Hello ,
I'm reading the guide pna-x 67Ghz on the part (option 029 and 028 of the noise).
I have two questions
1 - how to choose the bandwidth of noise (.8 Mhz, 2 Mhz ,,,, 24Mhz) in option 029 and .7 Mhz and 1.2 Mhz for option 028? and what does the relationship with the DUT bandwidth? and how the bandwidth of noise intervenes to measure the product bandwidth gain during the calibration
2 - why was the calibration of the RF source using the power probe to be 0dbm?
thank you very much
very cordially
Hello PhD-Noise,
Question 1.a:
How do you choose the bandwidth of noise in option 029 and 028
When making these measurements, you are trading off speed or accuracy and much of this decision really depends on what your particular needs are. The bandwidth of noise of 0.8 MHz will be very accurate but will take a long time while the reverse will be the case for 24 MHz. You will have to play around with the different noise bandwidths to suit your needs but, in general, you want to choose the largest bandwidth of noise. This is considering the averaging that takes place which slows down your noise measurements considerably. This will hold true for option 029 which only goes as far as 50 GHz and option 028 which will continue for the rest of your PNA-X's bandwidth which is done with the standard receivers.
Question 1.b:
Relationship to the DUT bandwidth
Here, you will have to consider the band pass of your DUT. As an example, if you are testing a filter with a 1 MHz band pass, you definitely want to avoid the 2 MHz or 24 MHz selection because they will pick up data that is outside your bandwidth of interest. Instead, you would want to go with the .8 MHz option because this bandwidth will be within the bandpass of your DUT.
Question 1.c:
How does the bandwidth of noise intervene with the measurement of the product bandwidth gain during the calibration?
When making a noise figure calibration, you really want your bandwidth of noise to stay within the linear part of your PNA-X receiver's frequency response. This ensures that the calibration is able to accurately remove the noise figure from the system and only pick up the noise figure from your DUT. With that said, the bandwidth of noise should not intervene with the gain-bandwidth product. This is because any of the bandwidth of noise selections are well within the bandwidth of the low noise receiver of option 029 (which goes up to 50 GHz) and the standard receiver of option 028. Note that 029 includes hardware and firmware that make very accurate noise figure measurements up to 50 GHz. Option 028, on the other hand, only includes the firmware of 029 but not the hardware.
Question 2:
Why was the calibration of the RF source done using a power probe set at 0dBm?
When an NA is calibrated at 0 dBm it ensures that power measurements at 0 dBm are very accurate. But why 0 dBm? This is because 0 dBm is simply a convenient point from which to compare to. When making power measurements on the PNA-X, it is easier to compare to 0 dBm as opposed to 3 dBm for example.
more information on power calibration at 1mW:
https://literature.cdn.keysight.com/litweb/pdf/5990-9078EN.pdf?id=2093568