Design and Implementation of a Wideband RF Front-end Add-on Module for Improving Spectrum Measurements in TV and Cellular Frequency Bands

The increasing number of new wireless systems, spectrum underutilization, and user congestion have become challenges in wireless communications. Certain technologies, such as software-defined radio (SDR), have been used for spectrum sensing, resource use, and management applications. The challenge in spectrum sensing implementation lies in both the hardware and the software. In this paper, a wideband RF add-on module consisting of an omnidirectional antenna and a low-noise amplifier was designed and fabricated as hardware improvement for off-the-shelf SDR spectrum sensors. The RF add-on module is targeted for operation at the frequency range of 500 MHz - 1 GHz. The designed printed circular monopole antenna was measured to have a peak return loss of -17 dB and a peak VSWR of 1.35 from 500 MHz to 1 GHz. The antenna has an omnidirectional radiation pattern and a gain of 2.23 dB to 3.94 dB. The implemented low-noise amplifier has a gain of 19 dB to 22 dB from 500 MHz to 1 GHz, with a gain compression point occurring at -1.2 dBm to 3.15 dBm input power level. The measured noise figure was found to be between 1 dB to 3 dB. A prototype of the RF add-on board was fabricated for performance characterization. Simulation and experimental results are provided showing that the designed RF add-on module is able to improve the signal detection across the 500 MHz to 1 GHz frequency band.