Measurement setup

The remoteUPCLab infrastructure, which allows users to remotely send and receive beyond 5G waveforms for DPD benchmarking, is based on a Rohde & Schwarz (R&S) SMW200A vector signal generator (VSG) and a R&S FSW50 signal and spectrum analyzer (SSA) communicating with a control PC running a MATLAB SFTP server application.

 This year’s competition centers on the linearization of a Load Modulated Balanced Amplifier (LMBA) operating in the 1.8–2.4 GHz frequency band. The LMBA employs a dual-input architecture built with Wolfspeed CGH40025F GaN transistors and was developed by Roberto Quaglia and his research team at Cardiff University. For this edition, the power amplifier (PA) will be driven by a 200 MHz instantaneous bandwidth signal centered at 2 GHz. This signal consists of five aggregated carriers, each occupying 40 MHz. Throughout the competition, the test signal will vary, with carriers being selectively activated or deactivated across iterations. The Digital Predistortion (DPD) algorithm must demonstrate robustness under these changing conditions.

The competition emphasizes not only improving linearity performance but also enhancing the power efficiency of the LMBA. Power consumption will be monitored, and power efficiency, along with output power, Error Vector Magnitude (EVM), and Adjacent Channel Power Ratio (ACPR), will factor into the overall score, as outlined in the Competition Details section. Additionally, the number of coefficients used in the DPD function will influence scoring.

 The remoteUPCLab server receives baseband IQ waveforms from a remote user. These signals are downloaded into the VSG, which generates and upconverts them into two RF signals: one for the balanced input port and another for the control port of the LMBA.

The Signal and Spectrum Analyzer (SSA) is in charge of RF down conversion and data acquisition of the waveform at the output of the PA, whose IQ data will be sent back to the remote user for DPD processing.

The PA will be operating with varying input signals with a maximum of 200 MHz instantaneous bandwidth. The baseband clock that will be employed in the signal processing operations is 1228.8 MHz, which also corresponds to the IQ A/D and D/A sampling frequencies. The peak output power level from the LMBA is limited to approximately 45 dBm (Psat@2GHz). The settings in the signal analyzer (reference level and input attenuation) are set in such a way as not to distort the measured signal even for the highest peak power levels allowed. This means that you will experience degradation in noise performance when using power levels lower than the maximum allowable level.

We appreciate the support from Rohde & Schwarz and the Cardiff University research group in building the remoteUPCLab.