June 17, 2010Digital MultiBeam Radar3Why Radar?• Radar penetrates objects that areopaque for other sensors• fog• dust• walls• clothes• soil• …• Non-ionising• Radar can measure• range• azimuth• elevation• radial velocity• material properties• dielectric constant• temperature
June 17, 2010Digital MultiBeam Radar5AMBERScalableEMERALDMultifunctionSAPPHIREImagingDIAMONDDistributedRadar Technology
June 17, 2010Digital MultiBeam Radar6Radar Fundamentals (1)Pulse radar• Range :• Example: t = 100 µs → R = 15 km• Range resolution :• Example: τ = 10 ns → ∆R = 1.5 mTransmitted pulse Echo pulseTime delay (t)Pulse length (τ)PeakPower (P)2tcR⋅=2τ⋅=∆cR
June 17, 2010Digital MultiBeam Radar7Radar Fundamentals (2)Frequency modulated continuous wave (FMCW) radar• Transmit and receive continuously and simultaneously• No blind zones in range• Highest possible duty cycle• Requires separate transmit and receive antennas for highest sensitivity• Simple transceiver• Sensitivity is limited by crosstalk between transmitand receive antennas and the stability of thetransmitted signalTransmitantennaReceiveantennaBeat signalCrosstalk
June 17, 2010Digital MultiBeam Radar8Radar Fundamentals (3)Frequency modulated continuous wave (FMCW) radar• Linear frequency modulation achieves lowest bandwidth on receive• Beat frequency• Example: B = 100 MHz (∆R = 1.5 m), R = 15 km, T = 1 ms → fb = 10 MHz• factor 10 sampling rate reduction w.r.t.pulse radar with the same range resolutionFrequencyTimeBeatfrequency (fb)Sweepbandwidth (B)Sweep time (T)TransmittedsweepEchocTRBTtBfb⋅⋅=⋅=2
June 17, 2010Digital MultiBeam Radar9Mid-Air Collision AvoidanceCrowded aerospace leads to accidents
June 17, 2010Digital MultiBeam Radar10Mid-Air Collision AvoidanceCooperative systems• Air traffic control (ATC)• well-established method• collision avoidance throughtransponders and voicecommunications with aircraft• does not work for aircraftwithout transponders and/orcomms• Traffic Collision AvoidanceSystem (TCAS)• based on interrogation oftransponders• independent of ATC• does not work for aircraftwithout transpondersNon-cooperative systems• Visual flight rules (VFR)• well-established method• depends on pilot’s eyes• does not work in bad weather• Electro-optical cameras• relatively mature• continuous coverage with widefield-of-view cameras• no range and range rate information• does not work in bad weather• Radar• all-weather conditions• range, azimuth, elevation and rangerate measurement• no continuous coverage (until now)
June 17, 2010Digital MultiBeam Radar11Mid-Air Collision AvoidanceVolume surveillance with radar10 km1.5 km1.5 km1 km
June 17, 2010Digital MultiBeam Radar12Volume Surveillance with RadarPencil beam scanning• single transmitter and receiver• long scan time with single pencil beam(no continuous coverage) GimbalTransmitterReceiverTransmitterReceiverMechanical scanningElectronical scanningPhased array antennaReflector antenna
June 17, 2010Digital MultiBeam Radar13Volume Surveillance with RadarDigital multiple beam radar• Floodlight transmit beam• Multiple beams on receive• Receiver behind each antenna element (continuous coverage)• Digital beamforming with 2-D FFT• Doppler filtering with FFT1-DFFT2-DFFTRxTransmitterRxRxRxdigitalarrayantennadigitalbeamformingdopplerfilter /rangingRx = receiver incl. ADC
June 17, 2010Digital MultiBeam Radar14Airborne Safety RadarDigital multiple beam radar• continuous coverage (no scanning beams)• (frequency modulated) continuous wave (no blind zone)• planar antenna arrays (easy to integrate in aircraft)
June 17, 2010Digital MultiBeam Radar18Conclusions• Novel digital multibeam radar concept for mid-air collision avoidance• Floodlight transmission with (FM)CW waveform → continuouscoverage• Planar receive antenna array with (many ) digital receivers• Multiple simultaneous beams created by digital beamforming• No mechanical or electronical scanning• Easy to integrate in aircraft• Radar concept proven during flight trial• Multiple radar functions• mid-air collision avoidance• ground proximity warning• hazardous weather detection• high resolution ground mapping
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