AGGA-4 : core device for GNSS space receiver of this decade - - PowerPoint PPT Presentation

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AGGA-4 : core device for GNSS space receiver of this decade - - PowerPoint PPT Presentation

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AGGA-4 : core device for GNSS space receiver of this decade Prepared by: J. Rosell, P. Silvestrin, G.R. W eigand, G. Lopez Risueo, J.V. Perello ESA/ ESTEC J. Heim , I . Tejerina Astrium GmbH (Ottobrunn) - - - - - - - - - - - - - - - - -

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AGGA-4 : core device for GNSS space receiver of this decade

Prepared by:

  • J. Roselló, P. Silvestrin, G.R. W eigand, G. Lopez Risueño, J.V. Perello

ESA/ ESTEC

  • J. Heim , I . Tejerina

Astrium GmbH (Ottobrunn)

  • - - - - - - - - - - - - - - - - - - - -

Presented by: J. Roselló Earth Observation Programme Directorate @ ESA/ ESTEC

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  • Applications using GNSS space receivers

– POD supporting other applications – Radio Occultation

  • Future GNSS receiver architecture

– AGGA-4: Baseband GNSS processor – RF chain and antennas

  • Implications of new GNSS signals
  • Conclusions

Table of Contents

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SUPPORT TO OTHER APPLI CATI ONS

  • Altim etry

( e.g. Sentinel-3 )

  • Solid Earth

– Gravity m issions ( e.g. GOCE m ission) – Earth Magnetic Field ( e.g. Sw arm )

  • Relative positioning

– ( e.g. Tandem -X, TerraSAR-X)

  • SAR interferom etry ,

– e.g. for Sentinel-1

  • Earth Science applications

– Radio Occultation ( e.g. METOP GRAS) – GNSS-R

Precise Orbit Determ ination ( POD)

Baseline

.. . .. . .. . .. ... . .. . .. . .. .

GNSS GNSS Measurements Measurements

Preliminary trajectory

Estimated tr Estimated trajectory ajectory with r with reduced dynamics educed dynamics

Continuous high accuracy Navigation O/B by combining:

  • Orbit knowledge
  • GNSS measurements

Better if done with post-processing on-ground

  • Longer orbit segments
  • available GNSS Tx clocks from ground (IGS)
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Requirem ents in POD

Key issues impose different GNSS receiver architectures and operational approach

  • data timeliness (real-time OB and / or post-processing OG)
  • robustness : high number of observations
  • accuracy

0.1 mm/s

(velocity. along) ACHIEVED

MetOp-GRAS (Occultations)

(launch: 2006)

2 cm rms (radial) 3 cm rms (radial) 8 cm rms (radial) 3 m. rms (radial) Sentinel-3 (Altimetry) 5 cm rms xyz 10 m. 3xyz Sentinel-1

(SAR interferometry)

< 10 cm rms Swarm < 2cm rms (ACHIEVED) < 10 cm rms

(ACHIEVED ~ 4 cm)

< 50 cm rms

(requirement)

GOCE

(launch: March 2009)

Non Time Critical (1 month) Slow Time Critical

STC, (1-2 days)

Non RT (1-3h) Real Time (RT) Mission

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Radio Occultation ( RO)

While a GNSS satellite ‘sets’ or ‘rises’ behind the horizon:

  • Additional bending of the GNSS signal’s ray path due to refraction in the atmosphere
  • The GNSS receiver measures the excess Doppler shift

 key measurement is CARRIER PHASE

  • derive vertical profiles (Temperature, Pressure, Humidty)

Performance is driven by very good clocks, open loop processing, high antenna gain

  • 500 occultations / day

(per GNSS constellation)

nb.5

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Future GNSS receiver architecture

Digital Beam forming LEON-2 processor FFT module interfaces AGGA-4 4 input modules 36 Channels + Aiding Units RF down conversion AD conversion

2 frequencies: L1 - L5 Power Level

Antenna Memory O/B computer or EGSE SpaceWire / UART / Mil-Std 1553

Synch.

‘n’ antennas and ‘n’ Rx

POD RO RO

EARTH GNSS Tx GNSS Tx Rx Attempt to make it as modular as possible (reproducibility & re-use) Difference POD and RO could be software and antenna

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Baseband GNSS processor developed under ESA guidance and contracts

AGGA-2: [ T7905E component] manufactured by Atmel in the year 2000

  • Targeted for EO applications: POD, Radio Occultation (RO), attitude determination.
  • Used in many missions:

– ESA: e.g. MetOp-Gras a/ b/ c for RO, GOCE, Sentinels 1/ 2/ 3, Swarm, EarthCARE, etc. – Non-ESA: e.g. ROSA in Oceansat Radarsat-2, Cosmo-Skymed, … Reasons to go for a new generation of devices

  • new scientific requirements & experience from current instruments like MetOp GRAS
  • new enhanced GNSS signals (GPS / Galileo / Compass / Glonass)
  • Advances in space ASIC technology allowing more on-chip integration

AGGA-4 : Next generation with more functionality

Digital Beam forming LEON processor FFT module interfaces AGGA-4 4 input modules 36 Channels + Aiding Units

In yellow the GNSS core AGGA = Advanced GPS / Galileo ASIC

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AGGA-4 overall architecture

LEON config AHB APB TIMERs Watchdog CIC PIC SPI GPIO

AHB APB

GPIO I/F SPI I/F SpaceWire I/F GNSS Signal I/F

LEON2FT

IU SRAM PROM IO SDRAM D-Cache I-Cache AHB Debug comm. link AHB AHB Trace buffer Debug Support Unit

SpaceWire

AHB | DMA AHB | DMA

GNSS core & GIC

Gaisler FPU write protect AHB Arbiter/ Decoder Status AHB Mem Ctrl

A H B

AGGA-4

36 MIL-Bus I/F

MIL-Bus 1553 AHB | DMA

UART I/F

UARTs

AHB | DMA UART / SpaceWire CRC AHB | DMA

FFT

AHB

  • Ext. interfaces
  • Int. interface

GNSS core

Legend

On-chip modules

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AGGA-4 vs AGGA-2

G N S S C H A N N E L S

6 IE observables (no DMA – interrupt based) 2 ME observables (no DMA – interrupt based) 16 Integration Epoch (IE) observables - DMA capable 5 Measurement Epochs (ME) observables – DMA capable Observables 0.5 micron from ATMEL, 160 pins GNSS clock up to 30 MHz 0.18 Micron from ATMEL, 352 pins GNSS clock up to 50 MHz (target) – LEON clock target 80 MHz TECHNOLOGY No Yes (2 Digital Beam Forming) BEAMFORMING Microprocessor I/F, Interrupt controller and I/O ports Two DMA capable UART, Mil-Std-1553, 4 SpaceWire SE, SPI I/F, DSU, S-GPO, 32 GPIO, SRAM I/F INTERFACES No FFT in hardware on-chip FFT MODULE No Check Redundancy Code in hardware On-chip CRC MODULE 2 bit (0.55 dB losses) (I/Q and real sampling) 3 bit (0.17 dB losses) (I/Q, real sampling and interface for IF. ~ 250 MHz) INPUT FORMAT Off-chip (typically ERC-32, ADSP 21020) LEON-2 FT on-chip with IEEE-754 compl. GRFPU Float.Point) MICRO-PROCESSOR ASC TBG Antenna Switch Controller (ASC) Time Base Generator (TBG) Common to all channels

  • No. Done in software

Yes: Code and Carrier aiding Aiding Unit per channel Hardware slaving Hardware and software slaving Channel Slaving Yes ( 4 P-code units) – ESA patent No Codeless P(Y) code 3 complex (I/Q), with E, P, L (L=Late)

NAV data bit collection requires software interaction

5 complex (I/Q) with EE, E, P, L, LL (E=Early ; P=Punctual) and autonomous NAV data bit collection in HW Correlators per channel 1 code generator per channel Fixed LFSR for certain primary codes only No secondary code and no BOC. (2 code generators per channel for Pilot and Data) Primary: LFSR and memory based Secondary codes and BOC(m,n) subcarriers Code Generators GPS L1 C/A Codeless L1/L2 Existing FDMA Glonass Galileo Open Service: E1bc, E5a, E5b Modernized GPS: L1 C/A, L1C, L2C, L5 Existing FDMA Glonass Potentially: Beidou, modernized Glonass Compatible signals 12 SF or 4 DF 36 Single Freq. or 18 Dual Freq (target) # of channels

AGGA-2 AGGA-4 Feature

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AGGA-4 GNSS Core

ASEO ASEI ASC Core Clk

Input Module 0 Front End Interface DBF Channel 0 Aiding Unit Code Generator Unit Correlator Unit Delay Line Unit Carrier Generator Unit 36 channels Channel Matrix Final Down Converter Digital Beam Forming Antenna Switch Controller Time Base Generator

ASE MEI PPSI MEO PPSO Reset

Power Level Detector Module

ExtClk

X

DBF 1

AUT ME AUT PPS IMT D/A Out 0 D/A Out 1 D/A Out 2 D/A Out 3 EC Half Sample Clk Input A0/B0 Input A1/A1 Input A2/B2 Input A3/B3

5I / 5Q I/Q scheme and IF scheme

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AGGA-4 Channel m atrix

* 3 6 single-frequency double-code * Very flexible primary code generator units: – a LFSR to generate very long codes (e.g. 767,250 chips in L2CL) – memory-based codes (e.g. for Galileo E1b and E1c). * Support of Binary Offset Carrier – BOC( m ,n) and secondary codes required in modernized GPS and new Galileo signals. * 5 com plex ( I / Q) code correlators, to allow the EE, E, Punctual, L, LL required for the processing of BOC signals. * hardw are Aiding Unit, allowing autonomous CODE and CARRIER aiding in order to compensate for the ‘predictable’ Doppler rate (Hz/ s) caused by high orbit dynamics

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Signals processed w ith AGGA-4

Memory BPSK(10) Pilot 20 10,230 10.23 L5-Q 1 SF LFSR BPSK(10) 100/50 10 10,230 10.23 L5-I 1176.45 L5 LFSR BPSK(0.5) Pilot No 767,250 10.23 L2CL 1 SF Memory BPSK(0.5) 50/25 No 10,230 10.23 L2CM 1227.6 L2C 1 SF LFSR BPSK(1) 50 No 1,023 1.023 L1 C/A 1575.42 L1 1 SF Memory BOC(1,1) Pilot 1800 10,230 1.023 L1Cp 1 SF Memory BOC(1,1) 100/50 No 10,230 1.023 L1Cd 1575.42 L1c Memory (idem) BPSK(10) (idem) Pilot 100 (idem) 10,230 (idem) 10.23 (idem) E5a-Q (E5b-Q) 1 SF (idem) LFSR (idem) BPSK(10) (idem) 50/25 (250/125) 20 (4) 10,230 (idem) 10.23 (idem) E5a-I (E5b-I) 1176.45 (1207.14) E5a (E5b) Memory BOC(1,1) Pilot 25 4,092 1.023 E1 C 1 SF (Sing. Freq.) Memory BOC(1,1) 250/125 No 4,092 1.023 E1 B 1575.42 E1 AGGA4 Nb. Channels LFSR/ Memory (config. AGGA4) Replicas in AGGA-4 Symbol/ Data Rate (sps / (bps) Secondary code length (chips) Primary code length (chips) Code Rate (Mcps) Compo nent Freq. (MHz) Band

  • Relying on Public signals (no PRS, SoL, … )
  • The double code generator allows to process the two component signals in one channel
  • High flexibility => also compatible with GLONASS and Beidou (as known today)
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AGGA-4 schedule

  • AGGA-4 is under development by Astrium Gm bH under ESA guidance and Contracts.
  • Extensive validation (acquisition & tracking) with:

– FPGA version (same as ASIC but with only 4 GNSS channels) – Block testing and use of E2E testing with Spirent simulator at ESTEC by Ruag Space Austria in August 2010

  • Deim os Engenharia also contributing to FPGA validation
  • ASIC components by Atmel in ATC18RHA 0 .1 8 m process (MQFP package with 352 pins).

– available for the whole European space industry (equal basis). – ASIC prototypes by 4Q-2011.

AGGA-4 FPGA Mezzanine Multi-interface testing board

AGGA-4 FPGA testing at ESTEC in Aug. 2010 with Spirent simulator

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Program m able RF ASI Cs

  • Saphyrion (former Nemerix) RF ASIC chipset developed under ESA R&D programmes and used

for POD applications in Swarm, EarthCare and Sentinel 1a/ b, 2a/ b, 3a/ b.

  • RF performance is even more important for Radio Occultation (carrier phase measurements)

– Good filtering against interference (Search & Rescue payloads) – Good frequency plan (e.g. integer values between all clocks in the receiver) – Clock coherency between bands – Low phase noise at 1 Hz & short term stability

  • ESA is preparing the next generation of RF ASICs:

– For POD, Radio Occultation and GNSS-R receivers

  • good RF performance and miniaturisation is important

– Compatible with AGGA-4 (including 3-bit Intermediate Frequency sampling)

RF down conversion AD conversion

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EQM m odel ( exam ple w ith AGGA-2 )

AGGA-2 RF Front End

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New GNSS signals and constellations ( Galileo, m odernized GPS, others)

More robustness thanks to:

  • More signals in Open Service = > (error detection / correction)
  • no semi-codeless: dual frequency available also with low SNR
  • Pilot components (no bit wiping) = > very good for EO needing carrier measurements.
  • secondary codes: ‘lengthen’ the spreading code, better autocorrelations while fast acquisition

Sm all im provem ent in accuracy (signals with better codes, but similar carrier)

  • Similar signal power levels
  • higher code bandwidths (e.g. 10 MHz), BOC modulations
  • but similar carrier measurements (driver in EO applications)

The new GNSS signals imply:

  • Com ponents m ore flexible and w ith m ore digital processing

– more channels to improve robustness and RO measurements – more digital functions (e.g. digital down conversion, carrier & code aiding, etc). – Flexibility (e.g. LFSR & memory-based code generators, more frequency plans)

  • Different software: no codeless processing or bit wiping, but more available signals

ESA preparing the AGGA-4, RF ASICs and antenna com ponents compatible with new GNSS. We can start developing the receivers (ASIC final pin layout known soon)

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Conclusion

Applications: – cm accuracy in Precise Orbit Determination demonstrated (GOCE) – Radio Occultation: excellent performance of MetOp GRAS AGGA-2 baseband processors: widely used in ESA and non-ESA missions ESA preparing the next generation of key GNSS receiver components that can be used for both POD and RO – AGGA-4 : compatible with Galileo, modernized GPS, Glonass, Beidou. Higher number of channels. Expected ASIC samples: 4Q-2011 for all European space industry under equal basis. – RF ASIC also important in performance and miniaturisation We start developing the receivers compatible with future signals: – more robustness (e.g. higher number of Open Signals, pilot components), – little accuracy improvements