Bode plots are diagrams used to analyze transfer functions (the ratio between an output function and an input function). The diagrams plot the magnitude and phase of the expressed function versus frequency. See Bode plot for more information.
Typical usage of Network Analyzer the WaveGen 1 output and Oscilloscope Channel 1 input of the device is connected to the filter input, Oscilloscope Channel 2 to the filter output. As shown in the picture below.
When the instrument is started, the Scope and WaveGen are stopped and their status shows Busy. The Network Analyzer takes control over the these instruments while running.
The analysis is performed from start to stop frequency in the specified number of steps. For each step the WaveGen channel is set to a constant frequency and the Oscilloscope performs an acquisition. Using the frequency transformation result from the index corresponding to the current frequency step, the magnitude and phase value is calculated. The magnitude of Channel 1 (filter input) is calculated relative to WaveGen Amplitude and the other channels magnitude and phase relative to Channel 1. The magnitude is expressed in decibels with the 20 * Log10 (gain) formula, where 1x gain equals 0 dB and 2 X gain equals ~6 dB. The phase is plotted with the maximum and minimum value as the one specified for the Phase Offset +/- 180° value.
With Channel set to none under WaveGen options, no WaveGen channel is controlled. The Oscilloscope acquisitions are expecting custom or external frequency sweep signal. The current frequency step is determined by peak frequency component with magnitude at least half of the specified WaveGen Amplitude value.
With Reference set to none under Scope Options, the magnitude for each channel is calculated relative to the set WaveGen Amplitude and no phase calculated.
See Menu in Common Interfaces.
The control area lets you adjust the settings for the Bode analysis.
Saves a channel as reference to compare with further analysis.
The Bode plot shows the magnitude and phase.
By default the Channel 1 magnitude is relative to the WaveGen amplitude. The other channels magnitude and phase values are relative to channel 1.
The drop-down button (in the top-right corner or mouse right-click) contains options for:
The HotTrack lets you take measurements by moving the mouse cursor. This shows a vertical cursor and the values at intersections with waveforms. The corresponding position is marked with a cross on Nichols and Nyquist plots.
The X cursors can be moved with mouse horizontal drag or keyboard arrow keys. Dragging with left mouse button moves the cursor and with right button the pair of cursors (X1 and X2) is moved keeping the distance between them.
The X or vertical cursors by default are in the bottom-left corner.
The time plot shows the oscilloscope acquisition of the last frequency step. This view is used to help adjusting the offset and gain of the oscilloscope input channels.
The Nichols plot is the magnitude and phase plotted in the polar coordinate system.
The Nichol's plot is the magnitude and phase plotted in the Cartesian coordinate system.
See Export in Common Interfaces.