Attention, non-political post! Has anyone used FR4 without a Rogers 3003 top layer for 77GHz automotive Radar purposes? If so, which kind/vendor? I know, I know, this ain't kosher but it's a cost-sensitive case and this one does not need to reach top-notch RF performance. And I promise not to try that on phenolic :-) -- Regards, Joerg http://www.analogconsultants.com/
77GHz Radar with FR4 board?
Started by ●April 1, 2019
Reply by ●April 1, 20192019-04-01
On Mon, 01 Apr 2019 07:42:42 -0700, Joerg <news@analogconsultants.com> wrote:>Attention, non-political post! > >Has anyone used FR4 without a Rogers 3003 top layer for 77GHz automotive >Radar purposes? If so, which kind/vendor? > >I know, I know, this ain't kosher but it's a cost-sensitive case and >this one does not need to reach top-notch RF performance. And I promise >not to try that on phenolic :-)We once did a board with mixed FR4 and microwave laminate layers. They looked like potato chips. I could lay one on my desk and give it a twirl and it would spin for a full minute. https://www.dropbox.com/s/rym97ts13dt4qp5/T420_Amoeba.jpg?dl=0 Actually, that didn't work very well so we did the next gen all FR4. https://www.dropbox.com/s/v9byymfy6ijh64g/T400_wiggles.JPG?dl=0 Is something intermediate-cost stuff better than FR4 at speed? Polyamide maybe? I can only evaluate to 20 GHz with my TDR gear, but short runs on FR4 look pretty good. On longer runs, the killer is not so much dielectric loss, but the horrible black oxide treatment of the traces which aids adhesion to epoxy. Peel one up. It's disgusting. Maybe somebody can fab FR4 boards with smoother copper. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●April 1, 20192019-04-01
On 2/4/19 1:42 am, Joerg wrote:> Attention, non-political post! > > Has anyone used FR4 without a Rogers 3003 top layer for 77GHz automotive > Radar purposes? If so, which kind/vendor? > > I know, I know, this ain't kosher but it's a cost-sensitive case and > this one does not need to reach top-notch RF performance. And I promise > not to try that on phenolic :-)What the hell kind of cost-sensitive semiconductor does anything in 12ps? Regardless of what material it's bonded to...
Reply by ●April 1, 20192019-04-01
On Tue, 2 Apr 2019 08:47:00 +1100, Clifford Heath <no.spam@please.net> wrote:>On 2/4/19 1:42 am, Joerg wrote: >> Attention, non-political post! >> >> Has anyone used FR4 without a Rogers 3003 top layer for 77GHz automotive >> Radar purposes? If so, which kind/vendor? >> >> I know, I know, this ain't kosher but it's a cost-sensitive case and >> this one does not need to reach top-notch RF performance. And I promise >> not to try that on phenolic :-) > >What the hell kind of cost-sensitive semiconductor does anything in >12ps? Regardless of what material it's bonded to...People are making shockingly cheap radar and lidar chips for cars. The markets are enormous. Joerg probably needs to make the patch antenna or something like that. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●April 2, 20192019-04-02
Joerg wrote:> Attention, non-political post! > > Has anyone used FR4 without a Rogers 3003 top layer for 77GHz > automotive Radar purposes? If so, which kind/vendor? > > I know, I know, this ain't kosher but it's a cost-sensitive case and > this one does not need to reach top-notch RF performance. And I > promise not to try that on phenolic :-) >I have some Megtron 5, R5775 Dk <=3.5 @1GHz, Dg<=0.005 @1GHz; 18x24 sheets 0.0366 double sided. Withstands 204C for hours (do not know how long); 185C without a peep. Megtron 5 was superior to the Rogers stuff at that time (5yrs ago). Panasonic Megtron 6 is current, and is VERY competitive with the current Rogers stuff (seems a number of people still dislike the Rogers).
Reply by ●April 2, 20192019-04-02
On Mon, 01 Apr 2019 07:42:42 -0700, Joerg <news@analogconsultants.com> wrote:>Attention, non-political post! > >Has anyone used FR4 without a Rogers 3003 top layer for 77GHz automotive >Radar purposes? If so, which kind/vendor? > >I know, I know, this ain't kosher but it's a cost-sensitive case and >this one does not need to reach top-notch RF performance. And I promise >not to try that on phenolic :-)One cute trick the super-high frequency guys use is "suspended substrate." Route out regions of the board from below, almost up to the layer 1 traces. That makes the dielectric mostly air. I've asked pcb houses if they can do that, and they all said "sure." -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●April 2, 20192019-04-02
On Tuesday, April 2, 2019 at 9:20:55 AM UTC-4, John Larkin wrote:> On Mon, 01 Apr 2019 07:42:42 -0700, Joerg <news@analogconsultants.com> > wrote: > > >Attention, non-political post! > > > >Has anyone used FR4 without a Rogers 3003 top layer for 77GHz automotive > >Radar purposes? If so, which kind/vendor? >part of the issue isn't just the loss, but also the tolerance or variation of dielectric constant from unit to unit. m
Reply by ●April 2, 20192019-04-02
On Tue, 2 Apr 2019 06:55:01 -0700 (PDT), makolber@yahoo.com wrote:>On Tuesday, April 2, 2019 at 9:20:55 AM UTC-4, John Larkin wrote: >> On Mon, 01 Apr 2019 07:42:42 -0700, Joerg <news@analogconsultants.com> >> wrote: >> >> >Attention, non-political post! >> > >> >Has anyone used FR4 without a Rogers 3003 top layer for 77GHz automotive >> >Radar purposes? If so, which kind/vendor? >> >part of the issue isn't just the loss, but also the tolerance or variation of dielectric constant from unit to unit. >mAir is pretty consistent. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●April 2, 20192019-04-02
On 2019-04-01 15:36, John Larkin wrote:> On Tue, 2 Apr 2019 08:47:00 +1100, Clifford Heath <no.spam@please.net> > wrote: > >> On 2/4/19 1:42 am, Joerg wrote: >>> Attention, non-political post! >>> >>> Has anyone used FR4 without a Rogers 3003 top layer for 77GHz automotive >>> Radar purposes? If so, which kind/vendor? >>> >>> I know, I know, this ain't kosher but it's a cost-sensitive case and >>> this one does not need to reach top-notch RF performance. And I promise >>> not to try that on phenolic :-) >> >> What the hell kind of cost-sensitive semiconductor does anything in >> 12ps? Regardless of what material it's bonded to... > > People are making shockingly cheap radar and lidar chips for cars. The > markets are enormous. Joerg probably needs to make the patch antenna > or something like that. >Yup, the antenna. Discrete hardware is also cheap. I made a TDR for a client that is in the 100psec range and the RF section is around a buck in cost. Even in low 1k qties you can get RF transistors with an ft around 80GHz for 15 cents. -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●April 2, 20192019-04-02
On 2019-04-02 01:01, Robert Baer wrote:> Joerg wrote: >> Attention, non-political post! >> >> Has anyone used FR4 without a Rogers 3003 top layer for 77GHz >> automotive Radar purposes? If so, which kind/vendor? >> >> I know, I know, this ain't kosher but it's a cost-sensitive case and >> this one does not need to reach top-notch RF performance. And I >> promise not to try that on phenolic :-) >> > I have some Megtron 5, R5775 Dk <=3.5 @1GHz, Dg<=0.005 @1GHz; 18x24 > sheets 0.0366 double sided. > Withstands 204C for hours (do not know how long); 185C without a peep. > Megtron 5 was superior to the Rogers stuff at that time (5yrs ago). > > Panasonic Megtron 6 is current, and is VERY competitive with the > current Rogers stuff (seems a number of people still dislike the Rogers). >Yes, if we need expensive material we'll shop around. FR4 would be best though if it somehow suffices. -- Regards, Joerg http://www.analogconsultants.com/
