• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.11 s.102
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• pp.1059-1066
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• 2005

This paper reports an application of Doherty amplifier for efficiency improvement of feedforward power amplifier(FPA). For performance analysis, we measured 15 W average output power using WCDMA 4FA input signal with a center frequency 2.14 GHz. The applied Doherty amplifier presents the characteristics of high efficiency and low linearity in comparison to the class AB amplifier, and it was used as main amplifier of FPA fir efficiency improvement. To analyze the change of characteristic, tow Doherty amplifiers whose linearity and efficiency are different were applied. The applied FPAs are improved about $2\%$ or more performance in efficiency, but decreased in linearity on 15 W average output power. We additionally modified the coupling factor(CF) of the error loop and the error amplifier capacity for linearity improvement. Aa a result, the efficiency improvement and high linearity resulted from the change of CF and error amplifier capacity. However, we think if the linearity of Doherty amplifier were more than 35 dBc, the FPA would improve the performance about $2\%$ or more efficiency and maintain enough linearity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.11
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• pp.1934-1939
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• 2006

Current digital communication system is selecting very various digital Modulation way. Need linear power amplifier necessarily to reduce interference for contiguity channel maximum in this communication system and at the same time, power amplifier of high efficiency is required. In this paper Compare with result of equilibrium power amplifier that design Doherty power amplifier of way that linearity and efficiency are improved at the same time through simulation optimization techniques and at the same time design through simulation, efficiency 20% linearity showed 10dB that is improved.

• Journal of Advanced Navigation Technology
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• v.12 no.3
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• pp.220-226
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• 2008

This paper proposes the Reconfigurable Doherty Amplifier(RDA) with asymmetric structure which has ${\lambda}/4$ impedance transformer for modulating the load impedance in peaking amplifier path. This structure is possible to implement a compact size for N-stage multi Doherty amplifier and to get almost same characteristics that is compared to conventional Doherty amplifier. To realize the high efficiency amplifier, we were implemented 45 Watts power amplifier at transmitter band of Wideband Code Division Multiple Access(WCDMA) base-station. As a result, in case of WCDMA 1 Frequency Allocation(FA) input signals, this amplifier has obtained a 26.3% Power Added Efficiency(PAE) at 8 dB back-off point from P1dB and an Adjacent Channel Leakage Power(ACLR) is -40.4 dBc at center frequency ${\pm}5MHz$ deviation.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.19-22
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• 2004

This paper implemented 2.14GHz band Adaptive Hybrid Doherty (AHD) amplifier, as well as, wished to improve the high power characteristics and efficiency by composing bias adjustment circuit with LDMOS. Finally, through CAE, confirmed that AHD amplifier have superior performance than hybrid balanced amplifier. Superior characteristics of AHD amplifier is expected to affect immensely in amplifier field hereafter.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.688-688
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• 2006

• JSTS:Journal of Semiconductor Technology and Science
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• v.6 no.4
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• pp.275-280
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• 2006

We propose Doherty power amplifier structure which can be integrated in Silicon RF ICs. Doherty power amplifiers are widely used in RF transmitters, because of their high Power Added Efficiency (PAE) and good linearity. In this paper, it is proposed that a method to replace the quarter wavelength coupler with IQ up-conversion mixers to achieve 90 degree phase shift, which allows on-chip Doherty amplifier. This idea is implemented and manufactured in CMOS 5 GHz band direct-conversion RF transmitter. We measured a 3dB improvement output RF power and linearity.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.1
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• pp.107-111
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• 2009

In this paper, the power added efficiency(PAE) of a Doherty amplifier has been improved by applying Photonic Bandgap(PBG) characteristics on the output of amplifier. As a result of the high order harmonics termination, excellent improvement in PAE, maximum output power as well as linearity is obtained. The PAE is improved as much as relatively 35% compared with a conventional Doherty amplifier. Moreover, size of LPF is reduced by PBG characteristics. Therefore the whole amplifier circuit size is considerably reduced by diminishing in size of the LPF as compared with a Doherty amplifier using conventional LPFs.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.8 no.1
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• pp.12-17
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• 2009

In this paper, We play it for the purpose of study about the power amplifier which applied DGS and adaptive bias circuit structure to general Doherty amplifier for the efficiency of a RF power amplifier and a linearity improvement in the WiBro band. As for the IMD3, 3.4dBc was improved with -26.3dBc when we did the measurement result existing Doherty power amplifier and comparison of the Doherty power amplifier which applied an adaptive bias circuit and the DGS which proposed in this paper, and the mean power efficiency verified what was increased in 37%. Also, we were able to know PAE of 36.6% with output power 34.0dBm in P1dB when magnitude of an input signal was 25.6dBm. we did 6dB back off in output P1dB in order to confirm the ACPR which was a nonlinear characteristic and measured the ACPR. we showed the -34.55dBc which was a value of -34.5dBc or below in the 4.77MHz off-set that was a transmission standard. Therefore, we were able to know that we were satisfied with a spectrum mask standard.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.813-822
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• 2009

We have investigated operation of a 1:2:2 asymmetric 3-stage Doherty PA(Power Amplifier) and implemented using the Freescale's 4 W, 10 W PEP LDMOSFETS at 1 GHz. By employing the three peak efficiency characteristics, compared to the two peak N-way Doherty PA, the asymmetric 3-stage Doherty can overcome the serious efficiency degradation along the backed-off output power region and maximize the average efficiency for the modulation signal. To maximize the efficiency characteristic, the inverse class F PA has been designed as carrier and peaking amplifiers. Furthermore, to extract the proper load modulation operation, the adaptive gate bias control signal has been applied to the two peaking PAs based on the envelope tracking technique. For the 802.16e Mobile WiMAX(World Interoperability for Microwave Access) signal with 8.5 dB PAPR(Peak to Average Power Ratio), the proposed Doherty PA has shown 55.46 % of high efficiency at an average output power of 36.85 dBm while maintaining the -37.23 dB of excellent RCE(Relative Constellation Error) characteristic. This is the first time demonstration of applying the saturated PA and adaptive gate bias control technique to the asymmetric 3-stage Doherty PA for the highly efficient transmitter of the base-station application.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.2 s.314
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• pp.32-38
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• 2007

This paper represents a Doherty amplifier (DPA) with analog predistorter (PD) to improve the linearity of the DPA while preserving the high efficiency. A third-order PD cancels fifth-order intermodulation (IM5) as well as third-order intermodulation (IM3) components by their same phase difference in the PD and DPA. This is accomplished by independently controlling their phase by using the phase-controlled error generator in the PD. Also, we confirm the phase-control ability of the error generator experimentally with a simple and accurate phase measurement setup. For experimental verification, a third-order PD has been implemented and tested in a 180-W DPA at the wide-band code division multiple access (WCDMA) band of 2.11-2.17 GHz. Two-tone test results show that significant cancellation of IM3 and IM5 components can be obtained. For four-carrier WCDMA applications, significant adjacent channel leakage ratio (ACLR) improvement is achieved over a wide range of output power levels. This technique is cost-effective and convenient due to its simple structure, compact size, and three control parameters.