• Journal of IKEEE
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• v.26 no.4
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• pp.537-544
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• 2022

This paper analyzes the occurrence and cause of bond wires fusing used in the manufacture of pulsed high power amplifiers. Recently GaN HEMT has been spotlight in the fields of electronic warfare, radar, base station and satellite communication. In order to produce the maximum output power, which is the main performance of the high-power amplifier, optimal impedance matching is required. And the material, diameter and number of bond wires must be determined in consideration of not only the rated current but also the heat generated by the transient current. In particular, it was confirmed that compound semiconductor with a wide energy band gap such as GaN trigger fusing of the bond wire due to an increase in thermal resistance when the design efficiency is low or the heat dissipation is insufficient. This data has been simulated for exothermic conditions, and it is expected to be used as a reference for applications using GaN devices as verified through IR microscope.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.6
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• pp.149-154
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• 2022

Due to high power capabilities and high linearity of GaN devices, GaN Low-Noise Amplifiers (LNAs) without a limiter can be implemented in order to improve noise figure and reduce chip area in radar receivers. In this paper, a GaN LNA is presented for Ka-band radar receivers. The designed LNA was realized in a 150-nm GaN HEMT process and measurement results show that the voltage gain of >23 dB and the noise figure of <6.5 dB including packaging loss in the target frequency range. Under the high-power stress test, measured gain and noise figure of the GaN LNA is degraded after the first stress test, but no more degradation is observed under multiple stress tests. Through post-stress noise and s-parameter measurements, we verified that the GaN LNA is resilient to pulsed input power of ~40 dBm.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.128-136
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• 2006

In this paper, design and implement 50W Doherty power amplifiers for 3GPP repeater and base station transceiver system. Efficiency improvement and high power property of ideal Doherty power amplifier is distinguishable; however bias control for implementation of Doherty(GDCHD) amplifier is difficult. To solve the problem, therefore, GDCHD(Gate and Drain Control Hybrid Doherty) power amplifier is embodied to drain bias adjustment circuit to Doherty power amplifier with gate bias adjustment circuit. Experiment result shows that $2.11{\sim}2.17\;GHz$, 3GPP operating frequency band, with 57.03 dB gain, PEP output is 50.30 dBm, W-CDMA average power is 47.01 dBm, and -40.45 dBc ACLR characteristic in 5MHz offset frequency band. Each of the parameter satisfied amplifier specification which we want to design. Especially, GDCHD power amplifier shows proper efficiency performance improvement in uniformity ACLR than Doherty power amplifier.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.3 s.333
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• pp.1-8
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• 2005

In this paper, design and implement 60W Doherty power amplifiers for 3GPP repeater and base station transceiver system. Efficiency improvement and high power property of Doherty power amplifier is distinguishable; however implementation of assistance amplifer is difficult, though. To solve the problem, therefore, GCHD (Gate Control Hybrid Doherty) power amplifier is embodied to gate bias adjusament circuit of assistance amplifier to General Doherty power amplifier. Experiment result shows that $2.11\~2.17GHz$, 3GPP operating frequency band, with 62.55 dB gain, PEP output is 50,76 dBm, W-CDMA average power is 47.81 dBm, and -40.05 dBc ACLR characteristic in 5MHz offset frequency band. Each of the parameter satisfied amplifier specification which we want to design. Especially, GCHD power amplifier shows proper efficiency performance improvement in uniformity ACLR than general power amplifier.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.9
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• pp.54-58
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• 2011

In this paper a dual-band Class-E power amplifier using Composite Right-/Left-Handed transmission lines and PIN diode is proposed. Dual-band operation is achieved by the frequency offset and nonlinear phase slope of CRLH TL for the matching network of power amplifiers. The proposed power amplifier has been realized by using in the input and the output matching network for high power added efficiency. PIN diode has been used to obtain the dual-band of power amplifier. The measured results show that output powers of 42.17 dBm and 41.43 dBm were obtained at 800 MHz and 1900 MHz, respectively. At this frequency, we have obtained the power-added efficiency(PAE) of 67.84 % and 65.31 % in two operation frequencies, respectively.

• The Journal of the Acoustical Society of Korea
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• v.37 no.1
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• pp.46-52
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• 2018

The piezoelectric single crystals used in piezoelectric transformers have a problem that power transfer capacity is comparatively low due to their high input impedance. In this study, we suggest a method to improve the power transfer capacity by reducing the high input impedance of the piezoelectric single crystal vibrator by connecting a capacitance increasing circuit to the electrical terminals of the piezoelectric single crystal vibrator where the circuit is a GIC (Generalized Impedance Converter) circuit using operational amplifiers. The result of measuring driving characteristics after applying the designed capacitance increasing circuit to the $128^{\circ}$ rotated Y-cut $LiNbO_3$ crystal vibrator confirmed that the input impedance decreased by 25 %, electromechanical coupling factor increased by 30 %, and the power transfer capacity increased by about 17 to 30 times in voltage conversion characteristics.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.3
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• pp.227-247
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• 2015

An X-band $8{\times}16$ dual-polarized active phased array antenna system has been implemented based on the substrate integrated waveguide(SIW) technology having low propagation loss, complete EM shielding, and high power handling characteristics. Compared with the microstrip case, 1 dB less is the measured insertion loss(0.65 dB) of the 16-way SIW power distribution network and doubled(3 dB improved) is the measured radiation efficiency(73 %) of the SIW sub-array($1{\times}16$) antenna element. These significant improvements of the power division loss and the radiation efficiency using the SIW, save more than 30 % of the total power consumption, in the active phased array antenna systems, through substantial reduction of the maximum output power(P1 dB) of the high power amplifiers. Using the X-band $8{\times}16$ dual-polarized active phased array antenna system fabricated by the SIW technology, the main radiation beam has been steered by 0, 5, 9, and 18 degrees in the accuracy of 2 degree maximum deviation by simply generating the theoretical control vectors. Performing thermal cycle and vacuum tests, we have found that the SIW array antenna system be eligible for the space environment qualification. We expect that the high efficiency SIW array antenna system be very effective for high performance radar systems, massive MIMO for 5G mobile systems, and various millimeter-wave systems(60 GHz WPAN, 77 GHz automotive radars, high speed digital transmission systems).

• Journal of Broadcast Engineering
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• v.18 no.6
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• pp.884-894
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• 2013

In this paper, we investigate the characteristics of power amplifiers and simplified memoryless non-linear power amplifier models for energy efficient communication system. First, we present the transfer function of GaAs FET (Gallium Arsenide Field Effect Transistor) that is widely used for high power amplifier. From those investigations, we introduce the instantaneous efficiencies and methods of amplification by assuming that the saturated current is constant, while perfect linearity is exploited under knee voltage. Then, we discuss four non-linear power amplifier models in a baseband signal processing. Finally, we explain the specified total power consumption model in a base station to achieve the resonable analysis for energy efficient communication.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.4
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• pp.229-235
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• 2013

In this paper, we investigate several important issues on the implementation of a totally implantable microsystem for brain-machine interface that has been attracting a lot of attention recently. So far most of the scientific research has been focused on the high performance, low power electronics or systems such as neural signal amplifiers and wireless signal transmitters, but the real application of the implantable microsystem is affected significantly by a number of factors, ranging from design of the encapsulation structure to physiological and anatomical characteristics of the brain. In this work, we discuss on the thermal effect of the system, the detecting volume of the neural probes, wireless data transmission and power delivery, and physiological and anatomical factors that are critically important for the actual implementation of a totally brain implantable neural interface microsystem.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.3 s.333
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• pp.9-14
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• 2005

OFDM(Orthogonal Frequency Division Multiplexing) is widely used in wideband wireless communication systems due to its excellent performance. However, OFDM has a disadvantage of high peak-to-average power ratio and SC-FDE(Single-Carrier with Frequency-Domain Equalization) was introduced to overcome the drawback. SC-FDE is less sensitive to nonlinear power amplifiers than OFDM while its complexity and performance is comparable. This paper proposes a frequency diversity technique for single-antenna BPSK SC-FDE systems using repeated QPSK transmissions with rearranged transmission patterns.