Moriyasu Miyazaki

Over 57% efficiency C-band GaN HEMT high power amplifier with internal harmonic manipulation circuits

In this paper, a high efficiency C-band GaN HEMT high power amplifier with internal harmonic manipulation circuits is presented. We employed a new circuit topology for simultaneous high efficiency matching at both fundamental and 2nd-harmonic frequencies. The developed GaN HEMT amplifier has achieved over 57% drain efficiency (50% power-added-efficiency) with 100W output power at C-band. This is the state-of-the-art efficiency of GaN HEMT high power amplifier at C-band to the best of our knowledge.

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.

5.8 GHz high sensitivity rectenna array

This paper presents the 5.8 GHz high sensitivity rectenna array with advanced microstrip-type rectifiers and circularly patch antennas achieving a good balance between a high-efficiency and RF weak power operation. The fabricated rectenna element has achieved RF-DC conversion efficiency of 54% at input RF power of 1mW. Furthermore, we have proposed the novel structure which enhances robustness to the breakdown of the diodes when the rectenna elements are arrayed.

A Millimeter-Wave Highly Linear VCO MMIC with Compact Tuning Voltage Converter

This paper presents a fully integrated highly linear and low phase noise voltage controlled oscillator (VCO) with a novel compact tuning voltage converter for millimeter-wave applications. The tuning voltage converter consists of only a few diodes and resistors and has nonlinear characteristics to correct varactor tuning curves. The authors fabricated the millimeter-wave VCO MMIC employing InGaP/GaAs HBT process. The MMIC chip size is 2.55 mm times 1.4 mm, in contrast the voltage converter has the size of 0.35 mm times 0.70 mm. The measured tuning sensitivity of 97 plusmn12 MHz/V is achieved for voltages between 0 V and 5 V, and the temperature dependency is very small. Also the phase noise performance is -110.7 dBc/Hz at 1MHz offset from the carrier when the oscillation frequency is 38.2 GHz. This linearization technique can greatly reduce the configuration of the conventional software linearization system

Design of compact-size high isolation branching OMT by the mode-matching technique

This paper presents the design and performance of a compact-size branching orthomode transducer (OMT) with high isolation characteristics. The design is performed using the mode-matching applied to the circular-to-rectangular waveguide Tjunctions. The design example demonstrates the high efficiency of this design method for X-band branching OMT without septa, and realizes excellent performance. The theory is verified by a good agreement with measurements.

An Rfmems Switched Capacitor Array for a Tunable Band Pass Filter

In this paper, we present an RFMEMS switched capacitor array, which is proposed as a RF component to achieve various kinds of tunable RF filters. Our RFMEMS switched capacitor array consists of RFMEMS direct contact switches and metal-insulator-metal capacitors. In order to obtain reliable capacitors, the metal sacrificial layer for the RFMEMS switch fabrication is also applied to the capacitor implementation. We have achieved a C- to Ku-band tunable band pass filter by using the RFMEMS switched capacitor array. The capacitance of capacitor is designed corresponding to each tuning state of the band pass filter, which is selected by the RFMEMS switch operation. The insertion losses of the band pass filter were 7.1dB, 4.9 dB and 6.2 dB at 8 GHz, 12 GHz and 16 GHz, respectively.

An S-band 100W GaN Protection Switch

A high-power protection GaN FET switch has been developed. Our invented switching circuit utilizes a new asymmetric series-shunt/shunt configuration. By using the proposed circuit, the power handling capability at isolated state is determined only by the breakdown voltage and the bias voltage of the FETs. So the gate width of the FETs can be determined independently of the power handling capability, and we can overcome the trade-off relationship between the insertion loss at transmission state and the power handling capability at isolated state by using FETs having high breakdown voltage. To verify this methodology, we fabricated the switch with an AlGaN/GaN FET technology, and the circuit achieved the power handling capability of over 100 W, the insertion loss of 0.97 dB, and the isolation of 18.7 dB at 10% bandwidth in S-band.

Dielectric resonator elliptic-function band rejection filter with external coupling waveguide

A Ku-band elliptic-function band rejection filter (BRF) has been developed which employs a rectangular waveguide, dielectric resonators (DRs), and an external coupling waveguide to obtain attenuation poles. The high-Q DRs and the coupling waveguide realize larger attenuation with smaller number of stages than that of conventional all-pole BRFs like Chebyshev or maximally-flat response. The BRF is designed on an equivalent circuit, which has symmetry and thus enables simple even- and odd-mode analyses. The external waveguide is connected to the BRF through coupling slots in E-plane of main waveguide to obtain negative coupling between the DRs.

A Grooved Monoblock Comb-Line Filter Suppressing the Third Harmonics

A grooved monoblock comb-line filter has been developed. By putting the grooves on the outer surfaces of dielectric block, the second passband is shifted to the higher frequency than the third harmonics. So this filter is very effective for suppressing the third harmonics, besides these grooves are effective for inter-resonator coupling.

X-Band 14W high efficiency internally-matched HFET

An X-Band 14W high efficiency internally-matched HFET has been developed. In order to achieve high efficiency, not only equal combining characteristics but also equal load impedance for each unit FET cell are designed in the input and output matching circuits using EM simulator. In addition to the power splitting and combining characteristics, the large signal load impedance of each FET cell is discussed. The degradation of the efficiency by unequal operation of each FET cell and by mismatch to the optimum load impedance are suppressed within 1% and 2%, respectively in the design. The developed HFET has achieved a power-added efficiency (PAE) of 49.8% and an output power of 41.6dBm(14.5W) in X-band.