I have looked for a figure of sensitivity in the data sheet, but I could not find it. My calculations show -90dBm, but that is assuming an SNR. Could you please specify SNR and sensitivity?
We supply Noise Figure and from this the sensitivity can be calculated for the
NO(dBm) = NF(dB)+kTO+10Log(BW)
NO = Output Noise
NF = Noise Figure
k = Boltzmann's Constant = 1.38 x 10-23 Joule/oK
TO = Absolute temperature of the receiver input (oKelvin) = 290 oK
NO(dBm) = 10 -174 + 60 = -104dBm for 1MHz BW
So for SNR of 10dB, sensitivity is -94dB
To improve the overall sensitivity of system, I put LNA with NF of 2.5 before ADF5904. Now, theoretically overall NF of the system is roughly 3.
To test the noise floor of the system, input of LNA is left open (i.e. not terminated) and output of ADF5904 is connected to D2S board and then to Spectrum Analyser. SA is set to fstart = 100KHz, fstop = 2MHz, RBW = VBW = 1KHz.
Observed noise floor on SA is from -85 dBm to -100 dBm.
Expected N0(dBm) = 3-174+63 = -108 dBm for 2MHz BW.
There is a lot of difference and this is causing poor radar range.