Pseudo-Rectification and Detection by Simple Bilateral Nonlinear Resistors

The diode, or other devices containing a unilateral element, is generally employed for rectification or detection. Ordinary carbon resistors, however, and to a more marked degree, certain symmetrical or bilateral nonlinear resistors containing no unilateral elements, can, when a pulse-type ac waveform is impressed upon them, perform a rectification process; this process may be considered solely as a circuit effect. Four basic ac-to-dc converting circuits, some of which are largely independent of temperature, and which employ symmetrical nonlinear resistors, are analyzed. If an asymmetrical waveform is available as a carrier for simple types of modulation, the symmetrical nonlinear resistor may be used as a detector with several signal-enhancing properties not usually present in the ordinary diode or square-law detection process. The nonlinear resistor detection circuit is capable of radically suppressing symmetrical interfering signals, such as Gaussian noise at one point in the signal spectrum following the detector, in this case, at zero frequency. For certain types of signal systems, this detection process can maintain for very weak signals a linear relationship between the impressed input and resulting output signal-to-noise ratios associated with the detector circuit. Two illustrative examples are given: a pseudo-rectification circuit supplying 3000-volt dc potential in a television receiver, and a circuit capable of enhancing the detection of very minute amounts of radiation impressed upon a photomultiplier.