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This paper reports on a wideband Gallium Nitride (GaN) Monolithic Microwave Integrated Circuit (MMIC) high power amplifiers (HPAs) operated in S to X bands. Two band-pass non-uniform distributed power amplifiers (NDPAs) are designed to obtain wideband and high power characteristics. One is a single-ended HPA which demonstrates output power of 17 to 26 W, power added efficiency (PAE) of 24 to 44% across 2.5 to 11.0 GHz with chip size of 4.2 mm2. The other is a two-way combined HPA which demonstrates output power of 27 to 61 W, PAE of 24 to 43% across 2.5 to 10.0 GHz with chip size of 9.6 mm2.

An ultra-broadband phase shifter MMIC has been developed. The phase shifter based on series all-pass networks and series inductors are loaded to the capacitors of APF. The series inductors adjusts frequency response of phase shifter. To verify the theory, the 45deg. unit bit phase shifter MMIC has been designed and fabricated. The measured phase shift is 43.4deg. +/-5.2deg. in 2GHz to 14.8GHz band.

A wideband GaN Doherty power amplifier (DPA) for 4G/LTE-Advanced base stations is presented. To break the inherent narrow band limitation of conventional DPA, a frequency dependency compensating circuit and a modified λ/4 inverter incorporating package parasitic elements are proposed. Measured DPA achieves 45.9–50.2 % drain efficiency with −50 dBc ACLR at 3.0–3.6 GHz under 20 MHz LTE signal after digital pre-distortion (DPD), which is very suitable for multiband radio and carrier aggregation in 4G. The use of the wideband efficient GaN DPA can reduce the complexity and energy consumption of radio, which further helps reducing the total cost of ownership (TCO) of base stations.

This paper presents a high-power, high-efficiency GaN HEMT Doherty power amplifier (DPA) for 3.5-GHz-band LTE macro-cell base-stations. To enhance the efficiency of the DPA, a new input matching circuit design based on a normalized peak amplifier's power ratio is proposed. A symmetrical DPA with the circuit is designed using 64.6% drain efficiency, 200W GaN HEMTs. The design shows significant improvement of both backed-off and peak efficiency of the DPA. At 3.51-GHz, high drain efficiency of 51.7% and 49.2 dBm (83 W) output power are achieved with a power gain of 13.5 dB and ACLR of −50.6 dBc using a LTE single carrier and digital predistortion system. This is the first demonstration of a GaN HEMT DPA of over 80W for 3.5-GHz-Band LTE macro-cell base-stations.

Large-area observations of dense molecular gas were made in NH3 (J , K) = (1, 1), (2, 2), and (3, 3) inversion lines with 4: 0 5 resolution toward the molecular cloud complex of the W 51 region. The observations were a part of a NH3 survey of the Galactic star-forming regions using the Tomakomai 11-m radio telescope. NH3 (J , K) = (1, 1) and (2, 2) emission was detected in the W 51 A and B complexes, while the detection of (J , K) = (2, 2) emission was marginal in W 51 B. The rotation temperature was � 40 K in the central part of the W 51 A complex, while being � 20 K in the other positions. A weak correlation is found that the ortho-to-para ratio decreases with increasing the rotation temperature, the far-infrared luminosity and the index of the star-formation efficiency. This tendency is explained if star formation has continued for more than the time scale of the transformation between ortho- and para-NH3: active star formation on a large scale, such as the interaction of molecular clouds with a spiral arm, has made the molecular gas warmer, even in a scale of � 10 pc, and the proceeding transformation has made the ortho-to-para ratio lower.

This paper describes a high efficiency and high output power GaN power amplifier for C-band space applications. The amplifier uses on-chip harmonic tuned FETs to improve dc-to-rf conversion efficiency. A 2nd harmonic input tuning circuit is incorporated into each unit on-chip FET cell and realizes high precise control of 2nd harmonic input impedance. In addition, 2nd and 3rd harmonic output impedances are optimized with external output matching circuits. A 100 W power amplifier with 4-chips achieves a 67.0% PAE (72.4% drain efficiency) at 3.7 GHz under CW operating conditions. To the best of our knowledge, this is the highest efficiency of C-band power amplifiers ever reported with over 100 W output power.

This paper describes a high efficiency (68%), high output power (100W), high reliability GaN HEMT amplifier for C-band space applications. The high efficiency is achieved by 2nd-harmonic frequency (2f o ) tuning circuits in the input and output matching circuits. The input circuit uses open-ended stubs located nearby FET gate terminals for setting the 2f o reflection-phase at the optimum phase. In the output circuit, the optimum 2f o reflection phase is realized using three transmission-line transformers while matching loss is kept low at fundamental frequency. In addition, a 3000 hour's RF overdrive life test reveals that an estimated mean time to failure (MTTF) is 1×107 hours at 150°C channel temperature, proving that the amplifier has sufficient reliability for space applications. To the best of our knowledge, the efficiency of 68% is the highest of 100-W class C-band amplifiers ever reported, and is also comparable to that of commercially available traveling wave tube amplifiers.

Regulations regarding automotive diesel engine emissions become more severe every year, and it is difficult to meet the requirements with only combustion improvement techniques. More effective post-processing technology is desired especially for particulate matter (PM), such as carbon soots. Although the use of a ceramic diesel particulate filter (DPF) is now a leading technology for PM removal, the problem exists for the soot removal or regeneration at low temperature, especially at cold start. In the present study, a regeneration of a DPF with collected PM was investigated using the low-temperature atmospheric pressure nonthermal plasma. The method is to use the NO/sub 2/ and radicals induced by the plasma reactor to burn carbon soots deposited on the DPF. First, three types of DPF plasma reactors were made and the performance of the conversion of NO to NO/sub 2/ was evaluated at various conditions. Next, a regeneration experiment was carried out using a barrier-type pulse corona plasma reactor. As a result, it was confirmed that the pressure difference decreased when the plasma was turned on and the regeneration of the DPF (approximately 75% of soot removal) was confirmed when the gas temperature was 250/spl deg/C.

A direct incineration or regeneration of DPF with collected PM was investigated using atmospheric pressure nonthermal plasma which was induced inside DPF. The method is to use the NO 2 and radicals induced by the plasma to burn carbon soots deposited on DPF. Conversion of NO to NO 2 was evaluated using three types of DPF honeycomb plasma reactors. Then, the regeneration experiment was carried out using a DPF honeycomb plasma reactor. As a result, it was confirmed that the pressure drop decreased when the plasma was turned on and the regeneration of DPF was confirmed at the low temperature of 200°C.