EMISAR System description

The function of the system can be explained as follows: A frequency modulated baseband pulse is computed and stored in the DSG (Digital Signal Generator) buffer. At 200 MHz rate this pulse is D/A converted, I-Q modulated onto a 300 MHz IF, up-converted to the SAR frequency (L- or C-band), amplified, and finally transmitted by the antenna. Echoes are received, amplified, down-converted, demodulated and digitized. An optional range pre-filtering (RPF) can then be performed whereafter the peak data rate is reduced by the buffer in the Digital Front End (DFE), thus facilitating the optional azimuth pre-filtering (APF). The pre-filtered data are recorded on a High Density Digital Tape (HDDT) as well as processed by the real-time processor (one channel only) for display on a monitor simultaneously with the data acquisition.

The H/V switch ensures that the pulses are alternately transmitted with horizontal and vertical polarization. Thus for each frequency one single transmitter is used, while a dual receiver system is needed to record both like and cross polar signals (or upper and lower antenna for single pass interferometry).

An important feature of EMISAR is the internal calibration loops. Just before and after mapping a scene, pulses having the same coding as the transmitted pulses, can be routed through all units of the radar excluding only the antenna. Thus the complex transfer function of practically the complete radar is measured and the results used to correct the echo data recorded between calibrations. Stability between calibrations is enhanced by temperature control of the analog sections of the radar.

 emisar_sys_des01red_jpg

 

emisar_sys_des02red_jpg


EMISAR C-band and L-band system parameters

 

System Parameters

 

 

Frequency

C-Band, 5.3 GHz

L-Band 1.25 GHz

TWT output power

2 kW

6 kW

Receiver noise figure

1.5 dB

1.5 dB

System loss (Tx + Rx side)

(3.1 + 0.9) = 4.0 dB

4 dB

Pulse length

0.64 - 20 µs

0.64 - 20 µs

Max. bandwidth

100 MHz

100 MHz

Antenna gain

27 dBi

18 dBi

Azimuth 3 dB beam width

2.4°

10°

Elevation pattern width

31°

42°

Polarization

Fully polarimetric

Fully polarimetric

Antenna cross polarization

< -30 dB

< -35 dB

Azimuth ambiguity

< -30 dB

< -30 dB

Resolution in slant range

2, 4 or 8 m

2, 4 or 8 m

Resolution in azimuth

2, 4 or 8 m

2, 4 or 8 m

Swath width

12, 24 or 48 km

12, 24 or 48 km

Flight altitude

Typically 41,000 ft

Typically 41,000 ft

Real-time processing

Full resolution

Full resolution

Range (Noise equivalent s o < -20 dB)

Max. 80 km

Max. 64 km

PSLR

-30 dB

-25 dB

ISLR

-28 dB

-21 dB

Intrinsic cross-talk terms

< -30 dB

< -35 dB

Calibrated cross-talk terms

< -35 dB

TBD

Weight, Equipment inside cabin

600 kg

Pod

240 kg

Power: 115 V, 400 Hz

5 kW,  6 kVA

28 V, DC

1 kW

Dimensions: Equipment inside cabin

3 x 19" racks, H=1.40 m

Pod

4.59 x 0.81 x 0.55 m