INTERFERENCE MITIGATION OF ADJACENT RADIO FREQUENCY SIGNALS ON A FLEXIBLE SOFTWARE-DEFINED RADIO TESTBED PLATFORM

Abstract

The radio frequency (RF) spectrum is crowded with users and adjacent frequency users are facing an increase in interference from each other. The spectrum governing body Federal Communications Commission (FCC) has the difficult task of allocating spectral bands for new users for mobile devices using 4G LTE technology. Telemetry (TM) is affected by the adjacent band 4G LTE users in terms of signal degradation. To minimize the interference between adjacent frequency users, several methods can be used. A common but inefficient method separates adjacent band frequencies using guard bands which leaves a big portion of the spectrum unused. Alternatively, adjacent RF signals can be separated using digital filtering techniques with the signal of interest being unharmed and reducing the signal power of the interfering signal. A digital filtering technique includes bandpass filter (BPF) rejection, which has the ability to filter out adjacent interfering signals. This is accomplished by designing bandpass digital filters where the passband and stopband frequencies are adjusted to achieve maximum signal power and reject the interfering signal by reducing its power. A flexible software-defined radio testbed is set up to experiment and analyze this scenario with ease and effective measures.