The Harmonics submenu controls the measurement of arbitrary harmonics or ratios between harmonics and the fundamental wave. Together with the Mixer measurement and the arbitrary configuration of generator and receiver frequencies (Port Configuration), the harmonics measurement is included in option R&S ZVA-K4.
Harmonics Measurements
Harmonics are signals at an integer multiple of the fundamental frequency. The fundamental is the first harmonic, the nth harmonic is n times the frequency of the fundamental. The production of harmonic frequencies by an electronic system when a signal is applied at the input is known as harmonic distortion.
The purpose of the Harmonics menu is to measure the harmonic distortion of a DUT. To this end the source remains at the fundamental frequency whereas the receiver is set to n times the fundamental frequency. Two different types of results are provided:
In the direct measurement, the nth harmonic of the stimulus signal is measured. The result is displayed as a wave quantity but can be modified and converted using the functions in the Trace menu.
In the relative measurement, the nth harmonic of the stimulus signal is divided by 1st harmonic (fundamental) received from the DUT. The result corresponds to the nth harmonic distortion factor.
Harmonic distortion measurements can be performed irrespective of the sweep type: A frequency sweep yields the harmonics as a function of the frequency, a power sweep yields the power-dependent harmonics at fixed frequency.
2nd Harmonic Port 1 to Port 2... activates the measurement of the second harmonic at port 2 with port 1 as source port.
3rd Harmonic Port 1 to Port 2... activates the measurement of the third harmonic at port 2 with port 1 as source port.
More Harmonics opens a dialog for higher harmonics and arbitrary source and receive ports.
Reset Frequency Conversion activates the measurement of the fundamental with the current port assignments and trace settings.
Relative Measurement calculates the ratio of the selected harmonic to the fundamental and displays the result as a new trace.
Harmonic Power Cal... opens a dialog to perform a power calibration of the signal source and of the receiver.
The result of several harmonic measurements can be displayed in a common diagram area (see Traces, Channels and Diagram Areas). To make the comparison of the fundamental trace and the harmonics easier the stimulus axis for frequency sweeps remains unchanged, and all fundamentals are displayed as a function of the stimulus frequency (rather than the harmonic frequencies). A warning Frequency out of range. Please check dialog Mode: Port Configuration. is displayed if one of the harmonic frequencies to be measured exceeds the frequency range of the analyzer. The harmonic traces are truncated at the maximum receiver frequency. The harmonic measurement mode is cancelled if the channel settings (e.g. port assignments, port frequencies) are no longer compatible with the selected harmonic.
Measuring harmonics
Activates the measurement of the second harmonic at port 2 with port 1 as source port. The active trace shows the wave quantity b2. It is possible, however, to display other quantities and change the trace settings. A label H2 in the channel list indicates that the second harmonic measurement is active.
In a frequency sweep the 2nd harmonic is displayed as a function of the stimulus frequency; see general note.
Remote control:
[SENSe<Ch>:]FREQuency:CONVersion:HARMonic:ORDer 2 [SENSe<Ch>:]FREQuency:CONVersion:HARMonic:RPORt 2 [SENSe<Ch>:]FREQuency:CONVersion:HARMonic:SPORt 1
Alternative: [SENSe<Ch>:]FREQuency:CONVersion SHARmonic
Activates the measurement of the third harmonic at port 2 with port 1 as source port. The active trace shows the wave quantity b2. It is possible, however, to display other quantities and change the trace settings. A label H3 in the channel list indicates that the third harmonic measurement is active.
In a frequency sweep the 3rd harmonic is displayed as a function of the stimulus frequency; see general note.
[SENSe<Ch>:]FREQuency:CONVersion:HARMonic:ORDer 3 [SENSe<Ch>:]FREQuency:CONVersion:HARMonic:RPORt 2 [SENSe<Ch>:]FREQuency:CONVersion:HARMonic:SPORt 1
Alternative: [SENSe<Ch>:]FREQuency:CONVersion THARmonic
Opens a dialog for higher harmonics and arbitrary source and receive ports.
The Source port provides the stimulus signal at the fundamental frequency.
The receive port (Harmonics Measured at:) measures the signal at n times the fundamental frequency where n is the Harmonic Order.
The Harmonic Order can be set in the range between 2 (2nd harmonic) and 100.
A label H<n> in the channel list indicates that the nth harmonic measurement is active.
In a frequency sweep all harmonics are displayed as a function of the stimulus frequency; see general note.
Use 2nd Harmonic Port1 to Port2 and 3rd Harmonic Port1 to Port2 to activate the measurement of the second and third harmonics with a single menu command.
[SENSe<Ch>:]FREQuency:CONVersion:HARMonic:ORDer <order> [SENSe<Ch>:]FREQuency:CONVersion:HARMonic:RPORt <port_no> [SENSe<Ch>:]FREQuency:CONVersion:HARMonic:SPORt <port_no>
Activates the measurement of the fundamental with the current port assignments and trace settings. This disables the harmonics measurement and all other frequency-converting measurements (e.g. scalar mixer measurements) for the active channel.
[SENSe<Ch>:]FREQuency:CONVersion FUNDamental
Calculates the ratio of the selected harmonic to the fundamental (harmonic distortion factor) and displays the result as a new trace. To avoid confusion between the original harmonic and the relative measurement, the harmonic is hidden (invisible) but can be retrieved using the Trace Manager.
The relative trace belongs to a new channel. In the dB Mag trace format, the trace points are dB values, after conversion to the lin Mag format, they correspond to the (dimensionless) ratio of two voltages:
Calculation of the Relative Trace
To obtain the relative trace the analyzer must measure the fundamental signal in addition to the active harmonic. In a frequency sweep the two measurements require different sweep ranges so that the fundamental is measured in a new channel. The relative trace is then calculated using trace mathematics.
Assume that the active 2nd harmonic belongs to channel Ch1 with a sweep range between 10 MHz and 2 GHz. The relative measurement involves the following steps:
1. The analyzer creates a new channel Ch2 with maximum sweep range, e.g. for a 24 GHz analyzer:
2. The harmonic trace is measured with Ch1 settings, the fundamental trace is measured with Ch2 settings.
3. The analyzer enables the trace mathematics and divides the harmonic trace by the fundamental trace:
4. The harmonic trace is hidden (invisible); the relative trace is displayed as a mathematical trace.
Performing a relative measurement
[SENSe<Ch>:]FREQuency:CONVersion:HARMonic:RELative ON
Opens a dialog to perform a power calibration of the signal source and of the receiver. A power calibration ensures accurate levels at the input of the DUT (source power calibration) and an accurate power measurement of the harmonic (receiver calibration). The necessary calibration steps are automatically performed across the entire frequency or power range of the harmonics measurement.
Harmonic power calibration procedure and example
Due to the different frequency ranges of the input and output signals, the harmonic power calibration must be performed in two steps. For a test setup where the DUT's input signal (fundamental signal) is provided by analyzer port 1 and where the harmonic is analyzed at port 2, the following test setups are required:
1. Source power calibration of the fundamental signal. A power sensor is connected to port 1. The source power (red) is calibrated over the selected sweep range. As a preparative for step 2 the analyzer also calibrates the source in the harmonic frequency range. The correction data for both calibration sweeps is stored.
2. Receiver power calibration for the selected harmonic. No external device is needed. The receiver (port 2) is calibrated at the harmonic frequency using the source signal from port 1 (red) calibrated in the first step.
The calibration procedure is controlled by means of the two buttons on the left side.
Take Cal Sweep in the two numbered panels start the calibration sweeps for the source and receiver calibration, respectively. The calibration sweeps are performed at the test settings shown on the right side (see also Source Power Cal and Receiver Power Cal dialogs). The progress of the calibration is shown in the calibration sweep diagram and the messages below. Abort Sweep aborts the calibration.
The control elements in the right part of the dialog give access to various settings:
Modify Settings... opens the Modify Source Power Cal Settings dialog.
Power Meter selects an external power meter that is used to measure the exact source power at the calibration point; see Power Meter Settings. Power meters (Pmtr1, Pmtr2, ...) must be configured in the System Configuration – External Power Meters dialog before they appear in the list.
Power Meter Config... opens the System Configuration – External Power Meters dialog.
Perform Verification Sweep after Cal enables or disables a verification sweep that the analyzer performs after the source power calibration. The sweep is also displayed in the calibration sweep diagram. Its purpose is to test the accuracy of the source power calibration after the final correction data has been acquired. The final power calibration results are applied starting with the first sweep after the verification sweep.