Pulse coding system

DETAILED DESCRIPTION The pulse coding system of the present invention comprises an encoder for encoding a received analog signal as a series of output pulses and a decoder for receiving the pulses output from the encoder and for generating an output signal corresponding to the analog signal received by the encoder.
The encoder includes a first decaying signal source for generating a decaying reference signal and a pulse-generating comparator circuit coupled to an input of the encoder for receiving the analog signal to be encoded.
The comparator circuit is further coupled to the output of the first decaying signal source for receiving the decaying reference signal.
The comparator circuit compares the amplitude of the received analog signal to the amplitude of the reference signal and generates and outputs a pulse whenever the amplitude of the decaying reference signal falls below that of the received analog signal.
The first decaying signal source is coupled to the output of the comparator circuit for receiving the generated pulses.
The first decaying signal source responds to the pulses by increasing the amplitude of the decaying reference signal a predetermined amount for each pulse that is received.
To decode the transmitted pulses, the decoder includes a second decaying signal source for generating the output signal by increasing the amplitude of the decoder output signal by a predetermined amount for each pulse that is received and subsequently allowing the amplitude to decay after each increase in amplitude.
Preferably, the decaying signals generated by both the decaying signal sources decays logarithmically as a function of the signal amplitude.
The generated decaying signals preferably decay at a rate that is greater than any expected rate at which the received analog input signal may fall in amplitude.
Such a system allows the pulses transmitted to be of uniform amplitude and duration.
Unlike the rate coding system described above, the present invention allows for the decoder to be responsive to each pulse that is transmitted, and therefore, the inventive system does not require the decoder to wait for a predetermined time period to determine how many pulses were received each time it has to determine whether or not to increase or decrease the amplitude of the output signal