Abstract:
An FET analog gate includes two equal-valued resistors, one in the source path and one in the drain path of the FET, and a differential amplifier, one input connected to the FET source terminal and the other input connected to the FET drain terminal.
Abstract:
A differential pulse code communication system is disclosed with sign prediction coding which reduces the number of digits required to describe the levels produced in the quantization of the differential signal. In the system the sign of the largest positive and negative levels of the quantizer are predicted by assuming that they have the same sign as the previous level. If the prediction is wrong a lower level with the correct sign is transmitted rather than the level with the predicted sign. Because of the prediction, additional levels may be added in the quantizer in the space otherwise reserved for the signs predicted without increasing the pulse rate of the system.
Abstract:
A differential pulse code modulation system substantially reduces sign redundancy by transmitting sign information only for actual changes in polarity between differential samples. Upon the occurrence of a change in sign when both differential samples of opposite sign do not exceed a predetermined level, one of two polarity words is transmitted in place of the code word that represents the differential sample with the smaller magnitude. One polarity word indicates a positive polarity while the other word indicates a negative polarity. Only the absolute magnitudes of the differential samples are transmitted between sign changes. When both differential samples of opposite sign exceed a predetermined level, the absolute magnitude is transmitted for both differential samples and a run-length code work indicative of the location of the change in sign together with a polarity word are transmitted at a later time.
Abstract:
To measure the spatial response characteristics of optical systems, control circuitry is provided to electrically generate a predetermined one-dimensional spatial waveform (e.g., sinusoidal) on the display screen of a cathode ray tube. The optical system to be tested (e.g., a television system) is placed between the spatial waveform display and a suitable detector which comprises a mask having a narrow slit followed by a photomultiplier. The output of the latter is then displayed on an oscilloscope, or measured in some other known fashion. A linear light modulation is achieved for the spatial waveform display by gating a linearly scanned electron beam with constant amplitude, constant duration, variable duty cycle pulses. Appropriate waveforms can be selected to evaluate the spatial frequency response, transient response, linearity, or steady state response of the optical system under test.