毫米波雷达

Albert Huizing Bits & Chips Hardware Conference Digital MultiBeam Radar June 17, 2010Digital MultiBeam Radar2 Outline • Why radar? • Radar fundamentals • Mid-air collision avoidance • Airborne safety radar • Concept • Block diagram • Hardware requirements • Conclusions June 17, 2010Digital MultiBeam Radar3 Why Radar? • Radar penetrates objects that are opaque 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 Radar4 TNO Radar Heritage Electronic listening device Passive phased array radar FUCAS Digital phased array radar AMBER 1938 1975 2006 Active phased array radar PHARUS 1995 June 17, 2010Digital MultiBeam Radar5 AMBER Scalable EMERALD Multifunction SAPPHIRE Imaging DIAMOND Distributed Radar Technology June 17, 2010Digital MultiBeam Radar6 Radar Fundamentals (1) Pulse radar • Range : • Example: t = 100 µs → R = 15 km • Range resolution : • Example: τ = 10 ns → ∆R = 1.5 m Transmitted pulse Echo pulse Time delay (t) Pulse length (τ) Peak Power (P) 2 tcR ⋅= 2 τ⋅ =∆ cR June 17, 2010Digital MultiBeam Radar7 Radar 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 transmit and receive antennas and the stability of the transmitted signal Transmit antenna Receive antenna Beat signal Crosstalk June 17, 2010Digital MultiBeam Radar8 Radar 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 resolution F r e q u e n c y Time Beat frequency (fb) Sweep bandwidth (B) Sweep time (T) Transmitted sweep Echo cT RB T tBfb ⋅ ⋅ = ⋅ = 2 June 17, 2010Digital MultiBeam Radar9 Mid-Air Collision Avoidance Crowded aerospace leads to accidents June 17, 2010Digital MultiBeam Radar10 Mid-Air Collision Avoidance Cooperative systems • Air traffic control (ATC) • well-established method • collision avoidance through transponders and voice communications with aircraft • does not work for aircraft without transponders and/or comms • Traffic Collision Avoidance System (TCAS) • based on interrogation of transponders • independent of ATC • does not work for aircraft without transponders Non-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 wide field-of-view cameras • no range and range rate information • does not work in bad weather • Radar • all-weather conditions • range, azimuth, elevation and range rate measurement • no continuous coverage (until now) June 17, 2010Digital MultiBeam Radar11 Mid-Air Collision Avoidance Volume surveillance with radar 10 km 1.5 km 1.5 km 1 km June 17, 2010Digital MultiBeam Radar12 Volume Surveillance with Radar Pencil beam scanning • single transmitter and receiver • long scan time with single pencil beam (no continuous coverage) GimbalTransmitter Receiver Transmitter Receiver Mechanical scanning Electronical scanning Phased array antenna Reflector antenna June 17, 2010Digital MultiBeam Radar13 Volume Surveillance with Radar Digital 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 FFT 1-D FFT 2-D FFT Rx Transmitter Rx Rx Rx digital array antenna digital beam forming doppler filter / ranging Rx = receiver incl. ADC June 17, 2010Digital MultiBeam Radar14 Airborne Safety Radar Digital 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 Radar15 Airborne Safety Radar Demonstrator • 1 transmit channel • 256 receive channels • scalable front-end: 8 × 32 channels • real-time digital beamforming • USB 2.0 interface • CompactFlash on-board storage “Frontware” “Middleware” June 17, 2010Digital MultiBeam Radar16 Airborne Safety Radar Trial Receive Antenna Transmit Antenna June 17, 2010Digital MultiBeam Radar17 Airborne Safety Radar Functions Weather hazard detection Mid-air collision avoidance High resolution ground mapping Ground proximity warning June 17, 2010Digital MultiBeam Radar18 Conclusions • Novel digital multibeam radar concept for mid-air collision avoidance • Floodlight transmission with (FM)CW waveform → continuous coverage • 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