Spread spectrum receiver
First Claim
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1. A signal processing circuit processing pulses received from a convolver in a spread spectrum receiver and sending processed pulses to an output terminal comprising:
- first comparison means for providing an output pulse responsively to receipt of each convolver pulse of amplitude greater than that of a first reference signal level supplied to said first comparison means;
second comparison means for providing to said output terminal a processing circuit output pulse responsively to receipt of each convolver pulse of amplitude greater than that of a second reference signal level supplied to said second comparison means;
means for supplying said second reference signal level as a given fraction of said first reference signal level;
reversible system counting means including first and second counter input terminal means for providing an output signal condition indicative of a number stored therein, and including means for incrementing said number responsively to pulses supplied to one of said counter input terminal means and means for decrementing said number responsively to pulses supplied to the other of said counter input terminal means;
pulsing means for supplying a train of pulses to said first counter input terminal means responsively to the presence of output pulses at said first comparison means and including means for supplying a train of pulses to said second counter input terminal means responsively to the absence of output pulses from said first comparison means; and
digital-to-analogue converter means responsive to said output signal condition of said system counting means for providing said first reference signal level so that said reference signal level rises responsively to the presence of said output pulses of said first comparison means and decreases responsively to the disappearance of said output pulses of said first comparison means.
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Abstract
A spread spectrum receiver using a correlator is disclosed, in which first and second comparing means comparing a correlation spike coming from the correlator with a first and a second reference voltage are used, the reference voltages being regulated, depending on the output of the first comparing means so that variations of the correlation spikes are followed precisely to obtain a two-valued correlation pulse.
45 Citations
18 Claims
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1. A signal processing circuit processing pulses received from a convolver in a spread spectrum receiver and sending processed pulses to an output terminal comprising:
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first comparison means for providing an output pulse responsively to receipt of each convolver pulse of amplitude greater than that of a first reference signal level supplied to said first comparison means; second comparison means for providing to said output terminal a processing circuit output pulse responsively to receipt of each convolver pulse of amplitude greater than that of a second reference signal level supplied to said second comparison means; means for supplying said second reference signal level as a given fraction of said first reference signal level; reversible system counting means including first and second counter input terminal means for providing an output signal condition indicative of a number stored therein, and including means for incrementing said number responsively to pulses supplied to one of said counter input terminal means and means for decrementing said number responsively to pulses supplied to the other of said counter input terminal means; pulsing means for supplying a train of pulses to said first counter input terminal means responsively to the presence of output pulses at said first comparison means and including means for supplying a train of pulses to said second counter input terminal means responsively to the absence of output pulses from said first comparison means; and digital-to-analogue converter means responsive to said output signal condition of said system counting means for providing said first reference signal level so that said reference signal level rises responsively to the presence of said output pulses of said first comparison means and decreases responsively to the disappearance of said output pulses of said first comparison means. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A level control circuit for stabilizing the height of pulses produced responsively to receipt of correlation spikes received from a convolver in a spread-spectrum receiver and having varying pulse height comprising:
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D/A converter means for producing analogue output signals varying responsively to the numerical value of digital signals supplied thereto; clock means for locally supplying a periodic train of pulse signals; first comparison means for comparing a first reference voltage derived from the output of said D/A converter means with the level of a received correlation spike and including means for supplying an output pulse whenever the level of said correlation spike bears a given relationship to said first reference voltage; second comparison means for comparing a second reference voltage derived from the output of said D/A converter means and different from said first reference voltage with the level of a received correlation spike and including means for supplying an output pulse whenever the level of said correlation spike exceeds said second reference voltage; switching means having first and second output ports for supplying pulses from said periodic train of pulse signals responsively to the presence or absence of said first comparison means output pulses respectively to said first and second output ports; up-down counter means for performing up-counting and down-counting responsively to pulse signals received from said first and second output ports respectively, and including means for supplying its resultant count value to said D/A converter means to govern said first and second reference voltages. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A level control circuit for stabilizing the height of pulses produced responsively to receipt of correlation spikes received from a convolver in a spread-spectrum receiver and having varying height comprising:
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D/A converter means for producing analogue output signals varying responsively to the numerical value of digital signals supplied thereto; clock means for locally supplying a periodic train of pulse signals; first comparison means for comparing a first reference voltage derived from the output of said D/A converter means with the level of a received correlation spike and including means for supplying an output pulse whenever the level of said correlation spike exceeds said first reference voltage; second comparison means for comparing a second reference voltage derived from the output of said D/A converter means and different from said first reference voltage with the level of a received correlation spike and including means for supplying an output pulse whenever the level of said correlation spike exceeds said second reference voltage; switching means having first and second output ports for supplying said pulse signals responsively to the presence or absence of said first comparison means output pulses to said first and second output ports respectively; first up-down counter means having an up count terminal and a down count terminal one of which is fed with pulse signals from said first port and the other of which is fed with pulse signals from said second port to activate up counting and down counting of said first counter means, said first counter means including means for outputting a first output signal when its count value exceeds a first given value, means for outputting a second output signal when said count value is below a second given value, and means for resetting said count to a given initial value when either of said output signals is sent out; and second up-down counter means for executing respectively up counting and down counting responsively to said first and second output signals, and including means for supplying its resultant count value to said D/A converter means to govern said first and second reference voltages. - View Dependent Claims (14, 15, 16, 17, 18)
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Specification