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An X-Band GaAs FET Oscillator Using a Dielectric Resonator
Abstract
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Microwave characteristics of the system Ba(Zn1/3Ta2/3)O3-BaZrO3 were investigated. Ba(Zn,Ta)O3 has a perovskite pseudocell and hexagonal superstructure; the superstructure was not formed after addition of BaZrO3. Both sintering and crystallization of Ba(Zn,Ta)O3-BaZrO3 were accelerated compared to those of Ba(Zn,Ta)O3 alone, and the microwave Q value was also improved. The material optimized for the dielectric resonator, Ba(Ni,Ta)O3-Ba(Zr,Zn,Ta)O3, has a dielectric constant of 30, Q value of 10000 at 10 GHz, and temperature coeficient of resonant frequency of 0 ppm/°C.
Dielectric materials are continuing to play a very important role
in the microwave communication systems. These materials are key in
realization of low-loss temperature-stable resonators and filters for
satellite and broadcasting equipment, and in many other microwave
devices. High dielectric-constant materials are critical to the
miniaturization of wireless systems, both for the terminals and
base-stations, as well as for handsets. In this paper, a sequential
evolution of the dielectric materials applications in microwave devices
will be reviewed. This includes dielectric waveguides, low-loss
temperature-stable ceramic materials, dielectric resonators, and
filters. The recent advances in the multilayer circuit modules,
dielectric antennas, and ferroelectrics are also described
Several compounds with the general formula A(B′II0.33TaV0.67)O 3, where A is a barium or strontium ion and B′ is a divalent metal ion, were prepared and studied by means of X-ray diffraction techniques. Results of this investigation show not only that the difference in the charge of the B ions causes ordering, but also that the difference in the size of these ions is an important factor in influencing the degree of long-range ordering which exists in the structure of these compounds.
High Q, temperature stable dielectric resonators are excellent stabilizing elements for microwave transistor oscillators. A 4 GHz Ba<sub> 2</sub>Ti<sub> 9</sub>O<sub> 20</sub> resonator integrated with a Si bipolar transistor in a compact oven has a frequency stability of 5 ppm/yr., 4° to 60°C (40 to 140°F). It is significantly simpler than alternative generators and has 10 to 20 dB lower FM noise. An 18 GHz generator is also described which uses a 4.5 GHz oscillator and a varactor quadrupler.
A 6 GHz GaAs FET feedback oscillator stabilized by a dielectric resonator with a new frequency tuning mechanism has been developed. The oscillator has a frequency tuning range of 50 MHz with a frequency stability of about t 10 PPM (0°C-50°C).
A novel technique for the measurement of dielectric and magnetic properties of a homogeneous isotropic medium in the range of approximately 3 to 100 kmc is described. An accuracy of /l.chemc/ 1 per cent is possible in the determination of permittivity or permeability in those cases where the loss tangent is sulliciently small. The measuring structure is a resonator made up of a right circular cyndrical dielectric rod placed between two parallel conducting plates. For measurement of permittivity two or more resonant TE<sub>onl</sub> mode frequencies are determined whereas for the measurement of permeability two or more resonant TM<sub>onl</sub> mode frequencies are determined. The dielectric or magnetic properties are computed from the resonance frequencies, structure dimensions, and unloaded Q. Since the loss tangent is inversely proportional to the unloaded Q of the structure, the precision to which Q is measured determines the accuracy of the loss tangent.
Dielectric Properties of Ba(Znl/3 Nb2/3)03-Ba(Znl/3 Ta2/3)03 Ceramics at Microwave Frequency
- S Kawashima
- M Nishida
- I Ueda
- H Ouchi
- S Hayakawa