how to measure SNR of mixer ?

[pankaj.patil]

Hello Sir

how to measure SNR of mixer practically and theoretically ?
please give me practical setup also.
VNA , signal gerator and spectrum analyzer are available to me , how to use it to measure SNR ?

Thank You

 

[Hadi-Alik]

Hello Panjak,

I think we can not directly measure or calculate a SNR of a mixer. First you find out the noise figure and then use it to calculate the SNR of your system. A mixer is not characterized by its SNR normally.

Regards
Hadi

 

[Hi-Tone]

To find the SNR, you need to know the signal strength on the input of the mixer (Signal Generator) and the output of the mixer (Spectrum Analyzer), but also the Noise Figure (Noise Figure Analyzer) of the mixer. Then calculate your SNR.

 

[enjunear]

Hello Sir

how to measure SNR of mixer practically and theoretically ?
please give me practical setup also.
VNA , signal gerator and spectrum analyzer are available to me , how to use it to measure SNR ?

Thank You

1. Attach Specturm analyzer to signal generator. Measure input SNR (be sure to check that the noise floor shown on the analyzer is the true noise floor, and not the noise floor of the analyzer. Hint: when you disconnect the signal generator and load the input of the spec. an. with 50 ohms, the noise floor should drop ~10 dB, to be confident in your noise floor measurement).

2. Connect input signal to mixer, attach Spec An. to output of mixer, measure output SNR.

3. SNR of mixer(dB) = SNR_in(dB) - SNR-out(dB).

 

[pankaj.patil]

1. Attach Specturm analyzer to signal generator. Measure input SNR (be sure to check that the noise floor shown on the analyzer is the true noise floor, and not the noise floor of the analyzer. Hint: when you disconnect the signal generator and load the input of the spec. an. with 50 ohms, the noise floor should drop ~10 dB, to be confident in your noise floor measurement).

2. Connect input signal to mixer, attach Spec An. to output of mixer, measure output SNR.

3. SNR of mixer(dB) = SNR_in(dB) - SNR-out(dB).

Thankx to answer my question
U have some doubt about this.
1. how to measure SNR from spectrum analyzer ?

2.when we connect input to mixer what about LO ?

3. please provide theoretical formula so I will compare it with practical output .

Thank You

 

[tony_lth]

1. Some SA have functions to measure SNR directly.
2. Link LO of course.
3. I dount this point, the formula should be "NF=SNRin-SNRout", not SNR of mixer.

 

[jupitorcuu]

It is tricky test, you must define SSB or DSB of mixer. The relationship with SNR will be individually from other RF behaviour. So you need a filter put before the mixer and let the Signal generator give a signal ( white noised signal with defined BW).Read signal with Pin On/off status at mixer output. You will get signal out and noise out.

Some key point of the test accuracy:
1. Calibrated input signal to mixer in
2. Good match input output
3. Carefully selection of input signal level, ( one experience is let the signal out is 3dB higher than signal off , the signal in is roughly equal to KTB, output SNR is 1 )