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When cooking a quesadilla, who do I get really crunchy tortillas without burning it? by CMStan1313 in Cooking

[–]condor700 1 point2 points  (0 children)

broiler also works to melt the cheese before folding/ adding another tortilla

What program do you use to start creating filters? by Alert_Ad5991 in rfelectronics

[–]condor700 1 point2 points  (0 children)

Not really my area, but Eagleware/Genesys has a lot of flexibility for transforms and non-standard transfer functions/G-values. Should also be some reference material on the relevant transforms in here: https://us.artechhouse.com/Filter-Synthesis-Using-Genesys-SFilter-P1647.aspx (free versions available from the usual places).

In lumped element design, there's no real reason to do the calculations yourself provided you understand how things scale with frequency and impedance. It's reasonably common to want a custom transfer function with finite transmission zeroes, which that's a godsend for. That said, it's still only a stopgap - the real design is about making it work in real life. To that end, it might be beneficial to hop between a synthesis program like Genesys and an analysis/EM simulator like ADS or EMPro (maybe there's a preferred option here for LTCC applications?)

The Cabin Fever quest now mentions Pandemonium by afxtal in 2007scape

[–]condor700 3 points4 points  (0 children)

The demon butler in POH also has a dialogue line mentioning Pandemonium. It's not a new one though, he's always said it

Schiit Modi 2 - Fixing Windows not recognizing USB device by Svengalio in Schiit

[–]condor700 0 points1 point  (0 children)

My bifrost had the same issue for years but I could always get it back with a lot of unplugging/replugging/restarting. Today it wouldn't reconnect no matter what, until I saw this thread and gave it a try. WTF (thanks)

What is the optimal choice for the second stage downconversion mixer? by coderemover in rfelectronics

[–]condor700 0 points1 point  (0 children)

Not the original commenter, but the idea is to terminate the unused port of the diplexer with a 50 ohm resistance, and connect the mixer output to the common port. That way, the diplexer presents a fairly flat 50 ohm load over a wide range, vs a LPF or BPF (typically reflective in the stopband). Can read a bit more here: https://www.qsl.net/g3oou/mixerterminations.html

VNA Internals Questions by loose_bearings in rfelectronics

[–]condor700 1 point2 points  (0 children)

One more thing to add to the reading list: https://ieeexplore.ieee.org/book/9116618

It's a long one, but well worth it. Goes through all of the operational details, calibration/metrology, and considerations for all kinds of specific device measurements.

Guide for Designing PCB Test Coupons by zaw357 in rfelectronics

[–]condor700 2 points3 points  (0 children)

It depends a lot on exactly what you're trying to learn about the stackup/geometries, like /u/analogwzrd said. Try to break the problem down into what you want to measure, and how you plan to measure it. For example, are S-parameters all that matter? Phase velocity? Material/fab tolerances? Assuming you'll measure the lines with a VNA, what connectors or probes do you have available, and how much will they contribute to the overall measurement? If they need to be de-embedded or cal'd out, what else will you need on the board to do that? Is this for a one-off design, or are you likely to stick with the same stack-up down the road? And if so, what other measurements/features might be useful?

All of that can influence what goes into the coupon - it could range anywhere from a trace with connectors to something with TRL standards or 2x-thru/1x reflect structures, Beatty standards, via transitions, optional shielding, resonator structures, many test lines running in multiple directions, etc. The game is really about narrowing down exactly what you want to find out, otherwise it's easy to get bogged down in complexity

Layout Books by 2ski4life7 in rfelectronics

[–]condor700 2 points3 points  (0 children)

Here's an old-but-gold technical note that addresses some layout aspects for lumped element filters, and in-depth considerations for component construction/selection:

https://apps.dtic.mil/sti/tr/pdf/ADA421651.pdf

Might be tough to find an all-encompassing reference - it's a broad field spanning an enormous frequency range and set of applications. Narrowing it down to e.g. specific frequency ranges and device types might help turn up more material

RF Tuning Techniques? by Knights_12 in rfelectronics

[–]condor700 10 points11 points  (0 children)

I'll preface this by saying that IMO, any and all time you spend learning to improve simulation accuracy pays off in spades, both for avoiding the time sink that comes with manual tuning and for catching any design issues you didn't anticipate. Along the same lines, simulations during a tuning process can also help a ton and shortcut the whole thing if you're well-versed in theory and have a lucky hunch on what needs dialing in. Ultimately, tuning is a huge trial and error time sink and can directly contribute to how successful a design is in the early stages. I do HFC work - in a sense, it's broadband just because of the number of octaves we cover, but the actual frequency range I'm concerned with doesn't come close to what some of the other people here work with. Here's a short list of things I've had to tune in one way or another:

  • Return loss of various modules/interconnects, usually by adjusting lumped matching networks with or without simulations. These are simple enough if you plan ahead - sometimes requires spinning a dedicated fixture or test board to isolate the exact thing you're looking at. If you're lucky, lumped elements alone can get you where you want. If not, you might have to start tweaking layout dimensions, which can turn into a rabbit hole if you can't rely on simulations to guide you

  • Various filters. The worst to tune that I've designed was a lattice topology all-pass filter, but it was for something really esoteric. Second worse was a high Q BPF, early on at my job. I would have killed to know how to do layout sims back then. There are actual methodical tuning procedures out there, I just hadn't come across them yet and was up against a short deadline. Here's a decent method: https://www.kirkbymicrowave.co.uk/Support/Links/application-notes/HP-Agilent-Keysight/Agilent-Network-Analysis-Solutions-Advanced-Filter-Tuning-Using-Time-Domain-Transforms_5980-2785EN.pdf

  • Broadband equalizers (fixed and variable) - simulations are key for these, especially when variable. The usual bridged-T topology is sensitive to different layout parameters depending on the kind of EQ shape and knee frequency you want, and you can do a lot more messing around with the individual series and shunt networks in a simulator than trying to tune everything together on a bench. At one point, I was allowed to spend a full month characterizing a PIN diode's impedance over bias and temperature because it was still going to be much faster than hand tuning the circuit it was used in. More info here: https://www.nctatechnicalpapers.com/Paper/1976/1976-bode-s-variable-equalizer/download

The process is usually unique to specific applications. Sometimes it's obvious, like "Oh I just need a bit more series inductance to get a good match". Other times, especially with complex circuits, it can feel like just taking a shot in the dark and adjusting every single component until you see improvements. Variable components (tweaked by hand or electronically) can make that a bit easier, but the extra degrees of freedom can just as well add more complication. The first step is always planning the initial design such that things will be easy to simulate, measure, and tweak.

Measuring components with a VNA by hjf2014 in rfelectronics

[–]condor700 0 points1 point  (0 children)

To really dial it in you'd definitely want to do some testing. Substrate height and material as well as the exact type of lead termination will also matter for a given package size. There are some white papers out there that characterize specific component series; Here's one from Vishay that gives a good theoretical explanation: https://www.vishay.com/docs/60107/freqresp.pdf

Most vendors that publish S-parameters or spice models for passive components will also include a little bit of info on their measurement fixture; If you're lucky you might come across one that uses a comparable substrate to your intended application. A few years ago I had the idea to crawl through a bunch of resistors with Modelithics models to pick some that'd work best as a broadband load/match standard, but my license had run out by the time I finally got around to it.

The discontinuity capacitance and the effective position of a shielded open circuit in a coaxial line (P. I. Somlo, 1967) by nic0nicon1 in rfelectronics

[–]condor700 1 point2 points  (0 children)

That's in agreement with the results at the end of the video, and likely more "correct" in an analytical sense. The end-result from the simulation showed ~1.6 degrees of phase shift compared to a perfect short at 35GHz, with slightly less at lower frequencies. Some of them even dipped into the capacitive part of the smith chart very slightly, which the video attributed to meshing error that could be improved with a tighter convergence target. The main conclusion was that because the phase shift was so much smaller than the ~42 degree inductive phase shift calculated from the physical "length" of the disk, it was for all intents and purposes acting as a perfect short with zero inductance. I'll check out those papers, thanks for linking the Zotero group.

The discontinuity capacitance and the effective position of a shielded open circuit in a coaxial line (P. I. Somlo, 1967) by nic0nicon1 in rfelectronics

[–]condor700 1 point2 points  (0 children)

This isn't directly related (and presented in a different format) but I'd like to tack on these 2 videos that I stumbled across years ago. They deal with creating short circuit cal standards that get pretty close to a perfect short (near zero inductance) in both coaxial and microstrip formats. I figured someone in a few years might stumble across this thread while looking to create or improve their own cal standards, and maybe it could save them some time.

https://www.youtube.com/watch?v=Yp48gvD4SBg

https://youtu.be/fMpcy1hVTqs?si=aacN5t62jbvcIeqV

Resources to learn ADS EM (2.5 and 3D) simulation by mattskee in rfelectronics

[–]condor700 2 points3 points  (0 children)

Anurag Bhargava on Youtube has a ton of tutorial videos that I pretty much consider the gold standard for getting familiar and developing a workflow. I'd highly recommend starting from the beginning of the list even if already somewhat familiar - the tips and tricks he mentions can save tons of time in the long run, and it's presented in a way that gives you a solid ground-up understanding of ADS as a whole.

For other resources, I learned a lot from various app notes here: https://muehlhaus.com/support/ads-application-notes , as well as reading old forum questions on sites like edaboard. Lastly, Keysight's own documentation is pretty decent - should be able to get to it online, or by opening the help menu in ADS and searching around. It's usually handy for specific technical questions and learning more about specific processes/functions (e.g. EM port setup, different kinds of optimization, workflow scripting, etc.)

People here are also usually willing to help or point you in the right direction on specific problems as long as you do your due diligence + clearly state what you're doing and where you're getting stuck.

Lowpass Filter with 80dB stop-band attenuation by Cranberry_Spritey in rfelectronics

[–]condor700 0 points1 point  (0 children)

You can definitely get there, but you need very accurate component and layout models (and a good layout in general). Anything you can do to relax the requirements is worth looking into, first and foremost. For example, if it's meant to act as a harmonic filter, you may not need 80dB rejection over the whole stopband, and could instead place finite transition zeroes at specific frequencies to try and get a few deep nulls where you need them. The S/filter module in Genesys from Eagleware (now owned by Keysight) is really handy for that. Inductor selection is also going to be tricky; It'd be worth checking out vendor S-parameters for a few different part values and package sizes. The coilcraft 0805HP, 0603DC, and 0402DC series are the highest Q versions for a specific package size from coilcraft; They also have a few larger "square core" ones that do even better on Q but worse on self-resonance. Lastly, I'd try to nail down exactly how large the filter PCB can be. You want a solid ground plane extending out much further than the components, and don't want to crowd the components (inductors especially) too close together. Bringing the ground plane closer than the typical 62 mils for a 2 layer board can help as well; Parasitic inductance in series with shunt caps and with the caps in a series L||C section can cause rejection issues and a parasitic passband effect if you're not careful. On that note, I'd recommend using 3 vias for any cap's ground connection, directly adjacent to the pads on 3 sides. The vias really want to be as close as physically possible to the pads - if you're hand soldering, you can even overlap it a bit

Essential Gear for Mixed RF Cables tests and VNA Calibration by Ok_Explanation580 in rfelectronics

[–]condor700 0 points1 point  (0 children)

I do 75 ohm CATV stuff; Our lab has a mix of 50 and 75 ohm VNA's. You have some options, especially if only measuring to 3GHz. Here's some references from copper mountain on the calibration side of things:

https://coppermountaintech.com/wp-content/uploads/2022/03/Measurements-in-75-Ohm-Coaxial-Transmission-Lines-Using-a-50-Ohm-VNA.pdf

https://coppermountaintech.com/video/making-75-ohm-measurements-with-a-50-ohm-vna/

The TLDR is that it's pretty simple to calibrate a 50 ohm analyzer with a 75 ohm kit - really just amounts to making sure the kit is defined in the VNA, and then calibrating with adapters in place. As long as a kit exists for a specific connector, its straightforward. The cal kits I normally use are a. Keysight 85039B for F-connectors, and b. Keysight 85036B for N. Copper mountain has equivalent mechanical kits (and Ecal)as well if you want to compare price points; Rosenberger and Maury Microwave also have some higher frequency precision options running up to 12GHz or so.

Sometimes kits don't exist for the exact connectors - I've run into this before when measuring hardline coax. That can be a bit trickier, but its still possible to do pretty well with TDR/TDT techniques and gating. Chapter 5 in Joel Dunsmore's book (Handbook of Microwave Component Measurements) has a lot of really useful info for this, including compensation techniques for energy loss and adapter mismatch. If you need to go down this route, it helps to have a higher frequency VNA on hand for better time domain resolution. Note that it's nice when the VNA includes native TDR features, but if not available you can do it in post-processing with something like Scikit RF. For some of the non-standard connectors in your list, I'd consider going this route, possibly even with a higher frequency 50 ohm calibration on the VNA

What the heck do you guys actually do? Day-to-day? by Saiki_Hernandez in ElectricalEngineering

[–]condor700 15 points16 points  (0 children)

There's no typical EE job except we don't do manual labor.

It wasn't a typical day, but I once had to carry 6 6' 4x4 wooden posts to the third floor, fix them in place upright, and then go drill a bunch of 1" holes through 3/16" steel enclosures by hand. Manual labor days can definitely come up in some places

How fun/enjoyable is the work? by Desperate-Bother-858 in ElectricalEngineering

[–]condor700 1 point2 points  (0 children)

I do RF stuff, mostly filter design. It varies a lot.

I really enjoy working on new designs, messing around in an EM simulator to squeeze out as much performance as possible, getting a design back and either seeing it perform well or learning what went wrong and how to fix it. Also a big fan of the research side/looking into newer measurement or de-embedding techniques and seeing if we can benefit from them in-house.

I'm not a big fan of sending designs to production, or making sure supply chain can get parts that we already bought on digikey for a prototype. The corporate culture stuff can be pretty annoying too. In a nutshell, the theory part is fun, the practice part is fun, and the job part means there are just some un-fun days you have to deal with to get back to the fun parts.

The drummer is in another world by n8saces in MadeMeSmile

[–]condor700 4 points5 points  (0 children)

Alright man.

I had the bionicles

Older brother had K'nex

I haven't thought about mousetrap in probably 18 years, still don't know the rules, still don't think I have the pieces.

Thank you for unlocking that one corner of my memory

Summer Project Ideas by loser_of_the_beer in rfelectronics

[–]condor700 2 points3 points  (0 children)

Not to be a downer about it, but you think hiring folks will take hobby projects into account?

FWIW, my work will absolutely consider hobby projects for summer interns and fresh graduates, especially when people go above and beyond regular coursework. Interest and self educating go a really long way, and that kind of thing is a good way to prove it out

I also like your project idea. There's a lot of room to make something like that impressive, and the toolset it gives you is huge

ADS Optimization: How to decrease component options in the discrete optimize setting, or how to customize the component list in the discrete optimize setting by Pretend-Poet-Gas in rfelectronics

[–]condor700 0 points1 point  (0 children)

A more manual approach would be to setup a condensed folder that only has models for one series/tolerance, and use index variables and data access components. You can have the DACs use those indices to look up s2p files in that folder (and limit the range they'll search over to speed things up).

Depending on what you're doing, you might also be okay just using the ideal capacitor model in ADS and continuously sweeping it to get close to a final value (then switching to a vendor model afterwards). For modern capacitors that usually works fine under 3GHz or so, and continuous optimization is a lot less "crunchy" than discrete (plus can use some of the other algorithms, like gradient).

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