Contents
- 1 What happens to the spectrum of the sampled signal when the signal frequency exceeds the Nyquist frequency?
- 2 What is the sampling rate of a signal when compared with highest frequency?
- 3 How does the power spectrum show the amplitude of a signal?
- 4 How is the frequency content of a power spectrum measured?
What happens to the spectrum of the sampled signal when the signal frequency exceeds the Nyquist frequency?
Above Nyquist frequency, seismic signal with higher frequencies are reconstructed in the form of seismic signal with lower frequencies. Note that if the sampled seismic data contains frequency components greater than 1/2 ▵t, aliasing will occur.
What is the sampling rate of a signal when compared with highest frequency?
Nyquist’s theorem states that a periodic signal must be sampled at more than twice the highest frequency component of the signal. In practice, because of the finite time available, a sample rate somewhat higher than this is necessary. A sample rate of 4 per cycle at oscilloscope bandwidth would be typical.
What is significance of sampling frequency?
The sampling interval is an important parameter which must be chosen carefully, if measurements of the direct, global, and diffuse irradiance or illuminance are carried out to determine their averages over a given period.
Why is peak frequency difficult to figure out?
Firstly, the spectrum is known only at discrete values of f and this frequency resolution may be relatively coarse as a result of the averaging processes described above. Secondly, the statistical variability of the spectrum [see for example Figure 9.3 b] makes the determination of the peak difficult.
How does the power spectrum show the amplitude of a signal?
The power spectrum shows power as the mean squared amplitude at each frequency line but includes no phase information. Because the power spectrum loses phase information, you may want to use the FFT to view both the frequency and the phase information of a signal.
How is the frequency content of a power spectrum measured?
FFTs and the Power Spectrum are useful for measuring the frequency content of stationary or transient signals. FFTs produce the average frequency content of a signal over the entire time that the signal was acquired.
How is the amplitude of a FFT related to the phase?
The amplitude of the FFT is related to the number of points in the time-domain signal. Use the following equation to compute the amplitude and phase versus frequency from the FFT. where the arctangent function here returns values of phase between –π and +π, a full range of 2π radians.