Filippo Parrini

Technologies for Environmental and Cultural Heritage Laboratory (TECHLab)Department of Electronics and Telecommunications

University of Firenze (Italy)

Ground based radar interferometry

Ground based radar interferometry

LINE OF SIGHTDISPLACEMENT

Multi-bistatic radar: operating principle

Three independent interferometric measurements:

•TX1 - RX (monostatic)•TX2 - RX (bistatic)•TX3 - RX (bistatic)

Multi bistatic radar: operating principle

d: target displacement d1,d2,d3: target displacement projections

Multi bistatic radar: issues

Instrumental issues Geometric issuesRadar issues

Cable thermal drift Multi-bistatic RCSof natural/artificial

targets

Measurement geometry

determination

Displacement componentsestimation

Instrumental issues: cable’s thermal drift

Highly phase stable cable

This effect has not been compensated yet

Radar issues: bistatic RCS

Natural or man-made reflectors usually havea very low RCS in multi bistatic mode

It is more difficult to have radar reflectorswith a good RCS in several directions

in order to perform a robust interferometric analysis

Geometric issues

2) The targets position in the reference system has to be determined (it can be retrieve from radar range measurement)

3) Target displacement vector (dx, dy, dz) has to be estimated(made with the following relation)

A measurement setup geometrywhich assure a small condition number for matrix A

is necessary for a good accuracy in displacement vector estimation

1) The multi-bistatic radar position in the reference system has to be known(it can be easily measured with additional instruments)

(d1,d2,d3) interferometric measurements

Experimental tests in controlled environment

No vertical baselinewas achieved

Experimental tests

Special multi-bistatic targetautomatically positioned and rotated

Side view Front view

Experimental test #1: displacement along y axis

Direction of the displacement during the 1st test

Displacement of target measured by three radar channels (d1,d2,d3)

Experimental test #1: displacement along y axis

Measurement displacement along the reference system axis(X = red, Y= blue)

Errors:

Mean: -0.01 mm

σ: 0.03 mm

Experimental test #1: displacement along y axis

Experimental test #2: displacement along any direction

Direction of the displacement during the 2st test (β=23.5)

Experimental test #2: displacement along any direction

Errors:

Mean: -0.02 mm

σ: 0.03 mm

Conclusions

The novel sensor was tested in a controlled environment showing good performances in term of measurement accuracy.

A novel multi-bistatic radar sensorhas now been designed and set up in order to provide three dimensional measurement capabilities.

Only LOS component of displacement is provided by traditional interferometric radar.

Measurement of displacement vector is of paramount importance in static and dynamic tests on civil structures.