We do not want to confuse the reader but let us start by defining that a digital signal is nothing else than a special<\/strong> analog signal.<\/p>\n\n\n\n The reason is that an electric signal is a signal and whether analog or digital. The physics of both signals are the same.<\/p>\n\n\n\n <\/p>\n\n\n\n Comparison<\/strong><\/p>\n\n\n\n Consider the amplitude characteristics of an analog signal. The analog signal’s amplitude can take unending instantaneous values<\/strong> between the minimum (negative amplitude) and maximum (positive amplitude).<\/p>\n\n\n\n The digital signal is just an analog signal with only 2 instantaneous values<\/strong>. <\/p>\n\n\n\n Modulation<\/strong><\/p>\n\n\n\n Modulation techniques make use of this because transmitting always uses analog signals. The (digital) modulation on the carrier happens by switching (keying) between two amplitudes, frequencies, or phases.<\/p>\n\n\n\n However, there is a solution to increase the bitrate in digital transmissions by choosing more than 2 instantaneous values of a signal. <\/p>\n\n\n\n Table<\/span> – number of analog states and the number of bits per symbol.<\/p>\n\n\n\n 0 -> 00 0 -> 000 0 -> 0000 We call symbols<\/strong> (similar to the unit Bauds) the number of bits we can send at once. The above example shows symbols<\/strong> of 2, 3, and 4 bits.<\/p>\n\n\n\n It is important because these techniques of sending multiple bits in one signal apply to all digital modulations.<\/p>\n\n\n\n The disadvantage of increasing the number of bits<\/strong> per symbol is that the number of values increases. When talking about amplitudes, the discrete <\/a><\/em><\/strong>amplitude values will be closer and more difficult to detect correctly. Their detection tolerance becomes smaller.<\/p>\n\n\n\n Remember that noise added to a signal will make the parameters wobble in their tolerance area.<\/p>\n\n\n\n The rule to detect the values precisely is that the more bits a symbol contains, the higher the signal-to-noise ratio should be. There will be an SNR threshold to detect a signal based on symbols correctly.<\/p>\n\n\n\n The parameters of the electric signal can be amplitude<\/strong>, frequency<\/strong>, and phase<\/strong>.<\/p>\n\n\n\n DAB\/DAB+<\/sup><\/strong><\/p>\n\n\n\n In DAB(+) the symbols<\/strong> contain 2 bits<\/strong>. The 1536 carriers<\/strong> in DAB Mode-I can carry 3072 bits<\/strong> in one modulation cycle.<\/p>\n\n\n\n The modulation used is DQP<\/strong>SK. The parameter of the carrier that changes is the Phase<\/strong>.<\/p>\n\n\n\n The Q means quadrature or 4 phases and. The 4 values indicate that the symbol contains 2 bits. “SK” means Shift Keying between the 4 values.<\/p>\n\n\n\n
When an analog signal can only have two instantaneous values, as is amplitude, we call it a digital signal.<\/p>\n\n\n\n\n
1 -> 01
2 -> 10
3 -> 11<\/p>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n
1 -> 001
2 -> 010
3 -> 011
4 -> 100
5 -> 101
6 -> 110
7 -> 111<\/p>\n<\/div>\n\n\n\n
1 -> 0001
2 -> 0010
3 -> 0011
4 -> 0100
5 -> 0101
6 -> 0110
7 -> 0111
8 -> 1000
9 -> 1001
10 -> 1010
11 -> 1011
12 -> 1100
13 -> 1101
14 -> 1110
15 -> 1111<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n