1. Field of the Invention
The present invention relates to an AM multiplexing broadcast apparatus for multiplexing a digital modulated signal independent of an AM modulated signal, in the same frequency band as the AM modulated signal.
2. Description of the Related Art
Such an AM multiplexing broadcast apparatus for multiplexing a digital modulated signal independent of an AM modulated signal, in the same frequency band as the AM modulated signal, is still not known. Conventionally, for such multiplication, both an AM transmitter and a digital transmitter are prepared and radio waves transmitted from respective antennas are synthesized in the air.
A single antenna shared by both an AM transmitter and a digital transmitter may be used for addition of radio waves of small power transmitters. However, it is very difficult to apply this method to transmitters of several kW to several hundreds kW.
In multiplexing a digital modulated signal independent from an AM modulated signal, in the same frequency band as the AM modulated signal, two antennas for an AM transmitter and a digital transmitter are required as in the above conventional case. This results in a bulky system of apparatuses.