Spread spectrum communication transmitter an LSI therefor
First Claim
1. A spread spectrum communication transmitter comprising:
- FSK modulation means for performing FSK modulation for switching frequency in correspondence with whether a binary level of each bit of the serial digital data to be transmitted is high or low, andSS modulation means for performing spread spectrum modulation of a resultant FSK-modulated signal and transmitting resultant data,wherein said FSK modulation means comprises a direct digital synthesizer and synchronizes an FSK modulation signal having a frequency corresponding to at least one binary level of said each bit with a PN code for the spread spectrum modulation, said PN code having a period which does not vary based upon a ratio of a number of said high level bits of said serial data to a number of said low level bits of said serial data.
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Abstract
High-sensitivity transmission can be performed in a wide temperature range, and spread spectrum communication free from jitters and bit errors in high-speed digital signal transmission can be performed. There is provided a spread spectrum communication transmitter for performing FSK modulation for switching the frequency in correspondence with the level of each bit of the serial digital data, performing spread spectrum modulation of a resultant FSK-modulated signal, and transmitting the data, wherein an FSK modulation unit (1) for performing the FSK modulation has a direct digital synthesizer and a synchronization circuit (19) is arranged to synchronize an FSK signal having a frequency corresponding to at least one level of the each bit with a PN code for the spread spectrum modulation.
79 Citations
6 Claims
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1. A spread spectrum communication transmitter comprising:
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FSK modulation means for performing FSK modulation for switching frequency in correspondence with whether a binary level of each bit of the serial digital data to be transmitted is high or low, and SS modulation means for performing spread spectrum modulation of a resultant FSK-modulated signal and transmitting resultant data, wherein said FSK modulation means comprises a direct digital synthesizer and synchronizes an FSK modulation signal having a frequency corresponding to at least one binary level of said each bit with a PN code for the spread spectrum modulation, said PN code having a period which does not vary based upon a ratio of a number of said high level bits of said serial data to a number of said low level bits of said serial data. - View Dependent Claims (2)
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3. An integrated circuit used in a spread spectrum communication transmitter for performing an FSK modulation of digital data, performing spread spectrum modulation of an FSK-modulated signal, and transmitting resultant data, comprising a direct digital synthesizer for forming the FSK-modulated signal in response to a first clock, a PN code generator for generating a PN code for the spread spectrum modulation in response to a second clock, said PN code having a sequence that is independent of serial digital data that is to be transmitted, and a synchronization circuit for synchronizing the first clock with the second clock.
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4. A spread spectrum communication transmitter comprising:
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PN generating means for generating a PN code sequence; FSK modulation means for subjecting serial digital data to be transmitted to a frequency shift keying modulation and outputting a resultant FSK-modulated signal; and SS modulation means for subjecting said FSK-modulated signal to a spectrum spread modulation using said PN code, said PN code having a sequence that is independent of said serial digital data that is to be transmitted, wherein said FSK modulation means comprises a direct digital synthesizer and at least one of FSK modulation signals for said frequency shift keying modulation is synchronized with said PN code. - View Dependent Claims (5, 6)
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Specification