Signal Processing for Communication Systems
The phase transition properties of the different variants of QPSK schemes and MSK, are easily investigated using constellation diagram. Let’s demonstrate how to plot the signal space constellations, for the various modulations used in the transmitter. Typically, in practical applications, the baseband modulated waveforms are passed through a pulse shaping filter for combating the phenomenon … Read more
Gaussian Minimum Shift Keying basics: MSK as CPM, Gaussian filter BT, smoother phase, and spectral compactness vs plain MSK.
Pulse-shaping Lab path:Nyquist zero-ISI → Raised cosine → Matched filter + SRRC → Eye diagramsTool: RRC filter & bandwidth calculator Key focus: Let’s learn how to simulate matched filter receiver with square root raised cosine (SRRC) filter, for a pulse amplitude modulation (PAM) system. Simulation Model A basic pulse amplitude modulation (PAM) system as DSP … Read more
Introduction to precoding Intersymbol interference (ISI) is a common problem in telecommunication systems, such as terrestrial television broadcasting, digital data communication systems, and cellular mobile communication systems. Dispersive effects in high-speed data transmission and multipath fading are the main reasons for ISI. To maximize the capacity, the transmission bandwidth must be extended to the entire … Read more
Impulse response and frequency response of PR signaling schemes Consider a minimum bandwidth system in which the filter $latex H(f)$ is represented as a cascaded combination of a partial response filter $latex Q(f)$ and a minimum bandwidth filter $latex G(f)$. Since $latex G(f)$ is a brick-wall filter, the frequency response of the whole system $latex … Read more
Consider the generic baseband communication system model and its equivalent representation, shown in Figure 1, where the various blocks in the system are represented as filters. To have no ISI at the symbol sampling instants, the equivalent filter $latex H(f)$ should satisfy Nyquist’s first criterion. If the system is ideal and noiseless, it can be … Read more
Pulse-shaping Lab path:Nyquist zero-ISI → Raised cosine → Matched filter + SRRC → Eye diagramsTool: RRC filter & bandwidth calculator In digital communications, an eye diagram (or eye pattern) is one of the most intuitive and powerful diagnostic tools for evaluating signal quality. Formed by overlapping consecutive symbol traces of a modulated signal over a … Read more
Why SRRC is used at Tx and Rx: matched filtering, overall raised-cosine Nyquist pulse, roll-off α, and links to the RRC tool.
Pulse-shaping Lab path:Nyquist zero-ISI → Raised cosine → Matched filter + SRRC → Eye diagramsTool: RRC filter & bandwidth calculator As mentioned earlier, the shortcomings of the sinc pulse can be addressed by making the transition band in the frequency domain less abrupt. The raised-cosine (RC) pulse comes with an adjustable transition band roll-off parameter … Read more
Key focus: Sinc pulse shaping of transmitted bits, offers minimum bandwidth and avoids intersymbol interference. Discuss its practical considerations & simulation. Sinc pulse shaping As suggested in the earlier post, the pulse shape that avoids ISI with the least amount of bandwidth is a sinc pulse of bandwidth $latex F_{sym}/2$. Here, $latex F_{sym}=1/T_{sym}$ is the … Read more