1. Lag Correlator Testing
Aria Meyhoefer
Carnegie Mellon University
Summer 2001

2. The Lag Correlator What it is How it works What I did with it
Reflections
Transmissions
Signal Response
Conclusions

3. 17 Unit Lag Correlator
Inductor
Diode Array
Capacitor
Balun

4. How It Works
Antennas read signals off the sky with path difference depending on source angle
Signals travel along paths of equal length to Correlator
Inside correlator delay lines remove signal path delays
Each element of mixer array in the correlator measures the power from a particular direction
The correlator also allows measurement of the spectrum of any signal detected

5. Testing the Correlator
Signal Response Test
Send same signal* into both inputs of correlator
Use different path lengths to create interference
Read response from oscilloscope
Reflections Test
Send signal* into correlator through directional coupler
Terminate other input and output
Power reflects back though directional coupler to oscilloscope
Transmissions Test
Send a signal* into one input of correlator
Read signal from other input of correlator
Find attenuation of correlator
* Same microwave signal of 9dBm from 0.01 to 26.5 GHz was always used

6. Compared to mixer results
Expected Response: One part in 158
Measured Response: One part in 6000
Correlator is only 2.6% effective

7. Reflections Results Left input reflects 21% of the power
Right input reflects 16% of the power

8. Transmission Results 0.03 mV from right to left
0.02 mV from left to right
Sweep generator outputting 0.4 V
Average attenuation of about 42 dB

9. Summary Correlator Response only 2.6%
Correlator Reflects about 18.5% power
Attenuation of 42 dB

10. Thanks Jeff Peterson – Carnegie Mellon
Jeff Rapadas – Device Technologies