New for July 2025.
This page is under construction and is contributed by Bertie.
What are FPGAs?
FPGA stands for field-programmable gate array. Is FPGA software or hardware? (the answer is yes!)
Target audience
The audience for this page could be someone who has an electrical engineering degree with some RF knowledge, or a student who is partly through electrical engineering and is about to take an RF course and is FPGA/digital curious.
Historical perspective on FPGAs
FPGAs were introduced in the mid 1980s, by Alterra and Xilinx. Before FPGAs were available, and for some time afterwards, special electronic functions were developed universally as application-specific integrated circuits (ASICs). An example might be a controller for a T/R module in a phased array. Inputs to to ASIC would include a clock and some data lines (which could be two-way), and some asychronous command lines. The ASIC would be used to store calibration data for the module (phase and amplitude states that are corrected for non-ideal behavior), the address of the TR module and its position in the array, the current antenna beam state and a lineup of future beam states, and attenuation settings to reduce sidelobes in receive. Th command lines would tell the module whether the module is in transmit or receive state, and to when to update phase and attenuation settings quickly to the hit the next beam position. If you look at the photo on this T/R module page, the ASIC module controller is that grey square on the right side of the module. For most of the prior century, the sparce number of transistors that were practical on a compact chip (say, 1cmx1cm) precluded the ability of an FPGA to handle all of these tasks. Todays FPGAs are more than capable of your wildest TR module dreams.
ASIC designers and RF engineers are two different breeds. ASIC design was a serious task and required deep knowledge and the ability (anf funding) to spin the circuit on silicon. Today, FPGAs have dumbed that task down so that a self-taught electrical engineer could take care of all of the special fuctions by programming a catalog item.
Trivia: did you know that RTX (Raytheon) Microelectronics facility in Andover MA, makers of gallium nitride power amplfiers for internal use, was born as silicon foundry for producing ASICs? And furthermore, the original building (on the right side of the Google view below) was atchtected to resemble an integrated circuit?
Why learn about FPGAs?
Then I would address the desire to broaden the reader’s skillset into FPGAs. I would tie all the concepts into familiar RF ones where I can. Plus, some concepts that the reader can further explore (timing, metastability, clock domains). I will refrain from explaining them too much because that is easily found via a google search once I throw the term out there. I interpret FPGAs to be a computer engineering subfield, and RF as an electrical engineering one, so I will keep that in mind when explaining things. For example, I know electrical engineers have taken a signals course, so I won’t dumb explain an FFT, but for a something like FPGA metastability, I will not assume much prior knowledge.
Why FPGAs are valuable from a curiosity and career standpoint, even if you already are down the RF rabbit hole (for career hedging, expansion of career, and to scratch that itch).
- Skills to hone: software principles like version control, patience, and how actually programming it looks like software but isn’t software (a big one is FPGA code runs in parallel, software runs sequentially).
- Crossover and integration with RF: signal integrity issues for high-speed digital resemble RF striplines, reusing some old EE knowledge like signals and DSP, and things like phased array antennas which can be programmed via FPGAs
- Mindset of an FPGA engineer: think like a hardware engineer (which the reader probably is if they’re working in RF), growth mindset, more valuable career wise if you’re end to end hardware
Conclude with empowering the curious and demystifying it,
Some RF system examples where FPGAs are used today
Here we could throw out a list of examples, and maybe take a deeper dive into one of them.
Learning about FPGAs
For an absolute beginner, I appreciate this guy’s website: https://nandland.com/. I recommend him specifically because his website is clearly laid out by FPGA languages, and the most important concepts. He also has corresponding YouTube videos which help more learning styles. He also designed a board called the Go Board (which you can purchase, and I have purchased for myself). The board has labs that help you start from the simplest thing to do, which blinking an LED, to programming a 7-segment display. I looked up the Arty board you bought and didn’t see any simple resources for doing projects on the board.
Interfacing to program FPGAs
How do you actually program it? what is the standard interface, or is there one?
Etc...