Amplitude (Spectrum)

The PXIe-5663/5663E vector signal analyzer can make signal measurements over a frequency range from 9 kHz to 2.7 GHz and over an amplitude dynamic range of greater than 100 dB.

Amplitude dynamic range is the difference between the maximum input level of a device and its minimum detectable signal level.

Dynamic range estimates the ability of the vector signal analyzer to distinguish and measure the amplitude difference of two signals.

Large amplitude signals can overload the system and cause spurious effects. These spurs may be large enough to be mistaken for signals. This effect can be avoided by properly adjusting the amplitude of the incoming signal. Achieving proper signal levels may involve attenuating the signal before it reaches the amplifiers and the mixer, either by programming the internal attenuators or by using external attenuation.

You must properly configure the PXIe-5663/5663E vector signal analyzer before making a measurement. A small signal can be mistaken for noise if the resolution bandwidth setting is too large or the input attenuation is too high. When measuring small signals, optimize the signal-to-noise ratio by minimizing input attenuation and resolution bandwidth. Ensure that the reduced input attention is not too low for large amplitude RF input signals.

For signals below the noise floor of the PXIe-5663/5663E, use an external low-noise amplifier (LNA) in front of the vector signal analyzer to raise the signal level. If the update speed is not fast enough to resolve a signal because of the processing demands imposed by a narrow resolution bandwidth, an LNA can help provided it does not significantly affect system linearity. For example, with a signal level of -100 dBm, set the resolution bandwidth to 1 kHz or less.