Digital Equalization for mmWave Analog Up-/Down-Converters
Time-interleaving of analog-to-digital converters (ADC) is used to increase the sampling rate of high performance digitizers. The new 10-bit digitizers from Guzik use Keysight ADCs, where 160 individual ADCs are interleaved to sample up to 64 GSPS-160 “slices” each sampling at 400 MSPS-to form two analog channels, each at 32 GSPS. Time-interleaving that many ADCs makes it challenging to achieve high spurious-free dynamic range. Guzik’s patented digital equalization technology reduces mismatch between slices, non-flatness of the frequency response and group delay of the digitizer to create a calibrated baseband receiver covering DC to 10 GHz with an input signal range from −32 to +22 dBm.
This same technology has been used to equalize the frequency response and group delay of up- and down-converters, working with the digitizer to create a “reference calibration plane” at the down-converter input (i.e., an RF reference plane) and the up-converter input (i.e., an IF reference plane). The equalization de-embedding technology significantly reduces the linear distortion of the external frequency converters. Non-flatness of the frequency response of the up- and down-converters was reduced from ±1.5 dB to ±0.1 dB, and non-flatness of group delay was reduced from ±1.25 ns to ±100 ps. At 28 GHz, the resulting residual error vector magnitude through the up- and down-converters was reduced from ~11 percent (−20 dB) to ~1 percent (−40 dB) for a 16-QAM, 625 Msymbol per second signal with a root-raised-cosine filter factor of 0.35. For signals with up to 2.5 GHz bandwidth, on the output of the mmWave down-converter, the equalization is performed real-time inside the Intel FPGA-based digital processor of Guzik’s ADP7000 series digitizers, using the patented digital down-converter.
Guzik Technical Enterprises
Mountain View, Calif.
Read more about these results in this article published in Microwave Journal.