| 摘要 |
The noise source generates a signal whose spectrum is preferably identical to that of a digital signal with frequency modulation applied by a frequency modulator to an amplifier in transmission equipment. The source replaces the modulator in order to estimate the behaviour of the amplifier, for example, for television signals. The spectrum is defined by a central frequency (Fc), the useful bandwidth (delta-F) and an inter-modulation product power (PI). A pseudo-random generator (1) follows a phase modulator (2) generating a pseudo-random signal whose spectrum is centred about the central frequency (Fc) and which is wider than the useful bandwidth (delta-F). A surface wave filter (3) filters the pseudo-random signal in the useful band (delta-F), with an inter-modulation noise power equal to the power of the inter-modulation power (PI). An amplifier (4) amplifies the filtered signal in a quasi-linear fashion.
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