# Question related to two closely separated signals that need to be analyzed by a spectrum analyzer

Question

The settings of a spectrum analyzer are given as following:

• Center Frequency = 1.89 GHz, RBW = 10 kHz, VBW = 10 kHz and Span = 50MHz.

• The Reference Level is set to -20 dBm and detector mode is Positive Peak.

• The RBW selectivity is $$\1:15\$$ for $$\RBW_{-3 dB}\$$ : $$\RBW_{-60 dB}\$$.

If we are studying a CW signal of 1890 MHz with -23 dBm output power, then

a) How close to your studied signal may a signal of the same amplitude be and still be measurable? Explain the conditions for close-in signals to be resolved.

b) How close-in signals with power level 50 dB below your studied signal can you detect?

My Attempt

Is my reasoning making sense to you?

a) "Thumb rule" (I guess?) for equally powered CW Carriers, they should be at least $$\RBW_{-3 dB}\$$ far apart in order to resolve and measure them.

b) For unequal powered signals CW Carriers (have power difference of 50 dBc), they should be at least $$\RBW_{-50 dB}\$$ far apart in order to resolve and measure them.