Abstract: An input carrier signal is applied to two paths. The two paths are such that the phase difference between the output of the two paths is substantially 90.degree.. At least one of the two paths responds to a modulating signal to select the polarity of the phase difference between the outputs of the two paths. The two paths are such that the phase angle between the output and input of the modulator is substantially independent of the amplitude of the modulating signal. In specific embodiments, one of the two paths includes a mixer or a quadrature hybrid with reflective diodes where the mixer or the diodes are operated in saturation. The outputs of the two paths are combined to provide a modulated carrier signal.

Abstract: Method and apparatus for amplification of an electrical signal whose frequency may range from zero to 300 MHz, and whose voltage level may range from 0.5 volt to 0.5 volt, with intermittent resetting of the zero voltage level provided for. One or two incoming signals are divided into low frequency and high frequency components, and amplification of each of these components is optimized by passage of the component through a separate amplification circuit. Input signals to the high and low frequency amplification circuits are intermittently chopped to allow resetting of the zero voltage levels of the amplifier.

Abstract: Apparatus and method for extending the effective dynamic range of pulse measure and pulse display devices by providing dynamic gain switching, with an associated gain or attenuation coefficient that assumes one of a plurality of two or more values, depending on the instantaneous magnitude of the signal received or upon the choice of an external controller. The amplification path may be one of a plurality of mutually exclusive parallel paths. Alternatively, the amplification path may be a serial combination of an arbitrary subset of a collection of amplification paths. The choice of amplification path may be made automatically by a fast-acting sensor such as a signal comparator or may be made by an external control provided by a human operator or computer and may be overridden by an externally produced control override signal.