Nion Sock Chang

Characteristics of millimeter-wave radiation in a corrugated ferrite 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. >

Azimuthally Dependent Magnetostatic Modes In The Cylindrical Ferrites (Correspondence)

The azimuthally dependent magnetostatic modes have been investigated for two cases: 1) a hollow ferrite pipe is enclosed in a perfectly conducting wall; and 2) a ferrite rod is located at the center of a round waveguide, partially filling the cross section. Our analysis shows that the presence of the dielectric medium has an important role in the determination of the upper bound frequency and the cutoff wave number of the magnetostatic surface modes.

Calculation of depolarization cancellation on Ka-band satellite-to-ground path

The distribution of cross-polarized phase relative to copolarized phase, which is important in the design of depolarization cancelers, is presented using the CS-2 beacon signal (19.45 GHz, right-hand circular. EL=49.5 degrees ), and its dependence upon rainfall rates is discussed. Also, additional depolarizations due to ice effects are estimated and a calculation is made to show the possibility of cancelling them on the complex depolarization plane. The analysis of the cross-polar phase characteristics of Ka-band depolarization indicates a possibility of its compensation by phase shifters within small rainfall rates, which do not exceed a general rain margin (<5-10 dB). Consideration of the differential phase shift cancellation mechanism on the complex depolarization plane suggests that the improvement for the ice effects is approximately estimated by the additional ice depolarization observed in the cross-polar discrimination (XPD) amplitude.<<ETX>>

Ice depolarizations on Ka band (20 GHz) satellite-to-ground path and correlation with radar observations

The ice depolarization events without appreciable copolarized attenuation are investigated using the CS-2 beacon signal (19.45 GHz) and the simultaneous radar observations. In these events, increase of instantaneous depolarizations of the beacon signal closely corresponds to appearance of intense radar echoes at the cloud top. Correlation of the time variations between the depolarizations and the radar echoes is, in general, found in the upper half of the ice region. In addition, the large depolarization events are primarily related to the radar echo intensities at 2.0–2.5 km above the bright band. In these heights the ice crystals may have the fastest growth rate around the temperature of −15°C. The impact of ice depolarizations on the satellite-to-ground path is shown to depend strongly upon the height and the background temperature at which ice crystals are first produced near the cloud top. This characteristic feature of ice depolarization is also confirmed in the stratus type events with considerable rain attenuation by theoretically subtracting the effects of raindrops from the total observed depolarization.

Characteristics of depolarization fluctuation of Ka-band satellite beacon with small attenuation

Ka-band, high-elevation-angle satellite beacon observation shows a considerable time percentage of ice depolarization with small attenuation even in a severe cross-polarization discrimination (XPD) degradation. The time percentage of ice depolarization was measured using a CS-2 beacon signal (19.45 GHz, right-hand circular, EL=49.5 degrees ). Temporal variations of XPD and cross-polarized phase are analyzed to assess the possibility of cancellation within a comparably small rain margin (5-10 dB). The distribution and fluctuation of the cross-polar phase suggest the possibility of canceling this type of depolarization using phase shifters. The autocorrelation function analysis, however, indicates that the time scale of the depolarization is slightly shorter than rain attenuation in a low attenuation range.<<ETX>>

Microwave tunable filter using ultra-thin magnetic film

The filter characteristics of magnetostatic surface wave propagating in a structure consisting of the strip-line antenna and a relatively thin YIG film are described. The performance theory of filter proposed here utilizes a peculiarity such as it is to be explained only in the passband characteristics of magnetostatic surface wave, when the external magnetic field and saturation magnetization of YIG film are given in the system. It was found that the loaded Q-value of filter on an ordinary magnetostatic surface wave transmission system composed of a stripline antenna with 200 μm width and a YIG film with 0.79 μm thick is about 1620 at s-band frequency.

Experimental investigation of the nonlinear interaction between optical guided waves and magnetostatic forward volume waves in a Bi-YIG film

We have observed experimentally the coupling effects between magnetostatic forward volume waves (MSFVW) and optical guided waves in a bismuth-doped yttrium iron garnet (BGYIG) film, and these effects were demonstrated in a short interaction length (5 mm). The detailed coupling mechanics existing between microwave frequency, high power and optical guided waves are not yet clear. This paper reports on optical-MSFVW interaction from an experimental view point. A microwave frequency range of S-band (2-4 GHz) was used to excite MSFVW in a Bi-YIG film. An optical wave with 1.152 /spl mu/m wavelength was directly injected through the side wall of the Bi-YIG film.

Characteristic changes in cross-polarization discrimination due to thunderclouds on satellite-to-ground path

It is known that ice crystals in rain clouds induce significant depolarization of microwaves and millimeter waves on satellite-to-ground path as well as raindrops. In thunderstorm events, moreover, the cross-polarization discrimination (XPD) and cross-polar phase often show very rapid changes with time scale of a second or less. These characteristic changes are usually explained by alignment of ice crystals in thunderclouds due to aerodynamic-gravitational and/or electrostatic forces. However, very little is yet known about mechanisms for producing this type of depolarization, such as direction and degree of the alignment of ice crystals or relationship between aerodynamic-gravitational and electrostatic forces. In this study, the characteristic XPD changes are investigated using the Japans CS-3 beacon signal (19.45GHz, right-hand circular polarization) which was observed every second in the thunderstorm events. These observations of Ka-band satellite signal radiowave have been conducted in our university for the past four years from 1990 to 1993. We have obtained more than 200 examples of rapid changes in twelve thunderstorm events during this observational period. The XPD changes are compared with time and location of cloud-to-ground (CG) lightning strokes which were recorded around our earth station by the Lightning Location and Protection System (LLPS) of a nearby electric power company. The effects of the ice crystal alignment due to electrostatic force and convective air flow are then discussed in the light of recent thunderstorm electrification theories.

Attenuation ratio of Ka-band to Ku-band satellite signals and correlation with cross-polar phase on satellite-to-ground path

As the demand for channel capacity of satellite communications increases, higher frequencies such as the Ku- (14/12 GHz) and Ka- (30/20 GHz) bands have been used. In this study, rain attenuation characteristics of Ku- and Ka-band satellite signals are compared, and correlation with phase of the cross-polarization component is presented, using the long-term database for both signals which have been observed in our university for five years. The Ka-band satellite signal has been obtained from the CS-3 (Sakura) beacon signal (19.45 GHz, RHCP, elevation=49.5/spl deg/) during the satellite communication experiments of Japans CS-3 Pilot Program. The Ku-band satellite signal has been obtained from Japans Broadcasting Satellite (BS, Yuri), and the level of carrier radiowave for a specific channel (11.84 GHz, RHCP, elevation=41.4/spl deg/) has been measured by a BS tuner, which is commercially obtainable. Also, the cross-polar phase of the Ka-band signal (19.45 GHz) is evaluated by the output of the phase-amplitude demodulator of the CS-3 beacon signal.<<ETX>>

Cross-polarization discrimination measurements on satellite-to-ground path using CS-3 beacon signal

Characteristics of cross-polarization discrimination (XPD) are investigated by the CS-3 beacon signal observations on a Ka-band satellite-to-ground path for the years of 1988-1992. It is found that severe depolarization is not so much correlated with rainfall rates as the attenuation that is primarily concentrated in the summer season, and the additional XPD degradation due to the ice effects is rather enhanced as the height is decreased in the cold seasons. Such depolarization is considered to be caused by a differential phase shift (DPS) between the major and minor axes of the ice crystals, which are aligned in nearly horizontal and vertical directions, respectively, in view of the distribution of the cross-polarized phases. The improvements of the observed XPD by the DPS cancellation is estimated to be larger than 10 dB at rainfall rates smaller than 10 mm/h which will not exceed a general rain margin.<<ETX>>