Active quadrature signal generator using load having low-pass and high-pass filter characteristics

摘要

The present invention relates to an apparatus for producing poly-phase quadrature signals necessary in the communication circuit and correcting the phase and amplitude errors. The apparatus uses a filter having high-pass and low-pass characteristics as a load of a transistor to amplify the signals and also produces quadrature phase using phase shift characteristic included in respective filters. Further, the present invention produces poly-phase quadrature signals using it as a differential structure and uses respective filter loads as a variable capacitor or a variable resistor to vary the phase and amplitude of the quadrature signal. Therefore, the present invention can reduce the loss of the signal in a common poly-phase quadrature filter having only resistors and capacitor, and additional power consumption for compensating for it. In order words, the present invention includes a method of using an inductor in order to overcome a problem that the common poly-phase quadrature filter could not be reliably implemented only using the resistors and the capacitor as the pole frequency become high at the high frequency band (several GHz—several tens of GHz). In order to correct the amplitude errors and mismatch of the quadrature phases between the quadrature signals due to difference in characteristics between the load of the low-pass filter characteristic and the load of the high-pass filter characteristic, the quadrature signals are alternately passed through the load of the low-pass filter characteristic and the load of the high-pass filter characteristic. After then, the quadrature signals which are in phase are added considering weight. Further, in order to control mismatch in the quadrature phase that is important in the system application precisely, respective loads are constructed using the variable resistors or the variable capacitors. The degree of the mismatch of the quadrature phase of the output signal is then sensed using a phase detector and a low-pass filter. Next, the degree of the mismatch and a reference voltage are compared by a comparator and the variable resistor and the variable condenser are then controlled using the compared voltage, thus correcting the phase error. ;Further, in order to reduce the signal error of each of the quadrature signals due to the coupling effect, the bandpass resonator for producing resonance at a corresponding frequency is coupled to the circuit. Therefore, the mismatch of the amplitude and the phase of the quadrature signal due to the coupling effect at the low frequency and the high frequency can be prevented.