Affiliation:
1. Department of Electronic Engineering Tsinghua University Beijing China
2. Institute of Electronic Engineering China Academy of Engineering Physics Mianyang China
3. ZTE Corporation Shanghai China
4. Intelligent RF Radio Laboratory (iRadio Lab) University of Calgary Calgary Canada
Abstract
AbstractHigh frequency (HF) transmitter implemented with the multioctave broadband power amplifier (PA) is always faced with the problem of interfering harmonics because of the nonlinearity of the PA. With the harmonic‐cancelation digital predistortion (HC‐DPD) scheme, the harmonics at lower frequencies can be canceled by the injected components and the harmonics at higher frequencies can be filtered out using a low‐pass filter (LPF). However, the HC‐DPD scheme brings the problem of unwanted spurs while lowering the requirements for sampling rate. In this article, a time‐delay neural network (TDNN) model is used to replace the conventional memory polynomial (MP) model in the forward modeling. Theoretical derivation and simulation results validate the effectiveness of the TDNN model in harmonic cancelation and spur suppression. Further, a frequency‐agile neural network (FANN) model is proposed based on the TDNN model. By adding the carrier frequency to the inputs of the network, the trained model can apply to all the trained carrier frequencies and is more friendly to the frequency‐hopping scenarios. Experiments were carried out on a 2–30 MHz HF transmitter testbench. Measurement results show that the harmonic‐to‐fundamental power ratio, the adjacent channel power ratio (ACPR), and the error vector magnitude (EVM) performances were all improved by more than 20 dB. Compared with the MP model, the unwanted spurs can be suppressed by up to 22 dB. In addition, the number of total model coefficients of the proposed FANN model is only 22% of that of the TDNN model under the frequency‐hopping scenario.
Funder
National Science Fund for Distinguished Young Scholars
Subject
Electrical and Electronic Engineering,Computer Science Applications,Modeling and Simulation
Reference29 articles.
1. Exploring channel diversity in HF communication systems: A matching-potential game approach
2. YinW ChengY ShenL.Adaptive frequency‐hopping in HF communications. Paper presented at: International Conference on Transportation Mechanical and Electrical Engineering (TMEE);2011:427‐430.
3. GuoJ GanL XieL WuS.A high speed HF frequency hopping system based on software radio. Paper presented at: International Conference on Wireless Communications Networking and Mobile Computing;2005:519‐523.
4. A Robust and Scalable Harmonic Cancellation Digital Predistortion Technique for HF Transmitters
5. Digital Front-End in Wireless Communication and Broadcasting