The Manastash Ridge Radar

Frank D. Lind
August 31, 1998


The Manastash Ridge Radar system is a passive radar system that utilizes common FM radio broadcasts as its signal source. The system is designed to observe ionospheric turbulence that occurs in the same region as the aurora, or northern lights.

This is an overview of the system.

The UW Receiver is located here in the new Electrical Engineering building.

The Manastash Ridge Observatory, where the remote receiver is located.

Looking approximately NE from MRO is Eastern Washington and its farming communities.

Here is a block diagram of the direct conversion receiver.

This is the UW receiver itself and the GPS unit. The computer is to the right.

Here is the IQ signal from the UW receiver taken with 12 bit data. Note an FM signal is constant modulus and should be a circle. The width of the circle is caused largely by ground clutter.

Here is a spectral plot of the same 12 bit data for 1 complete second. You can see the FM signal quite clearly.

The log plot of the cross ambiguity for the previous two signals shows what we believe to be a signal scattered by Mt. Rainier. We have seen the signature in most the data we have processed.

The zero doppler shift cut from the cross ambiguity of the two received signals. The precursor peak may be the direct signal leaking over the mountains, or perhaps a different scatterer.

This is the log plot of the self ambiguity of the signal that was transmitted. Note the sidelobes that show up here also show up in the cross ambiguity. The central peak is missing here due to a plotting problem.

This is the same self ambiguity but on a linear scale. Note the wonderful sharpness of the FM self ambiguity.

This is a cross ambiguity showing multiple aircraft as observed by the radar in 10 seconds of data. The processing was done for maximum doppler resolution and the aircraft is travelling at -21.5 +/- 1.5 m/s. The clutter at zero doppler is produced by signal propagating over the Cascade mountains and by scatter from Mt. Rainier. We have verified the scatter from Mt. Rainier by varying the antenna pointing.