Abstract: An RF amplifier system having closed cavity containing an amplifying device that includes at least a cathode, an anode and a grid and wherein the amplifying device exhibits an internal grid-to-anode capacitance. Apparatus is presented for use in neutralizing the internal capacitance. This includes a feedback circuit including an external capacitor of fixed value and a phase inverting transformer having a transformer primary winding connected in series with the capacitor to the cathode. The transformer has a secondary winding connected between the cathode and the grid for supplying a phase inverted negative feedback voltage to the grid for neutralizing the cavity by the feedback voltage. The transformer coupling is adjustable to vary the magnitude of the feedback voltage.

Abstract: A phase lock control system is presented for controlling a voltage controlled oscillator. The system includes a voltage controlled oscillator that produces a frequency signal exhibiting an output frequency that varies dependent upon the value of a control voltage applied thereto. A frequency deviation determining system employs a counter intermittently triggered ON for a fixed time by successive timing pulses received from a reference source and a comparator that determines any frequency deviation of the output frequency relative to a preset frequency. An error filter monitors the comparator for any frequency deviation for a plurality of samples of the frequency deviation determinations. A controller varies the control voltage to vary the output frequency in a direction to eliminate any frequency deviation.

Abstract: A phase lock control system is presented for controlling a voltage controlled oscillator. The system includes a voltage controlled oscillator that produces a frequency signal exhibiting an output frequency that varies dependent upon the value of a control voltage applied thereto. A frequency deviation determining system employs a counter intermittently triggered ON for a fixed time by successive timing pulses received from a reference source and a comparator that determines any frequency deviation of the output frequency relative to a preset frequency. An error filter monitors the comparator for any frequency deviation for a plurality of samples of the frequency deviation determinations. A controller varies the control voltage to vary the output frequency in a direction to eliminate any frequency deviation.

Abstract: A radio frequency (RF) transmitter system is presented having an input circuit for receiving an RF signal to be amplified and transmitted. A series circuit is provided which includes first and second cascaded amplifier networks located downstream from the input circuit and wherein the first amplifier network is located upstream from the second amplifier network and wherein the first and second networks respectively include first and second non-linear amplifiers that exhibit non-linear response characteristics to the RF signal and that introduce non-linear distortions into the RF signal and that the second network includes a filter that introduces linear distortions into the RF signal. The first correction circuit is located upstream from the series circuit for pre-correcting the RF signal in a manner to compensate for the linear and non-linear distortions introduced by the second amplifier network.

Abstract: A digital radio frequency transmitter system having an input circuit for receiving digital signals to be amplified and transmitted. A digital-to-analog converter converts the digital signals into analog signals. A series circuit is provided including a radio frequency filter and a radio frequency amplifier located downstream from the converter and wherein the filter and the amplifier respectively introduce linear and non-linear distortions into the analog signals for transmission by the transmitter. A digital pre-correction circuit is located upstream from the digital-to-analog converter for pre-correcting the digital signals in a manner to compensate for at least some of the distortions. An analog pre-correction circuit is interposed between the digital-to-analog converter and the series circuit for pre-correcting the analog signals to additionally compensate for at least some of the distortions prior to application to the series circuit.

Abstract: Apparatus and method are provided for linearizing a first amplifier having a non-linear signal response characteristic to an applied input signal wherein the amplifier is located between a signal source and a load. This is accomplished by selecting a second amplifier that exhibits a non-linear signal response characteristic to an applied input signal similar to that of the first amplifier. A portion of the input signal obtained from the signal source is then applied to the second amplifier to generate an output signal. A determination is made as to whether there is any difference between the input signal and the output signal and a difference signal is provided in accordance therewith. The difference signal is phase inverted to obtain an inverted difference signal. This inverted difference signal is combined with the input signal to provide a corrected input signal. The corrected input signal is applied to the first amplifier to obtain a corrected output signal therefrom.

Abstract: An inductive output tube (IOT) amplifier system is presented for receiving an RF input signal and providing therefrom an amplified RF output signal. The system includes a high tension DC voltage supply and an IOT tube. The IOT tube includes a cathode coupled to the voltage supply for emitting electrons, an anode coupled to the supply for accelerating the electrons, a collector located downstream from the anode that collects the electrons, and a grid located between the cathode and the anode for controlling electron emission from the cathode. The tube has an input for receiving a modulated RF input signal between the grid and the cathode. An output resonant cavity is interposed between the anode and the collector. An output is coupled to the cavity for providing amplified RF output signal. The tube exhibits an inherent interelectrode capacitance which may cause distortions in the output signal.

Abstract: In an amplifier circuit having an amplifier path, a new pre-distortion arrangement is provided. The amplifier circuit includes a signal source, an intermediate amplifier stage, and a power amplifier stage connected sequentially, in series along the amplifier path. The power amplifier stage includes one or more amplifiers operationally connected in parallel, and one or more pre-correction circuits. Each of the amplifiers subjecting an inputted signal to shifts away from their intended values. Each of the pre-correction circuits is associated with one of the amplifiers and connected between an output of the intermediate amplifier stage and the associated amplifier. Each of the pre-correction circuits pre-distorts the signal input to the associated amplifier to compensate for the distortion caused by the associated amplifier.

Abstract: An output amplifier having a non-linear signal response characteristic is linearized by selecting a preceding amplifier in a multistage amplifier network and providing feedforward overcorrection to the preceding amplifier to compensate for the non-linear signal response characteristics of the output amplifier.