1 of 22

Glaciers and Ice Sheets Interferometric Radar

(GISIR)

Center for Remote Sensing of Ice Sheets,

University of Kansas, Lawrence, KS 66045

2 of 22

• Science Goals– To measure surface and basal topography of

terrestrial ice sheets– To determine physical properties of glacier bed

• Instrument– Radar: 150 MHz (20 MHz Bandwidth) & 450 MHz (50

MHz Bandwidth)– Multi-phase center antenna

Introduction

3 of 22

• Design and simulate radar with multiple receivers at 150 MHz and 450 MHz

• Design and simulate the performance of antenna array for collecting multi-phase center data

• Construct and evaluate radar performance in the laboratory with simulated targets

• Integrate radar and navigational systems on an aircraft

Tasks List

4 of 22

• Conduct field experiments• Conduct a field campaign to collect data• Process and distribute data• Analyze and synthesize results for presentation

at conferences and publication in archival journals

Tasks List

5 of 22

• Design a new set of optimized antennas: We will build a model structure and measure its electrical performance

• End-to-end simulation of the system, including antennas

• Design and simulation of the radar

Tasks Addressed

6 of 22

Prototype Multichannel Radar System

• 6 Channel 140-160 MHz Radar System

• Single Board Computer• 3 Compact PCI Carrier

Cards• 1 Waveform Generator

Card• 3 Dual Channel Data

Acquisition Cards• 5 RF Modules

7 of 22

GISIR Radar System Block Diagram

• Expandable from 1 to 8 Receivers

• RF Subsystems Housed in Compact PCI Aluminum Modules

• Very Similar to Existing Single Band MultiChannel Radar

• High Power Switches Contained in external 2U 19” Rackmount Enclosure

8 of 22

16 bit 160 MHz Dual Channel Waveform Generator

• Used to create the chirped pulse input to the transmitter

• Requires 120-MHz 0-dBm sine input

• Generates 4-dBm output • 0.5 usec minimum pulse width• 60 usec maximum pulse width• Linear chirp from 10 - 50 MHz• Caltone from 0 - 50 MHz

2.9”

5.9”

9 of 22

12 bit 170 MHz Dual Channel Data Acquisition Card

• Used to capture the return from the receiver

• Requires 120-MHz 0-dBm sine input

• 0-dBm full scale analog input • 72-dB dynamic range• 1 Megasample Input FIFO• Directly samples 140-160 MHz

and 425-475 MHz return

2.9”

5.9”

10 of 22

Compact PCI Carrier Card

• Compact PCI interface• Holds two plug-on

modules• Generates timing

signals for waveform generator, data acquisition card, and RF module

• Buffers captured data before transferring to the single board computer

6.3”

9.2”

11 of 22

Compact CPCI Carrier Card Block Diagram

• Compact PCI interface

• Reconfigurable FPGA Design

• High Speed Plug-on Module Interface

• 10 MHz Reference Input

• Used to Implement Radar Timing Unit (RTU)

6.3”

9.2”

12 of 22

GPS Logging and Time Tagging

• Everything Synchronized Off 10 MHz STALO

• Implemented in CPCI Carrier FPGAs

• 64 bit Radar Time Counter

• Synchronizes GPS Time w/ Radar Time

6.3”

9.2”

13 of 22

GISIR Transmitter

• Selectable Upconverter Stage

• Single Sideband Mixer

• Output Switch Routes TX and Cal Signals

14 of 22

GISIR Receiver

• Calibration Tone Input Through 20 dB Coupler• Diplexer Input Filter• Selectable Receiver Gain (10 – 72 dB)• Selectable Output Filter Bank

15 of 22

GISIR Frequency Synthesizer

• Generates 120 MHz and 420 MHz Clocks• Transmitter Upconverter Stage Los• Waveform Generator Clock• Data Acquisition Clocks

16 of 22

1. Losses for back lobes radiation.

2. Non Uniform distribution for total gain.

3. Reduction – weakness at 45 and 135 degrees.

4. Nulls in the first and last 10 degree.

Antenna

17 of 22

1. Acceptable return loss at the frequency of interest.

2. Evident mismatch impedance.

3. Decide the best matching network considering that at 150 or 450 MHz we should accept a mismatch.

Antenna Return Loss

18 of 22

1. Acceptable voltage standing wave ratio VSWR.

2. Considered revised the model used for this simulation.

Antenna VSWR

19 of 22

• The radiation pattern shows that we do not have an equivalent distribution of the energy.

– At 45 and 135 degree the energy distribution is reduced at least -10 dB.– Two areas where a null could be verified: from 0 to 10 degrees and from 170 to

180 degrees.

• In terms of the return loss and VSWR we can verify:– Between -8 to -9 dB as a reflection coefficient at the frequency of interest (450

MHz).– Between 428 to 435 MHz, the simulation gives the best response. Hence,. Since

we are working with the same dipoles for 2 different frequencies, we might accept that in one of these frequencies our impedance will be mismatched.

• Finally, as an overall conclusion, it is very important to reevaluate and design a matching network that minimizes the return loss and VSWR effects. Also, we estimate that according to these results we should continue simulating before we re-evaluate a different antenna solution.

Antenna

20 of 22

ACORDS Antenna array installation in the Chilean Navy P-3A Naval-408

21 of 22

Antennas• Two options

– Leave it as is• 10-15 dB loss in S/N ratio

– Redesign antennas• An AE student is looking into designing new

dipoles– Two pieces

» 450 MHz and 150 MHz– Telescoping design

• Design will be done by the end of the summer 06