3 GHz PLL

[slashguitar]

Hello,
I have to test if a 3 GHz PLL is working (ADF4118). I probed the output with a 200Mhz Tek but there is nothing. Is there a way to see if the circuit is working without expensive spectrum analyzers?
Thanks

[Psi]

Depends what exactly you want to test.

You could buy 4x 3Ghz flip flops and make a 4 stage div/2 frequency divider.
That would give you 187Mhz that you could see on the scope.

Looking at digikey 3Ghz flip flops cost NZ$6.50

EDIT:  Actually, it would be cheaper to use two of these div/4 chips, which cost NZ$5.66
http://search.digikey.com/nz/en/products/SY100EL33LZG/576-1354-ND/771946

[slashguitar]

It looks like it might do the job.thanks
Unfortunately the shipping will take a week or so

[Psi]

What about electronic suppliers near you?

You could always build 4 flipflops out of 3ghz+ transistors if you wanted to get crazy.
And if 3ghz+ transistors are easier to source locally. (they usually are, being more basic components than div/4 chips)

[Rufus]

Depends what exactly you want to test.

You could buy 4x 3Ghz flip flops and make a 4 stage div/2 frequency divider.
That would give you 187Mhz that you could see on the scope.

Then he can post asking how to test if a 3GHz divider is working.

[mikeselectricstuff]

If all you want to test is whether or not the 3GHz is present, a simple diode detector on a scope probe would do it.

You may be able to do something clever by mixing the outputs of two PLLs to produce a difference signal with a more manageable frequency.

[ejeffrey]

If you make a frequency divider you have to watch out.  If you AC couple the input (which is often convenient) they will usually oscillate at a few GHz if there is no signal. 

[Zero999]

You're using the wrong tool for the job. You need a frequency counter not an oscilloscope which isn't much use here. Fortunately 3GHz frequency counters are quite common and cost the same as a low end oscilloscope.

[Fraser]

Simple SHF monitoring tools may be built....

1. A simple diode detector probe with suitable diode for 3GHz use. Works with a multimeter or oscilloscope to provide a dc level when RF is present. Frequency cannot be determined.

2. Prescaler for oscilloscope or low frequency frequency counter. SHF prescalers are now more available since the advent of satellite TV. They are cheap and can divide a frequency down to that which you equipment can display. Division factors of 64, 128 and 256 are common and cost a few dollars. Just search for prescaler on ebay. Hittie do lots of SHF prescalers.

3. A downconverter to convert an SHF frequency down to one that your equipment can cope with. A simple unit will consist of a cheap SHF VCO connected to an SHF mixer. The product of the mixing process must be less than 200 MHz in your case so a VCO in the frequency range of 3000 to 3200MHz or 2800 to 3000MHz would be good. VCO's are self contained little modules and just require a supply and control voltage to get them going. Again search on ebay for VCO. Frequency accuracy will be appalling but you will see if a 3GHz carrier is present in your PLL and what it is doing. RF filtering on the output of the mixer would normally be used to select only the desired IF frequency but you may get away without this in your case.

The above are fun little projects that are cheap and cheerful, yet provide a useful tool that may be used in the future.

Regards

Aurora

[Neganur]

Hello,
I have to test if a 3 GHz PLL is working (ADF4118). I probed the output with a 200Mhz Tek but there is nothing. Is there a way to see if the circuit is working without expensive spectrum analyzers?
Thanks

Do you have a schematic by chance? I use the ADF4118 in one of my spectrum analyser's local oscillators. It is connected to a VCO through a loop filter and an ultra low distortion opamp. You would want to probe for DC voltages there, not RF.

[slashguitar]

thanks for all your replies
@Neganur it's the ADI's demo board http://www.analog.com/static/imported-files/user_guides/UG-166.pdf