What will be the thermal noise floor if we connect these two components HMC752 and ADF5904?
If we have a setup as:
Noise Source (LO + Noise) -> HMC752 -->ADF5904 -> Spectrum Analyser
As per my understanding: Thermal noise floor = kTBF (in dBm)
kT = -174 dBm/Hz
B = 1 MHz = 60 dBHz
F = ? dB
What floor I will get on Spectrum Analyser?
What shall be the SA settings?
- Thermal Noise =kTB=-174dBm/1Hz therefore if you want to calculate for different bandwidth for example 1kHZ
Thermal Noise = -174dBm + 10*LOG1kHz= -144dBm/ikHz
- Noise Floor in SA is combination Thermal…
- Noise Floor in SA is combination Thermal Noise and Noise Figure of SA( Note:usually there is additional 1.5dB or 2dB as part of SA but you can neglect it for rough estimation.
Noise Floor can be adjusted by changing Resolution Bandwidth.
Example: NF of SA=20dB; Noise Floor=-144dBm/1kHz
Noise Floor = -144dBm+20dB=-144dBm/1kHz.
I am sendng you plot below so you can see how by changing RBW, Nosie Floor is changed.
- If you measure Low Levels, you need lower Noise Floor, otherwise you should not worry about that.
Settings always depends on what you are trying to measure.
Our SA noise floor is -117dBm/10kHz.
In the testup HMC752 input is terminated. Its output is connnected to ADF5904. We are interested to measure noise floor of the HMC752+ADF5904 chain at IF=500kHz.
For converting the differential output of ADF5904 to a single ended (to SA), a AD8130 with 1dB voltage gain is used.
What is expected noise floor of HMC752+ADF5904 combination ?