The staircase like waveforms represents approximation to the analog waveforms (after quantization distortion has been introduced. This is how one can generally obtain better fidelity at the cost of more transmission bandwidth Next Fig.2.18 compares the quantization of a strong versus a weak signal for uniform and non-uniform quantization. In real time communication message must not be delayed, and bits must move faster. More on quantization… Now, each sample will be represented by 4-bits, consequently we would have high data rates, improved signal quality or fidelity. If we double the number of levels to 16, what supposed to be the benifit? Thus increasing the number of levels will reduce the quantization noise. What could we do to improve the fidelity? We know that process of quantization replaces the true signal with an approximation (i.e., adds quantization noise). Also suppose that when we listen to the music in digital form, it’s quality is not good. More on quantization… Suppose that analog signal is a musical, which is sample at a Nyquist rate (fs ≥ 2fm).
Note that each sample is assigned to one of eight levels or a three bit PCM sequence.
Beneath the analog waveform x(t) are seen four representations of x(t) as follows:- The natural sample values, quantized sample values, the code numbers and the PCM sequence. The blog is about electronics and related projects and stuff. Each sample of the analog signal is assigned to the quantization level closest to the value of sample. The primary role of this blog is to bring up the pakistani universities engineering projects on the globe. The symbol values of M for a given value of n: Fig: waveforms of (a) ASK (b) PSK (c)FSK Depending on the variation of amplitude, phase or frequency of the carrier, the modulation scheme is called as M-ary ASK, M-ary PSK and M-ary FSK. More on quantization… The ordinate in fig.2.16 is labeled with quantization levels and their code numbers. More on quantization Block diagram of formatting and transmission of baseband signals Fig.2.2. M-ary orthogonal pulses… Cross correlation between any two rows is zero for e.g. M-ary orthogonal pulses Fig.3.34 shows one possible set of M orthogonal signals For example we may use M orthogonal pulses φ1(t), φ2(t), …, φM(t), with the following property:. There are other possible ways to structure M waveforms.Fig.3.33 shows just one possible M-ary scheme (multi-amplitude signaling).The PSK, being polar, requires 3dB less power than ASK or FSK for the same noise immunity i.e.Conclusion is that polar signaling is the most efficient scheme from the point of view of the noise immunity.Note that the bandwidth of FSK is higher than ASK or PSK.2- More error resilience than AM.Power spectral density (PSD)…of ASK,PSK and FSK Frequency Shift Keying (FSK): 1- Needs larger bandwidth.
The frequency of the signal during each bit duration is constant, and its value depends on the bit (0 or 1).ĥ FSK Modulator - One way to think about binary FSK (or BFSK) is to consider two carrier frequencies Switch between two oscillators accordinglyĦ ASK and FSK - Amplitude Shift Keying (ASK):ġ- Very simple. Both peak amplitude and phase remain constant while the frequency changes.
The frequency of the carrier signal is varied to represent binary 1 or 0. Lecture 5: Frequency Shift Keying (FSK) 2nd semester of E.E.E. 19 ELEC 7073 Digital Communications III, Dept. Presentation on theme: "Frequency Shift Keying (FSK)"- Presentation transcript: Amplitude Shift Keying (ASK) Phase Shift Keying (PSK) Frequency Shift Keying (FSK) ¾These could be applied to binary or M-ary signals.