Real-time Ultra-Wideband Frequency Sweeping Channel Sounder for 3-18 GHz

This paper presents system concept, calibration and example measurements of a novel ultra-wideband, real-time channel sounder. The sounder operates in the frequency range from 3 GHz to 18 GHz thus providing a Fourier delay resolution of 66.7 ps. The developed sounder measures overlapping sub bands of 1 GHz bandwidth to cover the whole frequency range. This allows us to use a waveform generator and a digitizer with relatively lower sample rates and significantly lowers the cost compared to sampling the whole band at once. With the transmit power of 40 dBm, the maximum measurable path loss is 132 dB without accounting possible antenna gains. In this work, we also describe the calibration procedure along with the method to patch sub-bands into a combined channel response. This approach is validated by comparing the results from vector network analyzer(VNA) measurements performed in the same static environment. In contrast to VNAs, however, our sounder is real-time and can measure in dynamic environments with maximum Doppler spreads up to 166.7 Hz. Additionally, we present sample results from the first measurement campaign performed in an urban cellular scenario covering 3-18 GHz.