January 2025 - pacsat-dev - mailman.amsat.org

pacsat dev mtg 1/30/2025
by Bill 30 Jan '25

30 Jan '25

*pacsat dev mtg 1/30/2025* Jan 30, 2025, 7:00 – 8:30 PM (America/Chicago) *Please join my meeting from your computer, tablet or smartphone.* https://meet.goto.com/872926061 *You can also dial in using your phone.* Access Code: 872-926-061 United States: +1 (872) 240-3212 <tel:+18722403212,,872926061> *Join from a video-conferencing room or system.* Meeting ID: 872-926-061 Dial in or type: 67.217.95.2 or inroomlink.goto.com Or dial directly: 872926061(a)67.217.95.2 or 67.217.95.2##872926061 *Get the app now and be ready when your first meeting starts:* https://meet.goto.com/install

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Status on DSP work
by Corey Minyard 28 Jan '25

28 Jan '25

Due to the frustrations trying to find a suitable receiver/transmitter chip, I decided to spend some time trying to figure out how to do a mixer from (sort of) scratch. I've spent a lot of time learning about mixers. I have come up with a design using a fully differential amplifier (FDA) and a MOSFET ring mixer. I have simulated it in spice and have been getting pretty good results. I also did a design in kicad and did a basic layout; I believe a full transceiver could be done in less than 1 square inch of board space. I did a 6th order Chebychev filter with LC components which takes up most of the space (you need 5 or 6 filters for a full transceiver), but a 4th order is probably good enough for transmit, certainly better than the switched capacitor filters that most on-chip solutions probably use. And I started with 150 ohm impedance; decreasing that using better MOSFETs is possible and will reduce the inductor sizes. I like this better because the individual chips are more available and easier to find in the temperature ranges we need. FDAs are plentiful at high speeds; they are commonly used to drive high-speed ADCs. Enough are available at extended temperatures to make me comfortable. MOSFETs are fairly plentiful, and of course the passive components are easy to get. It looks to use less power, too, but that's hard to tell. I would guess this is what most single-chip solutions do, but they don't tell. I still have questions. I have read in a couple of places that ring mixers perform better with transformer interfaces. We can't do that at baseband, of course. But I can't find anywhere that says how it performs better, or why. Just a few vague statements. On board layout, I've never done that. Others have done it for me. It brings up its own set of questions. Can you put vias on pads? How wide should the traces be? Lots of little details. Anyway, that's what I've been playing with. -corey

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No meeting tonight
by Bill Reed 23 Jan '25

23 Jan '25

I am unable to start the meeting tonight at 7PM. I apologize. If anyone is still interested in meeting tonight, send me an email and I will start the meeting around 9PM. Otherwise, see you next week. Bill

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Re: Status on looking at a DSP design
by Chris Thompson 20 Jan '25

20 Jan '25

We use the LTC5599 on all the Amsat BPSK spacecraft. The idea was to be able to support other modulations in the future, but it just uses one input and generates BPSK. But that is an IQ mixer that goes to 1.3G. With a suitable oscillator and some filters it would work, but we are then designing our own receiver chain .. On Sun, Jan 19, 2025, 15:58 Corey Minyard via pacsat-dev < pacsat-dev(a)amsat.org> wrote: > I've spent some time looking at a lot of aspects about this and it's > rather obvious now why sticking with the ax5043 is so attractive. > Finding workable parts is really hard, if not impossible. > > The processor/FPGA is pretty easy. Due to the automotive market, many > options exist. > > The ADCs and DACs are harder. There is the audio codec, the TI > TAC512. Its bandwidth is 96KHz, which is less than I would like. And > I don't know if it's going to handle DC offsets (I'm suspecting it > won't, but I can't find any info in the datasheet); if so there will > be a hole in the middle of the frequency range that's unusable. Maybe > that's ok. > > I have found an ADC, the Analog AD4680, and a DAC, the Analog AD5541A, > that would also work. They will go to 1 MHz and will interface > directly with the DSP. The AD4680 has a bipolar analog input, so it > has to have negative voltages that have to be created, costing a > couple of extra small chips to do that. For ADCs, that's about the > only one I could find. Very few are temperature rated and most won't > interface nicely with the TI DSPs. The slower speed (<10MS/s) ADCs > are really designed for industrial control, the faster ones are > workable but expensive and power hungry. For DACs, a few options are > available, but not many. Again, mostly designed for industrial > control. > > The really nasty part is the RF side. There's just nothing I could > find integrated available that is temperature rated to what we need > and is suitable. As Jim pointed out, the CMX991 might have problems > with availability. I'm also a bit worried that it's not going to work > at the temperature range. I can think of three reasons that the chip > wouldn't work full duplex: It would generate too much heat, there > would be internal interference, or it would not be able to draw that > much power. So I'm thinking it's not going to be feasible. > > So for the RF front end, I found the Analog LTC5562 mixer which is > rated to 105C. That was it. It might be possible to use it for I/Q > conversion, too, or it's possible to use direct conversion. Direct > conversion isn't so great for narrow bandwidth, but it might be > usable. As far as I can tell, there is no other available mixer with > an extended temperature range. I mean, not even a 612 mixer. Well, I > did find the MC1496B, but it would probably only go to 10MHz. > > So you might end up doing your own gilbert cell mixer. (For I/Q, you > can't do ring mixers as they have to be transformer coupled and that > doesn't work for I/Q since you need low frequency and DC, really). > Maybe a mixer could be designed with discrete parts on its own circuit > board and mounted vertically on the main board? I don't know. You > start doing all this stuff and it starts taking up a lot of board > space. > > If you need frequency agility, then there are yet more issues with RF > synthesis. But I was assuming the frequencies would be pretty fixed > on the satellite, so you could just use standard fixed oscillators. > Though I haven't looked much at that yet. > > So I don't know how feasible this will be. > > -corey > > ----------------------------------------------------------- > > pacsat-dev mailing list -- pacsat-dev(a)amsat.org > View archives of this mailing list at > https://mailman.amsat.org/hyperkitty/list/[email protected] > To unsubscribe send an email to pacsat-dev-leave(a)amsat.org > Manage all of your AMSAT-NA mailing list preferences at > https://mailman.amsat.org >

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Re: Status on looking at a DSP design
by Jim McCullers 20 Jan '25

20 Jan '25

I'm still amazed at how they got the functionality into the AX5043 and why it went extinct. I suspect LoRa had an influence. That is a popular protocol with chips similar to the AX5043. Another aspect of the AX5043 is that it has been radiation tested and certified and is flying in at least one or two cubesats. What we really need is a system and procedure to grade junk from good and purchase a lifetime supply. One can never be certain where an aftermarket supply originated. Jim McCullers WA4CWI I've spent some time looking at a lot of aspects about this and it's rather obvious now why sticking with the ax5043 is so attractive. Finding workable parts is really hard, if not impossible. The processor/FPGA is pretty easy. Due to the automotive market, many options exist. The ADCs and DACs are harder. There is the audio codec, the TI TAC512. Its bandwidth is 96KHz, which is less than I would like. And I don't know if it's going to handle DC offsets (I'm suspecting it won't, but I can't find any info in the datasheet); if so there will be a hole in the middle of the frequency range that's unusable. Maybe that's ok. I have found an ADC, the Analog AD4680, and a DAC, the Analog AD5541A, that would also work. They will go to 1 MHz and will interface directly with the DSP. The AD4680 has a bipolar analog input, so it has to have negative voltages that have to be created, costing a couple of extra small chips to do that. For ADCs, that's about the only one I could find. Very few are temperature rated and most won't interface nicely with the TI DSPs. The slower speed (<10MS/s) ADCs are really designed for industrial control, the faster ones are workable but expensive and power hungry. For DACs, a few options are available, but not many. Again, mostly designed for industrial control. The really nasty part is the RF side. There's just nothing I could find integrated available that is temperature rated to what we need and is suitable. As Jim pointed out, the CMX991 might have problems with availability. I'm also a bit worried that it's not going to work at the temperature range. I can think of three reasons that the chip wouldn't work full duplex: It would generate too much heat, there would be internal interference, or it would not be able to draw that much power. So I'm thinking it's not going to be feasible. So for the RF front end, I found the Analog LTC5562 mixer which is rated to 105C. That was it. It might be possible to use it for I/Q conversion, too, or it's possible to use direct conversion. Direct conversion isn't so great for narrow bandwidth, but it might be usable. As far as I can tell, there is no other available mixer with an extended temperature range. I mean, not even a 612 mixer. Well, I did find the MC1496B, but it would probably only go to 10MHz. So you might end up doing your own gilbert cell mixer. (For I/Q, you can't do ring mixers as they have to be transformer coupled and that doesn't work for I/Q since you need low frequency and DC, really). Maybe a mixer could be designed with discrete parts on its own circuit board and mounted vertically on the main board? I don't know. You start doing all this stuff and it starts taking up a lot of board space. If you need frequency agility, then there are yet more issues with RF synthesis. But I was assuming the frequencies would be pretty fixed on the satellite, so you could just use standard fixed oscillators. Though I haven't looked much at that yet. So I don't know how feasible this will be. -corey ----------------------------------------------------------- pacsat-dev mailing list -- pacsat-dev(a)amsat.org View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to pacsat-dev-leave(a)amsat.org Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org

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Status on looking at a DSP design
by Corey Minyard 19 Jan '25

19 Jan '25

I've spent some time looking at a lot of aspects about this and it's rather obvious now why sticking with the ax5043 is so attractive. Finding workable parts is really hard, if not impossible. The processor/FPGA is pretty easy. Due to the automotive market, many options exist. The ADCs and DACs are harder. There is the audio codec, the TI TAC512. Its bandwidth is 96KHz, which is less than I would like. And I don't know if it's going to handle DC offsets (I'm suspecting it won't, but I can't find any info in the datasheet); if so there will be a hole in the middle of the frequency range that's unusable. Maybe that's ok. I have found an ADC, the Analog AD4680, and a DAC, the Analog AD5541A, that would also work. They will go to 1 MHz and will interface directly with the DSP. The AD4680 has a bipolar analog input, so it has to have negative voltages that have to be created, costing a couple of extra small chips to do that. For ADCs, that's about the only one I could find. Very few are temperature rated and most won't interface nicely with the TI DSPs. The slower speed (<10MS/s) ADCs are really designed for industrial control, the faster ones are workable but expensive and power hungry. For DACs, a few options are available, but not many. Again, mostly designed for industrial control. The really nasty part is the RF side. There's just nothing I could find integrated available that is temperature rated to what we need and is suitable. As Jim pointed out, the CMX991 might have problems with availability. I'm also a bit worried that it's not going to work at the temperature range. I can think of three reasons that the chip wouldn't work full duplex: It would generate too much heat, there would be internal interference, or it would not be able to draw that much power. So I'm thinking it's not going to be feasible. So for the RF front end, I found the Analog LTC5562 mixer which is rated to 105C. That was it. It might be possible to use it for I/Q conversion, too, or it's possible to use direct conversion. Direct conversion isn't so great for narrow bandwidth, but it might be usable. As far as I can tell, there is no other available mixer with an extended temperature range. I mean, not even a 612 mixer. Well, I did find the MC1496B, but it would probably only go to 10MHz. So you might end up doing your own gilbert cell mixer. (For I/Q, you can't do ring mixers as they have to be transformer coupled and that doesn't work for I/Q since you need low frequency and DC, really). Maybe a mixer could be designed with discrete parts on its own circuit board and mounted vertically on the main board? I don't know. You start doing all this stuff and it starts taking up a lot of board space. If you need frequency agility, then there are yet more issues with RF synthesis. But I was assuming the frequencies would be pretty fixed on the satellite, so you could just use standard fixed oscillators. Though I haven't looked much at that yet. So I don't know how feasible this will be. -corey

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Pacsat dev mtg 1/16/2025
by Bill 16 Jan '25

16 Jan '25

*Pacsat dev mtg 1/16/2025* Jan 16, 2025, 7:00 – 8:30 PM (America/Chicago) *Please join my meeting from your computer, tablet or smartphone.* https://meet.goto.com/496794861 *You can also dial in using your phone.* Access Code: 496-794-861 United States: +1 (872) 240-3212 <tel:+18722403212,,496794861> *Join from a video-conferencing room or system.* Meeting ID: 496-794-861 Dial in or type: 67.217.95.2 or inroomlink.goto.com Or dial directly: 496794861(a)67.217.95.2 or 67.217.95.2##496794861 *Get the app now and be ready when your first meeting starts:* https://meet.goto.com/install

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Re: Last nights recording
by Corey Minyard 13 Jan '25

13 Jan '25

On Sun, Jan 12, 2025 at 01:13:36AM +0000, Cameron Castillo via pacsat-dev wrote: > Hi Bill, > > Interesting presentation! A couple notes: > > On the FPGA design for the SDR, a significant amount of the work can be > done via Xilinx IP. I think the team has the idea that most of the DSP and > hardware would have to be built from scratch in verilog. For almost any > design today, many people use the block diagram editor from Xilinx instead > of writing their own verilog. Not only are these guaranteed to work but all > the driver code is also available in their software platform (Vitis). I've > looked into some of the DSP blocks they have available and the list is > fairly comprehensive (IIR/FIR filters, FFTs, Freq. Synthesizer to name a > few off the top of my head). Yes, I'm aware of this. From what I can tell, the licensing is not open source on these. If that's so we can't use them on our platform. But maybe I'm wrong. Second, I am planning on custom modulation, so those would have to be written in VHDL or Verilog. Not a show-stopper, though. > > One of the other benefits is that many of Xilinx's products have hard > integrated processors or have the ability to integrate soft processors (See > Zynq and MicroBlaze respectively). The nice thing about these is that they > support Linux development and bare-metal/RTOS configuration. We might even > be able to remove the TMS570 and replace it with one of the multi-core > devices. Perhaps we could have a system where Direwolf and the other > processing functions are run on the same chip as the DSP. The downside to > this is that I'm not sure how parallelable that would be (i.e. could we > maintain four Rx channels). If you are going to use something like a Zynq processor, why do you even need a DSP or an FPGA for this application? ;-) You could even get those fancy Zynq processors that have built-in RF subsystems. They just cost $2000 and need gobs of power. I don't know much about the MicroBlaze, how powerful it is or whatnot. The big problem with these things is power. Zynq or Versal is right out. I'm looking to keep the entire power budget for everything outside of the PA to <1W. I think I can be successful if I play some tricks. I have no idea how much a MicroBlaze on an FPGA would use. Also, there's a lot of functional safety things tied into the TMS570 processors. Things like lockstep processing, parity/ECC on everything, extended temperature, etc. The MicroBlaze can do lockstep, it appears, meaning that it can't be superscalar and it will be slow. I guess it says it's Harvard architecture. I don't know how it would compare to a Cortex-R5F. > > I do a lot of work with Xilinx products and FPGAs at work. It's mostly for > video functions, but I've found it pretty easy to understand the > fundamentals of Vivado/Vitis in only a few months. With integrated > peripherals like AXI and the IP blocks, it probably wouldn't take as long > as everyone is thinking. I hardly ever touch verilog at work anymore... I'm not against using an FPGA, but it would take some research. Do you have any idea of the power they would use? > > As far as the amplifier project is coming, I'm back in the lab at work and > want to get some more prototyping done with our actual amplifier. Does > anyone on the team have extra stock of the transistor we're using for the > Tx amplifier (ATF05MS004NT1)? I'd also like to get an inductor kit like this > one > <https://www.amazon.com/First-Inductor-Assorted-1nH-270nH-42Valuesx50pcs/dp/…> > as > the one I have at work is all 0201s and I can't reliably solder it... A book of inductors :-). > > On that note, I'm happy to keep prototyping it if the team wants to go in > that direction, but I think it'd be faster to go with a premade power amp. > I've already created a schematic for a PA as a backup to the work I'm doing > now. If we want something for Jim's test board, I could probably get > something to at least prototype with a lot sooner even if we think we could > do better with the discrete option. Just a suggestion. Are you talking about a PA module as something that can be used on the satellite, or just something as a temporary solution to plug into Jim's board? And as I mentioned before, power is a big issue. I don't know much about these things, though. Thanks, -corey > > Thanks, > > Cameron Castillo > > > ------------------------------------------------- > > Cameron Castillo > > KJ7ILB > > *P*: (503) 752-8877 > > -------------------------------------------------- > > > On Fri, Jan 10, 2025 at 8:47 AM Bill Reed <bill(a)brconnect.com> wrote: > > > This is a better URL... > > > > https://github.com/AMSAT-NA/PacSatDocs/blob/main/SDR/MinyardSDR_1-9-2024.we… > > > > -------- Forwarded Message -------- > > Subject: Last nights recording > > Date: Fri, 10 Jan 2025 09:31:07 -0600 > > From: Bill Reed <bill(a)brconnect.com> <bill(a)brconnect.com> > > To: Cameron Castillo <camstillo2000(a)gmail.com> <camstillo2000(a)gmail.com> > > > > We discussed 2 things last night. > > > > 1: Start of SDR development to replace AX5043. Exciting stuff! > > > > https://github.com/AMSAT-NA/PacSatDocs/SDR/MinyardSDR_1-9-2024 > > > > 2: Discussion of 2025 budgets that haven't been approved yet. More to > > come....no video. > > > > I would like to discuss your project with you at some point. Can it be > > prototyped on the new launchpad that Jim is working on? > > > > Bill > > > > > > ----------------------------------------------------------- > > pacsat-dev mailing list -- pacsat-dev(a)amsat.org > View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] > To unsubscribe send an email to pacsat-dev-leave(a)amsat.org > Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org

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Re: Last nights recording
by Cameron Castillo 11 Jan '25

11 Jan '25

Hi Bill, Interesting presentation! A couple notes: On the FPGA design for the SDR, a significant amount of the work can be done via Xilinx IP. I think the team has the idea that most of the DSP and hardware would have to be built from scratch in verilog. For almost any design today, many people use the block diagram editor from Xilinx instead of writing their own verilog. Not only are these guaranteed to work but all the driver code is also available in their software platform (Vitis). I've looked into some of the DSP blocks they have available and the list is fairly comprehensive (IIR/FIR filters, FFTs, Freq. Synthesizer to name a few off the top of my head). One of the other benefits is that many of Xilinx's products have hard integrated processors or have the ability to integrate soft processors (See Zynq and MicroBlaze respectively). The nice thing about these is that they support Linux development and bare-metal/RTOS configuration. We might even be able to remove the TMS570 and replace it with one of the multi-core devices. Perhaps we could have a system where Direwolf and the other processing functions are run on the same chip as the DSP. The downside to this is that I'm not sure how parallelable that would be (i.e. could we maintain four Rx channels). I do a lot of work with Xilinx products and FPGAs at work. It's mostly for video functions, but I've found it pretty easy to understand the fundamentals of Vivado/Vitis in only a few months. With integrated peripherals like AXI and the IP blocks, it probably wouldn't take as long as everyone is thinking. I hardly ever touch verilog at work anymore... As far as the amplifier project is coming, I'm back in the lab at work and want to get some more prototyping done with our actual amplifier. Does anyone on the team have extra stock of the transistor we're using for the Tx amplifier (ATF05MS004NT1)? I'd also like to get an inductor kit like this one <https://www.amazon.com/First-Inductor-Assorted-1nH-270nH-42Valuesx50pcs/dp/…> as the one I have at work is all 0201s and I can't reliably solder it... On that note, I'm happy to keep prototyping it if the team wants to go in that direction, but I think it'd be faster to go with a premade power amp. I've already created a schematic for a PA as a backup to the work I'm doing now. If we want something for Jim's test board, I could probably get something to at least prototype with a lot sooner even if we think we could do better with the discrete option. Just a suggestion. Thanks, Cameron Castillo ------------------------------------------------- Cameron Castillo KJ7ILB *P*: (503) 752-8877 -------------------------------------------------- On Fri, Jan 10, 2025 at 8:47 AM Bill Reed <bill(a)brconnect.com> wrote: > This is a better URL... > > https://github.com/AMSAT-NA/PacSatDocs/blob/main/SDR/MinyardSDR_1-9-2024.we… > > -------- Forwarded Message -------- > Subject: Last nights recording > Date: Fri, 10 Jan 2025 09:31:07 -0600 > From: Bill Reed <bill(a)brconnect.com> <bill(a)brconnect.com> > To: Cameron Castillo <camstillo2000(a)gmail.com> <camstillo2000(a)gmail.com> > > We discussed 2 things last night. > > 1: Start of SDR development to replace AX5043. Exciting stuff! > > https://github.com/AMSAT-NA/PacSatDocs/SDR/MinyardSDR_1-9-2024 > > 2: Discussion of 2025 budgets that haven't been approved yet. More to > come....no video. > > I would like to discuss your project with you at some point. Can it be > prototyped on the new launchpad that Jim is working on? > > Bill > >

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pacsat dev mtg 1/9/2025
by Bill 09 Jan '25

09 Jan '25

*pacsat dev mtg 1/9/2025* Jan 9, 2025, 7:00 – 8:30 PM (America/Chicago) *Please join my meeting from your computer, tablet or smartphone.* https://meet.goto.com/915579293 *You can also dial in using your phone.* Access Code: 915-579-293 United States: +1 (872) 240-3311 <tel:+18722403311,,915579293> *Join from a video-conferencing room or system.* Meeting ID: 915-579-293 Dial in or type: 67.217.95.2 or inroomlink.goto.com Or dial directly: 915579293(a)67.217.95.2 or 67.217.95.2##915579293 *Get the app now and be ready when your first meeting starts:* https://meet.goto.com/install

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