An active balun circuit includes a CG transistor having a source terminal thereof connected to an input terminal and a gate terminal thereof grounded, a CS transistor having a gate terminal thereof connected to the input terminal and a source terminal thereof grounded, an asymmetrical transformer, a first output terminal, and a second output terminal. The asymmetrical transformer includes a primary coil and a secondary coil. The primary coil includes a first inductor connected to the CG transistor and a second inductor connected to the CS transistor. The secondary coil includes a third inductor associated with the first inductor and a fourth inductor associated with the second inductor. The first output terminal outputs a first signal generated at the third inductor, and the second output terminal outputs a second signal generated at the fourth inductor.

An active balun circuit includes a CG transistor having a source terminal thereof connected to an input terminal and a gate terminal thereof grounded, a CS transistor having a gate terminal thereof connected to the input terminal and a source terminal thereof grounded, an asymmetrical transformer, a first output terminal, and a second output terminal. The asymmetrical transformer includes a primary coil and a secondary coil. The primary coil includes a first inductor connected to the CG transistor and a second inductor connected to the CS transistor. The secondary coil includes a third inductor associated with the first inductor and a fourth inductor associated with the second inductor. The first output terminal outputs a first signal generated at the third inductor, and the second output terminal outputs a second signal generated at the fourth inductor.

Polyphase filter circuitry including: an input node to receive an input signal V.sub.IN having a dominant frequency f.sub.PPF; and a common-source amplifier circuit. The common-source amplifier circuit includes a field-effect transistor M1 with its gate terminal connected to the input node and with a capacitor C.sub.PFF connected to its source terminal; and for the common-source amplifier circuit, the output resistance R.sub.M1 at the source terminal of the field-effect transistor M1 and the capacitance of the capacitor C.sub.PFF are define the frequency response of the common-source amplifier circuit so that, based on the input signal V.sub.IN, a signal V.sub.LEAD is generated at the drain terminal of the transistor M1 which leads the input signal V.sub.IN in phase by a given phase shift .sub.LEAD and a signal V.sub.LAG is generated at the source terminal of the transistor M1 which lags the input signal V.sub.IN in phase by a given phase shift .sub.LAG.

A phase shifter, which carries out a ninety-degree phase shift of a sinusoidal input signal having an input frequency, at the same input frequency, envisages: a continuous-time all-pass filter stage, which receives the sinusoidal input signal and generates an output signal phase-shifted by 90 at a phase-shift frequency that is a function of a RC time constant of the all-pass filter stage; and a calibration stage, which is coupled to the all-pass filter stage and generates a calibration signal for the all-pass filter stage, such that the phase-shift frequency is equal to the input frequency of the sinusoidal input signal, irrespective of variations of the value of the input frequency and/or of the RC time constant with respect to a nominal value.

A phase shifter, which carries out a ninety-degree phase shift of a sinusoidal input signal having an input frequency, at the same input frequency, envisages: a continuous-time all-pass filter stage, which receives the sinusoidal input signal and generates an output signal phase-shifted by 90 at a phase-shift frequency that is a function of a RC time constant of the all-pass filter stage; and a calibration stage, which is coupled to the all-pass filter stage and generates a calibration signal for the all-pass filter stage, such that the phase-shift frequency is equal to the input frequency of the sinusoidal input signal, irrespective of variations of the value of the input frequency and/or of the RC time constant with respect to a nominal value.