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Take heart. The data from manufacturers, if corresponding to the parameters you put in your circuit equivalent, can be used. I have taken basic equivalent circuits for various transistor structures, and even added in circuit artifacts of my own caused by various external builds (stray...
Thanks for reply (biff44)
There is at least one extraordinarily precise, (and wildly expensive!!) large antenna out there (9m) that has mechanicals it can point to 0.0048 degrees when on the move.
I don't know how good it is for thermal expansion. Pointing droop is driven out by the servos in...
Add to this that any reference to "switched capacitors" is actually turning the situation from a DC to a type of AC, though possibly with a strange waveform.
Take it further - any time-varying feature would involve capacitor charging and discharging - so not DC.
Real capacitors may well have...
Assume fine engineering, with suitable shaft encoders good to about 300 milli-arc seconds (22 or 24bits for a circle), and servo-positioning systems that will point to (estimated) 0.02 degrees, or maybe better. The dish would be (say) dual-shaped Cassegrain, with surfaces measured and aligned...
Thanks for your reply Volker. I do agree. I think it is really asking for Axial Ratio.
It was the magnitudes that gave me concern. An antenna has to be quite bent, or the polariser performance quite poor to give such variation if the incoming wave plane is rotated.
How to measure it is a...
The requirement says..
"The elliptic ratio of the antenna shall be better than 1dB"
For a different lower frequency band, another value given was 3dB.
For me, I know what is Axial Ratio, and that it can be expressed as number ratio, or in dB, and the common values are not anything like 3dB...
Gosh - answering a very old thread here. Please allow that even in the original post, I had to kind of imagine what layout he was working with.
You can use varactors in place of capacitors. The only "extra" bit that involves is to find some way to add in the bias voltage, which alters the...
The device is a thyristor-based item used for soft-starting electric motors.
There are several good brands, but in this case, it is an older Schneider (Telemecanique LH4) type, which can be used for both 3-phase and single phase motors.
Not mentioned at all in the data sheets, but only at the...
Hi jiripolivka
Hmm - I am so sorry about the pictures. I don't know what happened there.
I shall try again. The words assume pictures are available, and can get meaningless without them.
The field patterns should show a TE11 and a TE21 mode in a coaxial waveguide. This takes a little mental...
Thanks for repies Jiripolivka and biff44
Re: Coaxial waveguides. These can look like a (usually short) version of a coaxial cable structure, but are very different in operation.
The difference is that in a coaxial (cable-type) structure, the centre part is not connected to the outside, but is...
Cable-fed probes inserted into a wavguide space are familiar to many. They generally insert about half way into the shorter space, and can be variously given cylinder or conical end shapes. Even the centre conductor of a coax cable inserted like this can give 10dB RLR.
Things get more awkward...
Huge number of reads but no replies?
I don't have much experience at this either, but I have tried pointing a circular polarized antenna at a satellite signal of known circular polarization, and checking the signal on the "wrong" polarization connector on the polarizer. This was in no way a...
At the present, I do not have any access to the PC that ran CST, so regrettably, I cannot help right now.
In general, you would be driving the feed point of the patch antenna via connection to a transmission line of some kind. It might be microstrip, or coplanar waveguide, or it might be the...
I think the circular horn will initially support the linear TE10 mode, in the plane it was launched in. For receiving incoming linear polarization, the horn would have to be rotated until the patch lines up with the incoming. I guess you could also have used a pyramidal horn.
Incoming circular...
While I am sure there are many elegant ways to do this, my mind always just thinks up a "quick and dirty"!
My first thought was ..
You can model it at a particular frequency, and find the feed point impedance. The problem is, you don't know how much of the reactive (ie. complex number) part is...
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