Spread spectrum open loop data recovery processor
First Claim
1. A spread spectrum open loop data recovery processor, comprising:
- a balanced demodulator receiving a single information channel bi-phase modulated spread spectrum RF signal and a fixed frequency signal, the balanced demodulator combining the two signals to provide and in-phase information signal and a (`Q`) quadrature information signal;
an oscillator for providing the fixed frequency signal; and
a digital processor receiving the in-phase information signal and the quadrature information signal and a predetermined spreading code, the digital processor filtering both the in-phase and the quadrature information signals for noise and correlating the filtered information signals with the predetermined spreading code, the digital processor defining an information signal quality based on the filtering and the correlation and determining which information signal has thee better signal quality, and selecting the better quality information signal for output as a received data signal and outputting a clock signal for use with the received data signal,whereby a single spread spectrum information channel is provided without phase locking to the received RF signal.
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Accused Products
Abstract
A spread spectrum open loop data recovery processor receives a single information channel bi-phase modulated RF signal and combines it with a locally generated fixed frequency signal having an accuracy of at least 5 ppm. A balanced demodulator combines the received and local signals to derive an `I` and a `Q` analog information signal. The remote transmitter modulates both channels with the same information. The `I` and `Q` analog signals `slip` with respect to one another. The accuracy of the fixed frequency signal insures that the rate of slip does not exceed the ability of the data recovery processor to attain an error rate of better than 1 ppm. The `slip` results in both analog signals periodically going through null. The quadrature phase relationship between the `I` and `Q` analog signals insures that both are not simultaneously null. An amplitude comparator determines which analog signal has the greater instantaneous amplitude. After noise filtering and correlation with a copy of a 13-bit Barker PN code used by the remote transmitter, the `stronger` signal is output as `received data.` The short PN code allows signal acquisition in less than one `byte,` resulting in rapid switching between transmit and receive modes.
54 Citations
11 Claims
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1. A spread spectrum open loop data recovery processor, comprising:
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a balanced demodulator receiving a single information channel bi-phase modulated spread spectrum RF signal and a fixed frequency signal, the balanced demodulator combining the two signals to provide and in-phase information signal and a (`Q`) quadrature information signal; an oscillator for providing the fixed frequency signal; and a digital processor receiving the in-phase information signal and the quadrature information signal and a predetermined spreading code, the digital processor filtering both the in-phase and the quadrature information signals for noise and correlating the filtered information signals with the predetermined spreading code, the digital processor defining an information signal quality based on the filtering and the correlation and determining which information signal has thee better signal quality, and selecting the better quality information signal for output as a received data signal and outputting a clock signal for use with the received data signal, whereby a single spread spectrum information channel is provided without phase locking to the received RF signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification