• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.11
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• pp.1-8
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• 1997

In this paper, we propose a new method for the improvement of linearizing and adaptive convergence charateristics of the feedforward linear power amplifier. In this circuit, errors at the signal cancellation stage can be compensated at the error cancellation stage and the overall linearizaton and adaptation characteristics of the linear amplifier are improved. The broadband characteristics and linearizing capability are improved without increasing the complexity of circuits and the signal processing structure.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.1
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• pp.37-43
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• 2001

In this paper, we designed a linear power amplifier considering its delay characteristics fur wideband operation. The power amplifier has the gain of 37 dB and is designed in 3-stage typ with 1W output power. The error amplifier has the gain of 55 dB and is designed in 4-stage typ. And directional coupler and power divider are designed. Vector modulator is used to adjust magnitude and phase of signal. A linear power amplifier, that is assembled with each modules, is designed considering the delay characteristics for 2.11~2.2 GHz. Its C/I3 ratio has been improved by B5 dB for bandwidth of 30 MHz.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.6
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• pp.1166-1173
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• 2009

In this paper, we studied on the power amplifier which has the output of the optimal to 100MHz-2GHz band. Optimal output power match was fabricated using the two types; one is the linear tapering and the other is the impedance transformer. In the case of output power match using linear tapering, output power was 35.35dBm at 2GHz and 31.41dBm at 100MHz. The other case of output match using impedance transformer, output power was 34.8dBm at 2GHz and 33.25dBm at 100MHz. Comparison of the results in the two cases, impedance transformer type present the improved results by l.84dB of output power.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.10
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• pp.998-1004
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• 2002

This paper reports a design of feedforward linear power amplifier using pilot tone for IMT-2000 band repeaters accepting multi-carrier. As this time pilot tone is applied to the circuit differently from the existing method. Only one pilot tone is used in both 1-st loop(IMD abstraction loop) and 2-nd loop(IMD cancellation loop) to cancell IMD signals automatically according to variation of frequency or power level of input signals. As an experiment, in range of 2110 MHz - 2170 MHz at LPA output power of $20 W_{avg}$, IMD characteristics of over 20 dB was improved maintaining below -60 dBc considering respective 20 MHz. Therefore the supposed feedforward linear power amplifier can be used for linear power amplifier in IMT-2000 band repeaters.

• JSTS:Journal of Semiconductor Technology and Science
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• v.11 no.4
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• pp.336-343
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• 2011

This paper introduces a simple variable gain amplifier (VGA) structure that shows an inherently dB-linear gain control property. Requiring no additional components for dB-linear control, the structure is compact and power efficient. The designed two-stage VGA shows a gain control range of 60dB with the gain error in the range of ${\pm}0.4$ dB. The power consumption including the output buffer is 20.4 mW from 1.2 V supply voltage with bandwidth of 630 MHz. The prototype was fabricated in a 0.13 ${\mu}m$ CMOS process and the VGA core occupies 0.06 $mm^2$.

• Journal of information and communication convergence engineering
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• v.17 no.4
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• pp.285-289
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• 2019

A 1.9-GHz linear CMOS power amplifier is presented. An adaptive bias circuit (ABC) that utilizes an AC ground to detect the power level of the input signal is proposed to enhance the linearity and efficiency of the power amplifier. The ABC utilizes the second harmonic component as the input to mitigate the distortion of the fundamental signal. The input power level of the ABC was detected at the AC ground located at the V_DD node of the power amplifier. The output of the ABC was fed into the inputs of the power stage. The input signal distortion was mitigated by detecting the input power level at the AC ground. The power amplifier was designed using a 180 nm RFCMOS process to evaluate the feasibility of the application of the proposed ABC in the power amplifier. The measured output power and power-added efficiency were improved by 1.7 dB and 2.9%, respectively.

• Journal of Navigation and Port Research
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• v.27 no.2
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• pp.209-215
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• 2003

In this paper. We tested and fabricated the error amplifier for the 15 Watt linear power amplifier for the IMT-2000 baseband station. The error amplifier was comprised of subtractor for detecting intermodulation distortion, variable attenuator for control amplitude, variable phase shifter for control phase, low power amplifier and high power amplifier. This component was designed on the RO4350 substrate and integrated the aluminum case with active biasing circuit. For suppression of spurious, the through capacitance was used. The characteristics of error amplifier measured up to 45 dB gain, $\pm$0.66 dB gain flatness and -15 dB input return loss. Results of application to the 15 Watt feedforward Linear Power Amplifier, the error amplifier improved with 27 dB cancellation from 34 dBc to 61 dBc IM$_3$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3C
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• pp.234-240
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• 2002

A power amplifier with AlGaAs/InGaAs/GaAs HBT's has been developed for customer premise equipments of the quasi millimeter-wave frequency-band broadband wireless local loop(BWLL) system. Parameters of the linear and nonlinear equivalent circuits for a common base HBT have been extracted by a fitting method. The amplifier has been designed through the linear and nonlinear circuit simulations and fabricated on a ceramic substrate for a hybrid IC. The amplifier has produced a 25.5-dBm output power with 35% power-added efficiency(PAE) at 24.4 GHz and achieved a 7.5-dB linear power gain at 24.8 GHz. In 24.25 ∼24.75 GHz band, the amplifier has exhibited a saturated output over larger than 22 dBm and PAE higher than 25%.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.8
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• pp.1407-1413
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• 2000

This paper presents a feedforward linear power amplifier (LPA) using error feedback technique to achieve low intermodulation distortions(IMD) of power amplifiers for base stations. Especially, the proposed linear power amplifier is applied to feedforward technique combined with error feedback technique, which has no loss of amplifier gain unlike typical feedback technique. The proposed LPA is designed by using HP ADS ver. 1.3, fabricated. When two-tone signals at 1850 MHz and 1851.25 MHz with -7 dBm/tone from synthesizers are injected into the main power amplifier with gain of 28 dB and P1dB of 1W, the proposed LPA could reduce more than 35 dB.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.341-344
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• 2000

Advanced FeedForward method use Predistortion method and FeedForward method simultaneously. This method better than original Feedforward method in linearity and supply smaller power to pre-power amplifier than different methods, and then it has higher power efficiency and better linearity than original Feedforward method. A linear power amplifier using Advanced feedforward method is designed and fabricated for IMT-2000 transmission system (2110㎒ -2170M㎓). This amplifier's power gain is about 40㏈ and it's 3-rd IMD(Intermodulation distortion) are smaller than about -55㏈c(@ 10MHz).