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Nexxim Simulator > Signal and Noise WaveformsThe signals and waveforms present in a system are Baseband Signals, Bandpass Signals, and Noise Waveforms Baseband Signals The general form of any baseband signal may be represented in the following form:
where VS(t) represents a time-varying voltage signal. Bandpass Signals A baseband signal becomes a bandpass signal once it modulates an RF carrier. The general form of any bandpass signal is:
Where fc
is the carrier frequency and The quantity
is known as the complex envelope of the bandpass signal S(t). IS(t) and QS(t) are the In-phase and Quadrature-phase baseband information-bearing signals. Noise Waveforms Noise is simply random fluctuations of a signal. This randomness is typically governed by a statistical distribution. For example, a White Gaussian noise process has a Gaussian distribution (i.e., the statistical distribution of the noise level obeys a Gaussian distribution). The noise processes supported by the Designer discrete time analysis are assumed stationary (i.e., the statistical distribution of the noise level does not vary with time). A baseband random noise signal may be represented in the following form:
where VN(t) is a time-varying noise voltage. A bandpass random noise signal, on the other hand, may be represented in the following form::
where fc is the carrier frequency. The quantity
is known as the complex envelope of the bandpass Noise N(t). IN(t) and QN(t) are the In-phase and Quadrature-phase baseband noise-bearing signals. Any noise process may be classified as uncorrelated or correlated. An uncorrelated noise process implies that the noise samples N(t) at time t and N(t + dt) at time t + dt are not correlated. A correlated process, on the other hand, implies that the samples N(t) and N(t + dt) tend to be correlated. An example of an uncorrelated process is White Gaussian noise. Examples of correlated processes are colored Gaussian noise and Rayleigh fading. The power spectral density of a noise process typically represents the correlation. For weakly correlated processes, this power spectral density tends to be wideband. A strongly correlated process, on the other hand, tends to have a narrowband power spectral density.
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Ansoft Designer / Ansys Designer 在线帮助文档：
is the phase
of the input modulated signal.
