This paper describes a realization problem of infinite dimensional, nonlinear, time-invariant dynamical systems. A necessary and sufficient condition that a given input/output behavior is to be realized by the above system is obtained. The theory of nonlinear semigroups plays an important role in our study.

A frequency modulator basically consists of an amplifier and a resonator employing a varactor diode, and the linearity of frequency modulators has been analyzed and discussed looking at the resonance frequency calculated from the capacitance-voltage characteristics of a varactor diode. However, as the oscillation frequency of the frequency modulator increases, it becomes essential for designer to evaluate the influences on the modulation linearity by the phase characteristics of the amplifier. This paper discusses the influences on the modulation linearity by the phase characteristics (the phase slope (or group delay) and the cross frequency f_c) and by the capacitance-voltage characteristics of varactor diodes, and the design of a UHF frequency modulator utilizing a hybrid integrated amplifier, is described. It is pointed out that, although the capacitance variation ratio n(log C(V)/log V) is less than 2, the capacitance variation ratio increases with the varactor diode bias voltage so that good modulation linearity can be obtained. Furthermore adopting a push-pull mode of operation, two UHF frequency modulators are connected to obtain a wideband frequency modulator (the bandwidth is f₀25 MHz). Finally a feedback-type frequency modulator operating at 6 GHz is discussed, as comparison to the result of the UHF frequency modulators.

The improved photoenhancement of the SAW convolution effect in monolithic convolvers with high-resistivity surface layer has been discussed. CdS monolithic convolvers with one or a half acoustical wavelength thick high-resistivity layer formed on semiconductive substrate are prepared in order to check the expected behavior. Due to much reduction of the acoustoelectric loss of SAW, the convolver with a half acoustical wavelength thick high-resistivity layer shows a remarkable photoenhancement, 20 times the value in the dark, when photocarriers are generated uniformly in the high-resistivity layer. Nonlinear capacitance mechanism can also induce photoenhancement of the convolution effect. It is first found that further enhancement of the convolution can be achieved by applying positive pulsed bias to the gate electrode under illumination of a light with high absorption coefficient.

A carbon granule microphone with carbonaceous electrodes, which is lower in cost and more convenient for mass production than the conventional microphone with gold plated electrodes, was studied as a telephone microphone. A molded piece made from a mixture of synthetic resin and carbon powder can be used for the back electrode and paint made from it can be used to coat the dome electrode. A new microphone, whose sensitivity is as high as a conventional microphone, shows higher resistance. This means that the efficiency of the new microphone seems to be slightly less. However, the sensitivity change in the new microphone under excitation by voice is less than that of the conventional microphone. The new microphone sensitivity dependence on DC input power is almost the same as that of a conventional microphone.

In this letter, we deal with the minicomputer system developed for imaging the degree of the decrease in a peak frequency of the first heart sound measured at 25 points on the chest surface and the similarity of one. This system provides a useful and powerful means to understand the diagnostic information rapidly.

A new technique for fabricating surface acoustic wave transducers is proposed. By using this technique, an IDT with oxide loaded in the space between the metal electrode fingers is easily realized. The fabricated transducers had ripple free response as well as the low velocity dispersion.