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Question on crystal oscilator

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arr_baobao

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Hi all,

I did a measurement on my 26MHz crystal oscilator and found something strange with different setting as below:
with ref level set to 10 dbm i got the weird measurement with a lot of sideband ripples. Did i over compress my signal? But the power lvl is only -13.67dbm, i assume using ref lvl 10 dbm is ok.
1.JPG

with ref level set to 20 dbm, i get a cleaner output.
2.JPG

Anyone tell me which setting is correct? or something wrong with my crystal oscilator output. thanks.

regards
Bao
 

Give more details like circuit and measurement setup.
 

its just a crystal oscillator to supply a ref in signal for mixer IC. i just probe with the crystal output to the input of the mixer IC with a probe.
 

What is the output of the xtal oscillator (sine or square wave)?

The levels of the spurs don't follow from setting to setting. You might be over driving your SA.

Or, reading your last post, these spurs may be mixer related. What does the XO look like without any connection?
 

is a sine wave. xtal oscillator.
but the pwr lvl is only -13/14 dbm base on my measurement with the SA, is there possible that i over drive my SA?
 

with ref level set to 20 dbm, i get a cleaner output.
Click to expand...
And even cleaner with 30 dBm reference level, because spurs are completely hidden by SA noise...

Overdriving the SA will generate oscillator harmonics, not a 600 kHz fence. Looks more like harmonics of a switch mode converter or logic circuit. And you surely don't overdrive it with the oscillator signal. You may want to watch 0 to 100 MHz band to if there are other high level signals.
 
FvM said:
And even cleaner with 30 dBm reference level, because spurs are completely hidden by SA noise...

Overdriving the SA will generate oscillator harmonics, not a 600 kHz fence. Looks more like harmonics of a switch mode converter or logic circuit. And you surely don't overdrive it with the oscillator signal. You may want to watch 0 to 100 MHz band to if there are other high level signals.
Click to expand...

thanks for the valuable input.
Are those spurs normal ? or there is something wrong with my hardware that caused those spurs?
 

I opt for "something wrong with the hardware". Of course it depends on the design requirements, what's the oscillator signal used for?

It's not even clear if the spurs are visible in the oscillator output. May be it's just unsuitable signal probing?
 
the oscillator signal are used as an ref signal for a mixer IC.
 

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