Time Reversal Scholar Team
From ECE Department Wiki
Contents |
General Description and Goals
We want to make a time reversal mirror. We have a page on Wikipedia that describes TRMs. In essence, it is a way to automatically focus a wave, without knowing any details about the medium that the wave travels through. The key is to record the wave at several points (an array of receivers), reverse each signal in time, and transmit the time-reversed signals. The output should be approximately the same as the received wavefront, but traveling in the opposite direction, and should converge back to the origial source.
Current Projects
Currently, we are making an audio TRM. In the future, we want to make an RF TRM.
The senior design team is making a daughtercard to get the signal into a TI 6416 DSK. You can find more information about the daughtercard on the senior design team's page.
The scholar team is making a tranceiver front end to interface an array of sensors and transmitters and the daughtercard.
We also have a GNU Radio Universal Software Radio Peripheral (USRP). We can use this in the same way as the DSP daughtercard, or in many other ways.
Transmultiplexor
We are reversing the signal in time with a DSP. Not only is it trivial to time-reverse a signal once it is digitized, but we can do other processing relatively easily. The goal is then to get many signals in to and out of the DSP.
The solution we have come up with is to make a transmultiplexor with a single, wideband interface to the DSP. For receiving, the transmultiplexor will combine many signals into a single, wideband analog signal. The daughtercard will digitize this signal and give it to the DSP. The transmit process is similar. We are using complex signals (I/Q), so the number of real channels is twice the number of complex ones.
The current design of the transmultiplexor is to have two levels. The first level consists of transmultiplexors that mix 3 signals into a composite signal. This composite signal has center frequencies at f0,2f0,4f0, where f0 is about 50 kHz. It is easy to have clock signals whose frequencies are related by powers of 2. Each of the composite signals from level 1 will go into another transmultiplexer of similar design, with center frequencies at 0,f1,2f1,4f1, with f1 at about 400 kHz. The center frequency of 0 means there is no mixing. Thus we have 3*4 = 12 complex channels = 24 real channels.
Hardware
We have decided on some hardware for the transmultiplexor. We have ordered some parts and hope to start building soon.
These devices may be of interest for our clock generation: http://www.analog.com/en/subCat/0,2879,1073%255F931%255F0%255F%255F0%255F,00.html
GNU Radio
GNU Radio is a project to create a software radio platform that is free and open for anyone to use, modify, and contribute to. You can look at the USRP as a fast data converter like the senior design daughtercard. The difference is that the USRP also has powerful digital up/down converters in it, but the processor (a Linux workstation) is less powerful than a DSP. The advantage is that there is a large amount of code written for GNU Radio already, and a good framework for producing new code.
Currently, our workstation is dead, due to hardware failure. We will get a new one shortly. The USRP worked before the death of the computer; we had gotten a few examples to work, including an oscilloscope and a frequency analyzer (up to 2 MHz).
Team Members
- Faculty advisor
- Senior Design Team
- Other Members
Related Pages
External Links
- Previous senior design team website
- Transceiver design
- Another transceiver
- Time Reversal Signal Processing, a Wikipedia article written by this group
- TRSP in communication, US Dept. of Energy
