wiki/ news/ 2003-12-09 - Field trip to NW EMC in Hillsboro to test CPA propagation

In attendace: Andrew, Glenn, Timr, Jared and Dave.

Special thanks to: NW EMC, Holly, and Rod for making this possible.

Summary: We took the LV2.1 airframe, along with the cylindrical patch antennas (CPAs) on the avionics module to NW EMC in Hillsboro to do propogation measurements. We did three polar plots of each cylindrical patch antenna at it's natural frequency (which was not the design frequency): one azimuth and two elevations (at 90 degrees to each other). We then took azimuth readings on a 2.422 and 1.253 GHz reference dipole, and finally took azimuth and a single elevation reading for the 1.5 GHz slot antenna.


Pre-lab:

Things to bring:

Would have been useful:


Test Plan:

  1. Test antennas.
  2. Measure the propagation of the v2 WiFi cylindrical patch antennas on the airframe:
    • At 2.422 GHz, 2.422 GHz + 15 MHz, 2.422 GHz - 15 MHz
      • Azimouth
      • Elevation at 0,90 degrees
  3. Measure the GPS CPA as possible
  4. Measure the ATV CPA as possible

  5. Measure and possibly tune the 2.4, 1.5, and 1.3 GHz reference dipoles at the freq, freq - BW, freq + BW.

  6. Measure 3 slots

Getting there:

We're meeting there at 5:00pm SHARP. Do NOT be late! We've got 20 hours of testing to do in 4 hours ;)

Northwest EMC, Inc. 22975 NW Evergreen Parkway, Suite 400 Hillsboro, OR 97124 (503) 844-4066

And you can get maps at their web site: http://www.nwemc.com/hillsboro.html


Testing Notes

Given the time constraints, we decided to do only three tests per antenna and throw out the idea of doing off-natural frequency tests (for bandwidth).

Holly and Rod calibrated the chamber for each of the cylindrical patch antenna frequencies: 2.29328, 1.52438 and 1.24259 GHz (as measured previously).

We then had to make a decision: how to set the vertical height of the receive antenna. Holly and Rod set the height during chamber calibration to maximize the signal strength of the calibration horn antenna. We really wanted the geometric scan to be correct - i.e., we wanted the receive antenna to be on axis to the rocket so we could really get the geometric cut through the propagation space we wanted. This apparently throws off the absolute measurements of the system, and thus the absolute calculations are called "pseudo-absolute" because of this lack of maximizing the signal.

"Configuration" Notes

To understand what test we did, we had to define the axes and test configurations (positions) of the antennas (and thus rocket). We used the inertial definitions of the rocket to be consistent: while on the launch tower, the +Z axis is straight up, the +X axis is straight out from the rocket away from the launch rail, and +Y follows the right hand rule (Z is the thumb, X is the index and Y is the middle finger).

To map this to the avionics module, this means the positive X axis starts at the center of the cylinder and goes out through the same vertical plane that cuts through the center of the camera lens. The Y axis is 90 degrees to the right looking down the tube (again, the right hand rule where Z is the thumb, X is the index and Y is the middle finger).

Z is through the cylinder's hieght, X through the front of the cylinder (parallel to the camer lens) and Y is off to the side following the right hand rule.
X,Y and Z axes defined for the Avionics Module. The circle with a "c" in it is the ATV camera lens.

Given these definitions, we then defined the test configurations as:

Configuration 1: Azimuth, rotation around the Z axis ("roll"): We put the rocket on standing vertially on top of a ~1.5 m block of styrofoam, using packing tape to secure the base and payload module in the middle.

Configuration 2: Elevation 1, rotation around the X axis ("pitch"): We laid the rocket down on its side with the X axis pointing straight up.

Configuration 3: Elevation 2, rotation around the Y axis ("yaw"): We laid the rocket down on its side with the Y axis pointing straight up.. similar to Configuration 2 but at 90 degrees.

Configurations 1-3 and X,Y,Z axes of rocket.
Sketches of Configurations and LV2.1 Axes. Note Configuration 1 starts with the X axis pointing towards the receive antenna.


Photo of LV2.1 in Configuration 1 from right in front of the receive antenna.


Photo of LV2.1 in Configuration 2 (which is similar to Configuration 3) from right in front of the receive antenna.


Reference Scans

Holly and Rod ran tests 1 - 5 in order to calibrate the chamber for absolute measurement.


WiFi Antenna

TEST 06: WiFi antenna, Configuration 2, RX antenna @ horizontal polarization

Changed height of receive antenna to the height of the center of the rocket: 1.77 m

TEST 07: WiFi antenna, Configuration 2, RX antenna @ horizontal polarization

TEST 08: WiFi antenna, Configuration 2, RX antenna @ vertical polarization

TEST 09: WiFi antenna, Configuration 3, RX antenna @ vertical polarization

TEST 10: WiFi antenna, Configuration 3, RX antenna @ horizontal polarization

TEST 11: WiFi antenna, Configuration 1 but rotated 180 degrees, RX antenna @ horizontal polarization

TEST 12: WiFi antenna, Configuration 1 but rotated 180 degrees, RX antenna @ vertical polarization


ATV Antenna

TEST 13: ATV antenna, Configuration 1 but rotated 180 degrees, RX antenna @ vertical polarization

TEST 14: ATV antenna, Configuration 1 but rotated 180 degrees, RX antenna @ horizontal polarization


GPS Antenna

TEST 15: GPS antenna, Configuration 1 but rotated 180 degrees, RX antenna @ horizontal polarization

TEST 16: GPS antenna, Configuration 1 but rotated 180 degrees, RX antenna @ vertical polarization

TEST 17: GPS antenna, Configuration 2, RX antenna @ vertical polarization

TEST 18: GPS antenna, Configuration 2, RX antenna @ horizontal polarization

TEST 19: GPS antenna, Configuration 3, RX antenna @ horizontal polarization

TEST 20: GPS antenna, Configuration 3, RX antenna @ vertical polarization


ATV Antenna

TEST 21: ATV antenna, Configuration 3, RX antenna @ vertical polarization

TEST 22: ATV antenna, Configuration 3, RX antenna @ horizontal polarization

TEST 23: ATV antenna, Configuration 2, RX antenna @ horizontal polarization

TEST 24: ATV antenna, Configuration 2, RX antenna @ vertical polarization


ATV Reference Dipole (1.253 GHz)

dipole @ 1.75m off ground

TEST 25: ATV dipole, RX antenna at same level and at horizontal polarization

TEST 26: ATV dipole, RX antenna at same level and at vertical polarization

TEST 27: ATV dipole, RX antenna at height maximized for signal strength and at vertical polarization

TEST 28: ATV dipole, RX antenna at height maximized for signal strength and at horizontal polarization


WiFi Reference Dipole (2.422 GHz)

dipole @ 1.75 m off ground

TEST 29: WiFi dipole, RX antenna at same level and at horizontal polarization

TEST 30: WiFi dipole, RX antenna at same level and at vertical polarization

TEST 31: WiFi dipole, RX antenna at height maximized for signal strength and at vertical polarization

TEST 32: WiFi dipole, RX antenna at height maximized for signal strength and at horizontal polarization


GPS Slot Antenna (1.575 GHz)

slot @ 2.05 m off ground

TEST 33: GPS slot antenna, "horizontal orientation" = configuration 1, RX antenna at same level and at horizontal polarization

TEST 34: GPS slot antenna, "horizontal orientation" = configuration 1, RX antenna at same level and at vertical polarization

TEST 35: GPS slot antenna, "vertical orientation" ~= configuration 2, RX antenna at same level and at vertical polarization

TEST 36: GPS slot antenna, "vertical orientation" ~= configuration 2, RX antenna at same level and at horizontal polarization

Found a loose connector, re-ran last two sweeps.

TEST 37: GPS slot antenna, "vertical orientation" ~= configuration 2, RX antenna at same level and at horizontal polarization

TEST 38: GPS slot antenna, "vertical orientation" ~= configuration 2, RX antenna at same level and at vertical polarization


Gratuitous Pictures.


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Here are pictures taken with Glenn's camera

Okay; Which end is up?

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