Software Defined Radio for FHSS monitoring - Page 1
Forum section: electronics / rf-microwave

author: hcglitte
author_rank: Regular Contributor
timestamp: February 05, 2019, 09:25:12 am
content: Hi,I am developing a FHSS protocol and would like a SDF to monitor the hopping pattern. The minimum packet duration is about 1 ms. Frequency 915 MHz ISM band (I would like to cover the whole band). I currently own a signal hound SA44B - but this only has a real time BW of 250 kHz. Anyone who has any recommendations?To distinguish 2 nodes I would simply set different power levels and hopefully the color on the waterfall display will separate the two communicating nodes.It would also be nice if there was an API available as well so I could write a script to sum the total air time for each node.

author: OwO
author_rank: Super Contributor
timestamp: February 05, 2019, 09:48:26 am
content: LimeSDR for prototyping and development. PlutoSDR if you ever need larger quantities because the IC (AD9363) is far easier to source and can be had for really cheap.

author: OwO
author_rank: Super Contributor
timestamp: February 05, 2019, 09:56:18 am
content: There are 24MHz worth of bandwidth on that ISM band. You need a fairly high end PC (CPU passmark >6000) to handle realtime FFT of that. If you want to do any processsing on the FPGA go for the PlutoSDR because it has DDR3 memory accessible via an AXI bus (no need for a controller as it is already taken care of). What Lime keeps getting wrong is having an underpowered FPGA with no meaningful amounts of memory.

author: hcglitte
author_rank: Regular Contributor
timestamp: February 05, 2019, 10:47:07 am
content: Thanks for the tips! Does any of these support a simple plug and play GUI for windows? I would rather not use Matlab etc while doing simple debugging.

author: OwO
author_rank: Super Contributor
timestamp: February 05, 2019, 11:47:21 am
content: I'm pretty sure GNU radio works with all of these, but last I checked PlutoSDR was easier to get set up.LimeSDR mini:pros: much better linearity (IIP3 at max gain).cons: only useful as a dev tool because the chip (LMS7002M) is currently unobtainable at reasonable prices; reports of software side being difficultPlutoSDR:pros: DDR3 SDRAM accessible from the FPGA; AD9363 is easy to source at $15 if you ever want to productionize a SDR system.cons: low IIP3. You will see image signals without a frontend filter.

author: jeremy
author_rank: Super Contributor
timestamp: February 05, 2019, 11:59:06 am
content: I have a limesdr mini. The software is indeed quite painful imo and documentation is either missing or scarce. Spec wise, it’s a pretty good device though.

author: Miek
author_rank: Regular Contributor
timestamp: February 05, 2019, 01:12:09 pm
content: You might struggle to catch every event with most waterfall tools, they tend not to run at full rate and will throw away samples between each FFT.I would look at using GNURadio with gr-fosphor, it's an OpenCL-accelerated spectrum visualiser that will use every sample and not miss bursts. There are some windows builds of GNURadio these days:https://wiki.gnuradio.org/index.php/WindowsInstallthough I'm on linux so I don't have any experience of them.If you can get a baseband recording then I recommendinspectrum(but I may be a little biased). This will let you browse through the recording and even do some basic demodulation to check your packets are coming out right. I believe the PothosSDR windows builds include a build of inspectrum, as well as GNURadio:https://github.com/pothosware/PothosSDR/wiki/Tutorial#id1

author: radioactive
author_rank: Regular Contributor
timestamp: February 05, 2019, 02:19:42 pm
content: Quote from: OwO on February 05, 2019, 11:47:21 amWhere can you find the AD9363 for $15?

author: tsman
author_rank: Frequent Contributor
timestamp: February 05, 2019, 03:06:29 pm
content: A problem with the PlutoSDR is that the USB 2.0 controller is a bottleneck. You can only get 3-4MSPS across USB before it starts dropping samples. If you want anything higher than you'll need to do your processing inside the Zynq.The AD9363 is officially rated for 20MHz bandwidth. You can set some configuration variables inside the PlutoSDR and make it like a AD9361 which expands it to 56MHz bandwidth + extended tuning range. It works on every PlutoSDR made so far but just be aware you're operating out of spec.

author: OwO
author_rank: Super Contributor
timestamp: February 05, 2019, 03:45:22 pm
content: Quote from: radioactive on February 05, 2019, 02:19:42 pmShenzhen market. These are the most recent quotes for AD9363BBCZ on the stock exchange. You could get them from downstream sellers on taobao but this isn't recommended if you are outside China.It's only cheap because this chip was used in a mass market product (DJI drones).

author: radioactive
author_rank: Regular Contributor
timestamp: February 05, 2019, 04:11:03 pm
content: Quote from: OwO on February 05, 2019, 03:45:22 pmWow, that part seems way overkill for a DJI drone product. Must have been for HD video? Anyway, I agree that the AD936x series would be an excellent way to track an FHSS transmitter. I found it quite easy to track a hopper with a simple signal threshold gating an FFT on the FPGA.

author: jujun
author_rank: Regular Contributor
timestamp: February 05, 2019, 04:47:57 pm
content: Quote from: OwO on February 05, 2019, 03:45:22 pmhttps://zhuanlan.zhihu.com/p/34590293https://github.com/o-gs/dji-firmware-tools/wiki/P3X-OFDM-Receiver-board