7 ms·

28Gbps Microstrip with Pepper Jack Cheese as Substrate (2016)

140 points by craigjb 7y ago

adonnjohn 7y ago
This of course begs the question: which cheeses act as the most efficient substrates, and why? I wonder if there's any organic materials that would work even better.
- jacknews 7y ago
  Indeed that "sandwich cheese" looks not dissimilar to PCB anyway.
- b3orn 7y ago
  I'd suggest a cheese with as little holes as possible, maybe Gouda, Cheddar or Parmigiano.
- IndrekR 7y ago
  > I wonder if there's any organic materials that would work even better. PCBs are using mostly organic resin. Mechanical constraints limit many otherwise excellent dielectrics. Also the cheese seems to have quite high loss tangent here. A quick test to this theory at 2.4 GHz involves a microwave oven, thermometer, pieces of RF laminate and dry cheese.
- willis936 7y ago
  Empirically, it boils down permittivity and conductance of the material. I am not familiar with the physical factors that influence that. For real applications there are other important factors too though. If your substrate gets moldy in a week then it would be hard to package and sell it to a customer.
  - mannykannot 7y ago
    Would those properties also relate to how well / fast the food can be cooked in a microwave oven?
    - willis936 7y ago
      Certainly. Those parameters and the geometry they're in can be distilled into impedance (see: S-parameters). The larger the difference in impedance, the less power gets through (see: return loss). For microwave ovens you only really care about material properties at 2.4 GHz, since that is where the power is. I'm under the impression this was chosen because water has a resonance at this frequency, and absorbs a lot of power.
  - wyldfire 7y ago
    > If your substrate gets moldy in a week then it would be hard to package and sell it to a customer. So you're saying I should be selling a substrate service subscription? I like it! MRR here I come!
  - peterwwillis 7y ago
    > If your substrate gets moldy in a week then it would be hard to package and sell it to a customer. Clearly you've not worked for Cisco...
    - cardiffspaceman 7y ago
      Sysco? (Only for the humor I have no idea what Sysco's reputation in food service is)
heyiforgotmypwd 7y ago
Parm is definitely better than cheddar in the resilience department, but I guess pepper jack might work. ;)
hatsunearu 7y ago
There's actually a lot of good nuggets of RF wisdom in this whack article. Love it.
wizardforhire 7y ago
Omg this is such great read! I’m nominating for best of HN! It’s got silliness, existential reveal, thorough methodical detailed explanations accessible to laypeople, excellent prose and is just a joy.
pjc50 7y ago
There's a pun about "queso factor" buried at the bottom of the comments too. This is a nice little article, there's something very Bob Pease about it. And it's good to remember that there can be quite a lot of margin in controlled impedance situations. I've done things like USB2-over-flat flexible cable for test fixtures before.
- cushychicken 7y ago
  >I've done things like USB2-over-flat flexible cable for test fixtures before. If it's never gonna see a radiated emissions test chamber, then why the heck not?
- MisterTea 7y ago
  > This is a nice little article, there's something very Bob Pease about it. "What's All This Queso Stuff, Anyhow?" RIPease <3
willis936 7y ago
Wow. This is so far up my alley that my masters thesis was on implementing testing from 802.3bj and I have made passive microstrip filters in a class. It’s cool that he simulated the eye diagrams, and getting your hands on a real transmitter is not easy, but I think it ends up being a little too optimistic. I don’t think this is meant to demonstrate a real world channel or else he could have just pulled IL and RL limits from various specs. Really cool stuff though.
deleted 7y ago
[deleted]
kosma 7y ago
Loosely related: ADSL over wet string https://www.revk.uk/2017/12/its-official-adsl-works-over-wet-string.html https://www.revk.uk/2017/12/its-official-adsl-works-over-wet...
fouric 7y ago
See also: custard antenna https://michaelcullen.name/2019/04/custard-antenna/ https://michaelcullen.name/2019/04/custard-antenna/

140 points by craigjb 7y ago

This of course begs the question: which cheeses act as the most efficient substrates, and why? I wonder if there's any organic materials that would work even better.

jacknews 7y ago
Indeed that "sandwich cheese" looks not dissimilar to PCB anyway.
b3orn 7y ago
I'd suggest a cheese with as little holes as possible, maybe Gouda, Cheddar or Parmigiano.
IndrekR 7y ago
> I wonder if there's any organic materials that would work even better. PCBs are using mostly organic resin. Mechanical constraints limit many otherwise excellent dielectrics. Also the cheese seems to have quite high loss tangent here. A quick test to this theory at 2.4 GHz involves a microwave oven, thermometer, pieces of RF laminate and dry cheese.
willis936 7y ago
Empirically, it boils down permittivity and conductance of the material. I am not familiar with the physical factors that influence that. For real applications there are other important factors too though. If your substrate gets moldy in a week then it would be hard to package and sell it to a customer.
- mannykannot 7y ago
  Would those properties also relate to how well / fast the food can be cooked in a microwave oven?
  - willis936 7y ago
    Certainly. Those parameters and the geometry they're in can be distilled into impedance (see: S-parameters). The larger the difference in impedance, the less power gets through (see: return loss). For microwave ovens you only really care about material properties at 2.4 GHz, since that is where the power is. I'm under the impression this was chosen because water has a resonance at this frequency, and absorbs a lot of power.
- wyldfire 7y ago
  > If your substrate gets moldy in a week then it would be hard to package and sell it to a customer. So you're saying I should be selling a substrate service subscription? I like it! MRR here I come!
- peterwwillis 7y ago
  > If your substrate gets moldy in a week then it would be hard to package and sell it to a customer. Clearly you've not worked for Cisco...
  - cardiffspaceman 7y ago
    Sysco? (Only for the humor I have no idea what Sysco's reputation in food service is)

heyiforgotmypwd 7y ago

Parm is definitely better than cheddar in the resilience department, but I guess pepper jack might work. ;)

hatsunearu 7y ago

There's actually a lot of good nuggets of RF wisdom in this whack article. Love it.

wizardforhire 7y ago

Omg this is such great read! I’m nominating for best of HN! It’s got silliness, existential reveal, thorough methodical detailed explanations accessible to laypeople, excellent prose and is just a joy.

pjc50 7y ago

There's a pun about "queso factor" buried at the bottom of the comments too. This is a nice little article, there's something very Bob Pease about it. And it's good to remember that there can be quite a lot of margin in controlled impedance situations. I've done things like USB2-over-flat flexible cable for test fixtures before.

cushychicken 7y ago
>I've done things like USB2-over-flat flexible cable for test fixtures before. If it's never gonna see a radiated emissions test chamber, then why the heck not?
MisterTea 7y ago
> This is a nice little article, there's something very Bob Pease about it. "What's All This Queso Stuff, Anyhow?" RIPease <3

willis936 7y ago

Wow. This is so far up my alley that my masters thesis was on implementing testing from 802.3bj and I have made passive microstrip filters in a class. It’s cool that he simulated the eye diagrams, and getting your hands on a real transmitter is not easy, but I think it ends up being a little too optimistic. I don’t think this is meant to demonstrate a real world channel or else he could have just pulled IL and RL limits from various specs. Really cool stuff though.

deleted 7y ago

[deleted]

kosma 7y ago

Loosely related: ADSL over wet string https://www.revk.uk/2017/12/its-official-adsl-works-over-wet-string.html https://www.revk.uk/2017/12/its-official-adsl-works-over-wet...

fouric 7y ago

See also: custard antenna https://michaelcullen.name/2019/04/custard-antenna/ https://michaelcullen.name/2019/04/custard-antenna/