albert huizing -_tno

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


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


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


AMBERScalable

EMERALDMultifunction

SAPPHIREImaging

DIAMONDDistributed

Radar Technology


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



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



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

Fre

quency

Time

Beat

frequency (fb)

Sweep

bandwidth (B)

Sweep time (T)

Transmitted

sweep

Echo

cT

RB

T

tBfb

⋅

⋅=

⋅=

2


Mid-Air Collision Avoidance

Crowded aerospace leads to accidents



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)



Volume surveillance with radar

10 km

1.5 km

1.5 km1 km


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


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


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)


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”


Airborne Safety Radar Trial

Receive Antenna

Transmit Antenna


Airborne Safety Radar Functions

Weather hazard detection

Mid-air collision avoidance

High resolution ground mapping

Ground proximity warning


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

albert huizing -_tno

Technology

pulse radar range

aircraft radar concept

mature continuous coverage

beam multiple beams

scanning beams frequency

range rate information

beat frequency example

radarpencil beam