RF amplifier having a dual slope phase modulator

An RF amplifier system having a phase modulator for varying the phase of an RF signal, comprising:

• an RF source for providing an RF signal made up of a first train of pulses exhibiting a fixed frequency and fixed duty pulse cycle and wherein each pulse is of a fixed amplitude and duration;
• said modulator including:
• an integrator connected to said RF source converting each pulse cycle of said RF signal into a dual slope symmetrical ramp signal which varies in magnitude from a minimum level to a maximum level and then back to said minimum level for each pulse cycle;
• a first level signal and a second level signal equally spaced from a reference level wherein said reference level is midway between said minimum and maximum levels of said ramp signal;
• dual slope comparator receiving said first and second level signals and said ramp signal and providing a first pulse signal for a time duration corresponding with the time duration that said ramp signal exceeds said first level signal and a second pulse signal for a time duration corresponding with the time duration that said second level signal exceeds said ramp signal;
• first and second pulse generators coupled to said dual slope comparator and respectively receiving said first and second pulse signals and providing therefrom first and second trigger pulses;
• a bistable circuit connected to said first and second pulse generators and responsive to said first and second trigger pulses to be in respective first state in response to a first trigger pulse and a second state in response to a second trigger pulse and providing an output RF signal made up of a second train of pulses of said fixed frequency and said fixed duty cycle of said first pulse train and being shifted in phase therefrom by an amount related to the magnitude of said first level signal or said second level signal.

A method of varying the phase of an RF signal that is made up of a first train of pulses exhibiting a fixed frequency and fixed duty pulse cycle and wherein each pulse is of a fixed amplitude and duration, said method including the steps of:

• integrating the RF signal by converting each pulse cycle of said RF signal into a dual slope symmetrical ramp signal which varies in magnitude from a minimum level to a maximum level and then back to the minimum level for each pulse cycle;
• providing a control level signal having a magnitude representing the desired phase shift of said RF signal and developing from said control level signal a first level signal and a second level signal that are equally spaced from a reference level which is midway between the minimum and maximum levels of the lamp signal;
• comparing the first and second level signals with a ramp signal and providing a first pulse signal for a time duration corresponding with the time duration that the ramp signal exceeds the first level signal and a second pulse signal for a time duration corresponding with the time duration that the second level signal exceeds the ramp signal;
• providing first and second trigger pulses in response to the respective first and second pulse signals;
• and,
• operating a bistable circuit in response to the first and second trigger pulses so that said bistable circuit is in respective first and second states in response to said first and second trigger pulses and providing an RF signal dependent on the operation of said bistable circuit so that the output RF signal is made up of a second train of pulses of said fixed frequency and said fixed duty cycle of said first pulse train and being shifted in phase therefrom by an amount related to the magnitude of said control level signal.