Wideband IQ modulator with RC/CR automatic quadrature network

A modulator comprising:

• a quadrature circuit having a signal input that receives an input signal to be modulated and having first and second quadrature outputs at which respectively appear first and second quadrature signals of the same frequency as the input signal but which are in quadrature with each other, the quadrature circuit also having first and second control inputs that respectively receive first and second control signals, the quadrature circuit responsive to the first control signal by producing corresponding alterations in the amplitude of the first quadrature signal and to the second control signal by producing corresponding alterations in the amplitude of the second quadrature signal;
• first and second amplitude detectors respectively coupled to the first and second quadrature outputs and producing respective first and second amplitude level signals;
• a difference amplifier having inputs coupled to the first and second amplitude level signals and having a difference output;
• an offset circuit coupled to the difference output and that produces the first and second control signals, the amplitude of the first control signal equal to that of the difference signal increased by a selected amount and the amplitude of the second control signal equal to that of the difference signal decreased by the selected amount;
• a first multiplier having an input coupled to the first quadrature signal and another input receiving a first component of a pair of signals representing program information to be modulated onto the input signal, and producing therefrom a first multiplier output signal;
• a second multiplier having an input coupled to the second quadrature signal and another input receiving the remaining second component of the pair of signals representing program information, and producing therefrom a second multiplier output signal;
• and
• a summer having first and second inputs respectively coupled to the first and second multiplier output signals and having an output at which appears the modulated input signal.