• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.221-224
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• 2005

This paper discribes the nonlinear distortion of a pHEMT power amplifier. In the paper, we have used some commercially available power amplifiers for analyzing the relationship between the $IMD_3$ and ACPR for wireless LAN. And the $IMD_3$ results using two-tone test have been compared with ACPR to satisfy the requited 802.11g standard ACPR value. Measurement result shows that $IMD_3$ of 20MHz tone-spacing need to be more than 18.45dBc for power amplifiers. The WCDMA signal is fed into the power amplifier, for analyzing relationship between the asymmetrical $IMD_3$ and ACLR. With measurement result, the asymmetrical $IMD_3$ characteristic has increased with the increase of two-tone spacing. $IMD_3$ measurement result with maximum 20MHz of the two-tone spacing, shows that the difference between $IMD_3(lower)$ and $IMD_3(upper)$ is about 7dB. And the measured ACLR shows 5dB difference at -4MHz and +4MHz offset from center frequency.

• Journal of Sensor Science and Technology
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• v.18 no.1
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• pp.63-71
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• 2009

It is said that the desirable bio-signal measurement and stimulation system should be an implantable type if the several problems such as biocompatibility, electrical safety, and so on are overcome. In addition to the biocompatibility issue, a robust RF communication and a stable electrical power source for the implantable bio-signal measurement and stimulation system are very important matters. In this paper, a wireless telemetry system which adopts the FCC's approved MICS (medical implant communication service) protocol and a wireless power transmission has been proposed. The proposed system composed of a base station (BS) and an implantable medical device (IMD) has the advantages that the interference with other RF devices can be reduced by the use of the specially assigned MICS frequency band of 402.MHz to 405 MHz. Also, the proposed system includes various functions of a multi-channel bio-signal acquisition and an electric stimulation. Since the electrical power for the IMD can be provided by the inductive link between PCB patterned coils, the IMD needs no battery so that the IMD can be smaller size and much less dangerous than the active type IMD which includes the internal battery. Finally, the validity as a wireless telemetry system has been demonstrated through the experiments by using the implemented BS and IMD.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.261-264
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• 2004

In this paper, we identify the memory effect of high power(125W) laterally diffused metal oxide-semiconductor(LDMOS) RF Power Amplifier(PA) by two tone IMD measurement. We measure two tone IMD by changing the tone spacing and the power level. Different asymmetric IMD is founded at different center frequency measurements. We propose the Tapped Delay Line-Neural Network(TDNN) technique as the modeling method of LDMOS PA based on two tone IMD data. TDNN's modeling accuracy is highly reasonable compared to the memoryless adaptive modeling method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.5
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• pp.999-1003
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• 2009

We have designed and fabricated a linear drive amplifier with a novel intermodulation distortion(IMD) canceller using $0.18{\mu}m$ CMOS process. The drive amplifier with IMD canceller is composed of a cascode main amplifier and an additional common-source IMD canceller. Since the IMD canceller generates IM3($3^{rd}$-order imtermodulation) signal with $180^{\circ}$ phase difference against the IM3 of the cascode main amplifier, the IM3 power is drastically eliminated. As of the measurement results, $OP_{1dB}$, $OIP_3$, and power-add efficiency are 5.5 dBm, 15.5 dBm, and 21%, respectively. Those are 5 dB, 6 dB, and 13.5% enhanced values compared to a conventional cascode drive amplifier. The IMD3 of the drive amplifier with IMD canceller is enhanced more than 10 dB compared to that of the conventional cascode drive amplifier for input power ranges from -22 to -14 dBm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.5
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• pp.450-457
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• 2003

In this paper, we studied the effect of asymmetrical 3rd order IMD of power amplifier due to changes in modulation frequency on IMD cancellation performance. The phase extraction method for determining asymmetric rate for phase distortion of IMD is proposed and the phase difference between lower and upper 3rd order IMD is measured by this method. The phase compensation circuit to decrease the phase difference is also designed and fabricated. From the measurement results using the phase compensation circuit applied to 5 W RF power amplifier fur PCS applications, the 3rd order IMD cancellation performance can be achieved up to 2-tone spacing 1.5 MHz (phase difference within 10$^{\circ}$).

• Journal of electromagnetic engineering and science
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• v.10 no.2
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• pp.73-77
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• 2010

This paper proposes a novel memory effect measurement technique in RF power amplifiers(PAs) using a two-tone intermodulation distortion(IMD) signal with a very simple and intuitive algorithm. Based on the proposed predistortive tone cancellation technique, the proposed measurement method is capable of measuring the relative phase and magnitude of the third-order and fifth-order IMDs, as well as the fundamental signal. The measured relative phase between the higher and lower IMD signal for specific tone spacing can be interpreted as the group delay(GD) information of the IMD signal concerned. From the group delay analysis, we can conclude that an adaptive control of GD as well as the magnitude and phase is a key function in increasing the linearization bandwidth and the dynamic range in a predistortion(PD) technique.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.2
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• pp.268-277
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• 2000

Nowadays, the interference between neighbor basestations is getting higher as mobile communication services expand, then the increase of the interference causes IMD(Intermolulation Distortion) problems for not only active devices but also passive devices. In this paper, we have designed and assembled several adapters having variable plating thickness and materials to analyze PIMD(Passive Intermodulation Distortion) mechanisms for coaxial cables which is one of the representative passive RF devices. The measurement results of the assembled adapters show that IM level depends on conductivity of plating materials, plating thickness, device structure, aging effect and so on. Furthermore, we have obtained PIMD mechanisms and some control methods of PIMD from the results.

• Journal of Advanced Navigation Technology
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• v.15 no.5
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• pp.789-794
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• 2011

This paper has analyzed the AM-AM and AM-PM characteristics of 7.9 GHz~8.4 GHz X-band TWT used for satellite communication and improved its linearity and IMD performance by using linearizer. The TWT amplifier with the linearizer shows better AM-AM and AM-PM conversion, and has increased 1 dB compression point by 12.3 dB and $2.0^{\circ}/dB$ phase distortion point by 10 dB. The 3rd order intermodulation distortion, IMD3 is measured to be 37.0 dBc that is 16.2 dB improvement at the operating output. This paper also proposed the measurement method of IMD for high power amplifier, and that TWT amplifier can have better linearity and output power by compensating for the AM-PM characteristics.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.11
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• pp.1081-1090
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• 2013

In this paper, a C-band 10 W power amplifier with internally matched input and output matching circuit is designed and fabricated. The used power transistor for the power amplifier is GaAs pHEMT bare-chip. The wire bonding analysis considering the size of the capacitor and the position of transistor pad improves the accurate design. The matching circuit design with the package effect using EM simulation is performed. To reduce the unsymmetry of IMD3 in 2-tone measurement due to the memory effect, the bias circuit minimizing the memory effect is proposed and employed. The measured $P_{1dB}$, power gain, and power added efficiency are 39.8~40.4 dBm, 9.7~10.4 dB, and 33.4~38.0 %, respectively. Adopting the proposed bias circuit, the difference between the upper and lower IMD3 is less than 0.76 dB.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.337-340
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• 2000

본 논문에서는 안테나의 PIMD 측정에 있어 신뢰성과 재현성에 관한 문제점을 검토하였으며, 향후 새로운 구조의 Anechoic Chamber의 필요성에 관해 기술하였다. 패치 안테나를 일반적인 안테나용 Chamber에서 PIMD를 측정한 결과 재현성에 있어 문제점이 있음을 확인하였으며, 그 원인이 피라미드 구조의 흡수체에 있음을 실험을 통해 확인하였다.