Transmitter and semiconductor integrated circuit for communication
View Patent ↗A transmitter adopting a polar loop system including a phase control loop for controlling the phase of a carrier signal outputted from a transmitting oscillator and an amplitude control loop for controlling the amplitude of a transmitting output signal outputted from a power amplification circuit, and designed to be capable of performing transmission using a GMSK modulation mode and transmission using an 8-PSK modulation mode. In the transmitter, the phase control loop is shared as a phase control loop for use in the GMSK modulation mode and a phase control loop for use in the 8-PSK modulation mode. A component similar to any one of components constituting a loop filter is provided in parallel therewith so that the component can be connected or disconnected in accordance with the modulation mode, for example, by use of a switching element.
1. A mobile phone which has a first communication function and a second communication function comprising:
an antenna;
a base band circuit;
a reception circuit which is coupled to the antenna and the base band circuit and which includes a mixer for converting a reception signal into a base band signal,
a transmission circuit including an orthogonal modulator which modulates I and Q signals from the base band circuit to a first signal to be transmitted;
a transmitting oscillator which generates a transmitting signal based on the first signal;
a power module which is coupled to the antenna and the transmitting oscillator and which includes a power amplifier for amplifying the transmitting signal and a power detector for detecting a power level of an output signal from the power amplifier to be transmitted;
a phase control loop which has a phase detector and controls a phase of the transmitting signal, and
an amplitude control loop which has an amplitude detector and controls an amplitude of the output signal from the power amplifier,
wherein the phase control loop includes a feedback path for supplying a signal in accordance with an output of the power detector,
wherein the amplitude control loop includes the feedback path for supplying a signal in accordance with an output of the power detector,
wherein the first communication function is a phase modulation mode using the phase control loop,
wherein the second communication function is a phase and amplitude modulation mode using both of the phase control loop and the amplitude control loop, and
wherein the phase control loop is shared by the first communication function and the second communication function.
2. A mobile phone according to claim 1 ,
wherein the reception circuit, the mixer, the orthogonal modulator, the phase detector and the amplitude detector are formed on a semiconductor integrated circuit device.
3. A mobile phone according to claim 2 , the semiconductor integrated circuit device further comprising:
a first variable gain amplifier which receives and amplifies the signal in accordance with the output of the power detector; and
a second variable gain amplifier different from the first variable gain amplifier,
wherein the amplitude control loop further includes the first variable gain amplifier and the second variable gain amplifier;
wherein the first variable gain amplifier is provided on the feedback path between the power detector and the amplitude detector and the second variable gain amplifier is provided on a forward path between the amplitude detector and the power amplifier; and
wherein a gain of the first variable amplifier and a gain of the second variable gain amplifier are controlled inversely with respect to each other on the second communication function.