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This paper is projected towards improving the adjacent channel power ratio (ACPR) for LInear amplification using Nonlinear Component (LINC) power amplifiers in OFDM based wireless systems using digital baseband filtering for branch signals. The IEEE802.11g standard, which operates at 2.4 GHz, is used to show the amount of improvement. Results show that the ACPR is improved using a least square filter,...
Modern radio-frequency transmitters require digital predistortion to fulfil linearity requirements while operating the RF PA in highly efficient modes. A least-squares process is typically employed to calculate the predistorter coefficients. The least-squares method requires complex mathematical operations and relies on the observation, at the input and output of the PA, of a specific realization...
A linerization technique for reducing the thirdorder intermodulation products that uses simultaneous injection of the second harmonics at the amplifier input and output has been investigated in this paper. This technique was considered in theory and by simulation. The amplifier with the second harmonics components were designed and simulated using Agilent Design System (ADS) program. The linearization...
In this paper, we present an investigation into the performance of digital pre-distortion (PD) techniques designed to compensate for power amplifier (PA) impairments that occur during the transmission of spectrally agile waveforms. Spectrally agile transmission techniques, such as non-contiguous orthogonal frequency division multiplexing (NC-OFDM), have been receiving an increasing amount of attention...
In this paper, an evaluation of unwanted effects in Multiple Input Multiple Output (MIMO) transmitters is described. Complete 2×2 and 4×4 MIMO Orthogonal Frequency Division Multiplex (OFDM) transmitters are simulated for the purpose of quantifying all potential unwanted effects such as Power Amplifiers' (PAs) nonlinearity, linear and nonlinear crosstalk, and IQ modulator imperfections. An experimental...
This paper examines the sources of Receive Band Noise (RxBN) in the Envelope Tracking Power Amplifier (ETPA) system. The Envelope Amplifier (EA) nonlinearity is found to be the dominant cause. The output spectrum of the ETPA is compared for the cases of highly linear class-A EA and nonlinear EA. To improve the out-of-band noise performance of the ETPA, Digital Pre-Distortion (DPD) on the envelope...
In this paper, we present an asymmetrical Doherty amplifier (DA) that can enhance the efficiency at a 9.5 dB backoff from its saturated output power (PSAT). The asymmetrical DA consists of a peak amplifier and a carrier amplifier with two and one 210 W gallium nitride (GaN) high-electron-mobility transistors (HEMTs), respectively. A Wilkinson combiner at the output of the peak amplifier enables the...
In this paper, we investigate the impact of a receiver amplifier on orthogonal frequency division multiplexing (OFDM) and single-carrier block transmission (SCBT) systems which are two potential air interfaces for future short-range wireless communications at 60GHz radio spectrum. We derive a generalized baseband equivalent model for the receiver amplifier by using a power series to capture the nonlinear...
In this paper we evaluate the effect of applying peak-to-average power ratio (PAPR) reduction and digital pre-distortion (DPD) on radio frequency power amplifiers when an orthogonal frequency division multiplexing (OFDM) signal is used. The PAPR reduction method, presented as a convex problem, is based on reshaping the time domain signal by redistributing its energy in the frequency domain, with respect...
RF circuitry plays a crucial role in the success of modern wireless communications. The linearity of RF devices, such as the power amplifier studied in this paper, is the key in determining the overall system performance. In communication systems adopting Orthogonal Frequency-Division Multiplexing (OFDM), non-ideal effects are summarized by the measurement of the Error Vector Magnitude (EVM). During...
This paper presents a practical application of a method for generating slew-rate limited envelopes in order to drive the dynamic supply of envelope tracking (ET) power amplifiers (PAs). The proposed method results useful to generate slower versions of the transmitted signal's envelope to cope with the slew-rate and bandwidth limitations of envelope amplifiers. Moreover, this paper shows experimental...
In this paper, an extended Hammerstein architecture for dynamic behavioral modeling of GaN power amplifier (PA) is presented. Static strong nonlinearities, long-term linear memory effects and first-order nonlinear dynamics are considered in the model. The parameters of the proposed model are estimated by least square algorithm. For experimental identification and validation, a 20MHz four-carrier orthogonal...
Increasing the efficiency of mobile communication networks while keeping operational and maintenance cost at reasonable level is a major task for operators. Multimode radios capable of operating according to various mobile broadband standards, such as WCDMA, WiMAX and LTE, represent the new trend for resolving these challenges. A transparent radio solution, agnostic to wireless standards, with high...
Fourth generation systems require the use of both amplitude and phase modulation to efficiently utilize the available spectrum and to obtain high data rates, hence imposing stringent requirements on the power amplifier in terms of efficiency and linearity and requires the power amplifier to operate linearly and efficiently. The B3G base station transceiver Doherty power amplifier was designed to operate...
Due to the escalating costs associated with testing of precision RF components, there is a pressing need for identifying novel test methods that allow RF circuits to be tested with low cost test instrumentation. Specifically, test costs can be lowered significantly if stimulus from a digital pattern generator can be adapted to serve as test stimulus for analog/RF circuits. In this paper, we propose...
This paper presents a time domain envelope measurement system that enables the study and the optimization of high efficiency and linear power amplifiers by applying both envelope tracking and digital base band predistorsion techniques. A man focus of this paper is the description of the set up architecture along with its capability to achieve in depth investigations on the dynamic behavior of envelope...
Recently a number of polar transmitters for the multi-mode transmission of Wireless-Local-Area-Network (WLAN) and Bluetooth signals have been proposed. These polar transmitters use envelope modulators based on digital-to-analog converters (DACs) as power amplifiers. Such an approach is very useful when the maximum theoretical efficiency of the power-amplifier digital-to-analog converter (PA-DAC) is...
Envelope elimination and restoration (EER) power amplifier architecture can achieve high efficiency and linearity. However, when used with modern modulation schemes such as orthogonal frequency division multiplexing (OFDM) and wideband code division multiple access (W-CDMA), it suffers from expanded bandwidth problem. This paper shows that, the straightforward bandwidth limitation results in poor...
This paper describes the design of a class E power amplifier (PA) destined to be used as the final stage of a polar transmitter under IEEE 802.16e Mobile WiMAX signal excitation. Based on a 60 W GaN HEMT device, the load condition for optimum efficiency is set close to the maximum value of the power generating function, as defined in, for an OFDMA modulating signal. The possible impact of such average-based...
The need for linearity is one of the principal demands in the design of modern power amplifiers for OFDM systems. QPSK or QAM signals are typically generated by modulating both I and Q subcarriers so the resultant of these two components has simultaneous amplitude and phase modulation which changes with the contents of the transmitted information. Despite the fact that the number of subcarriers is...
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