https://orcid.org/0000-0003-1742-5526This example shows how to characterize the impact of RF impairments such as IQ imbalance, phase noise, and PA nonlinearities in the performance of an NR RF transmitter. To evaluate the performance, the example considers these measurements:
Error vector magnitude (EVM): vector difference at a given time between the ideal (transmitted) signal and the measured (received) signal.
Adjacent channel leakage ratio (ACLR): measure of the amount of power leaking into adjacent channels and is defined as the ratio of the filtered mean power centered on the assigned channel frequency to the filtered mean power centered on an adjacent channel frequency.
Occupied bandwidth: bandwidth that contains 99% of the total integrated power of the signal, centered on the assigned channel frequency.
Channel power: filtered mean power centered on the assigned channel frequency.
Complementary cumulative distribution function (CCDF): probability of a signal's instantaneous power to be a level specified above its average power.
The model works on a subframe by subframe basis. For each subframe, the workflow consists of these steps:
Generate the baseband waveform using 5G Toolbox functions.
Upconvert the generated waveform to the passband frequency and apply RF filtering and amplification using RF Blockset.
Downconvert the transmitted waveform to baseband frequency.
Calculate the ACLR/ACPR, occupied bandwidth, channel power, and CCDF using the Spectrum Analyzer block.
Demodulate the waveform at the receiver to measure EVM This example demonstrates how to model and test an NR RF transmitter in Simulink. The RF transmitter consists of an IQ modulator, a bandpass filter and amplifiers. To evaluate the performance, the Simulink model considers ACLR and EVM measurements. The example highlights the effect of HPA nonlinearities on the performance of the RF Transmitter. We can explore the impact of altering other impairments as well. For example:
- Increase I/Q imbalance by using the I/Q gain mismatch (dB) and I/Q phase mismatch (Deg) parameters on the IQ Modulator tab of the RF Transmitter block.
- Increase the phase noise by using Phase noise offset (Hz) and Phase noise level (dBc/Hz) parameters on the IQ Modulator tab of the RF Transmitter block.
Additionally, you can check the occupied bandwidth, the channel power, and the CCDF measurements by using the Spectrum Analyzer block.
If you change the carrier frequency or the values in the Waveform Parameters block, you may need to update the parameters of the RF Transmitter components as these parameters have been selected to work for the default configuration of the example. For instance, a change in the carrier frequency requires revising the bandwidth of the filter.
If you select a bandwidth wider than 20MHz, you may need to update the Impulse response duration and Phase noise frequency offset (Hz) parameters of the IQ Modulator block. The phase noise offset determines the lower limit of the impulse response duration.
If the phase noise frequency offset resolution is too high for a given impulse response duration, a warning message appears, specifying the minimum duration suitable for the required resolution.
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