Hidema Uchishiba

L and S band low-loss filters using SAW resonators

This paper describes L and S band low-loss filters using one-port SAW resonators in a ladder circuit structure. Four kinds of filters were developed. Three types have a wide frequency band, with fractional bandwidth of about 4%. A 36° y-x LiTaO3 substrate was used for these. The last type of filter has a narrow frequency band, with 0.03% of fractional bandwidth, and used an ST-cut quartz substrate. To design these ladder type SAW filters, several important factors were considered, the static capacitance of IDT, the period of IDT and film thickness. For fabrication, i-line stepper and reactive ion etching was used to delineate fine IDT patterns with line and gap width of 0.4 to 0.7 μm. Minimum insertion losses of 2 dB were obtained for the three wide band filters. The insertion loss of the narrow band filter was 6 dB. The input and output impedance of these filters were 50 Ω. The filters were mounted in 3 mm×3 mm×1 mm or 3.8 mm×3.8 mm×1.5 mm SMT packages

Improved Power Durability of Surface Acoustic Wave Filters for an Antenna Duplexers

For portable telephone applications, we improved the power durability of ladder-type filters composed of one-port surface acoustic wave (SAW) resonators. In these ladder-type filters, the chip temperature was raised and power durability was weak around both cut-off frequencies in transmission characteristics. Power durability tests of a duplexer composed of ladder-type filters showed that the receiver filter (Rx) in which the power was leaked from the transmitter one (Tx) was weaker than the Tx. We therefore studied Rx in this work. In filter design, reducing the resonator resistance to suppress the rise in chip temperature improved power durability. The lifetime of electrode material was improved to up to 10,000 times longer than that of an Al-Cu single-layer film by use of a 3-layered film of Al-Cu/Cu/Al-Cu.

Improvement in power durability of SAW filters

This paper describes the improvement in power durability of SAW filters in terms of filter designs and electrode materials. In this study, we used the previously reported ladder-type filter composed of one-port SAW resonators. For filter design, short aperture length and reduction of resonant resistance improved power durability. We clarified the frequency dependence of chip temperature and lifetime in a ladder-type filter. For electrode materials, Cu sandwiched film has high power durability. This is caused by stone-wall-like structure and alloy formation in intermediate layers. The optimum Cu quantity for multi-layered film was significant for high power durability.

Effect of in‐plane magnetic field on bubble collapse field in ion‐implanted garnet films

Bubble collapse fields in several kinds of garnet films ion implanted for hard‐bubble suppression were measured in the presence of an in‐plane magnetic field and were found to vary according to the direction of the in‐plane field. That is, bubble collapse fields exhibit a threefold symmetry in response to the threefold symmetry of crystallographic axes. The appearance of this threefold symmetry was explained by the response of closure domains associated with bubbles to in‐plane fields. This phenomenon is shown to be dependent on the properties of garnet films and implantation conditions, i.e., dose, energy, and ion species used: H, Ne, and Ar.

Development of ladder type SAW RF filter with high shape factor

The paper presents ion implantation technology to improve the shape factor of a ladder-type SAW RF filters for mobile communication systems. The improvement of the shape factor was confirmed experimentally. However we found that the SAW phase velocity is decreased by ion implantation. To stabilize and recover the SAW phase velocity, several annealing conditions were investigated. At the annealing condition of over 450/spl deg/C/spl times/1 hour, SAW phase velocity was recovered to almost the same as the initial velocity. In the past, the shape factor values of ladder-type SAW filters using a LiTaO/sub 3/ substrate have been almost 1.7. The ion implantation technology has been applied to a PDC (personal digital cellular) -1.5 GHz SAW band pass filter using a LiTaO/sub 3/ substrate. We have obtained the shape factor value of 1.4 under the following conditions; ion: double charge Ar/sup ++/, dose: 5/spl times/10/sup 13//cm/sup 2/, acceleration voltage: 180 keV.

Internal bias effect of double layer epitaxial garnet films

A method of eliminating the external magnetic bias field necessary to sustain stable cylindrical magnetic domains (magnetic bubbles) is presented. This method uses double-layer garnet films. The films were grown on the

Temperature stable self-biasing bubbles in double layer films

One of the most important problems for a self-biasing bubble (SBB) device is the temperature stability of the SBB diameter. The temperature dependence of the SBB diamater was calculated on the basis of the force stability condition of the SBB and proved to be proportional to the temperature dependence of the characteristic length of the top layer. The proportional coefficient depended on h/l and that was more than -2.7. The smallest value of temperature sensitivity was +0.8%/°C in the system of (YCaEuYb) 3 GeIG/ (EuEr) 3 GaIG. No hard bubbles were observed in this self-biasing double layer film and the mobilities of the SBB were similar to those of the usual single layers. And SBB were generated, propagated and detected by means of the usual drive technique (T-Bar permalloy circuits) without any bias field, the operating margins were similar to those of the bubbles in the usual single layer films.

Growth and properties of stable self-biasing double layer epitaxial garnet films

One of the most important problems in maintaining self-sustained bubble domains in the top layer of double-layer epitaxial garnet films is stability of the magnetic saturation in the bottom layer, Because the stability depends on the nucleation field of the bottom layer, it is desirable to minimize any defects in the bottom layer. For this purpose double-layer epitaxial films were cut by a chemical etching technique to prevent any bad effect due to defects or magnetic spin disorder in the film edges. This method caused a drastic effect on the stability of the magnetic saturation in the bottom layers showing a high yield of more than 95 %. The second problem is the temperature sensitivity of the self-sustained bubbles which proved to depend on the temperature sensitivity of the characteristic length of the top layer. In the best result less than 3 %/°C was obtained so far. The self-biasing effect in the double layer epitaxial garnet films is discussed with respect to the wall energies and anisotropy fields of the various top and bottom layer films. The maximum effective field of 30 Oe was obtained in a (YSm) 3 GaIG/(EuEr) 3 GaIG system and 6 μm-diameter bubbles were driven by a conventional T-bar circuit.

Effects of in-plane magnetic field on bubble properties in ion-implanted garnet fims

In the ion-implanted garnet films for hard bubble suppression, there exist planar closure domains associated with bubbles, which are created or annihilated by a rotating in-plane magnetic field. We have investigated the effects of closure domains on magnetic bubble properties in the epitaxial films of (YEuYbCa) 3 (FeGe) 5 - O 12 implanted with Ne+ or H+ ions. Experimental results are summarized as, (1) static coercivity in the H+ implanted film exhibited a 3-fold symmetry, as in the bubble collapse field, in response to the behavior of closure domains when the in-plane field of 40 Oe was rotated. (2) Wall state switching for decreasing in-plane field in the film implanted with 2 \times 10^{14} Ne+/cm2at 100 keV depended on the directions of the in-plane field. When the in-plane field Hp was applied in the [ 11\bar{2} ] direction with the bias field applied in the [111] direction, distinct wall state transitions occured at about Hp=120 Oe, 40 Oe and 10 Oe. When Hp was applied in the [ \bar{1}\bar{1}2 ] direction, however, wall state changed continuously below Hp=120 Oe at which distinct wall state transition occured.

Dependence of growth induced anisotropy on growth rate and composition of YSmLuCaGeIG LPE films

The dependence of the growth-induced anisotropy energy(Kg) on growth rate and film composition was investigated for YSmLuCaGeIG LPE films. Kg was found to depend on site preference probability as a function of growth rate as well as on film composition. We improved Eschenfelders formula by taking growth rate into account. The site preference probability is expressed, f(V_{g}, \beta)= \exp(-\beta/V_{g}^{n}) , where β is the parameter related to film composition. The value of n is a constant of 2/3, and β decreases as the rare-earth ion-pairs increase. Excellent agreement between the calculated and measured values was obtained for SmLuCaGeIG LPE films.