An RF frontend IC device includes an RF transceiver to transmit and receive RF signals and a frequency synthesizer to perform frequency synthetization to operate within a predetermined frequency band. The frequency synthesizer generates an LO signal to the RF transceiver to enable the RF transceiver to transmit and receive RF signals within the predetermined frequency band. The frequency synthesizer includes a QPG circuit to generate signals shifted in phases based on the LO signal and a phase shifting circuit to generate quadrant signals based on the signals shifted in phases. Each of the quadrant signals corresponds to one of the four quadrants in phases in the respective quadrant spaces. The phase shifting circuit includes multiple phase switches operable in a collaboration manner to further shift in phase based on the signal shifted in phases to generate the quadrant signals in proper quadrant spaces.
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