Abstract: A video converter converts an input video signal conveying pixel data representing an M.times.K pixel image to an output video signal conveying data representing an N.times.L pixel image. The converter samples the input video signal to acquire an M.times.K matrix of pixel data, re-encodes each pixel data value as necessary to meet color coding requirements of the output video signal standard, and then employs digital interpolation and/or decimation filters to convert the M.times.K data matrix to an N.times.L data matrix. A simple digital output encoder operating at four times the output video signal subcarrier frequency is then employed to process the N.times.L matrix to produce a digital output data sequence which, when applied to D/A converter, becomes the output video signal.

Abstract: As frequency spectra are produced continuously at a speed that is too fast for realtime display, they are accumulated in a memory. After a block of these frequency spectra have been accumulated, they are read back from the memory and displayed on a display device that permits the display of multiple frequency spectra along a time axis. Markers allow delta-time measurements to be made between different spectra in the display. Continuous storage into a circular memory can be stopped and the display of the accumulated frequency spectra started by the detection of the occurrence of a pre-defined spectra event.

Abstract: An apparatus and method of using markers for identifying particular points on a quasi-3-dimensional display, such as a color spectrogram display or a waterfall display of multiple frequency spectra on an electronic spectrum analyzer, so that amplitude, time, and frequency values associated with a particular point can be conveniently read out, and so that differences in amplitude, time, and frequency between two points can be easily calculated and presented to the user. Two markers whose positions are ascertainable are generated on the quasi-3-dimensional display and are made subject to operator control. One of these markers is positioned by the operator on a particular point of interest and the values associated with that location are then displayed for readout with greater precision and convenience than would otherwise be possible. A second marker is placed at a second point of interest and the differences in the values of amplitude, time, and frequency between the two points are calculated and displayed.

Abstract: An apparatus and method for expanding the resolution of digital-to-analog converters is described. Two limited resolution digital-to-analog converters are cascaded in such a manner that one converts the low order bits of digital input signal and the other converts the higher order bits. The output of the higher order digital-to-analog converter is applied directly to a summing circuit while the output of the low order digital-to-analog is first passed through an attenuator. When the low order digital-to-analog converter receives all logical ones, a carry is performed to the higher order digital-to-analog converter. The low order analog-to-digital converter is then reset by a successive approximation technique. Operation is essentially the same for borrow operation.