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Design Notes

Digital to Analog Converter using VSS basic ADC and DAC blocks

This project demonstrates:

1.   The use of variables and equations to define the settings of a DAC

2.   The splitting of a complex baseband signal with root-raised cosine filtering into it real and imaginary component.

3.   The use of the peak-to-average ratio block to measure the peak voltage of the signal.  The peak voltage is used to calculate the offset value for the signal scale block.

4.   How to make an EVM measurement

5.   The use the input imbalance block to simulate amplitude and phase imbalance as well as DC offset on the signal of a mixer.

The EVM is measured in dB.  Table “EVM in dB” shows the peak voltage of the signal.  The value in this table has to be entered in the box "Calculations for DAC."  The spectrum is shown before and after the DAC, as well as an IQ plot.

System Diagram - QPSK Digital to Analog

Graph - REF and Meas IQ

Graph - Spectrum Before and After

Graph - BB_inphase and Analog_inphase

Graph - Peak V test point

Re(WVFM(TP.Peak_V,1,0,1,0,0,0,0,0)) (us) QPSK Digital to Analog Time Re(WVFM(TP.Peak_V,1,0,1,0,0,0,0,0)) QPSK Digital to Analog
200 4.90668

Graph - EVM in dB

DB(EVM(VSA.M1,1,1,1,1000,1,0,1,0,1,1,10,0,0,0,0,0)) (us) QPSK Digital to Analog Time DB(EVM(VSA.M1,1,1,1,1000,1,0,1,0,1,1,10,0,0,0,0,0)) QPSK Digital to Analog
193.364 -52.0504