Network Analyzer

The Network Analyzer is used to analyze transfer functions (the ratio between an output function and an input function). The Bode plot shows 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, while the Oscilloscope Channel 2 is connected 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 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 magnitude and phase values of the other channels are 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 a custom or external frequency sweep signal. The current frequency step is determined by peak frequency component with a magnitude of 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.

 

1. Menu

See Menu in Common Interfaces.


1.1. View

 

2. Control

The control area lets you adjust the settings for the network analysis.

 

3. Channels

3.1. WaveGen

The gear tool contains the following:

3.2. Magnitude


3.3. Phase


3.4. Custom One/Two

The custom plots lets you specify custom functions.


The gear tool contains the following:

The custom functions is evaluated for each frequency step. It receives as input Freq (Hz), Gain (magnitude in gain), Phase (radian), Real (real part), Imag (imaginary part).

The provided examples (capacitor and inductor with series/parallel approximations) expect a reference resistor. The value of this is defined in the rRef constant. The rScope is the scope input resistance and cScope the capacitance.

10 nF capacitor with 2kΩ reference resistor:

15 uH inductor with 5Ω reference resistor:


3.5. Add Channel

Saves a channel as reference to compare with further analysis.


3.6. Channel

The gear tool contains the following:

3.7. Reference

The Reference options contains the following:

4. Bode Plot

The Bode plot shows the magnitude and phase.

By default, the Channel 1 magnitude is relative to the WaveGen amplitude. The magnitude and phase values of the other channels are relative to channel 1.

The gear tool (in the top-right corner or mouse right-click) contains options for:

 

4.1 Quick Measure

See Quick Measure in Common Interfaces.
The corresponding position is marked with a cross on Nichols and Nyquist plots.

 

4.2. Cursors

See Cursors in Common interfaces.

 

5. Views

5.1. Time

The time plot shows the oscilloscope acquisition of the last frequency step. This view is used to help adjust the offset and gain of the oscilloscope input channels.

 

5.2. Nyquist

The Nyquist plot is the magnitude and phase plotted in the polar coordinate system.
The selected cursor or Quick Measure position is marked with cross on the plot.

 

5.3. Nichols

The Nichol's plot is the magnitude and phase plotted in the Cartesian coordinate system.
The selected cursor or Quick Measure position is marked with cross on the plot.

 

5.4. Cursors

The Cursors show cursor information in table view. See Cursors for more information.
This table shows additional information to cursor tooltips: the 1 / delta x frequency, delta y vertical difference, and delta y / delta x.

 

6. Export

See Export in Common Interfaces.