Planar Microwave Resonator Research Articles

Speed of a ferrite—ferroelectric microwave planar resonator

The speed of a ferrite—ferroelectric microwave planar resonator consisting of a YIG film and a barium strontium titanate plate is investigated. It is shown that the speed of the resonator is governed by the rate of resonance frequency electrical tuning and the tuning is accompanied by a change in the electrical bias. The rate of frequency tuning in the resonator is 1.3–3.3MHz/fus.

Planar ferrite-piezoelectric composite microwave resonator with electric and magnetic frequency tuning

A planar composite microwave resonator based on a bilayer structure comprising a single-crystal yttrium iron garnet (YIG) ferrite film on a lead magnesium niobate-lead titanate (PMN-PT) piezoelectric plate has been studied. The possibility of electric and magnetic tuning of the resonance frequency in this structure is demonstrated. The magnetic tuning in the frequency range of 2–18 GHz is effected by varying the magnetic bias field and the electric tuning within a 20 MHz bandwidth is achieved by applying a dc bias voltage to the piezoelectric layer. An increase in the central frequency of a YIG/PMN-PT composite resonator is accompanied by a growth in the resonator Q from 110 to 990, while the electric tuning bandwidth remains unchanged

A Simple and Low-Cost Measurement System for the Complex Permittivity Characterization of Materials

A microwave planar resonant sensor, its equivalent circuit, and the driving electronics for the measurement of the complex permittivity in compact areas of the material under test are presented. Compared to transmission or reflection sensors, the adoption of a scalar two-port measurement procedure reduces the cost of the system and improves its robustness. The measuring system requires only the calculation of two parameters, namely, the resonant frequency and the 3 dB bandwidth, thus achieving a substantial reduction of cost and computation time. Such a sensor can be adopted in moisture measurement systems, and its low cost is such as to allow its use even in a disposable manner.

Systematic design of resonant microstrip sensors with sensitive coating

AbstractA parameter study of multilayered sensor structures is presented. These consist of planar microwave resonators coated with a thin, sensitive membrane. The influence of the various layers on the sensor characteristics is studied, and design rules are formulated. Two sensors with a moisture‐sensitive coating are realized. The experimental results confirm the simulation. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 21–25, 2002.

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Quasifractal planar microstrip resonators for microwave circuits

We propose a new shape for microwave planar circuits using the self-similarity of the fractal geometry. This new shape allows the generation of numerous resonant frequencies for this microwave planar resonator due to the surface's encasing. The resonant frequency assessment can be useful for the concept of filters or wide frequency band matching loads as examples, without consuming circuit surface. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 433–436, 1999.

Ultra-high-Q resonators for low-noise, microwave signal generation using sapphire buffer layers and superconducting thin films

An analysis has been completed to provide guidelines for producing planar microwave resonators with Q-factors of the order of 106-108 at a temperature of 4 K and a frequency of 1-20 GHz using high-Tc superconducting thin films on sapphire shielded by suitable buffer layers. Buffer layers not only overcome the problems of film-substrate interactions and reduction of microcracks, but can also confine the field into the sapphire which enhances the Qr and Qc of the resonator.

Temperature depeddence of the microwave surface resistance of YBCO thin films from microstrip resonator measurements

The surface resistance of YBa2Cu3O7−x (YBCO thin films were obtined from measuring the Q-factor of inverted microstrip resonators at 6–7 GHz over the temperature range of 16–80 K. The inverted microstrip which included a sapphire spacer between the YBCO line and a YBCO ground plane has lower dielectric loss than of regular microstrips since sapphire has a much lower tangent than that of the film substrate. This enables the determination of Rs to a much higher sensitivity. We have examined good quality epitaxial YBCO films fabricated by several techniques; ion beam sputtering, pulsed-laser deposition, and off-axis magneton sputtering. Most films have Tc's of 85–90 K and Jc of 0.5−2×106 A/cm2 at 77 K. The loaded Q-factors were 2500–4800 at 77K increasing up to 77 000 at 16 K, which, to our knowledge, is the highest Q measured for a high-Tc microwave planar resonator. We have found that the surface resistances of the YBCO films of comparable Tc and Jc have similar values at relatively high temperatures (T>70 K) even though these films were grown by different techniques. The surfaces resistance, scaled to 10 GHz was in the range 0.44−0.7 Ωm at 77 K and as low as 37 μΩ at 16 K.