IQSTAR enables Spurious detection using a spectrum analyzer, and starting IQSTAR 1.5 release, Fast Spurious detection is also available using option S93090 of the PNA-X. This module allows a fast search and analysis of spurious signals, using the spectrum analyzer to recover the trace for each swept parameter. A processing algorithm is then employed to dissociate spurious frequencies from signal frequencies. Detection-per-frequency segment is possible when different criteria based are needed for each band.
Spurious detection is an important step in the Design Validation Testing (DVT) and the Production validation testing (PVT) of RF and Microwave power amplifiers. Spurious emissions decrease the system performance and cause interference in adjacent frequency bands. Some industries like aerospace and defense must detect very low-level spurs.
A classical technique consists of reducing the resolution bandwidth to the narrowest to lower the noise floor of the equipment. However, the implementation simplicity of this technique comes at the cost of a very long measurement time, especially since the spurious location cannot be predicted in advance, which imposes a full scan of a large frequency bandwidth at a very low RBW level.
Even with new fast spectrum analyzers, spurious detection can take hours or even days when combined with nested loops of frequencies, biases, power levels, VSWR circles…
IQSTAR takes advantage of fast spectrum analyzers using FFT filters to search spurs and reduce testing time. The spurious research algorithm embedded in IQSTAR automates and speeds up the process. A simple GUI is used to identify the frequency segments for the spurious detection with different noise levels, spurious threshold levels, number of points and more settings. The software optimizes the RBW level automatically to find the best trade-off between the detection threshold and the measurement speed.
In other words, the RBW is set to the lowest level to detect real spurs at required frequencies and higher in the ranges where no potential spurs have been detected. Spurs generated by the analyzer itself, called residuals, are identified and automatically removed from the result list.