SX-NSR 2.0 A Multi-frequency and Multi-sensor Software Receiver with a Quad-band RF Front End

Transcription

1 SX-NSR 2.0 A Multi-frequency and Multi-sensor Software Receiver with a Quad-band RF Front End - with its use for Reflectometry - N. Falk, T. Hartmann, H. Kern, B. Riedl, T. Pany, R. Wolf, J.Winkel, IFEN GmbH Space Reflecto st December 2010, Toulouse, France Page 1

2 Content Introduction NavPort-4 RF section overview Digital section overview Use for Reflectometry SX-NSR 2.0 Overview User extensibility Use for Reflectometry Page 2

3 Introduction NavPort-4 Fully configurable Quad-band GNSS front-end Sensor data On-board barometer IMU interface tightly coupled to IF samples Generates data stream for further processing 10MHz in/out, internal 10MHz TCXO, PPS out, Trigger in SX-NSR 2.0 Multi-Frequency and Multi-Sensor Software receiver Interacts with NavPort-4 Data logger Real-time and post-processing Configuration and Monitoring Page 3

4 NavPort-4 - GNSS signals Up to 4 different frequency bands Supported GNSS signals: L1/E1, L2, L5/E5a, E5b, E6, G1, G2 Available combinations: Galileo/GPS: L1/E1 + L2 + L5/E5a + E5b GPS/GLO: L1/E1 + L2 + G1 + G2 Galileo/GPS/GLO: L1/E1 + L2 + L5/E5a + G1 Further combinations on demand Page 4

5 RF/IF Section Main features : Built with discrete Components Heterodyne down converter from L-band to an intermediate frequency (IF) of approximately 92 MHz Signal bandwidth of 15 MHz Required Antenna gain: db Wide Dynamic Range: 40 db Provides antenna voltage (5 V) for active antennas With Automatic Gain Control (AGC) Each band could be switched on/off for power reduction First LNA with bypass mode Page 5

6 First LNA modes RF Input RF1 Mixer IF Output First LNA with Bypass mode 4-way Power Divider RF2 RF3 LO Mixer and LO Control Single band RF chain AGC RF4 First LNA in Operating Mode (15dB Gain) Noise Figure of 1.4dB Input 1dB Compression Point of -70dBm First LNA in Bypass Mode Input 1dB Compression Point (In-Band) of the complete RF/IF chain is -55dBm Noise Figure of 4dB CW interference of -35dBm only disturbs the equivalent signal band Page 6

7 Digital Section Quad-band analog-to-digital converter Stable inter-frequency bias Sample rate is MHz (offers best conditions for high performance FFT acquisition algorithms) FPGA based to reach high flexibility Forms data stream including combined GNSS data and time stamped sensor data Configuration of on-board peripheral (RF-section, sensor, etc.) Transmitted to PC via a single USB 2.0 interface Monitoring of hardware status Acts as a relay, no interpretation of data Page 7

8 Flexible data stream Select / Deselect each RF band and additional data, e.g. L1/E1 only L1/E1 + L5/E5a + additional data L1/E1 + L2 + L5/E5a + E5b + additional data Additional Data includes Hardware status Sensor data with sample counter NSR splits the data stream automatically Page 8

9 NavPort-4 - Use For Reflectometry Two - antenna support under development Therefore, different solutions will be analyzed NavPort-4 with two antenna inputs Up to 2x2 frequencies Synchronization of two NavPort-4 (one antenna input each) Standard NavPort-4 with synchronization feature Up to 4x2 frequencies Page 9

10 SX-NSR 2.0 Fully programmable Multi-Frequency and Multi-Sensor Software receiver with geodetic quality measurements ~ 20 real-time channels per CPU core Real-time cold start acquisition sensitivity < 20 dbhz, warm start 15 dbhz GPU optionally used for efficient signal acquisition Controlling the NSR Via GUI C/N 0 [db-hz] Via command (over TCP/IP) Acq. ramp test with fine time (< 1 ms) ass. 40 SV1 SV2 30 SV6 20 SV17 SV21 10 SV22 SV GPS Time [s] Integrate the NSR into your Matlab scripts (over TCP/IP) Record sample data and sensor data Page 10

11 NSR User Extensions SX-NSR acts as a software receiver Framework Extendable through user provided implementations via multiple APIs NSR may load DLLs (user code) C-language interface (MS Visual Studio, gcc,...) NSR calls DLL functions NSR uses multiple threads to speed up processing DLL must be thread safe Time tags Every API data is time tagged and synchronized to IF sample stream Page 11

12 GPS-INS Coupling API Programming Example Software receiver allows easy fusion of GNSS data with other positioning sensors NavPort-4 synchronizes IMU and barometer data with +/- 2µs accuracy to GNSS signal samples NSR provides positions, pseudoranges, discriminator values, correlator values or samples to allow all kinds of integration techniques Example User implementation ESA Project DINGPOS (uses NSR framework and extends functionality): Use the sensor API to detect steps and heading for dead reckoning Program an error state Kalman filter to merge GPS positions with DR Take control over channel NCOs (vector tracking) Page 12

13 ULTRA-TIGHT COUPLING (UTC) Page 13

14 SX-NSR - Use For Reflectometry 2D Multi-Correlator Large number of correlators in Doppler/code-phase grid around prompt correlator, long integration times Different integration schemes (coherent, non-coherent, constant Doppler) Data tight to raw measurement records 1D Multi-Correlator Like in H/W Receiver Number and position user configurable Data tight to integrate&dump records Slaving Channels for reflected signals may linked to line-of-sight channels via the acquisition and tracking API Page 14

15 Simulation and Detection of Multipath Effects User Motion Along circular ground track (R = 250m) Constant user velocity (v = 10 m/s) Reflector location Azimuth: A = 60 Distance: s = 100 m Height: h = 2 m Multipath characteristics One signal affected by multipath (PRN12) Multipath relative power: -3dB Multipath on Galileo E1/E5 NSR tasks: Detection and estimation of a multipath signal Determination of reflector position Page 15

16 Multipath Geometry View in horizontal plane: 2-dimensional problem e sat... unit vector in satellite direction e refl... unit vector in reflector direction v... user velocity d... distance to reflector Δτ... multipath delay Δf... Doppler difference f c RF f v erefl de e refl d sat e sat τ v -e sat -e refl GNSS antenna -e sat Reflector Insensitive to: clock errors, atmospheric delays, height changes Assumption: no vertical speed, reflector at same height as user d Page 16

17 Tasks Determine multipath delay Δτ and Doppler difference Δf of multipath signal with respect to the line-of-sight signal Invert f f c RF v erefl d 1e refl e sat e sat to obtain e refl and d Add (d e refl ) to user position and plot reflector position Page 17

18 Multi-Correlator Principle Compute correlation function on a code phase(=delay), Doppler grid Line-of-sight Multipat h 0.0/0.0 = prompt Correlator/channel NCO Doppler Delay Offsets with respect to channel NCO (~ line-of-sight signal) Page 18

19 Multi-Correlator Formula L, 0 exp 2 0 P f s c t i f f t i µ 1 µ µ µ µ P... multi-correlator value Δτ... delay offset [s] Δf... Doppler offset [Hz] s µ... received signal samples L... integration interval c... PRN code t µ... time of sample µ [s] τ 0... NCO code delay [s] f 0... NCO Doppler [Hz] φ µ... carrier factor [rad] Page 19

20 MultiCorrelatorOutput Multi-correlator logic compute values, wait for RINEX-epoch, attach values to raw data, compute values,... In our example, batches of s are evaluated every 3 s (= 1 s RINEX rate + 2 s idle time) A set of files is logged for each measurement ASCII files with Doppler/delay offsets, receiver position, time tag, satellite position,... Correlator values Raw correlator values (no Doppler offset, one row for each data-bitlong integration interval) Page 20

21 Result Inverse Problem has four solutions; two of them are correct Reflector Receiver trajectory Page 21

22 Further information Examples and demo version to be downloaded at: Includes NSR Software MATLAB tools API examples Indoor GPS C/A samples with IMU/baro/WiFi data Point-reflector samples (NCS, Galileo E1) L1/E1/E5a samples from the German Galileo test bed Page 22

23 Thank You for Listening! Page 23