# Recent content by Paul678

1. ### Phase Locked Loop Theory

Correct me if I am wrong, but it looks to me that for a PLL that I designed, that the open loop unity gain frequency (0dB) appears to be the same as the closed loop bandwidth frequency. And this frequency is also where the phase inflection point occurs, or where the open loop phase margin is...
2. ### Phase Locked Loop Theory

So do you agree that in this case, the zero would that be at s=-(1/T2)? And that the "Poles" in the denominator, would be at zero, and s=-(1/T1)?
3. ### Phase Locked Loop Theory

Ok, but if we want to find the "Zero", we have to find the value of "s" that makes the numerator 0, right? So wouldn't that be s=-(1/T2)? And wouldn't the "Poles" in the denominator, be at zero, and s=-(1/T1)? Am I missing something here? Or was this a typo?
4. ### Phase Locked Loop Theory

Ok, thanks everyone. Banerjee's book is very good. But is there a typo on page 42, in terms of where the zero and poles are in transfer function 7.1, on page 41? (See attached pic)
5. ### Phase Locked Loop Theory

From this paper: http://www.elenota.pl/datasheet-pdf/88472/National-Semiconductor/AN-1001 "When designing for a higher phase margin you trade off higher stability for a slower loop response time and less attenuation of the Reference Frequency." Is this true for ALL PLLs? And it...
6. ### Why are Air Boxes Used in Bandpass Filters in HFSS?

From page 1.2-1 of this: https://www.researchgate.net/profile/Sudipta_Maity2/post/How_to_figure_out_number_of_modes_in_HFSS/attachment/59d6582d79197b80779ae32f/AS%3A537418164076544%401505141883049/download/hfss_full_book.pdf "By default Ansoft HFSS assumes that all structures are completely...
7. ### Why are Air Boxes Used in Bandpass Filters in HFSS?

Thanks for the response, Volker. At what point in the video did you see them making the "background material" PEC? I don't remember doing that.
8. ### Why are Air Boxes Used in Bandpass Filters in HFSS?

I've followed this tutorial, and it was simple enough to copy what was done: But after I was finished, I realized that the air box was never turned into a Faraday cage. It remained an air box, and even the outside diameters of the "coax", remained a vacuum, with only the...
9. ### Output S22 is NOT Conjugately Matched to ZLoad in Class-C Broadband Amplifier

Good point. The Load Pull technique is really just a more sophisticated version of the "cut and try", empirical method of finding an output impedance matching network, that satisfies your needs. Here is a video using load-pull in Microwave Office:
10. ### Output S22 is NOT Conjugately Matched to ZLoad in Class-C Broadband Amplifier

It would appear most broadband amplifiers are conjugately matched on the input only, so that the S11's inductive or capacitive reactances are cancelled out by the opposite reactances of the input matching network, which is also called Z-source. This assured maximum power transfer into the...
11. ### Why pick Hairpin over Edge-coupled Bandpass Filter?

What are the pros and cons of the Hairpin topology versus Edge-coupled, when designing a distributed element bandpass filter? The most obvious advantage seems to be the smaller size of the hairpin design, which can save board space. But perhaps the "comebacks" (the S21 response at the...
12. ### Round-Rod Combline Band-Pass Filter in HFSS

Here is the video. Sorry for the Malay language! :lol: https://www.youtube.com/watch?v=3EuE9lq7Heg So I was able to copy this design, and my simulation results were pretty much the same as hers. But I have some questions, as usual: 1) The main filter box was simulated as a...
13. ### Can HFSS Display the 3-D Conformal Mesh of Tetrahedrals?

How do I display the 3-D conformal mesh of tetrahedrals in HFSS? I wasn't able to find the command to do this. Or maybe HFSS doesn't allow you to see the mesh? This is for a patch antenna, or a simple dipole. Also, why doesn't HFSS put "dBi" instead of just "dB"? It's clear they...