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Introduction Global Navigational Satellite Systems (GNSS) data acquisition frequently occurs in a variety of challenging environments, which include locations with elevated Radio Frequency (RF) noise characteristics. Tracking the relatively low powered GNSS carrier signals broadcast from space becomes even more challenging in the presence of adjacent band RF noise. The demand for terrestrial RF spectrum use for a variety of non-GNSS applications is ever increasing, which poses potential challenges for GNSS site operators who would like to acquire the highest quality data possible. In recent years, UNAVCO has observed an increase in the number of GNSS sites in our network which are negatively impacted by RF interference. In previous work, we have shown that telemetry systems utilizing the Iridium satellite constellation can degrade GNSS data quality, as the adjacent-band (1610-1616 Mhz) signals transmitted by Iridium data transmitters are close in proximity to the L1 frequency of GNSS. To better characterize GNSS receiver susceptibility to more general RF interference, we use a signal generator to provide a Continuous Wave (CW) noise source. We combine the CW noise with the incoming signal from the GNSS antenna before it enters the receiver. We vary the power and frequency of the generated CW noise. Changes in the recorded signal-to-noise measurements are then used to characterize each receivers susceptibility to a CW noise source. Test Receiver Signal Generator TRM59800 Test Configuration Reference Receiver TRM59800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 −50 0 50 L5 L2 L1 Iridium dB TRM29659.00 LNA 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 −50 0 50 dB L5 L2 L1 Iridium TRM59800.00 LNA 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 1100 1110 1120 1130 1140 1150 1160 1170 1180 1190 1200 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 -80 -70 -60 -50 -40 -30 -20 -10 Transmit Frequency [MHz] Transmit Power [dB] Signal-to-Noise Ratio 0 0.2 0.4 0.6 0.8 1 Septentrio PolaRx5 - Auto Notch Filter ON Septentrio PolaRx5 - Auto Notch Filter ON Septentrio PolaRx5 - Auto Notch Filter ON Septentrio PolaRx5 - Auto Notch Filter OFF Septentrio PolaRx5 - Auto Notch Filter OFF Septentrio PolaRx5 - Auto Notch Filter OFF Leica GR10 Leica GR10 Leica GR10 Trimble NetR9 Trimble NetR9 Trimble NetR9 Javad Sigma Javad Sigma Javad Sigma Topcon NetG5 Topcon NetG5 Topcon NetG5 Trimble NetRS Trimble NetRS 1 Normalized L1 SNR Normalized L2 SNR Normalized L5 SNR GPS Frequencies : L1 = 1575.42 MHz L2 = 1227.60 MHz L5 = 1176.45 MHz Receivers Tested (1) Septentrio PolaRx5, (2) Javad Sigma, (3) Leica GR10, (4) Trimble NetR9, (5) Trimble NetRS, (6) Topcon NetG5. Noise Power and Frequency Range - 8 discrete noise power levels were tested ranging from -80 to -10 dB. - 64 discrete frequencies were tested ranging from 1100 to 1730 MHz. - Each frequency and power level setting was held for 1 min. - The test duration for each receiver tested took approximately 8.5 hrs. Data Processing 1) Each test receiver’s 1Hz signal-to-noise values for each satellite were divided by the 1Hz signal-to-noise values recorded by a refer- ence receiver (collocated and not subject to interference). 2) The normalized SNR values for each satellite were then averaged for each epoch. 3) The figures display the computed normalized SNR values over a grid of tested frequencies (x-axis) and tested power levels (y-axis). 4) Cool colors show when the test receiver’s SNR values were lower than what was recorded by the reference receiver, indicating a sus- ceptibility to interference at the given frequency and power level. 5) Solid dark blue indicates the receiver stopped tracking all satellites. 6) The normalized SNR values for each GPS frequency (L1, L2, and L5) were each plotted separately. 2 2 3 4 5 Discussion 1 3 2 4 5 Septentrio’s PolaRx5 receiver includes an RF mitigation tool allowing users to apply an automatic digital notch filter in the receiver front end for CW noise sources. The test results improved when the filter was enabled. Some receivers showed interference susceptibility at frequencies near L1 when tracking L2 and L5. The frequency range over which each receiver was susceptible varied significantly between each make and model. Some receivers appear to employ notch filtering at frequencies that carry L-band correction ser- vices. Older GPS-only hardware seems to employ narrower filters in the RF front-end. Antennas Antennas were not tested in this experiment because the noise was introduced between the antenna and the test receiver. Antennas also play an important role in a given site’s susceptibility to RF interference. If the inter- ference is within the amplified range of the antenna’s LNA and of sufficient strength, the amplifier can saturate. Antenna LNA satura- tion can cause degradation of receiver track- ing performance. Some new antenna models include LNA’s with wider amplification bands to better support newer GNSS signals (Right, Bottom). UNAVCO has seen an increase in ob- servation noise at a subset sites where GNSS compatible antennas have replaced older GPS-only designs. This material is based on data, equipment and engineering services provided by UNAVCO through the GAGE Facility with support from the National Science Foundation (NSF) and National Aeronautics and Space Administration (NASA) under NSF Cooperative Agreement No. EAR-1261833 Testing the Susceptibility of GNSS Receivers to Radio Frequency Interference AGU FALL MEETING 2015 Henry Berglund ([email protected]), Warren Gallaher, Frederick Blume, UNAVCO, Boulder, CO 80301-5553
