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ABSTRACT: This paper presents a novel 3-way distributed Doherty power amplifier with an extended efficiency range for WCDMA repeater or base-station applications. This distributed Doherty amplifier consists of one main amplifier and two peaking amplifiers. In order to get high efficiency at a high back-off power, the peaking amplifier structure is based on the dual-fed distributed amplifier form. The 2140 MHz measured results of the 3-way distributed Doherty amplifier yielded 11 dB power gain, with 39.5 % power added efficiency (PAE) at 9.5 dB backoff power. High linearity performance of -54 dBc ACPR is achieved after using memory compensated digital predistortion.
Microwave Symposium, 2007. IEEE/MTT-S International; 07/2007
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ABSTRACT: A novel three-way distributed Doherty power amplifier with an extended efficiency range for WCDMA or OFDM repeater or base-station applications is presented. This distributed Doherty amplifier consists of one main amplifier and two peaking amplifiers. To achieve high efficiency at a high back-off power, the peaking amplifier structure is based on the dual-fed distributed amplifier form. The 2140 MHz measured results of the three-way distributed Doherty amplifier yielded an 11 dB power gain, with 39.5% power added efficiency at 9.5 dB back-off power
Electronics Letters 02/2007; · 0.96 Impact Factor
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ABSTRACT: This letter describes a novel iterative crest factor reduction (CFR) technique applied to a Doherty feedforward linear power amplifier (DFFLPA). This novel CFR technique is based on repeated peak cancellations and uses a scaling factor to reduce complexity. According to our results, only three iterations result in over 4-dB reduction for a two carrier WCDMA signal. Experimental results demonstrate that the proposed algorithm was able to enhance the DFFLPA system efficiency from 11.5% to 18.3%
IEEE Microwave and Wireless Components Letters 02/2007; · 1.72 Impact Factor
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ABSTRACT: This paper describes a predistorter (PD) based on piecewise pre-equalizers for use in multichannel wideband applications. The predistortion linearizer consists of piecewise pre-equalizers along with a look-up-table-based digital PD that together compensate for nonlinearities, as well as memory effects of power amplifiers (PAs). It takes advantage of multiple finite-impulse-response filters that significantly reduce the complexity when compared to memory polynomial methods. The proposed method was also compared with the conventional Hammerstein structure. A 300-W peak envelope power Doherty PA was first modeled by measured time-based samples in order to verify the adjacent channel power ratio (ACPR) performance in simulation using a multitone and single wideband code-division multiple-access (W-CDMA) carrier. Furthermore, the experimental results applying two W-CDMA carriers verify that the proposed method provided similar improvement to that of the memory polynomial approach. The experimental results verified the complexity reduction and superior ACPR performance over the conventional Hammerstein structure
IEEE Transactions on Microwave Theory and Techniques 10/2006; · 1.85 Impact Factor
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ABSTRACT: A high power and high gain Doherty amplifier is designed by using embedded driver amplifiers in the final stage. The operational characteristics of a two-stage Doherty amplifier are analyzed, as a function of the two-stage peaking amplifier gate biases. The peaking amplifier's driver has a significant effect on the total efficiency of the Doherty amplifier by reducing the leakage current. The driver stages and final output stages are implemented using two single-ended MRF21045s and a single push-pull packaged MRF5P21180. This two-stage Doherty amplifier demonstrated 27 dB gain with a PAE of 22 % at 15 W average output power, backed off 10 dB
Microwave Symposium Digest, 2006. IEEE MTT-S International; 07/2006
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ABSTRACT: An asymmetric high power extended Doherty amplifier, which has the extended peak efficiency over a 9-dB of output power and a linear dynamic range is presented in this paper. The power amplifier is designed by using two different LDMOS FET's for W-CDMA base station applications. To realize the peak efficiency extension and a linear dynamic range, a two times larger peaking device compared to the main device, and an unequal power divider is used. This asymmetric Doherty amplifier obtained a measured P1dB of 49.8 dBm. An efficiency of 31.1 % and an ACLR of -35 dBc are achieved at 9 dB back-off point, respectively
Microwave Symposium Digest, 2006. IEEE MTT-S International; 07/2006
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ABSTRACT: This paper presents a 40 W gallium-nitride microwave Doherty power amplifier for WCDMA repeater applications. The main and peaking amplifier are implemented using two 20 W PEP GaN HEMTs. Its performance is evaluated for broadband gain, power efficiency and adjacent-channel-power-ratio (ACPR). The experimental results of the GaN Doherty amplifier yielded a power gain over 11 dB from 1.8 GHz to 2.5 GHz, 65 % power added efficiency at 40 W peak power. Good linearity performance of -55 dBc ACPR is obtained after using a baseband digital pre-distortion technique
Microwave Symposium Digest, 2006. IEEE MTT-S International; 07/2006
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ABSTRACT: A 40 W gallium-nitride microwave Doherty power amplifier for WCDMA repeater applications is presented. The main amplifier and peaking amplifier are implemented using two 20 W PEP GaN HEMTs. Performance is evaluated for broadband gain, power efficiency and adjacent-channel-power-ratio (ACPR). Experimental results of the GaN Doherty amplifier yielded a power gain of over 11 dB from 1.8 to 2.5 GHz, 68% power added efficiency at 40 W peak power. Good linearity performance of -48 dBc ACPR is obtained at a peak-to-average ratio of 9.8 dB.
Electronics Letters 07/2006; · 0.96 Impact Factor
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ABSTRACT: A unique baseband derived RF predistortion system which uses lookup table coefficients extracted at baseband that directly RF envelope modulate a quadrature vector modulator is presented. The primary advantages of this architecture are that it combines the narrowband advantage of envelope predistortion with the accuracy of baseband predistortion.
Electronics Letters 05/2006; · 0.96 Impact Factor
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ABSTRACT: The linearity of a 30-W high-power Doherty amplifier is optimized using post-distortion compensation. A balanced high-power Doherty amplifier using two push-pull laterally-diffused metal-oxide semiconductor (LDMOS) field-effect transistors (FETs) is linearized by optimum adjustment of the peaking compensation line, shunt capacitors, and gate biases. The measured results of an optimized Doherty amplifier for a four-carrier wideband code division multiple access (W-CDMA) signal, achieved -43 dBc adjacent channel leakage ratio (ACLR) at a ±5 MHz offset frequency. This is an ACLR improvement of 12.2dB and 6.5dB in comparison to the Doherty amplifier before optimization and a ClassAB amplifier, respectively.
IEEE Microwave and Wireless Components Letters 12/2005; · 1.72 Impact Factor
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ABSTRACT: When compared to other linearization methods, adaptive DP provides sufficient linearization with less complex RF hardware by depending primarily upon DSP rather than analog manipulation. The adaptive DP system may be implemented in EDA software along with interconnected test equipment (arbitrary RF signal source and vector signal analyzer). Through the use of a training signal, a simple adaptive algorithm may be employed to update the LUT coefficients until an optimum setting is achieved and used to predistort the input to the amplifier. This "connected solution" approach can provide key information to design engineers for optimizing the DSP architecture of a PA. For future work, other issues are taken into account, such as temperature and electrical memory effects.
IEEE Microwave Magazine 10/2005; · 2.11 Impact Factor
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ABSTRACT: The linearity of a 30 W high power Doherty amplifier is optimized using post-distortion compensation. A balanced high power Doherty amplifier using two push-pull LDMOS FETs is linearized by optimum adjustment of the peaking compensation line, shunt capacitors and gate biases. The optimized Doherty amplifier measured results for a 4-carrier W-CDMA signal, achieved -43 dBc ACLR at a ±5 MHz offset frequency. This is an ACLR improvement of 12.2 dB and 6.5 dB in comparison to the Doherty amplifier before optimization and a class AB amplifier, respectively.
Microwave Symposium Digest, 2005 IEEE MTT-S International; 07/2005
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ABSTRACT: This paper presents a 50W current mode class-D power amplifier for the 1800 MHz frequency band using commercial LDMOS-FET. The amplifier is based on a switching mode push-pull structure which utilizes a shunt harmonic termination circuit and a 180° balun output transformer. The output termination topology is applied for minimizing power losses due to the existing parasitic capacitance of the LDMOS-FET power devices. From the measured results, a drain efficiency of 63% at 47 dBm output power was achieved.
Microwave Symposium Digest, 2005 IEEE MTT-S International; 07/2005
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ABSTRACT: This paper presents a RF high-power Doherty amplifier for improving the efficiency of a 30-W feedforward linear amplifier used in wide-band code-division multiple-access (W-CDMA) base-station applications. A high-power Doherty amplifier using a single push-pull LDMOS field-effect transistor is proposed as the main amplifier of a feedforward linear amplifier. The peaking amplifier's compensation line and gate bias effects are analyzed at the 6-dB backoff point. From the experimental results of a forward-link one-carrier W-CDMA, a 2.2% power-added efficiency improvement at an adjacent channel leakage power ratio linearity of -60 dBc is achieved in comparison to a conventional feedforward class-AB amplifier.
IEEE Transactions on Microwave Theory and Techniques 02/2005; · 1.85 Impact Factor
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ABSTRACT: Digital predistortion has been shown to effectively address the growing demand for highly linear and more power efficient amplifiers in base stations. Doherty amplifiers have demonstrated greater efficiency than traditional amplifiers but with a high adjacent channel power ratio. This paper describes a digital predistortion implementation within the ADS Ptolemy environment and a connected solution consisting of an electronic signal generator (ESG), power amplifier (PA), and vector signal analyzer (VSA). The connected solution enables the evaluation of a PA's performance with the addition of digital predistortion. A 30 W Doherty amplifier with a weak memory was evaluated within the connected solution. Two WCDMA carriers were applied to our system, and the results show 15 dB reduction at 5 MHz offset and 12 dB reduction at -5 MHz offset.
Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th; 10/2004
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ABSTRACT: This paper presents a RF high power Doherty amplifier for improving the efficiency of a 30 W Feedforward linear amplifier used in W-CDMA base-station applications. A Doherty amplifier using a single push-pull LDMOS FET is proposed as the main amplifier of the Feedforward linear amplifier. The peaking amplifier's compensation line and gate bias effects are analyzed, at a 6 dB backed off. From the experimental results, a 2.2% PAE improvement on the 30 W Doherty Feedforward linear amplifier is achieved in comparison to a conventional Feedforward linear amplifier.
Microwave Symposium Digest, 2004 IEEE MTT-S International; 07/2004
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ABSTRACT: The modulation frequency affects the asymmetric intermodulation distortion (IMD) products of a RF power amplifier. This effect reduces IMD cancellation performance of power amplifiers in connection with predistortion linearization. A phase extraction method to determine phase difference between upper and lower third-order IMD products and a phase compensation circuit using an envelope injection technique is proposed. The experimental results demonstrate a significant improvement in the third-order IMD cancellation performance.
IEEE Microwave and Wireless Components Letters 05/2004; · 1.72 Impact Factor
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ABSTRACT: A novel multi-order predistortion linearizer is proposed to achieve independent control of the third- and fifth-order intermodulation products in high power amplifier. The approach is based on a combination of the second harmonic technique and the difference frequency technique. The second harmonic and difference frequency terms are generated using an envelope detector and two frequency multipliers. The RF predistorter has the advantage of low insertion loss and the requirement of a short delay line. Experimental results demonstrate an adjacent channel power ratio (ACPR) reduction of 11 dB for W-CDMA, at 2140 MHz.
IEEE Microwave and Wireless Components Letters 11/2003; · 1.72 Impact Factor
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ABSTRACT: The modulation frequency affects the asymmetric intermodulation distortion (IMD) products of a RF power amplifier. This effect reduces IMD cancellation performance of power amplifiers in connection with predistortion linearization. A phase extraction method to determine phase difference between upper and lower 3<sup>rd</sup> order IMD products and a phase compensation circuit using an envelope injection technique is proposed. The experimental results demonstrate a significant improvement in the 3<sup>rd</sup> order IMD cancellation performance.
Microwave Symposium Digest, 2003 IEEE MTT-S International; 07/2003
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ABSTRACT: An RF predistortion linearizer using a combination of a second harmonic and a difference frequency technique is proposed to reduce 3<sup>rd</sup> and 5<sup>th</sup> order intermodulation products in high power amplifiers. The second harmonic and difference frequency terms are generated using an envelope detector and two frequency multipliers. The RF predistorter has the advantage of low insertion loss and a short delay line requirement. From the experimental results, adjacent channel power ratio (ACPR) reduction of 11 dB is achieved for W-CDMA at 2140 MHz.
Vehicular Technology Conference, 2002. Proceedings. VTC 2002-Fall. 2002 IEEE 56th; 02/2002
