Masatake Hangai

Tunable MEMS hybrid coupler and L-band tunable filter

Simultaneous control of frequency and coupling coefficient of a directional coupler provides a wide band tunable hybrid coupler. This hybrid coupler is combined with identical two tunable band rejection filters (BRF), to achieve a small-size wide-band tunable band pass filter (BPF). The BPF is called a reflection-type BPF and has a feature of converting rejection frequency bands of the BRF to pass frequency bands.

A grounded co-planar waveguide MEMS switch

A grounded co-planar waveguide (GCPW) MEMS switch is presented. The proposed switch has a movable SiN membrane with a signal line and ground lines above a dielectric-air-metal (DAM) cavity on which a ground metal is patterned, resulting in a structure of GCPW transmission line. The electrostatic force makes an RF short path to the ground metal on the bottom of the DAM cavity with metal-to-metal contact. The ground metal which covers silicon substrate makes the switch to be on a low-resistivity silicon substrate. The measured results of the switch validate the proposed structure of the switches utilizing the DAM cavity.

A Ka-band high-power protection switch with open/short-stub selectable circuits

A Ka-band high-power protection switch has been developed. Our invented circuit utilized new open/short-stub selectable circuit. By using this configuration, the gate widths of the FETs and the power handling capability at transmitting mode can be independently determined. So the circuit can keep low insertion loss at receiving mode while maintaining high power performance at transmitting mode. To verily this methodology, we have fabricated an MMIC switch, and the circuit has achieved the insertion loss of 2dB, the isolation of 25dB, and the power handling capability of 38dBm at 5% bandwidth of Ka-band.

A CPW hybrid coupler with an enhanced coupling microstructure

A new micromachined coplanar waveguide (CPW) 3-dB hybrid coupler has been demonstrated. A micromachined enhanced coupling structure at the middle of two coupled transmission lines is employed to obtain high directivity. The coupling structure is composed of alternately overlapping plated conductors employing micromachined air-gap structures. This structure relaxes the tolerance of the gap between the coupled transmission lines, and mitigates production error. Moreover, this coupling structure enhances the coupler directivity by equalizing phase velocities of both even- and odd modes. We fabricate the CPW hybrid coupler with the enhanced coupling structure on a silicon substrate to verify the performance. The results showed the return loss of better than 28 dB, the isolation of more than 25 dB over 11 to 15 GHz.

GaN HEMT high efficiency amplifier for Microwave Wireless Power Transmission

In this paper, GaN HEMT high efficiency amplifier for Microwave Wireless Power Transmission (MWPT) is presented. The effects of harmonic of 0.7μm and 0.25μm gate length GaN HEMTs were measured by harmonic load-pull measurement. In the measurement, it was revealed that the 0.25μm gate device included higher harmonics than 0.7μm gate device. It is because cuf-off frequency of 0.25μm gate device is higher than 0.7μm gate device. 0.25μm short gate length GaN HEMT which has 25GHz high cut-off frequency was used for amplifier. The matching circuit was designed so that 2nd and 3rd harmonics are tuned to obtain maximum power added efficiency (PAE). PAE of 75% was successfully obtained with 7W output power at 5.8GHz.

A resistor-loaded microstrip line resonator with a punched hole structure for ultra-wide-stopband bandpass filters

A novel microstrip line resonator is proposed for ultra-wide-stopband microwave bandpass filters. It consists of a stepped-impedance resonator (SIR) with a high-impedance transmission line on punched hole structure (PHS), and thin-film resistors implemented in the SIR for absorbing higher-order resonance power. A fabricated 2-stage microstrip bandpass filter at ƒ0 = 2.0 GHz has realized a spurious response level < −29 dB up to 25 ƒ0, which seems to be the superior wide-stopband performance among ever-reported ones in the category of microwave microstrip line filters.

A low phase-shift temperature compensation attenuator with variable-Q FET resonators

A low phase-shift temperature compensation attenuator has been successfully developed. Our invented circuit utilizes new variable-Q FET resonators. By using this configuration, the dynamic range of the attenuation can be arbitrarily determined and the phase shift with temperature change can be reduced. To verify this methodology, we have fabricated an MMIC attenuator, and the circuit has achieved the attenuation dynamic range of 16.9dB, the phase shift of ±5.2deg, and the minimum insertion loss of 4.5dB in X-band over 75 °C temperature variation.

High power handling capability of movable-waveguide direct contact MEMS switches

The authors presented the characteristics of high power handling capability with direct contact MEMS switches. The switch has a movable-waveguide, fabricated on a silicon cavity. Two types of MEMS switches with different number of contact points were fabricated. In high power handling experiments with hot switching mode, a multiple-contact type switch failed at 1.6 W in 7 GHz RF signal, while a single-contact type switch was succeeded up to 2.4 W. These results were considered from the viewpoint of contact force and surface asperities according to the relation between input power and insertion loss.

Millimeter-Wave High-Power MMIC Switch with Multiple FET Resonators

A millimeter-wave low-loss, high-isolation and high-power terminated MMIC switch is developed, and the design theory is formulated. Our invented switch is designed based on a non-linear relationship between the parallel resistance of an FET and its gate width. Our measurements of the parallel resistance with different gate width have revealed that the resistance is inverse proportion to a square of the gate width. By using this relationship, we have found the fact that the multiple FET resonators with smaller gate width and high inductance elements realize high-Q performance for the same resonant frequency. Since the power handling capability is determined by the total gate width, our switch circuit could reduce its insertion loss, keeping the high-power performance. We additionally describe the design method of this switch circuit. The relationships between the gate widths of the FETs and the electrical performances are described analytically. The required gate widths of the FETs for handling high power signal are represented, and the design equations to obtain lower insertion loss and higher isolation performances keeping high power capability are presented. To verify this methodology, we fabricated a MMIC switch. The MMIC had insertion loss of 2.86 dB, isolation of 37 dB and power handling capability of more than 33 dBm at 32 GHz.