77GHz Radar with FR4 board?

I was concerned about the belts as well but people told me it's accurate enough for such jobs. Similar to the old HP Deskjet printer which was remarkably precise. Until the belt gets old but then you can install a new one.

I lately use an SMA edge launch connector for these kinds of PCB tests. I usually get a free "solder sample" bare board to play with TDR or plane capacitances. We buy some nice SMA edge launch connectors for under $2.

That might be acceptable if it's not hoppy. I don't like hoppy.

The Giant(s) Milling Machine.

We had to move it from the old building into the basement here. I was surprised that it only weighs about 1800 lbs.

Well now, that *is* impressive :)

Joerg wrote in news: snipped-for-privacy@mid.individual.net:

Quoted:

Some circuit materials, such as FR-4 and pure PTFE, can undergo large variations in Dk with changes in temperature and they lack the consistency needed for maintaining constant impedance at millimeter- wave frequencies.

Yet another reason FR4 is probably a bad choice.

Joerg wrote in news: snipped-for-privacy@mid.individual.net:

Nah, that's 68 um wavelength. My tunnel junction stuff worked at 40 times that frequency. ;)

Cheers

Phil Hobbs

Phil Hobbs wrote in news: snipped-for-privacy@supernews.com:

There is some 10 bit 51GHz ADC out there.

My boss's daughter is a PhD down at Purdue, and she is developing a MEMS clock for it... She gets a Q of 50,000 (=very low noise) using a mere 0.8V @ 120uA in a size of 200nm x 200nm.

That's some clock!

It's from Signalhound, essentially a glorified SDR with a stepped pre-mixer up front. Does have it's downside such as software-only image rejection which will not work for pulsed signals. They now have a 12GHz version.

With the under-milling that John explained it won't be so bad because then teh dielectric consists mostly of air. Still not ideal but in this case "good enough" is gong to be the ticket if it becomes a project.

I have done 100psec pulse-echo on FR-4 without under-milling and it works great. What's an order of magnitude more? :-)

My Belgians are not hoppy at all but require to put the car keys aside.

We had several of those at my last employer. I'd always bolt those down. It it ever falls onto someone during an earthquake or some mishap it can kill.

Or even if you leave the box wrench on the head nut when you turn it on. A Bridgeport walking across the floor is no joke--it happened in our model shop at IBM one time.

Cheers

Phil Hobbs

Ah, the good ol' Bridgeport. Got one here, too. Not quite the same as yours, though. I mean, it's essentially a J-head mill like yours, but there are many different bits on yours compared to mine control-wise. Most glaring disparity is the motor on the top of yours. Looks about 1/3 the size of the one on mine. But you run on a funny voltage over there AIUI. Mine also has the coolant tank in the base casting with a wire gauze filter exactly on the front left hand side as you look at it. They're great. Mebe not as great as the Cincinnati equivalent, but OTOH, mebe better in certain other ways. It's difficult to source correct lubricants for this machine on the 'wrong side of the Atlantic' from you. Oh well. That's life.

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But not 4.4THz :)

Oh, sorry :-)

Of course, that was 4400MHz.