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This study describes the Ku -band 70- and 30-W-class internally matched gallium nitride (GaN) power amplifiers (PAs) for multi-carrier satellite communications (SatComs). The GaN PAs maintain low third-order intermodulation distortion (IMD3) over a wide offset frequency range of up to 400 MHz, whereas in the Ku -band, one PA can deliver a high peak output power of approximately 70 W and the other PA, a peak output power of higher than 30 W. To realize a wide offset frequency operation, our proposed output-matching circuit includes three different types of difference-frequency short circuits, two of which are embedded into a tournament-shaped output-matching circuit inside the PA package and the rest is embedded into the drain bias feed placed outside the package. To verify the short-circuit design and its effectiveness, two different power classes (70 and 30 W), Ku -band GaN PAs, were designed and fabricated, and then, their output transfer characteristics focusing on IMD3 were measured. The measurements show that the 70-W-class GaN PA achieves a peak output power of 48.6 dBm while maintaining a linear output power of over 40 dBm and an IMD3 of less than −26 dBc over wide offset frequencies ranging from 1 to 400 MHz. The 30-W-class GaN PA maintains a linear output power of over 36.3 dBm and an IMD3 of less than −27 dBc over wide offset frequencies of up to approximately 600 MHz. To the best of the authors’ knowledge, these PAs have a record output power level over a wide frequency range of 1–400 MHz or higher under the condition of a low IMD3 of less than −25 dBc, compared to previously reported Ku -band GaN PAs used for multi-carrier SatComs.

In this paper, an X-band 100 W class high power amplifier GaN monolithic microwave integrated circuit (MMIC) is presented. A GaN high electron mobility transistor (HEMT) with a power density exceeding 10 W/mm has been developed by achieving both electric field relief and high power density to increase the amplifier output. This high power amplifier GaN MMIC is manufactured using a GaN HEMT, which has high power density. Measurement results of the two-stage amplifier MMIC show output power of 80–100 W, a power added efficiency (PAE) of 42%, and a gain of 18 dB. This result is comparable with the best state-of-the-art X-band MMIC power amplifiers ever reported. This indicates that the developed amplifier has an advantage when it is utilized in a transmit module.

In this paper, 2.45 GHz ISM-Band high power and high efficiency GaN pallet amplifier for Microwave Heating is presented. To realize higher efficiency of the GaN high-power amplifier (HPA), we used both the input and output second harmonic reflection circuit in pallet amplifier. The fabricated pallet amplifier showed excellent performance, which is output power of 450 W and efficiency of 70 % with CW operation at the 2.45 GHz. To the authors' knowledge, this is one of the highest level oerformance amons ever-reoorted ones.

Confocal imaging of a breast tumor phantom embedded in a 3-D-printed breast phantom was demonstrated. 16 compact ultra-wideband (UWB) slot antennas were attached on the surface of the 3-D-printed breast phantom and confocal imaging of 192 combinations was carried out by a radar-based breast cancer detection system. The breast adipose, glandular and tumor tissues were made of acrylonitrile butadien styrene plastic, silicone and cured pork meat, respectively. The three dimensional confocal image of the tumor phantom at the position of x=55 mm, y=55 mm, z=30 mm was reconstructed.

Spatial resolution of 4×4 planar ultra-wideband (UWB) antenna array was investigated for a confocal imaging system using Gaussian monocycle pulses. Two separate breast tumor phantoms having 5×5×5 mm 3 embedded at the depth of 22 mm with the separation distance of 8 mm were resolved by use of 4×4 array antennas with 6 mm spacing due to the fact that the frequency characteristics of the antenna was improved in the frequency range from 6 to 10 GHz.

A new 65-nm-thick single-pole-eight-throw CMOS integrated switching matrix has been developed to control a multiple-input–multiple-output radar-based imaging system, and it can replace the conventional mechanical switching system. The switch has a minimum input and output matching bandwidth of 0–17 GHz with an average insertion loss of 3 to 10 dB from 2 to 17 GHz. A wide bandwidth was designed for the transmission of the 8-GHz-center-frequency, 16-GHz-bandwidth Gaussian monocycle pulse with low distortion. A bandwidth from 0–20 GHz of the switch on the printed circuit board was achieved by flip chip mounting, quarter-wave (λ/4)-length microstrip line impedance matching, and optimization of the board dielectric constant and thickness. With the utilization of two of these switching matrices on the PCB, it became possible to control 16 antennas in a 16-antenna-array breast cancer detection system to detect an aluminum target of 10 × 10 mm2 at a depth of 20 mm.

A compact planar ultra-wideband (UWB) antenna array was developed for radar-based breast cancer detection system in the supine position. The size of the antenna element was 11 mm × 13.1 mm. A 4×4 antenna array size was 44 mm × 52.4 mm. The bandwidth and the center frequency of the antenna were 12.5 GHz and 6 GHz, respectively. The permittivity and conductivity of the human breast tumor were measured and the phantom materials were selected to fit the characteristics of the human breast tissues. Confocal imaging was carried out using the phantom. It was confirmed that the compact antenna array for breast cancer detection could resolve the two separate tumor phantoms which were located at the depth of 20 mm with the separation distance of 20 mm.

A time-domain reflectometry breast cancer detection system was developed, which was composed of a Gaussian monocycle pulse (GMP) transmitter circuit fabricated by complementary metal oxide semiconductor (CMOS) 65 nm technology and an ultra wide-band (UWB) planar slot antenna array. The center frequency and bandwidth of the antenna were 6 and 9.2 GHz, respectively. The GMP train having the pulse width of 160 ps was generated by the 65 nm CMOS logic circuit with a core area of 0.0017 mm2 and was emitted by the 4 × 4 planar slot antenna array. The fabricated planar 4 × 4 antenna array with the matching layer could resolve the two separate 5 × 5 × 5 mm3 breast tumor phantoms, which were located at the depth of 22 mm with the spacing of 8 mm.