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This work describes the design and development of a radar receiver with a large dynamic range by means of carefully designed compression. The receiver is designed for ice sounding applications on the Antarctic and Greenland ice sheets and is designed to be usable over a large frequency range (VHF and UHF) and with multiple analog-to digital converters with only minor modifications. We present the receiver design, in which we have implemented an RF-power limiting feature so that the output power is monotonically increasing with respect to the input power over a large dynamic range. This allows the receiver to operate in the nonlinear region to compress the high-power returns into the dynamic range of the analog to digital converter while still achieving good sensitivity (low noise figure) for low power signals. We discuss design considerations, hardware description, initial lab test results, the architecture of the design and results from recent field deployments. Lastly, we discuss the future work on the decompression mechanism to recover the uncompressed signals. 

We present the design and field test results for a 600 to 900 MHz polarimetric ice penetrating radar that can be operated on the ground or from an airborne platform. This system is part of a development to build a dual band (VHF/UHF) polarimetric ice sounding radar suite. The VHF radar operates over 140-215 MHz and is essentially a modified version of the multi-channel 3D imaging system reported in [1]. The UHF radar, the focus of this work, is an adaptation of the CReSIS Accumulation Radar, which operates from 600 to 900 MHz [2]. The radar system uses a custom-designed, dual-polarized 4x4 antenna array with increased peak and average transmit power levels, which together provide additional sensitivity with respect to prior system renditions. The UHF radar incorporates a new receiver [3] that uses controlled analog compression via RF limiters to increase the instantaneous dynamic range. We designed the instrument setup to be towed by snowmobiles and operated at nominal speeds of 4 to 8 m/s. The relatively slow motion helps improve SNR through an increase in coherent averaging due to the longer dwell time. Although the focus of the field test is on ground-based work, the electronics are designed to also support airborne operation. 

This paper demonstrates the design and implementation of two dual-polarized ultra-wideband antennas for radar ice sounding. The first antenna operates at UHF (600–900 MHz). The second antenna operates at VHF (140–215 MHz). Each antenna element is composed of two orthogonal octagon-shaped dipoles, two inter-locked printed circuit baluns and an impedance matching network for each polarization. We built and tested one prototype antenna for each band and showed a VSWR of less than 2:1 at both polarizations over a fractional bandwidth exceeding 40 %. Our antennas display cross-polarization isolation larger than 30 dB, an E-plane 3-dB beamwidth of 69 degrees, and a gain of at least 4 dBi with a variation of ± 1 dB across the bandwidth. We demonstrate peak power handling capabilities of 400-W and 1000-W for the UHF and VHF bands, respectively. Our design flow allows for straightforward adjustment of the antenna dimensions to meet other bandwidth constraints.