Hawaslsh
Full Member level 3
- Joined
- Mar 13, 2015
- Messages
- 164
- Helped
- 5
- Reputation
- 10
- Reaction score
- 7
- Trophy points
- 1,298
- Location
- Washington DC, USA
- Activity points
- 3,422
Hello all,
I attached a much more detailed analysis with all the measured and simulated data, but I will give a summary here as well.
For over a year we have been working with a specific vendor and specific flexible substrate; Dupont Pyralux AP915R, 5 mil of polyimide with copper cladding on both sides. We have had three fabrication runs for various projects. Each run contains a few test coupons we can measure to ensure our circuit models, substrate, and fabrication are all within tolerance.
The first fabrication run centered around 24 GHz and we had a 24 GHz patch antenna test coupon to test. To model and predict the antenna performance, we use Cadence's Microwave Office. For this first fabrication run we relied on the material's data sheet when modeling the substrate within Microwave Office. This first run worked as predicted. There were slight variations in the predicted loss and resonant frequency, but nothing out of the ordinary when comparing simulations to reality.
The second fabrication run centered around 5.8 GHz and we had a 5.8 GHz patch antenna test coupon to test. Again we used Microwave office to design and predict the performance of the test coupon. The simulated antenna modeled fairly well as compared to the fabricated antenna, see attachment for the actual data.
The third run fabrication run had two projects, centered around 5.8 and 11.3 GHz. Instead of patch antennas, the test coupons were slot antennas. The slots were designed using the same method as before, however, the measured values were drastically different than our models predicted. There is always some variation between simulated and measured results, but this discrepancy was too large to be attributed to fabrication tolerance and slight variations in the substrate.
I tried a lot of different things in my model to try and pinpoint where I might have been wrong. Out of frustration I tried a crazy change to the dielectric constant of the material, from the nominal 3.4 to 4.4. That change alone made both the 5.8 and 11.3 GHz models match their measured counterparts.
The attachment has a lot more detail and data to back up my claim, but I think the substrate my vendor used the last run is different than my prior runs. And not slightly different, VERY different. Am I ok to call out my vendor (as nicely as possible) and ask if something changed or if they actually used the right substrate? Is there some other reason someone can think of for my last fabrication run to be so drastically different than my prior runs?
Sorry for the long post, happy to provide more context.
Thanks Sami
I attached a much more detailed analysis with all the measured and simulated data, but I will give a summary here as well.
For over a year we have been working with a specific vendor and specific flexible substrate; Dupont Pyralux AP915R, 5 mil of polyimide with copper cladding on both sides. We have had three fabrication runs for various projects. Each run contains a few test coupons we can measure to ensure our circuit models, substrate, and fabrication are all within tolerance.
The first fabrication run centered around 24 GHz and we had a 24 GHz patch antenna test coupon to test. To model and predict the antenna performance, we use Cadence's Microwave Office. For this first fabrication run we relied on the material's data sheet when modeling the substrate within Microwave Office. This first run worked as predicted. There were slight variations in the predicted loss and resonant frequency, but nothing out of the ordinary when comparing simulations to reality.
The second fabrication run centered around 5.8 GHz and we had a 5.8 GHz patch antenna test coupon to test. Again we used Microwave office to design and predict the performance of the test coupon. The simulated antenna modeled fairly well as compared to the fabricated antenna, see attachment for the actual data.
The third run fabrication run had two projects, centered around 5.8 and 11.3 GHz. Instead of patch antennas, the test coupons were slot antennas. The slots were designed using the same method as before, however, the measured values were drastically different than our models predicted. There is always some variation between simulated and measured results, but this discrepancy was too large to be attributed to fabrication tolerance and slight variations in the substrate.
I tried a lot of different things in my model to try and pinpoint where I might have been wrong. Out of frustration I tried a crazy change to the dielectric constant of the material, from the nominal 3.4 to 4.4. That change alone made both the 5.8 and 11.3 GHz models match their measured counterparts.
The attachment has a lot more detail and data to back up my claim, but I think the substrate my vendor used the last run is different than my prior runs. And not slightly different, VERY different. Am I ok to call out my vendor (as nicely as possible) and ask if something changed or if they actually used the right substrate? Is there some other reason someone can think of for my last fabrication run to be so drastically different than my prior runs?
Sorry for the long post, happy to provide more context.
Thanks Sami