ZnO Thin Film Transducer

Low Insertion Loss Microwave Ultrasonic Delay Device Using a ZnO Thin Film Transducer

A Frequency-Stabilized Microwave Band-Rejection Filter Using High Dielectric Constant Resonators

The high permittivity dielectric resonator is a low loss microwave filter element whose size is substantiality less than metal waveguide cavities. Temperature stabilizing their resonant frequency increases the applicability of such elements. A temperature compensated 3-section band-rejection filter using dielectric resonators has been fabricated and tested. The measured electrical performance was comparable to metal waveguide filters and the frequency stability for temperature variations was comparable to brass waveguide cavity filters which are not temperature compensated.

An Adjustable Narrow Band Microwave Delay Equalizer

A simple low loss microwave delay equalizer for the delay equalization of narrow band microwave bandpass filters has been explored. This equalizer is quite small and does not require the use of additional components such as circulators or hybrids. It exhibits a reflection coefficient of less than 1 percent and possesses two very valuable and convenient features: a continuous adjustment of the delay shape and of the center frequency. The structure is analyzed theoretically, an equivalent circuit is derived, and expressions for both delay and loss are given. Also presented are design data and experimental results concerning the actual delay equalization of a bandpass filter and the temperature behavior of the equalizer and the filter-equalizer combination.

Carbon Disulfide Traveling-Wave Kerr Cells

Carbon disulfide has identical microwave and optical dielectric constants, as well as extremely low optical and microwave loss. These properties make it possible to construct long travelingwave light modulators at microwave frequencies using the Kerr electrooptic effect induced in CS(2) by an electric field propagating on a TEM transmission line.Several experiments with traveling-wave Kerr cells consisting of resonant strip transmission lines immersed in CS(2) are described. A decrease in the microwave power required for modulation by a factor of two, by cooling the modulators to a temperature of -55 degrees C, is demonstrated. Simultaneous modulation of light at two microwave frequencies by excitation of two of the longitudinal modes of the strip line resonator is also described. Relatively high efficiency modulation with long devices of this type is also reported. In these experiments, the microwave power required for large depths of modulation is reduced by almost two orders of magnitude compared to previously reported CS(2) light modulators, and is within less than a factor of two of the calculated power for cells up to 44 cm in length. For longer cells, increasingly larger than predicted powers are required.

Carbon disulfide traveling-wave Kerr cells

Carbon disulfide has identical microwave and optical dielectric constants, as well as extremely low optical and microwave loss. These properties make it possible to construct long traveling-wave fight modulators at microwave frequencies using the Kerr electrooptic effect induced in CS 2 by an electric field propagating on a TEM transmission line. Several experiments with traveling-wave Kerr cells consisting of resonant strip transmission lines immersed in CS 2 are described. A decrease in the microwave power required for modulation by a factor of two, by cooling the modulators to a temperature of -55°C, is demonstrated. Simultaneous modulation of light at two microwave frequencies by excitation of two of the longitudinal modes of the strip line resonator is also described. Relatively high efficiency modulation with long devices of this type is also reported. In these experiments, the microwave power required for large depths of modulation is reduced by almost two orders of magnitude compared to previously reported CS 2 light modulators, and is within less than a factor of two of the calculated power for cells up to 44 cm in length. For longer cells, increasingly larger than predicted powers are required.

H/sub o1/ Mode Circular Waveguide Components

A convenient method of launching the H/sub o1/ mode in round waveguide is described. Four resonant slots are employed in a compact end-feed transition design. Construction details and performance curves are given. Also described is a developmental bend which avoids the H/sub o1/-E/sub 11/ mode degeneracy problem by employing a superimposed pair of "E" and "H" plane rectangular waveguide bends. A mode absorber is described which is capable of reducing the mode impurities inherent in the transition design to a level of less than 0.1% of the emerging H/sub o1/ mode power. Other possible applications of the H/sub o1/ wave to problems other than low loss microwave transmission are briefly considered.