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The carrier frequency is 1800 Hz, meaning that the lower cut off frequency is 1,800 − 1,200/2 = 1,200 Hz, and the upper cutoff frequency is 1,800 + 1,200/2 = 2,400 Hz. A V.34 modem may transmit symbols at a baud rate of 3,420 Bd, and each symbol can carry up to ten bits, resulting in a gross bit rate of 3420 × 10 = 34,200 bit/s.
As a result, ATSC 3.0 will be incompatible with all current ATSC 1.0 receivers, and viewers will need a new TV with a compatible tuner or a converter box. [5] Unlike the previous digital TV transition which was mandated by the FCC, the "transition" to ATSC 3.0 will be completely voluntary.
In a 6 MHz channel, the data rate is at most 36 Mbit/s (for 64-QAM or 8-VSB); the 8-VSB ATSC achieves a data rate of 19.3926 Mbit/s while the 64-QAM J.83b achieves a data rate of 26.970 Mbit/s. While both systems use concatenated trellis/RS coding, the differences in symbol rate and FEC redundancy account for the differences in rate.
The unit interval is the minimum time interval between condition changes of a data transmission signal, also known as the pulse time or symbol duration time. A unit interval (UI) is the time taken in a data stream by each subsequent pulse (or symbol).
For example, in a 64QAM modem, M = 64, and so the bit rate is N = log 2 (64) = 6 times the baud rate. In a line code, these may be M different voltage levels. The ratio is not necessarily an integer; in 4B3T coding, the bit rate is 4 / 3 of the baud rate. (A typical basic rate interface with a 160 kbit/s raw data rate operates at 120 kBd.)
The chip rate of a code is the number of pulses per second (chips per second) at which the code is transmitted (or received). The chip rate is larger than the symbol rate, meaning that one symbol is represented by multiple chips. The ratio is known as the spreading factor (SF) or processing gain:
It is typically necessary in Polarization Division Multiplexing systems: the data sources to be transmitted are coded and mapped into QAM modulating symbols at the system's symbol rate and upconverted to a carrier frequency, generating two radio streams radiated by a single dual-polarized antenna (see feed pattern of Parabolic antenna).
ASTEC UM 1286 UHF modulator, top cover taken off. An RF modulator (radio frequency modulator) is an electronic device used to convert signals from devices such as media players, VCRs and game consoles to a format that can be handled by a device designed to receive a modulated RF input, such as a radio or television receiver.