Abstract: A simulator generates a simulated broad-band signal that may include up to nd in excess of 150 harmonics for communication and signal processing applications. Clock signals are fed to a number of counters which cyclically address an EPROM storage that provides a digital waveform pre-programmed as to bandwidth and harmonic content. The digital pre-programmed waveform is fed to a digital to analog converter having a high bit resolution, in excess of 14 bits, so that a broad-band signal having 150 or more harmonics can be accurately generated. The EPROMs may be reprogrammed in accordance with a desired output signal to give a considerable flexibility with regard to bandwidth and harmonic content.

Abstract: A reliable, repeatable and stable VLF/LF atmospheric noise generator is cble of producing noise with known or given amplitude probability distributions and temporal characteristics such as pulse duration, pulse spacing, pulses per unit time and the discharge fine structure between pulses. A pseudo random noise carrier signal is multiplied in a plurality of digital-to-analog converters with the discharge envelopes created in a plurality of interconnected discharge envelope generators. The discharges are representative of cloud-to-ground discharges, intercloud discharges, the discharge rate, strokes per discharge and the discharge fine structure. All of the discharges are readily modifiable by suitably reprogramming operatively coupled memories and microprocessors in accordance with selected loading instructions.

Abstract: An improved pseudo-atmospheric noise generator includes the capability for roducing noise in the VLF/LF spectrum with known amplitude probability distributions while controlling the temporal characteristics of the simulated impulses. The outputs from a number of pseudo-random bit generators are selected by a microprocessor in accordance with expected or anticipated atmospheric disturbances from a number of geographical regions. The microprocessor selected outputs are fed to a digital-to-analog converter which feeds the converted signals to a summer. An independent Gaussian noise source is coupled to the summer and the outputs from the Gaussian noise source and the digital-to-analog converter are combined to create a composite pseudo-atmospheric noise signal. The improvement also includes capability for self-testing and set up.

Abstract: A reliable, repeatable and stable generator capable of producing noise with nown or given amplitude probability distributions up to 96 dB dynamic range, commonly found in atmospheric noise VLF/LF frequency bands. A continuous impulse noise amplitude probability distribution is digitally synthesized in a piece-wise fashion in 6 dB amplitude increments. These increments are linearly combined with a digitally generated Gaussian noise component for simulation of VLF and LF atmospheric noise.