[SOLVED] Help in selecting Noise Source

[shashy.br]

Hi all,

I don't know how to select a noise source for my system,

i looked into the details and found the term ENR ,

but i am not clear with the selection of ENR requirement.

How should i calculate my ENR requirement ?

my frequency of operation is X band.

 

[G4BCH]

Your question does not give enough information for any definitve answer to your problem. Here are a few pointers to help you solve it for yourself

First ENR stands for Excess Noise Ratio, usually given on dB. This is the number of dB above thermal noise ktB that the noise doide will generate.
i.e a 15dB ENR noise source will generate -174+15dB dBm/Hz of noise at the calibrated frequency.

Before you can decide on the ENR of the noise source you should know why you are putting the noise source in the system in the first place. If it is to monitor the noise figure, and the system noise figure is low then you need a low ENR at the receiver input, this means a coupler with low insertion loss and a high coupling loss together with a high ENR source. If it is to measure the noise figure directly then it means a low ENR source connected directly to the LNA input. A low ENR source has the advantage that the impedance does not change significantly between the on and off states. This can be a source of error in low noise systems.
If it is just a simple system check you need or you are injecting noise for some other reason then ENR may not be so important.

Peter