Applied Science Thank you. It means a lot coming from you.

Hey Ben, any DIY RF ASIC stuff on the radar? :D

Thank you. :)

Did you notice how the "quench rate" affected each other's super-regen receivers when in proximity too?

the width of cutout did effect the bandwidth/gain

Hi, do you think this module can trigger a car radar detector at some meaningful distance, let say 50-100m?

@@ivanilarionov1893 not enough RF power.

I believe that is a painting a viewer sent him.

ProdigalPorcupine Yea, I noticed the tape also. wish I even had some...

plywood is mostly transparent at 24 GHz.

As he said in the video, it appears to be thin generic FR4. This is an $11 item (including shipping).

Similar question: if the rat-race would give the difference on port 4 anyway, why not just tap the doppler signal from there? Why the diodes? Probably someone cand answer both at once.

1) I think so. 2) Yes. 3) They are cold biased at around 0V. The LO signal swings above and below GND. Save as RF.

Diodes are the non-linear devices required for frequency conversion. The linear difference alone would not be at IF, it would still be at the same frequencies as RF and LO.

Thank you very much for the response!

For CW you're measuring only doppler. You transmit a signal at a steady frequency, say 24.000000000 GHz. That signal goes out, bounces off a moving object and comes back either slightly higher or lower in frequency, depending on if the object is moving toward you or away from you. The amount it shifts depends on the speed of the object. Lets say the frequency shifts up by 100 Hz, to 24.000000100 GHz. When it comes back, you mix the reflected signal with the transmitted signal, and you get the sum and the difference between them. You filter it so only the difference comes out, and you get a 100 Hz signal on the IF. That tells you the speed of the object. This is how police traffic radar works. Now for FM (not what was done in this video), if you constantly vary the transmit frequency in a linear sawtooth way, the frequency going out is constantly changing. If it hits a stationary object and reflects back, the time delay between when it left and when it gets back means there's a difference in frequency between the transmitter and the receiver. That frequency difference determines the length of time the signal took round trip, and therefore determines the distance to the object. You measure the frequency difference like you did with CW, and the output if tells you the distance to the object. This is how the adaptive cruise control in your car keeps you 3 car lengths from the vehicle in front of you.

The idea behind the rough adjustment quality of that osc is that all computation happens in the frequency/spectral domain so you might not care so much about the fine tuning of emitting freq as long as you get sharp and distinguishable peaks for both (transmitted+recieved) signals. Another possibility is that you can tune the working frequency by the voltage a little. AFAIK in radar theory range information ideally suppose minimal or even 0 pulse width (Dirac's delta) of emitting signal and a precise calculation of TOF/delay time thus both high rise and attenuation of the oscillator are required. This particular circuit isn't suited for such yet you could attach a fine discriminator and counter for fun. Forcing it to emit short spikes with minimal FWHM you'd get a coarse TOF but the precision strongly depends on time-domain characteristics e.g. attack/decay parameters of the ckt.

The con is: Reasonably priced spectrum analyzers aren't good enough to measure PN. You have to have one in the nosebleed price range.

Yes, you'll get an audio output on the IF pin. The frequency will be related to the speed of the fan.

You are right, it does affect the impedance. That also in turn can affect the BW. Notches on the other side would excite the other polarization.

Having tuned RHCP patches on a hi-K PCB dielectric, everything affects everything else in some way :) even giving the antenna too nasty of a glare. its almost maddening at times. All of those are coax fed from underneath, so I'd imagine shifting the feed there has less of an effect than matching the microstrip in. The in-depth videos are definitely enjoyed though. RF stuff on coax is 'easy' once you know the devices gotchas. Electrically large/distributed stuff can be a good mental exercise in 'thinking like RF'