Setting DPSK Demod Block Parameters
Hello community, I am working on demodulating 1030 MHz Mode S traffic. As this signal uses DBPSK demodulation I'm using the deprecated GNU radio block 'DPSK Demod'. However, there are a few parameters within this block that I can't figure out how to set: * Excess bandwidth: I've read that in general the more excess bandwidth supplied the better you can expect your synchronization algorithm to perform. This is [0,1], and when I set it to 1 it's noise resilience appreciably increases. * FLL Bandwidth (assuming this is the same as filter lock-in bandwidth): This and the two subsequent values default to 6.28/100. I believe the higher this bandwidth is the faster the phase locked loop can adjust the output of the frequency. This leads me to believe I want this as high as possible, however I don't know where 6.28 and 100 come from. * Phase Loop Bandwidth: I know that lower values lead to reduced levels of phase noise and refence spurs at the expense of longer lock times and less phase margin. I'm assuming I want the least phase noise possible, however I don't know where 6.28 and 100 come from. * Timing Bandwidth: A dsp exchange question mentions that optimum loop bandwidth is usually somewhere between R/100 and R/20, where R is the symbol clock rate being recovered. My symbol rate is 2 due to it being BPSK, is this the same as symbol clock rate? Where do the 100 or 20 denominators come from? Should this value mirror the values of FLL and Phase Loop bandwidths? My end goal is being able to identify the Mode S message preambles within the demodulated bitstream. Any help is appreciated, thank you! Adam Gorski Virginia Tech Applied Research Corporation (VT-ARC) Lead Communications Engineer 410-818-3188
Re: [VOLK] Release v2.4.1
It's a submodule, so "git pull" gives you the latest submodule pointer, not the latest commit. To get the latest: cd gnuradio/volk git checkout v2.4.1 git submodule update --init Ron On 12/21/20 16:33, Cinaed Simson wrote: Hi Johannes - I'm running gnuradio 3.8.2.0. I did a git pull in the source for gnuradio, rebuilt and -re-installed gnuradio. When I run volk-config-info -v it returns 2.0. Did I mess up some where? -- Cinaed On 12/17/20 8:59 AM, Johannes Demel wrote: Hi everyone! We have a new VOLK bugfix release! We are happy to announce VOLK v2.4.1! We want to thank all contributors. This release wouldn't have been possible without them. Our v2.4.0 release introduced quite a lot of changes under the hood. With this bugfix release, we want to make sure that everything works as expected again. You can find the release news on [libvolk.org](https://www.libvolk.org/category/news.html) ### Contributors * A. Maitland Bottoms * Johannes Demel * Michael Dickens * Philip Balister * Ron Economos * Ryan Volz ### Changes * Build - cpu_features CMake option - Add cpu_features to static library build. - Use static liborc-0.4 library for static library build. - cmake: Detect if cpu_features submodule is present. * Install - Check for lib64 versus lib and set LIB_SUFFIX accordingly. * CI - Add CI test for static library build. * Releases - project: Include git submodules (i.e. cpu_features) in release tarball. - scripts: Add GPG signature to release script * Other - readme: Update TravisCI status badge
Re: [VOLK] Release v2.4.1
Hi Johannes - I'm running gnuradio 3.8.2.0. I did a git pull in the source for gnuradio, rebuilt and -re-installed gnuradio. When I run volk-config-info -v it returns 2.0. Did I mess up some where? -- Cinaed On 12/17/20 8:59 AM, Johannes Demel wrote: Hi everyone! We have a new VOLK bugfix release! We are happy to announce VOLK v2.4.1! We want to thank all contributors. This release wouldn't have been possible without them. Our v2.4.0 release introduced quite a lot of changes under the hood. With this bugfix release, we want to make sure that everything works as expected again. You can find the release news on [libvolk.org](https://www.libvolk.org/category/news.html) ### Contributors * A. Maitland Bottoms * Johannes Demel * Michael Dickens * Philip Balister * Ron Economos * Ryan Volz ### Changes * Build - cpu_features CMake option - Add cpu_features to static library build. - Use static liborc-0.4 library for static library build. - cmake: Detect if cpu_features submodule is present. * Install - Check for lib64 versus lib and set LIB_SUFFIX accordingly. * CI - Add CI test for static library build. * Releases - project: Include git submodules (i.e. cpu_features) in release tarball. - scripts: Add GPG signature to release script * Other - readme: Update TravisCI status badge
Re: Question on Gnuradio Polyphase Channelizer Block?
You should probably use an add block instead of Streams to Stream. Here's an example flow graph. http://www.w6rz.net/pfb-filter-10.grc Ron On 12/21/20 11:20, George Edwards wrote: Hello, I have three signals routed to the Gnuradio Polyphase Channelizer Block. The system operates at a sample rate of 90 kHz with 3 channels spaced 25 kHz apart. One channel is centered around DC and the other two at +/-25 kHz. The 3 waveforms are routed into a Gnuradio Streams to Stream Block, so that a simple concatenated stream flows into the Gnuradio Polyphase Channelizer. I also set the Channelizer Block to use 120 Taps and provide 3-outputs. Here are my questions on observing the outputs Q1. I was expecting each output (block set to 3 outputs) to be at the sample rate (90 kHz/3 =) 30 kz in each of the 3-plots. The plots show a sample rate based on the original rate of 90 kHz. Why is this? Q2. I expected each output waveform to be centered around DC, but they were instead centered around -25 kHz. Why? Q3. The output bandwidth for each waveform seems a little bigger than the input, why? I will appreciate any help that assists to point me in the right direction. Regards, George
Question on Gnuradio Polyphase Channelizer Block?
Hello, I have three signals routed to the Gnuradio Polyphase Channelizer Block. The system operates at a sample rate of 90 kHz with 3 channels spaced 25 kHz apart. One channel is centered around DC and the other two at +/-25 kHz. The 3 waveforms are routed into a Gnuradio Streams to Stream Block, so that a simple concatenated stream flows into the Gnuradio Polyphase Channelizer. I also set the Channelizer Block to use 120 Taps and provide 3-outputs. Here are my questions on observing the outputs Q1. I was expecting each output (block set to 3 outputs) to be at the sample rate (90 kHz/3 =) 30 kz in each of the 3-plots. The plots show a sample rate based on the original rate of 90 kHz. Why is this? Q2. I expected each output waveform to be centered around DC, but they were instead centered around -25 kHz. Why? Q3. The output bandwidth for each waveform seems a little bigger than the input, why? I will appreciate any help that assists to point me in the right direction. Regards, George
Re: qt gui frequency sink in frequency hopping
Hi Without a flowgraph anyone can help. The first thing I would check : verify the sampling rate used in each block. When using several sampling rate, when one is uncorrectly set it can stop your simulation and freeze time or frequency sink. Sincerely, Christophe On 21/12/2020 11:50, Ali G. Dezfuli wrote: Hi all, I work on a Frequency Hopping (FH) Tx and Rx in the same grc flowchart in 3.7.13.4 in Ubuntu 16.04. At the end of the Tx chain, I put a "Qt GUI Frequency Sink", but it just shows part of subchannels in the spectrum!!! I changed its parameters especially "Update Period" but no change. The very interesting point is that when I remove the Rx chain (lessen the complexity), it shows the spectrum of FH correctly! I really wonder why. Thanks, AGD
qt gui frequency sink in frequency hopping
Hi all, I work on a Frequency Hopping (FH) Tx and Rx in the same grc flowchart in 3.7.13.4 in Ubuntu 16.04. At the end of the Tx chain, I put a "Qt GUI Frequency Sink", but it just shows part of subchannels in the spectrum!!! I changed its parameters especially "Update Period" but no change. The very interesting point is that when I remove the Rx chain (lessen the complexity), it shows the spectrum of FH correctly! I really wonder why. Thanks, AGD
