Comments

  • load pull amplifier
    1) ignore matching the output to 50 ohms... just match to the ZL that gives best performance. Not that ZL for max efficiency is not the same as ZL for max power. It is a compromise.

    3) There are papers on harmonic terminations... I am no expert. But it is correct that high impedance is required. At first harmonic, you might want a short circuit. This could be done with an open stub close to the FET that is quarterwave at 2F0. Nothing that you add to the matching network after a short circuit will change the termination impedance at 2F0. At F0, it will look like a capacitive stub that you can work into the output matching network, and get to your load-pull match. The power amp will perform much better if you take care of that second harmonic. Dealing with the third harmonic is probably a lot harder and will have diminishing returns. Like "milking mice" as my old boss used to say...

    I hope this helps

    Steve
  • Low noise amplifier (LNA) using CE3520K3
    I took a fast look at that FET but could not stabilize it in the ten minutes I spent, without messing up the minimum noise figure. I hope to mess with it later, I don;t like it when instability wins.

    Does anyone have any experience with balanced LNAs? A friend of mine claims that almost automatically stabilizes the circuit but I am skeptical.

    Steve
  • Temperature sensing microwave oven
    This is a really cool system, I wish I had time on my hands to make one. You can imagine the fiber optic cables getting tangled up. An opportunity for someone to develop a rotary joint to bring out the data, to a blue-tooth arrangement outside the oven. Or maybe tiny sensors inside that send out data through the door at 94 GHz?

    Hopefully, one of you reading this can point to a company that already markets such a product.
  • What are popular Benchtop Thermal Testing Requirements?
    I am at a small company, we have shied away from low temperature testing. One problem is condensation, which can affect measurement accuracy or in worst-case destroy hardware. Temperature chambers are better suited compared to platforms in my opinion. The chamber design should pay attention to how to maintain zero humidity inside. Is this available?

    Another thing I once encountered was near asphyxiation in a lab that had a large number of temperature chambers using N2. It makes you very sleepy, as opposed to speeding up your heart like CO2 chambers do. It seems like very few labs have N2 concentration sensors

    https://en.gazdetect.com/gas-information/nitrogen-gas-detector-n2/
  • Beyond Maximum Stable Gain of an RF Transistor
    I have read at least one published paper on positive feedback in the second stage of an LNA. Not sure if this is the article, I don't have ieeexoplore access, but the title sounds useful...

    https://ieeexplore.ieee.org/document/5161354

    I used the technique and convinced myself I could get one dB more gain beyond MSG. I left the company before the chips came out so I never saw the data...

    Thanks for the design notes!

    Steve
  • Newbie question lambda g
    I believe you should use lambda guide, as described here

    https://www.microwaves101.com/encyclopedias/waveguide-mathematics

    But I would hold out for a second opinion!

    Steve
  • Coplanar capacitor
    Just curious, how do you know the field is non-uniform? is this a series cap or a shunt cap?

    10cm is ~7% of a wavelength, 24 electrical degrees, I think there should not be much of a distributed effect. but you could try two 5cm line/pairs in parallel.... or five 2.5cm lines that have four uniform gaps...

    Steve
  • Wideband MMIC DA amplifier biasing
    I have never designed a distributed amplifier so I don't have any great suggestions except look at spiral inductors for the drain supply line.... also, if you send me an email I can send you a presentation that you might find valuable

    Steve
  • Options for low gain flat bandwidth amplifier
    Larry
    The best way to find what you need is to go to EverythingRF and type in the freq band (in MHz) and you will see more options than you will ever need. Hopefully this link retains the search parameters (freq 4000-8000 MHz, gain 4-6 dB)

    https://www.everythingrf.com/search/microwave-rf-amplifiers/filters?page=1&country=global&sfrequency_min=4000&sfrequency_max=8000&sgain_min=4&sgain_max=6

    NOt all companies have their products on EverythingRF. fRor low gain amps you can look at Miller Microwave

    http://www.millermmic.com/product/products_lna.jsp

    Engin-IC has some tasty amps as well.

    http://www.engin-ic.com/amplifiers/

    I hope this helps
    Steve
  • Working out the dimensions of an 'end launch' waveguide to coax transition
    My advice is to buy a used one, hack it open and try to scale the dimensions to the band of interest. Then use HFSS to check performance....

    Steve
  • Tuning L and C
    This really is the art of microwaves, knowing what to touch and what to leave alone. Some people might look on a Smith Chart to see which direction to move reflection coefficient(s). Others may use trial and error. I often use an optimizer in Microwave Office to get the response I want. The thing that helps the most is experience, which you should be building on now.
  • Capturing the microwaves...
    I think the simple answer is that many antenna elements need to be used to cover the area. Or perhaps multiple reflectors that focus energy to a small number of antennas.

    of course, the farther from the source, the more antennas will e needed.

    Good luck!
  • Lumped Element Filter SW?
    Also, call me a conspiracist, but...

    I am always suspicious of on-line filter calculators, as a possible means of intelligence gathering. If you work at Boeing, Lockheed, NG, Raytheon, etc. I would expect that a lot of those sites are blocked.
  • Lumped Element Filter SW?
    http://tonnesoftware.com/ also has some nice freeware. One problem is that parasitics of lumped elements are not taken into account in any freeware I have seen.
    Steve
  • Modified Wilkinson HFSS
    That is an interesting network, is it published somewhere? I don't know HFSS well enough to help with that, but maybe you need to consider how far the cables are from ground. The outer jacket of one of the cables will be hot with RF energy, allowing it to be close to ground may change the result do you have a 3D image we can look at?

    Steve
  • EMScan belly up?
    I did some checking around. That firm seems to have disappeared without a trace. If anyone knows if there is another company picking up the product line please let us know and we can add it to where-are-they-now.

    A guy I knew long ago used to say "chicken today, feather pillow tomorrow". Maybe we can identify this particular pillow!

    Steve

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