Patent ID: 7823047

Claim:
A base band signal generating device comprising: base band signal generating means for converting data consisting of bit strings, in which at least a part of the bit strings is distinguished as a protection object portion, into a base band signal representing a sequence of symbols of four values; and communication quality judging means for judging whether a communication quality of an external transmission path for transmitting the base band signal has reached a predetermined standard, wherein the base band signal generating means operates, in a state in which it is judged that the communication quality of the transmission path has not reached the standard, to convert the data into the base band signal such that at least a part of the symbols belonging to the sequence of the symbols includes a bit belonging to the protection object portion and a predetermined redundant bit, and operates, in a state in which it is judged that the communication quality of the transmission path has reached the standard, to convert the data into the base band signal such that at least a part of the symbols belonging to the sequence of the symbols includes a bit belonging to the protection object portion and additional data converted into the base band signal together with the data, and wherein a value of the redundant bit is set to a value that makes an instantaneous value of a point representing the symbol including the redundant bit in the base band signal always converge to a maximum value or a minimum value among four values to which the instantaneous value can converge.