Digital amplitude modulation apparatus and control method of digital amplitude modulation apparatus

摘要

A digital amplitude modulation apparatus is provided with a measuring section, a fast surge protection section, a slow vector protection section, and a controller. The measuring section detects a voltage and a current from an RF signal. The fast surge protection section calculates an SWR from a detection signal of the measuring section, and obtains a first upper limit of the number of power amplifiers which can be put into an ON state based on the SWR and generates a first control signal. The slow vector protection section obtains a reflection coefficient from the output detection signal of the measuring section, and obtains a second upper limit of the number of the power amplifiers which can be put into an ON state based on the reflection coefficient and generates a second control signal. The controller controls the power amplifiers to be ON/OFF.

主权项

1. A digital amplitude modulation apparatus which power-amplifies a transmission signal by a plurality of power amplifiers arranged in parallel, each of which is controlled to be ON/OFF in accordance with a voltage amplitude level of a signal to be modulated, combines outputs of the respective power amplifiers by a combiner, to generate an amplitude modulation signal as an RF (Radio Frequency) signal, and transmits an amplitude modulation wave to a prescribed broadcast service area, the digital amplitude modulation apparatus comprising:
a measuring section which detects a voltage and a current from the amplitude modulation signal, and outputs a detection signal including a detection current and a detection voltage; a fast surge protection section which calculates an SWR (Standing Wave Ratio) using the detection signal outputted from the measuring section, compares the SWR with a predetermined threshold value, obtains a first upper limit of the number of the power amplifiers which can be put into an ON state and generates a first control signal including the first upper limit when the SWR is larger than the threshold value; a slow vector protection section which is connected in parallel with the fast surge protection section, calculates a reflection coefficient using the detection signal outputted from the measuring section, obtains an SWR from the reflection coefficient, compares the SWR obtained from the reflection coefficient with the threshold value, and obtains a second upper limit of the number of the power amplifiers which can be put into an ON state and generates a second control signal including the second upper limit when the SWR obtained from the reflection coefficient is not more than the threshold value; and a controller which controls the power amplifiers to be ON/OFF in accordance with the voltage amplitude level of the signal to be modulated within the first upper limit upon receiving the first control signal, and controls the power amplifiers to be ON/OFF in accordance with the voltage amplitude level of the signal to be modulated within the second upper limit upon receiving the second control signal.