1 / 18

UltraWideband Radars (FM-CW) for Snow Thickness Measurements

UltraWideband Radars (FM-CW) for Snow Thickness Measurements. Outline. Introduction Typical FM-CW Radar Background FM-CW radars design considerations Results Sea ice Land Future Conclusions . Basic FMCW Concept and some issues. f. Transmit Receive Mixed (Beat Freq ). k.

stefan
Download Presentation

UltraWideband Radars (FM-CW) for Snow Thickness Measurements

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. UltraWideband Radars (FM-CW) for Snow Thickness Measurements

  2. Outline • Introduction • Typical FM-CW Radar • Background • FM-CW radars design considerations • Results • Sea ice • Land • Future • Conclusions

  3. Basic FMCW Conceptand some issues f Transmit Receive Mixed (Beat Freq) k FFT t fB=kτ • Mixing the tx and rx signals produces single tone cw signals. • FFT transforms into target delay. • Transmitting and receiving at the same time. • Transform has sidelobes (windowing and amplitude variations). • Linear Chirp Considerations: for slow chirps and close targets, chirp non-linearities are near coincidental in tx and rx and tend to cancel.

  4. Basic FM-CW Conceptand difficulties with airborne applcations f f Fast chirp to sample Doppler (High PRF) and avoid target de-correlation. Longer range t t • Airborne applications require fast chirps and far targets. • Even slight non-linearities can cause major degradations. • Loss in resolution and FFT sidelobes.

  5. FM-CW Radar • Application of FM-CW radars for snow studies started in 1970s • Used linearized VCOs • YIG oscillators • Surface-based systems • Interfaces mapping was demonstrated • A number of systems have been built and used • Ultra-Wideband >500 MHz • FM-CW • Easy to implement • Low-sampling • Low power • Disadvantages • Linearity • RX/TX Isolation • Sidelobes

  6. Background 2-18 GHz Surface-based • We started our work in 2000 • Small grant from NASA to develop a system • Collaboration with Thurston Markus, GSFC • Instruments being used on aircraft • Long-range • Short-range Fast chirp problems Airborne, 2006

  7. Background • Solved chirp problems in 2008 • Fast-settling PLL + ultrawideband VCO

  8. Typical FM-CW Radar Antenna Feedthrough Two antennas Fast Chirp Fast PLL +VCO DDS + Multiplier LO feedthrough High isolation amp Multiple reflections Minimize cables and connectors

  9. Radar Instrumentation

  10. DC-8 and P-3B Antenna Configurations MCoRDS, Accumulation, Snow, and Ku-band radars

  11. Results – Arctic and Antarctic

  12. Results – Snow and Ku-band Radar Comparison

  13. Results – Greenland 2011 Snow Radar Ku-band Radar 0.9 km 0.9 km 10 m 10 m

  14. Future • Backscatter data at number frequencies • Invert data to estimate snow density and particle size • Combine these with sounder-mode data to determine snow thickness • Extend frequency range • 2-18 GHz • 1-17 GHz • Quad polarization • Digital beamforming • 16-32 receivers • Measure backscatter as function of incidence angle

  15. Future: Radar Instrumentation

  16. Array Performance Ideal 8-element array patterns at 5, 10 and 15 GHz 2D infinite dual-pol array simulation

  17. Conclusions • Advances in RF and Digital technologies enabled us: • To develop low-power and high sensitivity ultrawideband radars • Wide use over sea ice • FCC permit to operate over land

More Related