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Heya folks, cheers for the feedback - it's been years since I've been in this forum and it's nice to see many of the familiar faces still around :)
To cover off on some of your suggestions:
* Aye, the freelancer site doesn't seem an encouraging place to do professional engineering unless you...
Good evening folks,
I'm helping put a course together using avalanche transistors to explore time domain reflectometry etc techniques and I could really use a hand with creating a simulation model based around ADS. I've packaged up the (paid) task and posted it to freelancer(.)com for anyone...
You should certainly spend the money to buy one - indeed, what you are proposing to build is essentially a VNA anyway!
Buying one will a) let you build your own system more expediently, and b) provide a truth against which to compare your own measurements.
I'd actually suggest a reason c)...
All you need is a "bias tee" (https://en.wikipedia.org/wiki/Bias_tee). This lets you apply a DC bias current to your laser diode (or LED) to set its intensity to the desired value and AC couple on your RF modulation.
You can buy prepackaged (and SMA/BNC/etc terminated) bias tee's or roll your...
> wouldn't that change the characteristic impedance ...
Yes!
> and hence reflection would increase?
Well, that depends on what your stub is doing.
Concentrating on the first part then, yes, you need to model the effect of the via(s) linking the upper microstrip layer to the underlying ground...
I'm not sure of your specific requirements, but a simple logarithmic amplifier/RF power detector IC (perhaps preceded by a bandpass filter if there's other signals present you wish to ignore) might fit the bill.
Have a look at Analog Devices' portfolio of chips...
> should build some vias instead for black wire in the pic. to the ground)?
Definitely!!!
Those wires aren't included in your ADS model and are a gross departure from the idealised ground connections shown in your schematic.
I've found achieving practical RF "ground" connections in a...
I've seen this sort of behaviour before as a result of the "AR" (auto regression) filter which seems to auto-enable itself in some situations/scenarios...
[I haven't identified the pattern yet, maybe it's related to the template used? Either way, whenever I come across screwy results with...
Hey Asimov,
While your solution is an order of magnitude more powerful than anything I've created/needed, here's a reference that offered me some inspiration when I needed to drive capacitive loads with a few hundred+ volts at MHz rates in our optics lab. I would have loved to have tried the...
> I need the 49.9 ohm series resistor on the output of the BUF634, to match the line, yes?
No, not at all! Dump it and get your 6 dB back :)
> Otherwise I'm subject to reflections across the cable.
Not necessarily...
The resistor on the BUF634's output is a form of "source termination" and...
Re: Voltage reduction of a battery pack
Yup! Use the buck converter. I've used that module before and it's a nifty (+easy) way to power all sorts of things from variable, high battery voltages.
Your current requirements (200mA) are well within its capabilities and operating at such a...
Hey Fred, it sounds like you're after a "conformal coating". Have a Google around - there's 1001 suppliers and products and most contract assembly/electronics manufacturers can do it for you.
(Or you can by something that'll probably work for you in a spray can from Farnell if you've got a few...
> Will it work at 10 watt output?
Depends entirely upon the core volume (and operating frequency). For a core the size of a peppercorn, no it won't. For a core the size of a grapefruit, absolutely! You'll have to dig up the relevant design equations - I can't recall them offhand (although...
Yup!
Although I've found using ferrite cores at low power levels such that the cores don't saturate works OK, better performance is easily obtained using smaller cores + small gaps (a piece of paper slipped between the core halves gives a cheap repeatable gap of a few tenths mm). Iron powder...
Not a problem at all :)
The only thing to be aware of is that the final phased array beamwidth is a function of the overall array aperture. i.e. a 3x3 array with 0.1 wavelength spacing between antennas wont achieve the same narrow beamwidth the same 3x3 array array will with 0.5 wavelength spacing.
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