Method and apparatus using first and second parallel channels, one of

Abstract

In certain types or electrical systems such as pulse modulators, it is extremely important that the systems have a high on/off ratio. To accomplish this, an electrical system is provided having first and second channels coupled in parallel to a frequency source. If the system is a pulse modulator, the first channel is the pulse modulation channel, and includes a first combining means coupled to the carrier frequency source and a modulation input pulse source to produce a pulse modulated output signal with 'on' and 'off' periods. The second channel includes a second combining means which is coupled to the carrier frequency source and a constant voltage signal to produce a continuous output signal. An inverter is provided in one of the channels to invert the carrier frequency signal going to one of the combining means. The outputs of the first and second combining means are then combined by an addition such that the continuous output signal of the second combining means is effectively subtracted from the pulse modulated output signal of the first combining means during both the 'on' and 'off' periods of the pulse modulated output signal due to the inversion in one of the channels. This allows for significant reduction of the undesired output signal of the first combining means caused by imbalance in the first combining means during the 'off' period. And, it only causes a negligible reduction of the desired output signal during the 'on' period.