1. Real Time Spectrum Sensing using SDR for RFI Analysis
Mentees: Haozhong Guan, Kevin Minkue Kim PI: Lara Waldrop Mentors: Benjamin Eng, Gonzalo Cucho, Yamuna Phal
Background
Radio Frequency Interference (RFI) is a disturbance generated by an external source that affects an electrical circuit e.g (1) in wireless communication, intermittent connectivity loss, degraded performance or total stop in functioning (2) in radio astronomy, signal loss in Radar Back Scatter, received at the Arecibo observatory (AO)
Objectives
Capture example RF spectrum in the FM (97.5 MHz) and UHF (430 MHz) bands as initial processing step to find RFI
Develop an instrument that measures signal power at a particular band
Measure power content in RF Spectrum
Understand the distribution of energy through time
Figure 3: Spectrogram showing temporal variation
Example Spectra - UHF
Approach
Figure 4: (a) Top plot : real component (Time Domain)
(b) Mid Plot : imaginary component (Time Domain)
(c) Bottom plot : FT (Frequency Domain)
Figure 1: Block Diagram of SDR
Features of RTL2832U
Frequency Range: MHz
USB 2.0 Interface
Cost: $10 - $30
Required 3.3V external power
Embedded with an advanced ADC(Analog - Digital Converter)
Supported Software: Gqrx (Spectrum Viewer)
Figure 5: Spectrogram showing temporal variation
Example Spectra - FM
Conclusions
Developed successful initial prototypes
of a highly diverse spectrum measurement device
Demonstrated ability to track temporal changes in frequency spectrum
Established a framework for RFI algorithm development
Future Work
Detect and remove unwanted RFI
Develop visualization capabilities
Put an algorithm to find power within a spectrum in Gqrx and implement this on SDR
Figure 2: (a) Top plot : real component (Time Domain)
(b) Mid Plot : imaginary component (Time Domain)
(c) Bottom plot : FFT (Frequency Domain)
Acknowledgements & References erence
We would like to sincerely thank the mentors and PI for instructing this research and PURE committee for their help and support.
A.C. Singer and D.C. Munson, Signal Processing of Discrete-time Signals
Realtek company - RTL2832U
Figures 2 and 4 (a)-(b) show the plot of the complex voltages received in time domain. Fourier Transform of the same signals is shown in (c). Based on the FFT plot, we can calculate the power of the signal. Figures 3 and 5 show the power variation over time.