Transmitter and mobile communication terminal using the same

A mobile communication terminal comprising:

• a baseband circuit for processing baseband signals;
• a transmitter for receiving transmission-baseband signals outputted from the baseband circuit, and generating a transmission signal on the basis of the transmission-baseband signals;
• a power amplifier for amplifying the transmission signal;
• a receiver for outputting receive-baseband signals to the baseband circuit;
• an antenna switch for changing over between connection to an output of the power amplifier, and connection to an output to the receiver;
• an antenna connected to the antenna switch;
• and
• a band-pass filter for interconnecting the antenna switch, and the receiver,
• the receiver receiving a receive signal received by the antenna through the intermediary of the band-pass filter to thereby generate the receive-baseband signals,
• said transmitter comprising:
• a first variable-gain amplifier;
• a second variable-gain amplifier having an input terminal electrically connected to an output terminal of the first variable-gain amplifier;
• a phase feedback loop for synchronizing a phase of an output signal of the first variable-gain amplifier with a phase of a reference signal generated on the basis of a transmission signal as inputted;
• and
• an envelope feedback loop for causing an envelope of output signals of the first variable-gain amplifier to follow up an envelope of the reference signals,
• said transmitter being capable of coping with a first transmission mode using the envelope feedback loop to generate a transmission signal to be sent out, and a second transmission mode not using the envelope feedback loop to generate a transmission signal to be sent out,
• the first variable-gain amplifier being shared by the phase feedback loop, and the envelope feedback loop, and configured so that synthesis of phase information outputted by the phase feedback loop, and envelope information outputted by the envelope feedback loop is implemented by gain control,
• the second variable-gain amplifier being configured so that average power of a transmission signal to be sent out is controlled,
• the phase feedback loop being shared between the first and second transmission modes when generating a transmission signal to be sent out, and
• the envelope feedback loop comprising an envelope comparator for outputting a difference between the envelope of the reference signals and an envelope of feedback signals as fed back by the envelope feedback loop and filters for passing a lower frequency component of an output signal of the envelope comparator,
• wherein the filters comprise capacitors, and the capacitors are recharged during a period when operated in the second transmission mode, a settling operation of the envelope feedback loop after transition of operation from the second transmission mode to the first transmission mode being executed by use of the potential of the capacitors as recharged.