S93070xB Modulation Distortion Application for the PNA-X

Modulation Distortion – Fast and Accurate EVM, ACPR or NPR Measurements

The S93070xB Modulation Distortion Application combined with the PNA-X Vector Network Analyzer and a Vector Signal Generator, VSG, enables users to measure the nonlinear behavior of power amplifiers under the wideband modulated stimulus conditions. The new frequency-domain measurement method delivers lower residual EVM and faster EVM measurement speed. The VNA-based vector calibration accurately extends the reference planes of the signal generator and the analyzer to the DUT planes. As a result, users can achieve an excellent signal fidelity and accurate modulated measurement at RF and mmWave frequencies.

The PNA-X X microwave network analyzer with the new Modulation Distortion application allows complete characterization of an amplifier that would have taken two separate test stations or the use of a complex and expensive switching matrix which degrades performance. This helps speed device test through R&D, DVT by reducing design cycle times, as well as, speed manufacturing throughput.

For example, when wafer probing devices only a single-touch is needed which improves overall throughput or enables testing that was difficult in the past. The single touch to the device also eliminates unnecessary wear to bonding pads which ultimately improves device quality.

The modulation distortion application delivers faster, more accurate, and repeatable EVM, NPR and ACPR measurements than conventional signal analyzers.

• Lowest residual EVM
• Fast and accurate measurement
• Simple and intuitive setup
• Cost-effective solution

Modulation Distortion Analysis Theory

The Modulation Distortion Analysis application uses the PNA-X’s measurements of the input and the output spectrum, as well as, their complex ratio across the complete in-channel and out-of-channel bandwidth.

A Vector Signal Generator is used to generate a repetitive signal with a given CCDF (Complementary-Cumulative-Distribution-Function) and PSD (Power Spectral Density). The VNA then measures the amplitude of the input spectrum |X(f)|, the amplitude of the output spectrum |Y(f)|, and the phase relationship of the tones relative to each other, φ(Y(f))-φ(X(f)).

Calculation of the spectral correlation between the input and output enables decomposition the output spectrum into linearly correlated and non-linear spectrum and analysis of the distortion product EVM, ACPR and NPR

• The spectral correlation enables to determination of the linear and nonlinear distortion solely introduced by the DUT, eliminating contributions from the signal generator
• Repetitive test signals are designed to faithfully represent the amplitude statistics as well as the power spectral density of the modulation format of choice
• The total amount of distortion measured in the frequency domain is equal to the total amount of distortion in the time domain as measured using the existing EVM method

Modulation Distortion Measurements

The measured data is available for the input signal, output signal and calculated contribution of the DUT. For example, it is possible to measure the NPR into the device, the output NPR and the distortion NPR that is added by the device only.

The modulation distortion application performs the following measurements (see PNA-X help file for complete list of measurement parameters):

• EVM o Equalized EVM of the DUT (non-linear contribution)
  • Un-equalized EVM of the DUT (Includes non-linear and linear distortion due to frequency dispersion)
• ACP o Upper and lower side bands of the input signal
  • Upper and lower side bands of the output signal
  • Upper and lower side bands contribution of the DUT
• NPR o Input NPR
  • Output NPR
  • NPR contribution of the DUT
• Band Power o Input Band Power
  • Output Band Power
  • Band Power Gain of the DUT (magnitude and phase)