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Recent broadcast standards support Layered Division Multiplexing (LDM) to achieve graceful degradation as signal quality degrades at the receiver. LDM is accomplished by using different constellations within the same Radio Frequency (RF) spectrum. LDM thus enables delivering multiple service tiers in a single broadcast channel. LDM when used in conjunction with scalable source coding codecs such as...
In this paper, we present an augmented radial basis function (RBF) neural network (ARBFNN) to linearize a wideband Doherty RF power amplifier with strong memory effects., A 51-dBm Doherty RF power amplifier and a 25 MHz mixed test signal were utilized to validate the performance of the ARBFNN nonlinear model and predistorter. The validation results illustrated that the ARBFNN nonlinear model outperforms...
This paper presents design and linearization of an inverse class-F RF power amplifier using a GaN HEMT transistor, which is operated at the band of 910MHz-950MHz. A harmonic control network is utilized to compensate the parasitic effect brought from the parasitic parameters network. The measured results with a 930-MHz continuous-wave (CW) signal illustrated that highly efficient operation is achieved...
<?Pub Dtl?>Accurately modeling the memory effects is critical in modeling and nonlinearity pre-compensation for wideband radio frequency (RF) power amplifiers (PAs) with strong memory effects. In this paper, the memory effects are divided into two categories: lagging memory effect and leading memory effect, which are defined based on the input samples located after and before the current output...
How to accurately control the gate bias voltage of a Doherty RF power amplifier is an important problem that has to be resolved for developing high efficiency RF power amplifiers. This paper proposes a digital bias solution to obtain adjustable accurate bias voltage, and discusses the implementation procedure of high-accuracy bias voltage control software for Doherty RF power amplifiers in detail...
In this paper, a memory polynomial nonlinear model-based pre-distorter is utilized to linearize a wideband RF power amplifier for a TD-LTE system. The nonlinear model is briefly introduced and frame structure of the TD-LTE signal has been described in detail. In addition, the compensation results of nonlinear distortions for the TD-LTE signal are presented, which illustrated that the memory polynomial...
In this paper, digital pre-distorter based on the memory polynomial model is utilized to compensate the nonlinearity of the Multi-Carrier TD-SCDMA RF power amplifiers (RFPA). Three-carrier TD-SCDMA signals with three different sub-frame configurations are used as test signals, a 47-dBm peak-envelope-power LDMOS power amplifier is designed to validate the performance of the pre-distorter. The digital...
Based on the bias control technique for RF power amplifiers, this paper discusses the design of automatic temperature compensation software which can accurately control the gate voltage of RF power amplifiers with the variation of the temperature. At first the paper analyzes the temperature characteristics of RF power amplifiers, and then a solution to automatically implement temperature compensation...
An intelligent gate voltage control system is proposed in accordance with changes of temperature and drain current. The system is implemented in an embedded ARM platform ADuC7026 (ARM7), in which the uC/OS-II operating system is utilized to the control the compensation process for the deterioration of the LDMOS power amplifier (PA) at different temperatures in real-time. With the interrelation of...
In Time Division Duplex(TDD) system, the radio frequency (RF) power amplifier in a repeater is turned on only when it receives RF signal, thus implementing the sub-frame synchronization and the second conversion point of timeslots is important in TDD system. This paper introduce a bias circuit design to realize the control of the RF power amplifier in the down-link through envelop detection of the...
In this paper, a low-cost hardware implementation of a Look-up-Table(LUT) based digital predistorter (DPD) using Field Programmable Gate Array(FPGA) for power amplifier linearization is proposed. The LUT predistoter is implemented in Altera Stratix II DSP Development Board to simulate the inverse model for memoryless wide-band RF power amplifiers. The parameters of the LUT predistoter are identified...
In this paper, the nonlinearity of an RF power amplifier is divided into the static nonlinearity and the dynamic one. A Hammerstein-like nonlinear model is presented accordingly. The dynamic nonlinearity mainly attributes to the memory effect. The memory effect is divided into linear memory effect and the nonlinear one. The linear memory effect can be simulated by a linear filter, and the nonlinear...
Wideband wireless transmitters will exhibit strong memory effects which heavily compromise the linearization performance of traditional memoryless predistorters. In this paper, the nonlinear behaviors of a wideband wireless transmitter are analyzed. According to the nonlinearity analysis, a novel memory effect separation based linearization technique is presented to linearize the wideband wireless...
In this paper, FPGA implementation of augmented Hammerstein predistorters for linearizing wideband RF power amplifiers with memory effects is presented. The augmented Hammerstein nonlinear model based predistorter is briefly introduced. The implementation method of the augmented Hammerstein predistortion on FPGA is described in details. The experimental platform based on Agilent vector signal generators...
Generalized Hammerstein models can be used to accurately mimic the dynamic nonlinear behaviors of RF power amplifiers or transmitters. A high efficient parameter extraction algorithm for the generalized Hammerstein model is an essential problem for implementing the nonlinear model in a cheap microprocessor. In this paper, a modified systolic array based QRD-RLS algorithm, which is suitable for implementing...
This paper presents a design approach for high efficiency RF power amplifiers with dynamic biases for TDSCDMA systems. The design principle of a PA with dynamic bias is described in detail. The improvement of the power-added efficiency (PAE) is achieved by the drain bias control technique according to the variation of the input power. The simulation results illustrated that this PA can achieve high...
Systolic array is a hardware implementation of fast speed signal and data process using parallel pipeline method. The first systolic implement of QRD-RLS algorithm presented by Gentleman and Kung in 1981, is only suitable to solve the linear problem. In this paper, we will present how to use modified systolic array based QRD-RLS algorithm to identify the model parameters of the memory polynomial nonlinear...
In this paper, the concept of linear and nonlinear memory effects are proposed to explore the internal mechanism of the memory effects. The identification procedure of the linear and nonlinear memory effects is discussed in details. Finally the experimental validation results demonstrate that the nonlinear memory effects are significant for wideband RF power amplifier and cannot be ignored.
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