Dual-band Power Amplifier for Wireless Communication Base Stations

In wireless communication systems, multiple standards have been implemented to meet the past and present demands of different applications. This proliferation of wireless standards, operating over multiple frequency bands, has increased the demand for radio frequency (RF) components, and consequently power amplifiers (PA) to operate over multiple frequency bands. In this research work, a systematic approach for the synthesis of a novel dual-band matching network is proposed and applied for effective design of PA capable of maintaining high power efficiency at two arbitrary widely spaced frequencies. The proposed dual-band matching network incorporates two different stages. The first one aims at transforming the targeted two complex impedances, at the two operating frequencies, to a real one. The second stage is a dual-band filter that ensures the matching of the former real impedance to the termination impedance to 50 Ohm. Furthermore, an additional transmission line is incorporated between the two previously mentioned stages to adjust the impedances at the second and third harmonics without altering the impedances seen at the fundamental frequencies. Although simple, the harmonic termination control is very effective in enhancing the efficiency of RF transistors, especially when exploiting the Class J design space. The proposed dual-band matching network synthesis methodology was applied to design a dual-band power amplifier using a packaged 45 W gallium nitride (GaN) transistor. The power amplifier prototype maintained a peak power efficiency of about 68% at the two operating frequencies, namely 800 MHz and 1.9 GHz. In addition, a Volterra based digital predistortion technique has been successfully applied to linearize the PA response around the two operating frequencies. In fact, when driven with multi-carrier wideband code division multiple access (WCDMA) and long term evolution (LTE) signals, the linearized amplifier maintained an adjacent channel power ratio (ACPR) of about 50 dBc and 46 dBc, respectively

Two Port Network Theory Based Design Method of Broadband Doherty Power Amplifier

LTE-Advanced (LTE-A) is a widely used communication standard and it mainly features Carrier aggregation (CA). CA increases the user data rate and efficiently exploits the fragmented spectrum by combining various carrier frequencies. The intrinsic multi-band and multi-standard of CA, along with the existing high peak-to-average power ratio (PAPR), brings the challenges of broadband requirement and back-off (BO) efficiency enhancement when designing radio frequency power amplifiers (PA). The above two challenges inspire research interest in designing of broadband Doherty power amplifiers (DPAs), which maintain the high efficiency at BO power level and perform constantly versus frequency. In this work, the continuous design space was discussed. Output combining and matching network (OCMN) and its impact on the impedances shown to the two transistors were analyzed based on two port network theory. ABCD parameters of matching networks was formulated to accommodate continuous class-B (class-J) operation to DPAs. Second harmonic was terminated to avoid clipping and efficiency degradation. By enlarging design space, the bandwidth was substantially expanded. The proposed design methodology allowed the adsorption of parasitics which was the one of the bandwidth limiting factor. To validate the proposed methodology, an 8 Watts DPA was simulated to operate from 3 GHz to 5 GHz using Cree Gallium nitride (GaN) High-electron-mobility transistors (HEMTs). And simulation results showed that the 6dB BO efficiency was above 40% and Peak-envelope-power (PEP) of 50% over the frequency range of 3GHz to 5GHz. The Doherty power amplifier prototype is fabricated on substrate of Rogers4003C and assembled in house. Continuous wave measurement showed that the PA could provide 8.2 - 10.6 dB gain in the frequency band of 2.7 to 4.3 GHz. The 6 dB back off efficiency was 40% to 43%. And at peak power, the drain efficiency reached 48% to 60%. 80 MHz inter-band modulated signal and 15MHz dual band signal measurement were carried out to investigate the linearizability. In the inter-band measurement, average power around 33dBm and average drain efficiency of 46% was obtained with PAPR of 6.4 dB. ACLR above 48.7 dBc after DPD verified the easiness of linearization for this PA. Dual band measurement using two carriers at 2.8 and 3.2 GHz showed even when the PAPR of two band were 7.6 and 8.0 dB separately, average power of 32.3 dBm power can still be extracted with average efficiency of 40.5%. ACLR of 49.5 and 46.7 dBc of those two bands were good endorsement of the capability of inter-band concurrent amplification

Demonstration of a switchless Class E/Fodd dual-band power amplifier

A 250 W dual-band power amplifier belonging to the Class E/F switching amplifier family is presented. The amplifier operates in the 7 MHz and 10 MHz HAM bands, achieving 16 dB and 15 d B gain with power added efficiencies (PAE) of 92% and 87% in those bands, respectively. It utilizes dual-resonant passive input and output networks to achieve high-efficiency Class E/Fodd operation at both frequencies of operation, allowing the same passive networks to be used for both frequency bands without the use of band-select switches

A Fully-Integrated Reconfigurable Dual-Band Transceiver for Short Range Wireless Communications in 180 nm CMOS

© 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.A fully-integrated reconfigurable dual-band (760-960 MHz and 2.4-2.5 GHz) transceiver (TRX) for short range wireless communications is presented. The TRX consists of two individually-optimized RF front-ends for each band and one shared power-scalable analog baseband. The sub-GHz receiver has achieved the maximum 75 dBc 3rd-order harmonic rejection ratio (HRR3) by inserting a Q-enhanced notch filtering RF amplifier (RFA). In 2.4 GHz band, a single-ended-to-differential RFA with gain/phase imbalance compensation is proposed in the receiver. A ΣΔ fractional-N PLL frequency synthesizer with two switchable Class-C VCOs is employed to provide the LOs. Moreover, the integrated multi-mode PAs achieve the output P1dB (OP1dB) of 16.3 dBm and 14.1 dBm with both 25% PAE for sub-GHz and 2.4 GHz bands, respectively. A power-control loop is proposed to detect the input signal PAPR in real-time and flexibly reconfigure the PA's operation modes to enhance the back-off efficiency. With this proposed technique, the PAE of the sub-GHz PA is improved by x3.24 and x1.41 at 9 dB and 3 dB back-off powers, respectively, and the PAE of the 2.4 GHz PA is improved by x2.17 at 6 dB back-off power. The presented transceiver has achieved comparable or even better performance in terms of noise figure, HRR, OP1dB and power efficiency compared with the state-of-the-art.Peer reviewe

4.5-/4.9-GHz-Band Selective High-Efficiency GaN HEMT Power Amplifier by Characteristic Impedance Switching

A 4.5-/4.9-GHz band-selective GaN HEMT high-efficiency power amplifier has been designed and evaluated for next-generation wireless communication systems. An optimum termination impedance for each high-efficiency operation band was changed by using PIN diodes inserted into a harmonic treatment circuit at the output side. In order to minimize the influence of the insertion loss of the PIN diodes, an additional line is arranged in parallel with the open-ended stub used for second harmonic treatment, and the line and stub are connected with the PIN diodes to change the effective characteristic impedance. The fabricated GaN HEMT amplifier achieved a maximum power-added efficiency of 57% and 66% and a maximum drain efficiency of 62% and 70% at 4.6 and 5.0GHz, respectively, with a saturated output power of 38dBm, for each switched condition

High Efficiency Power Amplifier Based on Envelope Elimination and Restoration Technique

Due to complex envelope and phase modulation employed in modern transmitters it is necessary to use power amplifiers that have high linearity. Linear power amplifiers (classes A, B and AB) are commonly used, but they suffer from low efficiency especially if the transmitted signal has high peak to average power ratio (PAPR). Kahn's technique based on envelope elimination and restoration (EER) is based on idea that high efficiency power supply (envelope amplifier) could be used to modulate the envelope of high efficient non linear power amplifiers (classes D or E). This paper presents solutions for power amplifier that performs envelope modulation and class E amplifier that is used as a non linear amplifier. The envelope amplifier is implemented as a multilevel converter in series with linear regulator and can provide up to 100 W of instantaneous power and reproduce 2 MHz sine wave. The implemented Class E amplifier can operate at 120 MHz with efficiency near to 85%. The envelope amplifier and class E amplifier have been integrated and efficiency and linearity of the implemented transmitter has been measured and presente