Spectrum analyzer is a commonly used analytical instruments in RF or electronic industry, mainly for the detection and analysis of radio frequency and microwave signal. Spectrum analyzer is widely used in a number of areas. There are some common problems about spectrum analyzers that may make users confused or require user’s attention, we will provide answers to these questions and hope this may do some help to you.

Question:

How to set a spectrum analyzer to get the best sensitivity. How to observe weak signals.

Answer:

Firstly, set Center Frequency, Span and Reference Level according to the measured Signal; if the spectrum analyzer does not show any overload indication, gradually reduce the attenuation value. If the SNR of the measured signal is lower than 15db, then to gradually reduce RBW value. The lower RBW value, the lower the noise floor and the higher sensitivity.

Figure 1. Measurement Result with 10dB Attenuator

Saluki spectrum analyzer set attenuator to 10Db in default in order to avoid damage from high power input signals. Set a higher attenuator, the SNR of signal will come down as shown in figure 2.

Figure 2. Measurement Result with 20dB Attenuator

In order to get a better SNR, set the attenuator manually to 0Db. Result as shown in figure 3.

Figure 3. Measurement Result with 0dB Attenuator

If the spectrum analyzer has pre-amplifier,turn on pre-amplifier. Pre-amplifier can improve the spectrum analyzer’s noise figure, thereby promote the sensitivity. For low SNR signal, reduce the VBW, turn on averaging, this will help to smooth the noise and reduce fluctuations.

Figure 4. Measurement Result with 2kHz RBW

Please be noted, the measurement results are the sum up of input signal and internal noise of spectrum analyzer. So, in order to make the measurement accurate, the SNR should be greater than 20dB.