RFSoC Development Kit Getting Started Guide
Page 14
Experiment 1: Generating a CW Tone through the TX Path
The power amplifier (PA) output in each channel of the Qorvo RF card is routed back to an RF-ADC
through a directional coupler, providing an observation path typically used for digital pre-distortion of the
PA. In this experiment we shall generate a CW tone in the digital domain from the RFSoC Explorer
graphical user interface (GUI) running under MATLAB on the host PC. The digital signal data will be
downloaded to the ZCU111 over TCP/IP and stored in DDR4 memory dedicated to the RF-DACs.
Once download is complete, the signal data will be read out of the memory buffer through DMA and
routed to the digital up-converter (DUC) within the RF_DAC tile, interpolated to a higher sampling rate,
frequency-shifted to 1842 MHz through the complex mixer and converted to the analog domain by the
RF-DAC. This process repeats indefinitely, constantly looping back to the start of the data in the memory
buffer after reaching the end to generate a CW tone at the output of the DAC. To avoid discontinuity
between the start and end loop-points of the CW tone, RFSoC Explorer automatically adjusts the signal
length to an integer number of cycles, thereby ensuring a smooth zero-crossing upon looping back to
the start of data.
The directional coupler at the output of the PA routes the RF signal back towards an RF-ADC on the
ZCU111, with 20 dB of attenuation. Normally intended as an observation path for digital pre-distortion
and PA linearization, this provides a convenient means of re-acquiring the PA output signal into the
digital domain without any external connections. Our objective here is simply to demonstrate usage of
RFSoC Explorer to generate and acquire signals and control the RF signal chain; we shall leave PA
linearization for another day.
Figure 10 - TX signal chain and DPD observation path
1. Start MATLAB R2019b
2. In MATLAB, go to the APPS tab and click the
icon for
Avnet RFSoC Explorer
.
