High frequency data acquisition system

[hykwei]

Good Day everyone:

I would like to construct a multi-channel (around 10 channels...)high speed data acquisition system, the receiving signal from each channel is going to be a fixed frequency (15 MHz) sinusoidal signal. So the system need to be able to detect the magnitude and the phase change compare to a reference 15MHz signal.

since the signal's frequency is quite high and fixed, and I have also got a reference signal...I am thinking maybe an analogue synchronous I/Q demodulation will be the right approach....

It's my first time to design such a high frequency system..so I don't know whether there is anything that I need to be aware of when prototyping the electronic circuit? (like can I use breadboard and normal wire to build the circuit? as there is going to be lots of radiation + electric coupling at high frequencies...etc)

And also, does anyone know any good high speed op-amp, programmable gain amplifier and mixers? low noise, low distortion one would be perfered...I have look through the Analog Device's website and apparently there is a AD8333 chip that can do the trick for me...but I actually don't know about its accuracy + performance compare with normal I/Q demodulation circuits...

Thank you very much for the help!!

 

[Nigel Goodwin]

I'm not really very clear what you're doing?, but attempting to use a breadboard at anything other than audio frequencies is likely to cause problems - there's far too much stray capacitance.

 

[hykwei]

Basically I have my driving signal (15MHz cos wave)...passing through a system, which will cause some magnitude and phase change with respect to the driving signal, and these will be my receiving signal... I want my data acquisition system will be able to detect those small magnitude and phase change...

I don't know whether it makes the problem a bit clearer...hope it does!

The problem comes from high frequencies...the components that I tried didn't work well with high frequencies...sigh...or maybe it's the breadboard problem...

Thx!

 

[Sceadwian]

So you're trying to measure the doppler shift in a 15MHz signal? How are you differentiating the channels?! You really need to explain EXACTLY what you're atempting to do and how you're going about it. You've started at the wrong end in describing the problem, as you've only described you current perceived best method, with absolutly no practical details.

 

[hykwei]

Hi....um....ok...let me put is this way....I would like to construct a I/Q demodulation circuit which can measure the magnitude and phase change of the incoming signal (15MHz)..with respect to a reference signal...

I have constructed a 20kHz demodulation cct beforehand....everything works fine...but once I moved into a 15MHz condition...things just doesn't work...(of course...all the opamps and mixers hav been switched to high speed component...)

At the moment...I use LM6361 for opamp and MC1496 for mixer...

I don't know whether it's the component problem (wrong component selection..) or there is anything that I need to be aware of when operating at high frequency which I didn't do...so I would like someone who has experiences on I/Q demodulation and high frequency electronics can give me some useful suggestion...


Thx!

 

[Nigel Goodwin]

You're still giving us no clue as to what you are trying to do?, and very often these sorts of questions mean you're going about it entirely the wrong way.

So tell us EXACTLY what you're trying to do, and not how you think it needs to be done.

 

[hykwei]

I am doing some mutual inductance experiments....to make it simple...let's assume there are only 2 channels - one transmitter and one receiver

The transmitter and receiver are made by coils, where transmitter are driven by a 15MHz sinusoidal signal (reference signal)...and because of the mutual inductance, the response at the receiving coil (which has a 15cm distance away from transmitter) will be a 15MHz signal as well...

And if I put an object between the transmitter and receiver, because the magnetic field will be disturbed by the object, it will cause certain amout of phase shift and magnitude change to the signal at the receiver side...which is the things that I would like to measure...

The aim of this experiment is to determine the the size of the object by looking at the phase and magnitude change at the receiver...so I need a circuit which can do the trick for me...at 15MHz...