3 research outputs found
RF Power Amplifier and Its Envelope Tracking
This dissertation introduces an agile supply modulator with optimal transient performance for the envelope tracking supply in linear power amplifiers. For this purpose, an on-demand current source module, the bang-bang transient performance enhancer (BBTPE), is proposed. Its objective is to follow fast variations in input signals with reduced overshoot and settling time without deteriorating the steady-state performance of the buck regulator. The proposed approach enables fast system response through the BBTPE and an accurate steady-state output response through a low switching ripple and power efficient dynamic buck regulator. Fast output response with the help of the added module induces a slower rise of inductor current in the buck converter that further assists the proposed system to reduce both overshoot and settling time. To demonstrate the feasibility of the proposed solution, extensive simulations and experimental results from a discrete system are reported. The proposed supply modulator shows 80% improvement in rise time along with 60% reduction in both overshoot and settling time compared to the conventional dynamic buck regulator-based solution. Experimental results for a PA using the LTE 16-QAM 5 MHz standard shows improvement of 7.68 dB and 65.1% in ACPR and EVM, respectively.
In a polar power amplifier, the input signal splits into phase and amplitude components using a non-linear conversion operation. This operation broadens the spectrum of the polar signal components. The information of amplitude and phase contains spectral images due to the sampling operation in non-linear conversion operation. These spectral images can be large and cause out-of-band emission in the output spectrum. In addition, during the recombination process of phase and amplitude, a delay mismatch between amplitude and phase signals, which can occur due to separate processing paths of amplitude and phase signals, causes out-of-band emissions, also known as spectral regrowth. This dissertation presents solutions to both of the issues of digital polar power amplifier: spectral images and delay mismatch. In order to reduce the problem of spectral images, interpolation of phase and amplitude is proposed in this work. This increases the effective sampling frequency of the amplitude and phase, which helps to improve the linearity by around 10 dB. In addition, a novel calibration scheme is proposed here for the delay mismatch between phase and amplitude path in a digital polar power amplifier. The scheme significantly reduces the spectral regrowth. The scheme uses the same path for phase and amplitude delay calculation after the recombination that allows having a robust calibration. Furthermore, it can be executed during the empty transmission slots. The proposed scheme is designed in a 40 nm CMOS technology and simulated with a 64-QAM IEEE 802.11n wireless standard. The scheme achieved 7.57 dB enhancement in ACLR and 84.35% improvement in EVM for a 3.5 ns mismatch in phase and amplitude path
RF Power Amplifier and Its Envelope Tracking
This dissertation introduces an agile supply modulator with optimal transient performance for the envelope tracking supply in linear power amplifiers. For this purpose, an on-demand current source module, the bang-bang transient performance enhancer (BBTPE), is proposed. Its objective is to follow fast variations in input signals with reduced overshoot and settling time without deteriorating the steady-state performance of the buck regulator. The proposed approach enables fast system response through the BBTPE and an accurate steady-state output response through a low switching ripple and power efficient dynamic buck regulator. Fast output response with the help of the added module induces a slower rise of inductor current in the buck converter that further assists the proposed system to reduce both overshoot and settling time. To demonstrate the feasibility of the proposed solution, extensive simulations and experimental results from a discrete system are reported. The proposed supply modulator shows 80% improvement in rise time along with 60% reduction in both overshoot and settling time compared to the conventional dynamic buck regulator-based solution. Experimental results for a PA using the LTE 16-QAM 5 MHz standard shows improvement of 7.68 dB and 65.1% in ACPR and EVM, respectively.
In a polar power amplifier, the input signal splits into phase and amplitude components using a non-linear conversion operation. This operation broadens the spectrum of the polar signal components. The information of amplitude and phase contains spectral images due to the sampling operation in non-linear conversion operation. These spectral images can be large and cause out-of-band emission in the output spectrum. In addition, during the recombination process of phase and amplitude, a delay mismatch between amplitude and phase signals, which can occur due to separate processing paths of amplitude and phase signals, causes out-of-band emissions, also known as spectral regrowth. This dissertation presents solutions to both of the issues of digital polar power amplifier: spectral images and delay mismatch. In order to reduce the problem of spectral images, interpolation of phase and amplitude is proposed in this work. This increases the effective sampling frequency of the amplitude and phase, which helps to improve the linearity by around 10 dB. In addition, a novel calibration scheme is proposed here for the delay mismatch between phase and amplitude path in a digital polar power amplifier. The scheme significantly reduces the spectral regrowth. The scheme uses the same path for phase and amplitude delay calculation after the recombination that allows having a robust calibration. Furthermore, it can be executed during the empty transmission slots. The proposed scheme is designed in a 40 nm CMOS technology and simulated with a 64-QAM IEEE 802.11n wireless standard. The scheme achieved 7.57 dB enhancement in ACLR and 84.35% improvement in EVM for a 3.5 ns mismatch in phase and amplitude path
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Design and Linearization of Energy Efficiency Power Amplifier in Nonlinear OFDM Transmitter for LTE-5G Applications. Simulation and measurements of energy efficiency power amplifier in the presence of nonlinear OFDM transmitter system and digital predistortion based on Hammerstein-Wiener method
This research work has made an effort to understand a novel line of radio frequency
power amplifiers (RFPAs) that address initiatives for efficiency enhancement and
linearity compensation to harmonize the fifth generation (5G) campaign. The objective
is to enhance the performance of an orthogonal frequency division multiplexing-long
term evolution (OFDM-LTE) transmitter by reducing the nonlinear distortion of the
RFPA.
The first part of this work explores the design and implementation of 15.5 W class AB
RF power amplifier, adopting a balanced technique to stimulate efficiency enhancement
and redeeming exhibition of excessive power in the transmitter. Consequently, this work
goes beyond improving efficiency over a linear RF power amplifier design; in which a
comprehensive investigation on the fundamental and harmonic components of class F
RF power amplifier using a load-pull approach to realise an optimum load impedance
and the matching network is presented. The frequency bandwidth for both amplifiers was
allocated to operate in the 2.620-2.690 GHz of mobile LTE applications.
The second part explores the development of the behavioural model for the class AB
power amplifier. A particular novel, Hammerstein-Wiener based model is proposed to
describe the dynamic nonlinear behaviour of the power amplifier. The RF power amplifier
nonlinear distortion is approximated using a new linear parameter approximation
approach. The first and second-order Hammerstein-Wiener using the Normalised Least
Mean Square Error (NLMSE) algorithm is used with the aim of easing the complexity of
filtering process during linear memory cancellation. Moreover, an enhanced adaptive
Wiener model is proposed to explore the nonlinear memory effect in the system. The
proposed approach is able to balance between convergence speed and high-level
accuracy when compared with behavioural modelling algorithms that are more complex
in computation.
Finally, the adaptive predistorter technique is implemented and verified in the OFDM
transceiver test-bed. The results were compared against the computed one from
MATLAB simulation for OFDM and 5G modulation transmitters. The results have
confirmed the reliability of the model and the effectiveness of the proposed predistorter.Fundacão para a Ciência e a Tecnologia, Portugal, under
European Union’s Horizon 2020 research and innovation programme ... grant agreement H2020-MSCA-ITN- 2016 SECRET-722424
I also acknowledge the role of the National Space Research and Development Agency (NASRDA)
Sokoto State Government
Petroleum Technology Trust Fund (PTDF