Lag Correlator Testing Aria Meyhoefer Carnegie Mellon University Summer 2001

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

17 Unit Lag Correlator Diode Array Inductor Capacitor Balun

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

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

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

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

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

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

Thanks Jeff Peterson – Carnegie Mellon Jeff Rapadas – Device Technologies