# Wide-Band Interference Mitigation in GNSS Receivers Using Sub-Band Automatic Gain Control +
## 4 Test Setup
### Test Procedure  
Several interference waveforms are tested: a single waveform per test. The output power of the Agilent signal generator starts at \(-70\,\mathrm{dBm}\), increases in \(1\,\mathrm{dB}\) steps to \(0\,\mathrm{dBm}\), then decreases in \(1\,\mathrm{dB}\) steps back to \(-70\,\mathrm{dBm}\). The dwell time on each power step is \(30\,\mathrm{s}\) to provide the receiver with sufficient time to stabilize. Consequently, a single test takes \(1\,\mathrm{h}\) and \(10\,\mathrm{min}\). These tests are long, resulting in a significant risk that several satellites are not visible for the entire duration of the test.  
The interference signals are composed of nine generated interferences, which are replayed using an Agilent MXG-series vector signal generator. The generated interferences include single-tone, wide-band chirp signals, frequency hopping signals, noise signals, and pulsed signals. These interferences are chosen as they represent different scenarios, stressing the resilience capabilities of all receivers. The list of interference with a summary of their properties:  
* [label=0., ref=0]
* Interference #1--CW: single-tone interference at \(1.57542\,\mathrm{GHz}\),
* Interference #2--fast chirp: wide-band linear chirp with \(10\,\mathrm{MHz}\) bandwidth and a chirp repetition rate of \(10\,\mathrm{\SIUnitSymbolMicro s}\),
* Interference #3--slow chirp: wide-band linear chirp with \(10\,\mathrm{MHz}\) bandwidth and a chirp repetition rate of \(100\,\mathrm{\SIUnitSymbolMicro s}\),
* Interference #4--slow hopper: frequency hopper with a dwell time of \(100\,\mathrm{\SIUnitSymbolMicro s}\) and a frequency range of \(35\,\mathrm{MHz}\),
* Interference #5--fast hopper: frequency hopper with a dwell time of \(1\,\mathrm{\SIUnitSymbolMicro s}\) and a frequency range of \(35\,\mathrm{MHz}\),
* Interference #6--noise: filtered noise with \(4\,\mathrm{MHz}\) bandwidth,
* Interference #7--noise: filtered noise with \(35\,\mathrm{MHz}\) bandwidth,
* Interference #8--slow pulse: filtered pulsed noise with \(35\,\mathrm{MHz}\) bandwidth, \(50\,\mathrm{\SIUnitSymbolMicro duty cycle}\), and \(1\,\mathrm{ms}\) pulse width,
* Interference #9--fast pulse: filtered pulsed noise with \(35\,\mathrm{MHz}\) bandwidth, \(50\,\mathrm{\SIUnitSymbolMicro duty cycle}\), and \(100\,\mathrm{\SIUnitSymbolMicro s}\) pulse width.  
Note that only a subset of the interference signals is presented and discussed in Section 5. However, all interference types are available in the Appendix A for the interested reader, and the results for all satellites are published as Supplementary Material to the article.  
The \(C/N_{0}\) for all satellites and the PVT solution reported by each receiver for each interference is recorded and analyzed. First, the \(C/N_{0}\) is evaluated to determine the stand-alone benefit of the IM. This is the classical interference analysis approach. In Section 5, only selected GPS L1 C/A satellites with selected interference signals are presented and discussed. However, the results of both GPS L1 C/A and Galileo E1B/C are available in the Appendix B. Second, the position errors and the PVT availability is evaluated to determine the end-to-end impact of IM. This brings the analysis closer to system-level verification and testing.  
Lastly, for additional information and insight, an interference detector is included. It uses machine learning (ML) and features extracted from a low-cost NeSDR digital video broadcasting - terrestrial (DVB-T) dongle. The detector is still under development and will be showcased in a future publication. Nevertheless, it still provides additional insight into mitigation performance.