초록 ▼

A digital circuit is used to demodulate a linear chirp spread spectrum signal. The digital circuit uses a counter which is clocked so as to count during the time period between the pulses of a chirp signal. The circuitry also uses a digital filter to determine whether the frequencies of the linear c

A digital circuit is used to demodulate a linear chirp spread spectrum signal. The digital circuit uses a counter which is clocked so as to count during the time period between the pulses of a chirp signal. The circuitry also uses a digital filter to determine whether the frequencies of the linear chirp signal are within the correct bandwidth. The output of the counter is compared with the previous count to produce a difference count. A processor uses this difference count value to determine the characteristics of a chirp signal being decoded. A difference signal test circuit provides a digital filter for the difference count to eliminate spurious noise conditions.

대표청구항 ▼

[ What is claimed is:] [1.] A circuit for demodulating an input chirp signal, the input chirp signal including pulses, the frequency of the input chirp signal increasing or decreasing over a period of time, the circuit comprising:digital circuitry including a counter updated by a fixed frequency clo

[ What is claimed is:] [1.] A circuit for demodulating an input chirp signal, the input chirp signal including pulses, the frequency of the input chirp signal increasing or decreasing over a period of time, the circuit comprising:digital circuitry including a counter updated by a fixed frequency clock signal, the counter being adapted to produce a count indicative of the time period between pulses of the input chirp signal the digital circuitry including a digital filter includes minimum and maximum test registers loadable with minimum and maximum test values, the digital filter further including minimum test circuitry and maximum test circuitry connected to receive the minimum and maximum test values respectively from the minimum and maximum test registers, the minimum test circuitry adapted to produce a first signal indicating whether the count of the counter is less than the maximum value and the maximum test circuitry adapted to produce a second signal indicating whether the count of the counter is more than the minimum value; anda processor electrically connected to the digital circuitry, said digital processor adapted to determine whether the frequency of the input chirp signal is increasing or decreasing over the period of time.