Micro Controller, FPGA or ??, I need USB HS and alot of analog

[andersm]

Yeah that is kind of a big deal the difference in performance gap. How did that happen, someone in marketing order a engineer from another product line or something? that makes no sense.

It's probably no coincidence that the PIC32MZ was pushed through the door unfinished, and untested, just before the end of the year. My personal guess is that Microchip had some contractual obligations to meet, because I can't see anyone being happy with the device in its current state.

[thewyliestcoyote]

It's probably no coincidence that the PIC32MZ was pushed through the door unfinished, and untested, just before the end of the year. My personal guess is that Microchip had some contractual obligations to meet, because I can't see anyone being happy with the device in its current state.

Not to long after the PIC32MX first came out I got my hands on a couple. I bricked all of them with silicon bugs that microchip had not fixed(Something with programming with the pikit3 and the PIC32's did not like each other). Guess it is not the first time Microchip has pushed something out the door before it was ready. If all someone wanted was a RAM and flash upgrade of the PIC32MX then I am sure they are happy. I still cant get over that whole ADC thing. Something is just not adding up to be a order of magnitude off. I mean what happened? how does a company say that they will have a product that can meet some spec and be that far off? They not do there homework? not know how to design a ADC?

Either way still does not have a on-board DAC or have not found a cheap external DAC so does not effect me.

[tggzzz]

If there was a RTL-SDR that was also a transmitter and could extend into the 6GHz range. This way students could have some hands on expense with channels that are more then 1 or 2 lambda and have a lot of multi-path.

I am a little confused why you are recommending the Red Pitaya. Seem like a great product and I have been interested in getting my hands on one for some time now for personal use. It does not any of the things that I need for undergraduate and graduate communications classes. It seems to have a -3dB point of just 50MHz.

I'm not recommending the Red Pitaya. It appeared you had rejected it (OK no problem with that) based on misunderstanding what it could do (which might have been a shame).

Good luck getting 6GHz bandwidth ADCs DACs and processors at a reasonable cost! I haven't seen what bandwidth you want, but most people would up/down-convert a baseband signal to 6GHz or whatever.

Certainly 50MHz is sufficient to see multipath in cellphone systems, and for a rake receiver to extract the next 3dB.

[thewyliestcoyote]

Good luck getting 6GHz bandwidth ADCs DACs and processors at a reasonable cost! I haven't seen what bandwidth you want, but most people would up/down-convert a baseband signal to 6GHz or whatever.

Certainly 50MHz is sufficient to see multipath in cellphone systems, and for a rake receiver to extract the next 3dB.

There is almost certainly a bit of confusion here on both our parts. I have only rejected it for my current assignment. Cost is the factor that is making this possible. As much as I would like to say I am done and move on to the next project. $450 each with with frequency range of 0 to 50MHz is a failure of about 10 times the end cost and missing much needed function. I do work for the government but for a university not the defense system where cost over runs seem to be encouraged  .

There is no transverter build into the Red Pitaya so it can not be used for frequencies of greater then 50 MHz or so. I am not sure of the input topology so it may have some aliasing problems. (when pushed most things seem to, High end scopes and spectrum analyzer included. ) This is would not be a problem it as 50 MHz of bandwidth is well beyond what I need here.

But going back to the original goals of the project I only need 1 Rx and 1 Tx channel, 4 MHz of analog bandwidth equivalent for capture, and a frequency range of about 80MHz to 6GHz. Looking at the Red Pitaya it uses linear tech ADC LTC2145CUP-14 and a  DAC1401D125HL. The ADC has a unit cost of $60 for 100 of qty. The DAC seems a bit better at $11 in qty of 250. Still a bit on the high side but maybe possibility. It does seem to be a bit over kill at 125MSps. maybe something half or 1/3 the cost with 1/10 the sample rate would be just fine.

[Rasz]

But going back to the original goals of the project I only need 1 Rx and 1 Tx channel, 4 MHz of analog bandwidth equivalent for capture, and a frequency range of about 80MHz to 6GHz.

another ghetto idea - how about designing only the TX part? you can leave rx to a pair of RTLSDRs. You can sync couple of dongles by using same clock source.

[Howardlong]

Good luck getting 6GHz bandwidth ADCs DACs and processors at a reasonable cost! I haven't seen what bandwidth you want, but most people would up/down-convert a baseband signal to 6GHz or whatever.

Agreed. The OP may not be aware, but I have been involved commercially in this space with products of my own design for several years.

The standard method for much over a few tens or hundreds of MHz is to downconvert in the analogue domain either to ZF or low IF, ADC, and digital downconvert if not already at baseband. You can use harmonic sampling too, but you'll need and ADC with sufficient bandwidth, plus some nice bandpass filtering in the analogue domain. If you're trying to subsample a 6MHz bandwidth signal on a 6GHz carrier, that's going to need quite some filter, and if you want frequency agility too, you'll need a lot of them!

Similarly for transmit, unless you're transmitting constant envelope, a similar method is used in reverse.

So just for the analogue down conversion for the receiver and up conversion for the transmitter you need to find a wideband LO, and a very wideband quadrature modulator and demodulator. There are a very few devices at do this in a single integrated package.

In addition for transmit, you may want to consider if half duplex is reasonable depending on your image and LO leakage mitigation if required. Being able to operate full duplex means you can also correct DC offset and IQ imbalance in your transmitter.

Basically, if you think you can make your design for peanuts, you are going to have to try very hard. If you do a BOM and assembly cost for those RTL dongles, it's not actually possible to make them for the price they're sold at retail unless you are making hundreds of thousands of them.

[thewyliestcoyote]

But going back to the original goals of the project I only need 1 Rx and 1 Tx channel, 4 MHz of analog bandwidth equivalent for capture, and a frequency range of about 80MHz to 6GHz.

another ghetto idea - how about designing only the TX part? you can leave rx to a pair of RTLSDRs. You can sync couple of dongles by using same clock source.

Oddly enough for another project I have tried something like this. I had 9 of them linked to gather to do angle of arrival estimation. Short answer is this was kind of point less at it is not possible to get phase lock form those devices. Fun project tho.

The standard method for much over a few tens or hundreds of MHz is to downconvert in the analogue domain either to ZF or low IF, ADC, and digital downconvert if not already at baseband. You can use harmonic sampling too, but you'll need and ADC with sufficient bandwidth, plus some nice bandpass filtering in the analogue domain. If you're trying to subsample a 6MHz bandwidth signal on a 6GHz carrier, that's going to need quite some filter, and if you want frequency agility too, you'll need a lot of them!

I am currently looking at a 2 stage conversion to baseband. I have kind of a high some where from 900MHz to 1600MHz IF but that is because of some other components and design choices. I have no plans of doing a zero IF design or anything like that. That is just not what is needed here or reasonable. The IF is very narrow relative bandwidth thanks to cheap saw filters. For the base band I have designed a couple elliptic filters that meet all the specs that I need. For the front end there is 3 or 5 band pass filters in parallel selected by a switch network. Nothing is final yet so all subject to change.

In addition for transmit, you may want to consider if half duplex is reasonable depending on your image and LO leakage mitigation if required. Being able to operate full duplex means you can also correct DC offset and IQ imbalance in your transmitter.

This is half duplex. I cant think of a reason that needs full duplex here. Always nice to have more features but I am not sure that full duplex has a place here. Maybe some one will persuade me and I will be forced to add it in.

[Rasz]

But going back to the original goals of the project I only need 1 Rx and 1 Tx channel, 4 MHz of analog bandwidth equivalent for capture, and a frequency range of about 80MHz to 6GHz.

another ghetto idea - how about designing only the TX part? you can leave rx to a pair of RTLSDRs. You can sync couple of dongles by using same clock source.

Oddly enough for another project I have tried something like this. I had 9 of them linked to gather to do angle of arrival estimation. Short answer is this was kind of point less at it is not possible to get phase lock form those devices. Fun project tho.

did you feed all of them from the same clock source? people tried with success and little phase noise
http://gnuradio.4.n7.nabble.com/dual-coherent-channel-rtl-sdr-td43784.html
http://kaira.sgo.fi/2013/09/16-dual-channel-coherent-digital.html
+need tuned 820 pll code (disabled dithering).

[Howardlong]

The reason for full duplex is that that I offered, i.e. a way to correct for IQ imbalance and/or LO leakage in the exciter by analysing your own signal in real time. If you're not interested in that, or it's unnecessary in your design then that's fine, I was just offering a suggestion to you. It's just that it's quite common to do exactly that in single conversion quadrature upconverters by analysing the output in real time and correcting for it by tweaking the baseband. If you're not doing that, then that's fine, I was just trying to offer you some help and suggestions!

[thewyliestcoyote]

did you feed all of them from the same clock source? people tried with success and little phase noise
http://gnuradio.4.n7.nabble.com/dual-coherent-channel-rtl-sdr-td43784.html
http://kaira.sgo.fi/2013/09/16-dual-channel-coherent-digital.html
+need tuned 820 pll code (disabled dithering).

Glad to hear that some one got it to work. I wish I had seen that when I was trying that. I am still not sure that it would have worked for what I was doing. I found that out after a lot of time with the chip set documentation. It is designed for frequency lock, not phase lock between 2 or more of them. What I needed was phase lock because of doing angle of arrival form time of arrival. I am sure that I could calculate the phase offset in real time, but that was more then I wanted to do. Solution by a better set of radios. BTW for the clock source I was using a couple different things, mainly a signal generator with a very nice 10MHz reference.

The reason for full duplex is that that I offered, i.e. a way to correct for IQ imbalance and/or LO leakage in the exciter by analysing your own signal in real time. If you're not interested in that, or it's unnecessary in your design then that's fine, I was just offering a suggestion to you. It's just that it's quite common to do exactly that in single conversion quadrature upconverters by analysing the output in real time and correcting for it by tweaking the baseband. If you're not doing that, then that's fine, I was just trying to offer you some help and suggestions!

Hmm, had not though about that for the use for this. The DAC's and ADC's have a common baseband (cost savings).

Maybe something I can do it in the baseband to adjust the balance. I will give it some thought. I don't really have the hard on the board to have it transmitting and receiving at the same time. This is not the highest preforming device tho like I said. As much as I would be the one that builds the next best VNA, VSG, and VSA all in one but this is not the project for it. I am trying to get something like ~35dB of range of the captured signal. A lot of the mixers that I am looking at have LO rejection of better then 40dB when used correctly. Total dynamic goal has not been selected yet.

And many thanks for the suggestions.
I am always welcome to hear them, even if I sometimes sound like a ass-hole sometimes.
I am not trying to be one.