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Signal generator and spectrum analyzer vs VNA

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hazif

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I have a reflectarray antenna, which function as a reflector.

I measure that antenna in chamber using signal generator (as transmit signal source) and spectrum analyzer (to receive reflected signal).

Does that mean i measure S21 since i use two different terminal/port?

And why the data plot (in term of power dBm vs theta) is different when i use VNA; in which VNA port 1 as transmit signal source and port 2 as receiver of reflected signal - which have a similar setup as sig gen and spec analyzer.

The VNA data plot is significantly differ from simulation. And the sig gen and spec analyzer data plot is much similar to the simulation.

So, i want to know is there any extra procedure i need to use for VNA setup...so that i can get the same plot if using sig gen and spec analyzer?

Plz help and tq so much...
 

pragash

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Does that mean i measure S21 since i use two different terminal/port?

no. antenna is single port component. an amplifier and filter is dual port. whatever device (antenna, filter or amplifier) which needs two network analyzer ports to connect is two port and so forth. Did you use the same antenna for both signal generator and spectrum analyzer? Anyway, the measurement you did in chamber is radiated power. it cannot be compared to S11 of an antenna.
 

hazif

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Did you use the same antenna for both signal generator and spectrum analyzer?

yup the same antenna...

Anyway, the measurement you did in chamber is radiated power. it cannot be compared to S11 of an antenna.

ok sir i understand...so the concept is i actually measure the reflected signal power right? it is not same with s11 (neither magnitude nor phase) parameter right?

So sir, i would like to know if i can measure that radiated power using VNA? or vna only capable to measure s parameter of a microwave signal?
 

pragash

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usually reference antenna will be used for TRP and TIS measurement in the chamber because the characteristic of reference antenna is known and the only unknown here is you DUT (antenna).

TRP is a measure of how much power is radiated by an antenna when the antenna is connected to a transmitter. TRP measurement method can be used to measure antenna gain but it cannot be used to measure S11 since its reflected power over incident power at port 1.

you cant measure radiated power using VNA nor S-parameter using spectrum analyzer and signal generator. both are different.
 

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