8-bit Current-Steering DAC
(1) I-V conversion is accomplished using a single-ended TIA.
(2) Waveform generator implemented in ADALM2000.
The pattern generator is used to generate an 8-bit sawtooth signal. Only static parameters are fully characterized for the DAC.
DAC produced a stair-step function with voltages. Change from a minimum of 20 mV to a maximum of 5.02 V.
The data from the static test for every input was collected and written in an excel file. The DNL and INL of the result are calculated below. The maximum value of DNL and INL is 2 LSB and 2.5 LSB respectively.
8-bit SAR ADC
(1) Analog Discovery is used to generate the clock signal and differential input signal. It is also used as a logic analyzer.
(2) Only dynamic parameters are fully characterized for the ADC.
Ramp signal in the time domain. 256 steps, each step lasting for 32 us.
The blue signal is the modulating chirp, and the yellow signal is the output of the radar.
Sweeping Spectrum Analyzer Signal Chain
The blue signal is the triangular wave used for modulation, the green signal is the radar's output.
The green signal is the output of the radar and the blue signal is after mixing with the sweeping LO.
The green signal is the pulse width modulated sweeping LO. The blue signal is the output signal of the mixer filtered by the anti-aliasing filter. Note that the amplitude of the sweeping LO is not decreasing over time, the droop is due to the limited sampling rate of the oscilloscope. The signal has a deterministic pattern at 250 Hz which is the same as the chirp signal. This signal is here because the radar frontend has a strong TX to RX leakage and the modulating pattern is coupled to the RX directly. This signal needs to be filtered out.
The serialized data will be sent to the FPGA and then sent to Matlab where a 64-tap lowpass FIR filter is used to filter the pattern due to TX to RX leakage. Then the result of I^2 + Q^2 is plotted to find out the power at a certain frequency. As shown above, the result of a 1-meter-away object and a 1.5-meter-away object are shown above.