MODULATION OR DEMODULATION CIRCUIT

摘要

PURPOSE:To output a modulation signal that always keeps the phase value at pi/2rad regardless of the frequency by providing two phase shifters consisting of the series circuits of the same resistance, and capacity or inductance value. CONSTITUTION:The high frequency voltage e(t) and the current i20(t) i30(t) are inputted to the phase shifters 20 and 30 from a signal source 10. The unit 20 includes an RC series circuit consisting of a capacity element 21 and a resistance element 22 and extracts the voltage V20(t) through both ends of the element 22 to apply this voltage to one of both input terminals of a product detector 40. Meanwhile, the second phase unit 30 includes an RC series circuit consisting of a resistance element 31 and a capacity element 32 and extracts the voltage V30(t) through both ends of the element 32 to apply this voltage to the other input terminal of the detector 40. The detector 40 secures a product of the V20(t) and V30(t) and reproduces this result as an original modulation signal. The same value is set to the common elements C21/C32 and R22/R31 of both units 20 and 30 respectively.