A high speed passband phase modulation apparatus and method are provided. In the phase modulation apparatus, an RF phase shifter modulates a phase of a local signal that is generated in a VCO according to a digital input. The RF phase shifter is controlled by a phase-controlled loop so that a baseband phase shifter is phased locked to a modulation reference signal from the local signal and a reference clock signal according to the digital input. The phase-controlled loop phase-locks using the modulation reference signal so that the phase-modulated signal generated in the RF phase shifter has a phase value according to the digital input.

The present invention provides a semiconductor integrated circuit for communication (RF IC) operable in a mode for receiving a received signal subjected to phase modulation and amplitude modulation and a mode for receiving a received signal subjected only to phase modulation. In the semiconductor integrated circuit for communication, a frequency band of a loop filter in a PLL circuit is switched and set so as to become large in a reception mode and become small in a transmission mode.

The invention relates to an apparatus for precise modulation of signal phase and signal delay, respectively, and signal amplitude, comprising a first fixed-delay device having its input coupled to an input signal, a first variable delay device having its input coupled to said input signal and having a control input for delay adjustment, a first amplitude control device in series with the first variable delay device, providing at its output an amplitude controlled signal and having a control input for adjusting the output amplitude, a phase detector with linear characteristic having its two inputs connected to the output of the fixed-delay device and the output of the first amplitude control device, an error measurement device having its negative input connected to the output of the phase detector and its positive input connected to a control signal, an amplifier with low-pass characteristic having its input connected to the output of the error measurement device and its output to the control input of the first variable delay device.