Inexpensive software defined radio and evolved fractal antennas. - Page 1
Forum section: electronics / general

author: diracshore
author_rank: Regular Contributor
timestamp: August 01, 2012, 10:21:44 am
content: Hi all,Here is a rant if you are bored. This is why I don't drink coffee.I was surprised to see this software defined radio hack of a usb TV tuner donglehttp://www.hamradioscience.com/the-rtl2832u-elonics-e4000-sdr-radio-aka-the-20-sdr/Apparently this $20 dongle is able to receive 64 – 1700 MHz with 2MHz bandwidth @ 8 bit sample rate. You can compare that to the 16MHz on the ettus research B100 @ $650 sans daughter boards.So no longer do people have to pay $1000 to use software defined radio. I am slowly realizing how disruptive that could be. Software defined radio is no longer just a research tool. There is not a whole lot of applications as yet for SDR mainly because I think in addition to cost the interdisciplinary knowledge of software, electronic engineering, RF, and antenna design is too complex for developers to integrate. There is no vision of a single product, no framework as yet.The USRP contains really inexpensive hardware. The main board is just a very dated Xilinx FPGA with some headers, which in turn connect to daughter boards that clear up one frequency range or another, when combined with a matching antenna. The production cost is a small fraction of the price. Certainly that is true of any engineered product. The USRP design has not kept up to date with modern FPGAs such as Virtex 7. Perhaps a better way to look at it, what I am trying to say is that the cost to manipulate RF bandwidth is dropping.I have been wondering how this type of deflation will play out for us and what the next step in the development might be.I was considering how antennas will develop. The most interesting trends in antenna design are fractal antennas and evolved antennas.A few years ago NASA created an antenna design using genetic programminghttp://alglobus.net/NASAwork/papers/Space2006Antenna.pdfFractal antennas such as this pattern allow a dramatic reduction in size and increase in bandwidth compared to previous techniques. It is also possible to create directional 3D fractal antennas that are orders of magnitude more powerful.With enough time it is possible I think to create evolved fractal antennas as well. And fractal designs are portable. With a laser cutter anyone can take one of these patterns and etch out a ultra wide band antenna on copper foil. That could allow a community to collectively create and revise a series of high performing wide band antennas which combined with the coming wide band, large bandwidth, low cost SDR development platforms could be the foundation of a new communication infrastructure. Such as a global mesh.A global mesh would use a series of personal routers using SDR and advanced antenna systems, with adaptive network protocolshttp://ww2.cs.fsu.edu/~guidry/AI/AntColonyOptimization.pdfand cryptographic overlayshttps://www.torproject.org/about/overview.html.ento create an alternate internet that does not rely on the existing fiber optic backbone. Something that would not be so very susceptible to censorship and surveillance. With communications decentralized and systems such as bitcoin maturing, I see a series of interdependent emerging technologies driven by the open source community that can establish a new standard.In much the same way as the music industry was unable to enforce laws regarding piracy, the FCC will not be able to regulate the airwaves when SDR becomes ubiquitous. Using techniques such as spread spectrum over a wide bandwidth has never before been possible because of the reliance on analog circuitry and the limitations in cost and size and bandwidth of antennas.If a online community got together and created a open database, something like thingiverse for various fractal antenna designs, those that were products of genetic algorithms or just the best designs people come up with cross referenced with performance, then I think we have a feedback system that can create the next generation of antennas to complete the SDR paradigm shift.Yawn.

author: vk6zgo
author_rank: Super Contributor
timestamp: August 01, 2012, 12:23:06 pm
content: When you get away from the hype,Fractal Antennas are not well regarded,nor are they particularly efficient.There are always antennas which purport to do wonders,but they all disappear,like "crossed field" antennas,& "spray on antennas".I read the NASA link,& it doesn't mention fractals anywhere.Genetic programming has been covered extensively in Ham books & sitesThe second link was just a "Gee Whiz" booster for Fractals.

author: diracshore
author_rank: Regular Contributor
timestamp: August 01, 2012, 07:48:56 pm
content: NASA did not use fractals. I was suggesting combining the two techniques. Taking various fractals and assessing fitness through simulation.