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[Discuss-gnuradio] Active RADAR minimum pulse

From: Jeffrey Lambert
Subject: [Discuss-gnuradio] Active RADAR minimum pulse
Date: Tue, 22 Jun 2010 02:39:56 -0400
User-agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv: Gecko/20100512 Thunderbird/3.0.5

Hello to all,

I am working on what approximates an active RADAR for the interrogation of a temperature sensitive microwave resonator. For this project, I will be using GNU Radio libraries and a USRP 1 device. In my research, I have discovered some issues that might pertain to this project in attempt to use the USRP in a RADAR application. Among these seem to be the lack of synchronization between transmit and receive, issues related to coherence with all but the BasicRX and BasicTX daughterboards (and for these two boards, coherence depends on front-end provided by the user), and a high minimum pulse width due to interpolation of the output signal.

With regards to the issue of synchronization, I believe that for my application I should be able to work around this problem as I do not require precise time measurement. I do, however, need to be able to ensure a particular response can be tracked with the excitation waveform. This seems likely to be simple to implement. I do not require phase coherence for my application, so this is not an issue either.

What I do need however, is to generate relatively short RF pulses. For my application, a pulse time between 10 - 50 ns should be sufficient. It seems to me that there is no way to bypass the interpolation that occurs during digital up-conversion and thus the only way to operate the DACs at there maximum rate is to interpolate. Can anyone confirm this?

What I am wondering is, could there be some way to create a buffered output that can be used to generate a highspeed waveform that is not interpolated or upconverted. For obvious reasons this waveform would have to be periodic, but for my application and others like it, I don't see the issue here. Has this been done already? Any thoughts on how to implement it?

~Jeffrey Lambert, K1VZX

~Jeffrey Lambert,  K1VZX

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