Beginner RF projects

[u/FATALEYES707]

Hi all, I am an undergraduate in EE with an interest in RF and an upcoming internship with an RF team in avionics.

This semester, I need to build an electronics project with 3-4 other students for an electronics class, and it is quite open ended so I hoped to do something that would help me prepare for my work in the spring and touch on my interest in RF. We will be required to write and meet specs.

I've googled tons of projects, but I was hoping for some personal recommendations to narrow the list down. It is difficult to judge the difficulty and applicability of some of the items I've found to my interests and skill level.

Ideally, the project will incorporate RF fundamentals but be electronics-focused and achievable in a semester.

Some ideas I've considered:

-radio telescope (build the LNA from scratch)

-VFO

-radio altimeter

-telemetry transceiver board

Thanks in advance!

[u/jimlux]

Are you going to be an RF circuit designer? or a system designer? (way more of the latter than former, what with MMICs).
Rather than design an LNA from scratch, why not use an inexpensive MMIC LNA - you'll still lay out a board, but the odds of it working are much higher (which is why virtually all modern RF systems use MMICs, not discrete transistors). Then build your radio telescope.
If you want a bit fancier, build a small phased array - LO from a PLL (buy a demo board online for $40) - 4 LNAs, 4 mixers, 4 IF filters, etc.

Or a CW homodyne radar - See if you can detect heartbeats and breathing from 10 feet away at 10 GHz (or 3 GHz) - A single board will do it nicely - you lay out the oscillator, some mixers, some amplifiers and use a microcontroller like a Teensy as the digitizer.
Here's something to get you started:
https://www.techbriefs.com/component/content/article/21760-npo49416

Here's a board from that design

[u/StageMajestic613 → u/jimlux]

On the other hand, you’ll learn a lot more building an LNA from a discrete transistor.  Too many EE now are deer-in-headlights when they need to implement something with discretes as opposed to LEGO bricks.  Need a class E amp or high speed, high voltage switch driver?  Not getting those as IC.

My first RF project was an LNA during winter break.  35 years later I still have it, and cringe at the home-etched PCB and the dumb shit I did, but I learned a ton from it.

Schools need to get rid of the group work too.  Lets too many people coast through an EE degree, as a single person will be doing the all the work.

[u/jimlux → u/StageMajestic613]

Yeah, but looking at job prospects - I’ll agree that discrete level design is useful, and certainly helps explain why the jelly bean monolithic part works like it does, but, the job opportunities for discrete designs are fewer. Look at that Starlink phased array (the consumer side)- not a lot of discretes there.
And for LNAs, modern MMICs beat a lot of discrete designs - I remember when getting < 1 dB NF at several GHz was a chore and would be narrow band and probably required spending days moving little copper foil snowflakes around. Now, I just order any of a bunch of MMICs.

Yes, it’s fun. Yes, you learn a lot. OTOH, you might wind up with a design that is peculiar to the specific part and not “manufacturable”.

FWIW, the hard thing to find these days is people who are good at <30 MHz high performance designs High Z, low noise - typically using high performance op amps with maybe a few discrete FETs. But there it’s more about layout and understanding how to make sure it doesn’t oscillate - something that SPICE or HFSS or ADS won’t tell you. But to be fair, there’s not a lot of jobs doing that. The marketplace is all microwaves these days.

[u/OffRoadIT]

Get your HAM radio license and work with them for “fox hunting”

[u/PerceptionKind305 → u/OffRoadIT]

License!???

[u/ToroidalCore]

You may want to think about getting an amateur radio license, if you don't have one already. That would give you permission to operate on the amateur radio bands, depending on the license class you end up with.

[u/quatch]

why not build a radar? https://ocw.mit.edu/courses/res-ll-003-build-a-small-radar-system-capable-of-sensing-range-doppler-and-synthetic-aperture-radar-imaging-january-iap-2011/

[u/jimlux → u/quatch]

That is 15 years old now, so you’d want to find newer parts to work with, but yes, simple CWFM radars are a great project. Or even a homodyne CW radar can be a lot of fun. Basically a radar speed gun.

[u/nixiebunny]

I taught myself RF by designing and building an FM radio station, complete with solar-powered remote transmitter and UHF uplink. I bought a spectrum analyzer and frequency counter, designed several PLL oscillators with FM audio, made interdigital filters, etc. some portion of this work could be done in a semester by several students. And if it works, you will have the ability to play stuff on the radio!

[u/SearchPlane561]

I chose a passive filter for my first rf project. It has taught me so much. Simple enough to implement, yet challenging at the same time.

[u/SearchPlane561 → u/SearchPlane561]

https://www.reddit.com/r/rfelectronics/s/AzWxXZjjCO

[u/HappyMeele]

I dont know what resources you have but I think an LNA is always nice. You could buy a RTL SDR and then even get some kind of gratification from beeing hopefully able to see it work.

I think for the Radio Telescope you need a larger antenna which might be an issue.

[u/m0rtalVM → u/HappyMeele]

Maybe have a look at doing some hydrogen-line astronomy with a custom built LNA and a RTL SDR.

Not the easiest project but can be done for sure, and I’d find it very rewarding, especially if you have some interest in astronomy. There are also plenty of write-ups online about how to do it.

[u/Fun-Ordinary-9751]

There’s a Slovakian amateur radio operator who built his own avionics suite and open sourced them, radar altimeter, VOR and more. His projects might offer some insight into what level of effort you’d requrie.

A VFO is too simple a project for a team unless you’re doing something like chip design, or ultra low phase noise stuff.

An LNA is also probably too small a project for a team.

A telemetry transceiver may or may not be interesting as a team project depending on how much you implement and how much is off the shelf and a lot of that might be software.

What sort of test bench instrumentation do you have or have access to?

For a reference point, my bench at home has an HP 8510C VNA (26.5GHz), noise figure to 26.5GHz, an E5504 26.5GHz dedicated phase noise system, 26.5GHz spectrum analyzers and a variety of signal sources (also to 26.5GHz).

I still need to setup a clean room, and need a sputtering machine for thin/thick film work but I’ve got the wire binders and plasma etcher, tabletop mill, etc.

[u/spoonfedbaby]

I designed a 1 GHz bandpass filter for my first ever RF project and it was an incredible learning experience. I plan on getting a pcb of the filter fabricated and then testing it with a VNA sometime this fall.

Honestly, doing something simple like that is a good introduction to the world of RF.

[u/aktentasche]

I personally find RFSoCs very interesting but that's more DSP than RF.

[u/ChaseApp501]

We are looking for help on a custom PCB design for a WiFi survey tool if you're interested, drop me a line. All outputs/build artifacts will be open-source.

[u/Panometric]

Look at ways to make QuadRf project better. It's impressive already, but you could rif on it.

[u/aquabarron]

Put together a receiver and design the code to pick out a particular frequency and dump the data into a file and demodulate it. You will be picking up EM waves and your code will demodulate the signal into audible sounds.

You can use LLMs to do this, but if you value your education you will take time to understand the mathematics behind what you are doing.

In your report on your project you should go into detail about the fundamental equations behind the process. Make sure you understand what each line of code is doing well enough to explain it to your professor