Design and performance Assessment of an Airborne Ice Sounding Radar Front-End
Cilla Hernández, C; Krozer, V; Vidkjær, J; Dall, J
Technical University of Denmark

The paper describes the design and experimental performance assessment of the RF front-end of an airborne P-band ice sounding radar (P-sounder). The European Space Agency has initiated this airborne demonstrator project to enable an assessment of the detection of internal ice layers, reflection from the base of the ice sheet and validation of data processing algorithms for future satellite missions. The system is in the assembly and testing phase.

The P-sounder features newly developed compact high power RF components with a relative bandwidth of 20% at a centre frequency of 435 MHz:

- High power in-phase and out-of-phase power dividers with more than 75W CW power handling.
- High power SPDT PIN switch with 90W CW power handling and 0.5 µs switch-on time.
- 70W CW High efficiency LDMOS power amplifier with >60% power-added efficiency.

Both experimental results and simulations agree well in most cases for the individual components and the relative bandwidth requirement of >20% is realized with most components. The system comprises also a microstrip patch antenna array and a direct digital processing of the signals employing a digital signal generator, a digital front-end and a control unit.

Measurements of the assembled transmitter and receiver performance will be demonstrated in the paper. Great care has been devoted to matching of the individual ports. The transmitter front-end is composed of a high power high-efficiency amplifier (HPA), a high power PIN switch, a circulator, a slow high power relay for internal calibration, and high power splitters. While the compact power splitters and an early version of the HPA have already been published, the PIN switch and the assembly results are new. The receiver front-end is composed of a limiter, a low-noise amplifier, band pass filters and a variable gain amplifier that provides sufficient gain to drive optimally the A/D converters in the digital acquisition unit. It has been found that the limiter in front of the LNA deteriorates both the noise figure of the overall system but also the recovery time of the receiver.

The first data acquisition campaign will take place in Greenland in May 2008.