Circuit for the frequency multiplication of an angle modulated signal using a pll and method

Abstract

Is disclosed a method and a relative circuit adapted to transfer to a microwave transmission carrier the angle modulation of an intermediate frequency signal. The conveyor of angle modulation is a PLL ( ) which VCO ( ) generates the microwave carrier (RF) modulated like the intermediate frequency signal (S ), taken as reference for the phase comparator ( ) of the PLL. The comparator receives moreover a copy of the signal generated by the VCO, converted at intermediate frequency (S ) by means of a subharmonic mixer, and it generates an error signal (S ). The PLL comprises further a regulator circuit ( ) which maintains automatically constant relation K between the locked band of the PLL and the bandwidth of the reference signal (S ), the lanter being a signal susceptible of band width variations, generally due to the choice of different transmission speeds. Regulator circuit (101) includes an error peak detector ( ) and an operational amplifier ( ) that compares the peak (S ) with a reference value (VR), obtaining from the difference a control signal (S ) of a variable attenuator ( ) of the error signal (S ) which controls the VCO.