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I am studying as a graduate student in electrical and electronics engineering. For my thesis, with FPGA, I am going to process an input which is 240Mhz or 1.3GHz RF sine wave. After a user defined delay, I am going to generate an output digital signal which has the same period and frequency such as the input had.
I am quite new at this area, I need your advices on FPGA selection, ADC selection and the other needs for this study. I am planning to use VHDL, so any technical advise on communication protocols would be great for me as well! Cost efficient way would be prefered ofc
IMO, you are in a hard place as direct digitization of a 240 MHz is on the edge of FPGA performance when we consider Nyquist. The 1.3 GHz will require a proper RF front end to down-convert the signal.
Welcome to the DigiKey TechForum! In addition to APDahlen’s recommendation above, I encourage you to check out the “Education” section of the TechForum. It may have some insight that you’re looking for in regard to FPGA and the communication protocol used, as well as some additional considerations for your project.
Thanks for the recommendation, but it is an enstitution project that is a part of a greater project which is going on so i have to do it as the exact values or closer to these. I can of course lower the frequency but not that much like 1 MHz.
Still in need of a FPGA that contains proper ADC or that support an ADC with high speed sampling rate (MSPS at least). If you recommend anything else, it would be awesome. Plus, I am gonna apply an MSc fundation support program. Not much but one is greater than zero, right
So you know, it’s only necessary to post one thread per topic–it’s the same people reading pretty much everything on this end.
Describing the specific needs in much more detail would likely be very helpful in for identifying possible solutions. What exactly do you mean by “process” an input for example?
It’s one thing (for example) to detect whether an input has a frequency of 240Mhz or 1.3GHz for example, but a very different thing indeed to digitize a signal at those frequencies. ADCs of the sort that would let a person do the latter are not inexpensive or easy to use, and FPGAs that can deal with data at the rates that it comes out of such a conversion process aren’t cheap either. (Sampling a 1.3GHz signal at Nyquist rate with 8-bit depth makes data at 2.6GB/s)
There are techniques such as interleaving ADCs that can can be used in high-speed conversion applications, but they’re not without their own difficulties.
However, if all you’re doing is measuring the frequency (period is the same thing, expressed as an inverse…) of a sine wave, then a decent linear comparator might be a much easier/cheaper conversion device, and delay line devices do exist that might amply serve the mentioned delay function.
Defining the problem appropriately here could very easily mean the difference between $20 and $20,000 in cost of hardware to do the job…
Thanks for the answer Rick!
To clearify the topic then, first i have to detect the input if it’s the one which is needed. It is 1.3GHz or 240 MHz on this application To detect them I need to use proper interface according to the ADC and FPGA pairing. Then I have to calculate its duration, period, frequency etc. and then I need to set a delay getting by user via UART. After the delay i need to trigger an output which could be a square wave or an analog output not sure about this part which has the same frequency and period.
As an opinion, I consider that maybe i can work on lower frequencies to make a design that could be used on higher frequencies in the future, and then I can complete my thesis and provide some paper.
I thought, i need to get information about what i should buy and to do as method first. But yes, it has to be cost-efficient and applicable in the limited time like 12 months. Any help from you would be precious for me.
The best advice I can offer at this point would be to spend some time developing a very detailed description of your application’s requirements.
Start with the input signal: what’s it’s amplitude? Is it singe-ended or differential? To what is it referenced? What’s the source impedance? What kind of noise will it contain?
The measurements that are mentioned: what signal features need to be measured? To what degree of accuracy or precision? How often do the measurements need to be made?
The output signal: what it to receive it, and what requirements occur as a result? What signal features (amplitude, frequency, etc) matter? How accurate to these signal features need to be?
This delay that is mentioned: What range of delay is required? How accurate does it need to be? How rapidly does it need to be changed? What other limitations or requirements does your application have?
These are some of the questions that you will probably need answers for before you can make choices about hardware. Taking the time to carefully define the problem, so that you understand what things matter and what things do not will have a large effect on your success.
Your answer is quite useful and precious for me, enlarged my horizon.
At this point I have no further details but the signal length is around 100 us and so is the delay.
No idea about the peak value of the signal yet, I haven’t made observation of the experiments and the applications in the institute.
Measurement should be done anytime momentarily the input triggered.
Source would be an RF signal generator, kind of a golden unit. I do not expect much of a noise caused by the source but the higher the frequency, the more tricky it gets to say something certain. For this, I will also ask some opinion to the responsibles.
For now, I have limited knowledge that my advisor given to me. We are in the very beginning of the study.
Tomorrow, my advisor arrenged a meeting. So, in this meeting i am gonna ask some questions that have been supported by the questions you provided. I am going to give further details according to the meeting outcomes.
It took time to get some answers from the institute. I arranged answers for your questions. Firstly to clarify, I am gonna detect a input signal by its Vrms or any amplitude value before working on its frequency and then trigger a digital output as a square wave with certain values for a high voltage pulser to trigger an trigatron. The scope of the thesis is to detect the input and generate the square wave part with a certain delay.
The input signal is single ended and referenced to the ground. It has 50 ohm source impedance and the SNR is between 20 and 30 dB. The signal is quite stable and generated by a sensitive RF signal generator. The important part is to measuring the amplitude with a timing importance.
The input pulse duration is between 1 and 20 usec. The pulse repetition frequency is between 10 - 150 Hz and the output pulse duration is between 15 - 60 nsec. The accuracy is approximately 99%, it could have a jitter with around 1 nsec.
The first thing to do is detecting the signal presence by its amplitude, which the thesis is going to cover, far before calculating the frequency. Then according to the user defined delay between 50 and 2000 nsec and signal duration around 50 and 2500 nsec generating an output which has 10 Vpp with the user defined values of delay and pulsewidth. In my opinion 10 Vpp could be 10 V to 0 V for the square wave instead of 5 V to -5 V.
The delay and pulse width could be defined by the user via UART.
You may wish to consider products in the RF Detector family for such a task. Depending on the character of the signal and the application’s timing requirements, a linear comparator of the type mentioned above may also be useful.
There are high-speed devices in the Counter and Divider family which may be useful for frequency measurement and/or delay synthesis, and Direct Digital Synthesis products that are useful for generating square waves of a specified frequency. Amplifiers of some type (see also the RF Amplifier family) may also be useful for buffering the input/output signals.
Please understand that I/we are not able to simply hand you a list of devices that will achieve your desired task. We’re happy to point out various devices that are available which may be useful and possible techniques, but it will be up to you to understand their capabilities and develop a signal chain that will satisfy your needs.
Going back to the original question, using an FPGA and data converters to develop a solution may be one possible design approach, but will likely involve significant cost and design effort. Such a design approach might be better suited for developing a cell phone base station where complex calculations need to be made.
Since the task described seems to be much simpler, I’m suggesting that you consider the use of linear/analog components to handle high-speed concerns and a modest microcontroller for the simpler tasks such as user interface that occur at slower time scales.
Which approach is right for your needs? Unfortunately, that is a question that is up to you to answer.
Actually I can study and develop on a lower frequency. At first need to detect Vrms or some voltage level to compare on a threshold I would define on FPGA. So I can use a cost efficient product as well as good at performance. My mentor would like to develop the system on FPGA instead of other computing platforms, so it seems it is the one I need and must.
My opinion is that I would convert the signal via ADC and save it. Then, calculate the voltage value types we desided to process. While doing that, I also need to be able to use interfaces like UART, SPI, I2C. Then 10 Vpp out trigger should be off to go.
I need help on defining the system needs on product side. An ADC, FPGA, USB to TTL, etc… I am not on hardware design side of the work. I need boards to work on. Any suggestions around this and the previous information I gave above would be perfect. I know and understand you cannot give brands as suggestions but I have to choose a product on Digikey correctly by any knowledge and guidance.
