Use DPD Measurement for Cost-Effective Linearization

Introduction

Power  amplifiers (PA) are essential to the overall performance of RF and microwave communication systems. They provide high output power but also introduce nonlinearity to the system. The nonlinearity of PAs generates spectral regrowth, leading to adjacent channel interference and violations of the outof-band emissions standards regulatory bodies mandate.

Digital pre-distortion (DPD) is one of the most cost-effective linearization techniques. It offers the ability to preserve overall efficiency and takes full advantage of advances in digital signal processors and analog-to-digital converters. Therefore, characterizing the nonlinearities of PAs is key for better design choices and device-under-test performance.

Use Case Summary

The power amplifier can operate at a lower power within the linear portion of its operating curve to reduce the nonlinearity of your system. However, newer transmission formats, such as Wideband Code Division Multiple Access (WCDMA) and orthogonal frequency division multiplexing , have high peak-to-average power ratios — large fluctuations in their signal envelopes. Therefore, the power amplifier needs to back off well below its maximum saturated output power to handle infrequent peaks. Those peaks result in very low efficiencies (typically less than 10%). With greater than 90% of the DC power turned into heat and lost, the amplifier’s performance, reliability, and ongoing operating expenses are all degraded.

Solution Overview

The Keysight power amplifier DPD measurement solution enables both pre-DPD and post-DPD, with VXG and UXA hardware serving as the integrated PA testing system. The Keysight VXG signal generator delivers a modulated signal to the PA, and the Keysight UXA signal analyzer measures the output of the PA. The solution helps you reduce distortion and nonlinearity and enables you to troubleshoot your PA under different scenarios.

Learn more at: Digital Pre-distortion and Hardware Verification

Summary

• High-power amplifiers constitute a significant building block of RF and communication systems.

• Characterizing the distortion performance of a transmit amplifier requires a stimulus test signal with low distortion that will not mask the amplifier’s actual performance.

• To achieve the required performance, system designers must characterize and evaluate nonlinear distortion for each subsystem and component.

For more information: Power Amplifier DPD Measurement