Tsutomu Hashimoto

Multilens system design with an athermal chart

We have introduced an athermal chart that plots chromatic dispersive power and thermal dispersive power on a Cartesian coordinate, and we give the design method of a multilens system in contact that satisfies achromatism and athermalization. The advantages of this chart are (1) that the condition of achromatism and athermalization is clear and (2) that the approximate power of the lenses that compose the multilens system is easily found on the chart. Design indices are given through a few design examples with an athermal chart.

Broadbanding of corrugated conical horns by means of the ring-loaded corrugated waveguide structure

Broadbanding of corrugated conical horns is investigated with the ring-loaded corrugated circular waveguide (RCWG) structure devised by the authors. The useful frequency bandwidth in which the corrugated horn is effective for the improvement of antenna properties is limited by the frequency characteristics of the horn-aperture field and input VSWR of the horn. By the precise analysis of the RCWG, the maximum frequency range in which the desirable field is obtained is much wider than that in the conventional corrugated circular waveguide, and is achieved almost independent of ring thickness, when ring width is about 20 percent of slot depth. The characteristic impedance of the RCWG is nearly equal to that of the homogeneous circular waveguide when ring thickness becomes large. Therefore, a good transformer between the RCWG and the homogeneous circular waveguide is achieved by increasing ring thickness from the RCWG toward the homogeneous waveguide. From the above investigations, it is found that in the ring-loaded corrugated horn, the useful bandwidth is 1.35 times broader than that in the conventional corrugated horn. The theoretical results are verified by the experimental results.

The ring-loaded corrugated waveguide

The ring-loaded corrugated waveguide is shown to be very effective for frequency broadbanding of the waveguide and improvement of the transformer between the corrugated and uncorrugated waveguides.

A Sectoral Planar 6-Way Hybrid Power Divider with a Resistive Slot

A sectoral planar six-way hybrid power divider has been developed with an isolation higher than 20dB, over a 30 percent frequency bandwidth in X-band. The output-port isolation is obtained by a resistive slot in the sectoral part and resistive sheets between the adjacent output lines, ¿/4 apart from the junction.

Broadband Tunable Oscillator with Two MSW Resonators

A broadband tunable oscillator with two MSW resonators has been developed. The resonators with different sizes of YIG films are placed in the same magnetic field. The tunable bandwidth extends over 2 octaves up to 20 GHz.

Input impedance of an inhomogeneous side coupler

This paper presents simple formulas for coupler characteristics of an inhomogeneous side coupler. The formula for the input impedance of the coupler explicitly represents that an inductive reactance remains even though the most appropriate characteristic impedance is selected for impedance matching of the coupler. These impedance characteristics are experimentally verified.

8 and 11 GHz Bands Low Noise FET Amplifiers Operating at Room Temperature

8 and 11 GHz bands low noise FET amplifier operating at room temperature have been developed. Noise temperature of these FET amplifiers are 105 K and 185 K at 8 and 11 GHz bands, respectively.