## What is angle domain?

Angle domain analysis is a technique for viewing data acquired from rotating machinery. Data is referenced to the angle of rotation rather than the time domain. Referencing data to angle is useful in identifying the root causes of noise and vibration issues in rotating machinery.

## How do you sample a given signal?

Sampling a continuous time signal produces a discrete time signal by selecting the values of the continuous time signal at evenly spaced points in time. Thus, sampling a continuous time signal x with sampling period Ts gives the discrete time signal xs defined by xs(n)=x(nTs).

**What is the role of frequency domain sampling in digital signal processing?**

The Fourier series describes periodic signals by discrete spectra, where as the DTFT describes discrete signals by periodic spectra. These results are a consequence of the fact that sampling on domain induces periodic extension in the other.

### How may the original signal recovered from the sampled signal?

The original signal is recoverable from its sampled form when the highest frequency component is less than the Nyquist frequency, ωs/2. In Fig. 12.42, the band V1(ω) is a replica of V(ω) centered at ωs. It has frequency components below ωs that overlap with the positive frequency components of V(ω).

### What is sampling in frequency domain?

In the frequency domain, sampling of the original signal is described as the convolution of the original signal with a comb function (with peaks repeating at the sampling frequency).

**What is the sampling theorem in frequency domain?**

The sampling theorem essentially says that a signal has to be sampled at least with twice the frequency of the original signal. Since signals and their respective speed can be easier expressed by frequencies, most explanations of artifacts are based on their representation in the frequency domain.

#### Why sampling is used in communication?

If the signal contains high frequency components, we will need to sample at a higher rate to avoid losing information that is in the signal. In general, to preserve the full information in the signal, it is necessary to sample at twice the maximum frequency of the signal.