Table of Contents
- 1 Why use a raised-cosine filter?
- 2 What is a raised cosine function?
- 3 Why is pulse shaping needed?
- 4 What does a Nyquist filter do?
- 5 Why is raised cosine pulse used in digital communication system?
- 6 Why do we need duo binary pulse over raised cosine pulse?
- 7 What is the difference between rect and raised cosine pulse filters?
- 8 What is the cut-off frequency of a cosine filter?
Why use a raised-cosine filter?
Raised cosine filters are used for pulse shaping, where the signal is upsampled. Therefore, we also need to specify the upsampling factor.
Why raised-cosine filter is used instead of ideal low pass filter in practical system?
A raised cosine filter response is wider than the ideal low-pass filter, due to the transition band. This excess frequency bandwidth is controlled by a parameter called the “roll off” factor. The frequency response is plotted for several different roll off factors.
What is a raised cosine function?
The raised-cosine filter is a filter frequently used for pulse-shaping in digital modulation due to its ability to minimise intersymbol interference (ISI). Its name stems from the fact that the non-zero portion of the frequency spectrum of its simplest form ( ) is a cosine function, ‘raised’ up to sit above the.
Which filter is used for pulse shaping?
The Gaussian filter is a pulse shaping technique that is typically used for frequency shift keying (FSK) and minimum shift keying (MSK) modulation. This filter is unlike the raised cosine and root raised cosine filters because it does not implement zero crossing points.
Why is pulse shaping needed?
Its purpose is to make the transmitted signal better suited to its purpose or the communication channel, typically by limiting the effective bandwidth of the transmission. In RF communication, pulse shaping is essential for making the signal fit in its frequency band.
Why is pulse shaping technique used?
Why is pulse shaping technique used? Explanation: Pulse shaping techniques reduces the intersymbol interference. They are also used to reduce the spectral width of the modulated digital signal.
What does a Nyquist filter do?
A Nyquist filter is an electronic filter used in TV receivers to equalize the video characteristics. The filter is named after the Swedish–US engineer Harry Nyquist (1889–1976).
What is the Nyquist criterion for zero ISI how a raised cosine pulse reduces ISI?
Raised cosine response meets the Nyquist ISI criterion. Consecutive raised-cosine impulses demonstrate the zero ISI property between transmitted symbols at the sampling instants. At t=0 the middle pulse is at its maximum and the sum of other impulses is zero.
Why is raised cosine pulse used in digital communication system?
Raised cosine pulses, minimizing the frequency over shots of the spectral density, may be used for spectral shaping optimization and intersymbol interference reduction. Figure 3.4a presents the normalized power spectrum, for NRZ modulation format.
Why do we need pulse shaping filter?
In communications systems, two important requirements of a wireless communications channel demand the use of a pulse shaping filter. These requirements are: 1) generating bandlimited channels, and 2) reducing inter symbol interference (ISI) from multi-path signal reflections.
Why do we need duo binary pulse over raised cosine pulse?
Both duobinary schemes provide practical pulse shaping methods to achieve the symbol rate of twice the bandwidt (=2í µí±Š). … Clearly the proposed duobinary system maintains the signal property of the Fast-OFDM system and hence the real part of received symbols can be correctly recovered.
What is the ideal solution for zero ISI?
What is the difference between rect and raised cosine pulse filters?
A rectangular pulse filter (rect) is very simple, but has infinite frequency response. The raised-cosine filter is a compromise between the rect filter (in the time domain) and the corresponding box filter in the frequency domain (which has infinite length in the time domain).
What is the passband shape of the cosine filter response?
To better see the passband shape, it is plotted linearly, rather than logarithmically (dB). It has a cutoff frequency of 500 kHz, the same as our ideal low-pass filter. A raised cosine filter response is wider than the ideal low-pass filter, due to the transition band.
What is the cut-off frequency of a cosine filter?
It has a cutoff frequency of 500 kHz, the same as our ideal low-pass filter. A raised cosine filter response is wider than the ideal low-pass filter, due to the transition band. This excess frequency bandwidth is controlled by a parameter called the “roll off” factor.
What is a raised-cosine pulse?
(iii) Raised-cosine pulse:This is a pulse widely used in practice. The pulse shape and the excess bandwidth can be controlled by changing the roll-off factor (0≤α≤1, where 0 means no excess bandwidth, and 1 means maximum excess bandwidth). The frequency-domain expression of raised-cosine filter is given in (1.1):