Design and Modelling of Comb Generator for EMI/EMC Test Chamber Validation

Comb generator circuit is a broadband signal source for quick EMI radiated emissions test site verifications. Its output spans the frequency range of 30 MHz to 1 GHz in 30 MHz steps. The Comb generator produces spectra at frequency based on crystal’s oscillatory frequency. An electronic circuit which produces a train of impulses is fed to the dipole antenna for radiating the energy. In a typical Radiated emission test environment, the receiving antenna picks up these spectra to check the RF level emitted by the Comb generator to verify the RF setup and also to ensure the repeatability of the testing over a period of time, carried inside the test chamber. In this paper, the electronic circuit which produces the train of impulses is designed in a Multisim software tool and its pulse train is imported to the FEKO 3D EM modeling tool and fed to a dipole antenna so as to observe the spectra at a distance governed by the standards.