Can a Network Analyzer be used in place of a signal generator

I checked the HP and Tektronics gear I have on my workbench and found If it has a Sweep Mode selection called Manual Sweep, it can put out a single frequency with all the controllability and accuracy of the product specification. Another possible choice would be if it has Span selection where you can select Zero Span, and again it will put out a single frequency. Plus five dBm should be within the range of most network analyzers.

Chuck

Great, thank you for your help

Ebay.

HP 8664A to 3 GHz for $1700 and a day left.

Look up the specs on the Agilent.com site. Should do exactly what you want.

Because network analyzers have filters on the input, sometimes they don't put out the cleanest signals, where a signal generator might have a cleaner signal. [Usually only an issue if testing high speed ADCs.] Otherwise, I don't see a problem, other than it ties up a nice piece of test gear. ;-)

I have a 8660c. A boat anchor, but a nice boat anchor. I had to do a lot of lets make a deal to get it working, so I'd never suggest buying one on ebay.

Another eBay option would be to buy a YIG oscillator module such as:

200616317161 or 150614694236 or 200616317159

You would need a 1A variable voltage bench power supply to drive the tuning coil and a low-current psu to drive the oscillator. Frequency stability will not be anywhere near as good as the network analyzer unless you use a phase locked loop drive system which may be over- complicated for your project. (Suitable pll modules such as

160589712611 appear regularly on eBay.) Google will find you instructions for using YIG oscillators.

John

The brand & model number?

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It's easy to think outside the box, when you have a cutting torch.

Probably so. Read the manual!

What's the 2.4 GHz going to do?

John

I will post the brand and model # when I find out, I have yet to see this device, but I'm told we have it.

Stupid question time: Can the network analyzer be used to create a

2.4GHz signal on the output(like my previous question), and then, at the same time, read another signal at the input, and produce a frequency spectrum plot?

I feel like a total electrical noob with all of this stuff.

That's precisely what a network analyzer does!

Well, it used to be that one person could understand most of electronics. No more; it's just too complex. Nowadays it takes a bunch of years to get exposed to things, and even then it's easy to get stuck in a niche. I've been fortunate to always work for companies with terrible marketing departments, so got to work on all sorts of unorganized stuff.

I'd recommend you get the manual for the analyzer and read it. There's probably some tutorial stuff.

What's the 2.4 GHz going to do?

John

On some analyzers it is called "zero span". The screen still runs but it won't change the frequency. This is how I once tuned a piano (no joke).

But be aware that some analyzers briefly interrupt the "transmission" when the sweep restarts at the left of the screen. So you'll see a modulation. You could turn the sweep time to the maximum possible to at least reduce the number of those events.

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Regards, Joerg

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I don't think so, the output signal is usually synchronous with the sweep isn't it?

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John Devereux

There's an oscillator or synthesizer that's swept, and a tracking scalar or vector voltmeter. Usually you can set the sweep width to very narrow or no sweep at all.

John

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the 2.4 GHz is going to be used to encode another signal and transmit it.

this may be a stupid question, but is there any way to convert a 15 MHz signal into a 2.45 GHz, or even a 868 MHz signal, using frequency multipliers or anything? I'm running into a lot of resistance getting any good equipment, my adviser is pushing me to try and find a way of making a basic signal generator (15 MHz max frequency) work for this project. would it be possible to use a lot of frequency mixers to step up the frequency up a lot? like use 8 frequency mixers starting with a signal generating

9.57 MHz, going int both the IF and LO inputs, and then the output being 19.14 MHz going into another frequency mixers IF and LO inputs and outputting 38.28125 MHz, and so on until you get 2.45GHz? It seems to me like that wouldn't work due to the difference in the resistances causing reflections and the output would need to be amplified quite a bit if it wasn't distorted beyond recognition.

I'm still new to anything above 1 MHz, but I feel like i'm learning a lot.

Let me know what you think, Thanks

You most likely want a mixer: You feed your 15MHz signal along with a 2.3GHz local oscillator (this can come from your VNA behaving as a source) into it, and out pops your signal at 2.45GHz... as well as 2.15GHz, which may or may not bother you (i.e., mixers produce the sum and difference of the frequence at their ports... they actually produce other frequencies as well -- both leakage of the LO frequency and your 15MHz, as well as various "mixer spurs," but for just testing something out at lower powers you can often ignore them... but beware if you're going to be using a power amplifier and putting this on-air).

Note that you could have also used 2.6GHz as the LO, in which case you'd have gotten 2.45GHz and 2.75GHz out.

If the undesired output does bother you, it's better to start at 868MHz and use an LO of either 1.582GHz or 3.318GHz and you'll end up with 2.45GHz as well as a (potentially unwanted) signal at 714MHz or 4.186GHz -- those are quite easy to filter out, if necessary.

A page like this one:

... has lots of mixers that would be appropriate. "Level 7" means that you're supposed to feed the LO port with 7dBm (500mV RMS in a 50ohm system); it's probably the most popular level for passive mixers out there (you can be off a bit and the performance won't change that much).

See above. I think you're confusing mixers with frequency multipliers (which is really just a mixer with its "IF" and "LO" ports connected together). If you've using a signal that doesn't rely on an amplitude (envelope) modulation, you can use a bunch of multipliers as you've outlined. However, if you do need to preserve amplitude information, it'll change going through each multiplier, and -- as you allude to -- while in theory you can figure out how to "pre-disort" the input amplitude to obtain the desired output, in practice this is a non-trivial problem that, given your current background, I wouldn't recommend tackling.

BTW, it sounds as those your adviser probably doesn't have much real-world experience in RF design. If that's the case, I suggest you see if you can find some local company that could provide you with someone who does have that sort of experience and is willing to provide it as a form of public service to the school (and to gain some recognition on your reports); this will dramatically increase the chance of your project actually working, IMO. :-) All the better if said company is able to loan you the sort of equipment you're after! (Bigger places like a LeCroy or Agilent or Tektronix can pretty much *always* find spare network analyzers, frequency sources, spectrum analyzers, etc. to loan out for a project like this.)

---Joel

Reading through your post again, it's clear you go understand the difference between frequency multipliers and mixers in terms of their function and construction; please ignore my comment that you might not.

Lots of questions. How precisely does the 2.45 GHz signal have to be in frequency tolerance?

To answer your question about frequency multipliers, remember that they have to be done in integer multiples. If you require precisely

2.45 GHz., the 163rd harmonic of 15 MHz. is 2.445 GHz. and the 164th is 2.46 GHz.

What the hell does 868 MHz. have to do with it?

Google "step recovery diode". HP had a whale of a lot of good multiplier design information back in the late 60s and early 70s.

Understood. I put myself through undergrad school doing VHF. J-band transceivers, and C-band radar repair for the airlines, so I had a hell of a head start coming out of college. Lots of my friends had zero experience on anything above a couple of MHz. coming out of school.

Just remember that the transition from lumped constant (coils and capacitors) starts to blur somewhere around a GHz. Below that you can probably wind coils that will work and above that mostly sections of transmission line.

Jim

Thanks for the advice, and the 868 MHz was referring to another option for my antenna, as opposed to the 2.4 GHz antenna I was planning on using.

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what are you really trying to do?

get an evaluation board like this:

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-Lasse

It can't plot a spectrum because the receiver is essentially just a glorified scalar RF voltmeter. It will only plot a frequency response through the device under test but it won't even do that with the output stuck on 2.45GHz.

It sound to me as if the OP wants it to display some sort of modulated spectrum coming off of the other side, and that it won't do.

[...]

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Regards, Joerg

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