Communication system and control circuit therein

摘要

A communication system includes a baseband processor, an RF (Radio Frequency) transceiver, a power amplifier, an antenna, and a control circuit. The power amplifier generates an amplified signal. The control circuit includes a coupler, an AC-to-DC (Alternating Current to Direct Current) converter, a comparator, and an attenuator. The coupler generates a transmission signal and a coupling signal according to the amplified signal. The AC-to-DC converter is coupled to the coupler, and converts the coupling signal into a DC (Direct Current) signal. The comparator compares a DC voltage of the DC signal with a reference voltage so as to generate a control signal. The attenuator is coupled between the coupler and the antenna, and attenuates or does not attenuate the transmission signal according to the control signal.

主权项

1. A communication system, comprising:
a baseband processor, generating a baseband signal; an RF (Radio Frequency) transceiver, modulating the baseband signal so as to generate an RF signal; a power amplifier, amplifying the RF signal so as to generate an amplified signal; an antenna; and a control circuit, comprising:
a coupler, generating a transmission signal and a coupling signal according to the amplified signal;an AC-to-DC (Alternating Current to Direct Current) converter, coupled to the coupler, and converting the coupling signal into a DC (Direct Current) signal, wherein the AC-to-DC converter comprises a half-wave regulator and a DC filter;a comparator, comparing a DC voltage of the DC signal with a reference voltage so as to generate a control signal; andan attenuator, coupled between the coupler and the antenna, and the attenuator is configured to selectively attenuate the transmission signal by a factor as dependent upon the comparator control signal, and the attenuator is also configured to selectively not attenuate the transmission signal as dependent upon the comparator control signal,wherein when a conductor is close to the antenna, an antenna impedance of the antenna is changed such that an output power of the power amplifier is changed using the comparator control signal of the attenuator to attenuate the transmission signal by the factor, andwherein the factor is selectively set to values substantially equal to 6 dB and 10 dB.