77GHz Radar with FR4 board?

Maybe, but what about the mechanical routing?

Reply to
Robert Baer
Loading thread data ...

My point was: The Megtron 5 technology is about 5 years old, and was not expensive WRT FR4 then, and i have some. And, unlike some suppliers, i do not demand a minimum qty of 20. Package weight, 1 PCB, 5 lbs; I use the very thick cardboard like that used for pumpkins or water heaters for rigidity.

Reply to
Robert Baer

Shockley did not invent the transistor; it was patented in the early

1930's. Actually TWO patents, and they were FETs!
Reply to
Robert Baer

  • Smoothness lies in the beholder, and the app. Remember, that smooth copper top has a bottom/back side that has as much, if not more effect on traveling waves/reflections.

Seems that a lot of the effort for better RF transmission, is to have precise, controlled and refined glass weave underneath; then add a smooth surface...

Reply to
Robert Baer

Or is measured in micro-inches RMS.

Most of the energy in a microstrip is propagated on the underside, where the dielectric constant is higher than air. And regular FR4 boards have an ugly adhesion treatment on the underside that adds massive skin losses.

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
 Click to see the full signature
Reply to
John Larkin

The antenna traces would, of course, be up to. However, when the FR4 underneath them causes a substantial pro delay delta the antenna tuning might get out of whack.

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

If this project flies we'd have to make half a bazillion.

5lbs? Yikes!

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

Which is why it would be fun to mill out most of the FR4 from underneath. But the underside copper should be smooth.

Cutting away FR4 would also help equalize the prop delay dispersion inherent to microstrip, although that could be tuned out in a narrowband antenna.

A lot depends on whether you can give up some noise figure to make the board cheaper. Avoid hitting cars and not worry about bicycles and baby buggies maybe.

That Murata dc/dc appears to be milled and then laminated and plated. So maybe one could fab the antenna as a very thin low-loss board, maybe even kapton flex, and then glue that to some cheap FR4 board that has a cavity slot, to make suspended substrate with farside ground plane.

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
 Click to see the full signature
Reply to
John Larkin

fredag den 5. april 2019 kl. 22.55.45 UTC+2 skrev John Larkin:

motive

nd

omise

hey

.

R4

ric

ds

effect loss due to the copper surface roughness is overwhelming, something like 2.2dB per inch. They have a super smooth copper laminate and applicat ion process that improves this considerably- just exactly how much I seem t o have missed. So they do have a product with this super surface smoothness laminated onto an FR4 substrate to make it more economically feasible in c ost conscious applications. The other stuff with dielectric loss, radiation and leakage losses remains acceptable.

s

maybe just a fr4 frame you can get flex/fr4 combined

formatting link
ing_ce_rohs_standard.jpg

Reply to
Lasse Langwadt Christensen

This is going to be a wideband app, several GHz BW though at 77GHz that's still less than 5%.

As a cyclist I must object! :-)

Yes, flex is a nice method but it does at substantial cost.

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

So that would be a rigid-flex assembly where the flex is the antenna itself, sticking off the edge of the FR4 pcb.

Rigid-flex isn't expensive in volume. Lots of things like LCDs do that.

formatting link

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
 Click to see the full signature
Reply to
John Larkin

Am 02.04.19 um 19:59 schrieb John Larkin:

One could metal plate it and use it as a wave guide.

cheers, Gerhard

Reply to
Gerhard Hoffmann

I'd expect that there is a waveguide geometry with metal on top and bottom and dielectric (or vacuum) on the sides. There are all sorts of improbable prop modes, like slotline. Agoston Agoston used trenches milled into a metal block.

formatting link

--
John Larkin         Highland Technology, Inc 

lunatic fringe electronics
 Click to see the full signature
Reply to
John Larkin

My mother knew Bardeen, personally (first name basis). She always said that if there are room full of people and you knew he was in the room, he would be the last you'd suspect of being a twice Nobel laureate.

Reply to
krw

  • Mostly in the heavy-duty cardboard for stiffness to protect the PCB. Alternate package would be a larger box with engineered spacing between all box sides and PCB.
Reply to
Robert Baer

Too bad, Digikey's best price breaks start at a bazillion.

At quantities, rigid-flex would be cheap.

--
John Larkin         Highland Technology, Inc 

lunatic fringe electronics
 Click to see the full signature
Reply to
John Larkin

Boy, you guys are acting silly on this one. Go take a look at the 47 and 76 Ghz Ham Radio web sites..

No one plays any tricks with anything like Fr4 above 10 Ghz for a reason. The losses are huge.

Steve

Reply to
sroberts6328

Quartz or alumina...for starters..

formatting link

My practice is limited to 10.5 Ghz, but when I attend the summer amateur radio conferences I assure you I see no FR anything above 10..

Steve

Reply to
sroberts6328

Bell Labs was wonderful. Shockley was the rare jerk.

I have a good book about Bell at home. I'll post the link.

It's been said that all the great discoveries were made by people who had lunch with Harry Nyquist.

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
 Click to see the full signature
Reply to
John Larkin

Well, those hams *are* amateurs. And they don't manufacture in the bazillions.

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
 Click to see the full signature
Reply to
John Larkin

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.