Fourier pööre signaalitöötluses

Kontrollküsimused 3. osa kohta

There are several kernels for 2D image blurring. Two common kernels are the Boxcar and Gauss. Which of these 2 creates less distortions and is preferred, but is slightly more complex to compute?

Boxcar

Gauss

Single SideBand suppressed carrier (SSB) is a technique used for amplitude modulation. What are the reasons to use it?

Carrier does not contain information, but consumes energy. Hence it does not need to be transmitted and power could be saved.

Both sidebands of an AM-signal contain the same information. We can transmit only one and compute the other from the one received. It helps to save spectrum as two times less spectrum is used to transmit the same information.

Two sidebands contain the same information, but power is spent on transmitting both of them. It helps to save power to transmit only one sideband.

The use of only single sideband helps to reduce errors. As narrower bandwidth is used it is less likely that interference with other signals happens.

Consider these two kernels:

Connect right filter with right kernel.

A	highpass Unselect lowpass Unselect
B	highpass Unselect lowpass Unselect

Consider these spectra:

A	Amplitude modulation Unselect Phase shift keying Unselect Frequency modulation Unselect
B	Amplitude modulation Unselect Phase shift keying Unselect Frequency modulation Unselect
C	Amplitude modulation Unselect Phase shift keying Unselect Frequency modulation Unselect

Low-pass filters are commonly used to filter out high-frequency noise. Ideal filter has very sharp frequency response. That means up to a given frequency f_l all the frequency components are passed and over that frequency f_l all frequency components are completely discarded.

All real filters have softer transition from passed to blocked frequencies.

Consider these kernels:

Connect the time-domain kernels (impulse response) with the corresponding edge sharpness.

A	Sharpest frequency response edge Unselect Medium frequency response edge Unselect Soft frequency response edge Unselect
B	Sharpest frequency response edge Unselect Medium frequency response edge Unselect Soft frequency response edge Unselect
C	Sharpest frequency response edge Unselect Medium frequency response edge Unselect Soft frequency response edge Unselect