Combined OOK-FSK/PPM modulation and communication protocol scheme providing low cost, low power consumption short range radio link
First Claim
1. A communication system comprising a transmitter exclusive of an up-conversion local oscillator that is operative to transmit an RF signal modulated with a baseband signal as on-off keyed (OOK) modulation and one of frequency shift keyed (FSK) and pulse position/width modulation (PPM/PWM), and a receiver that is operative to receive and demodulate said RF signal and recover information contained therein.
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Accused Products
Abstract
A communication system provides robust, short range radio communications between battery operated devices by using ON-OFF-KEYED (OOK) modulation and either frequency shift keyed (FSK) modulation or pulse position/width modulation (PPM/PWM), in combination with a prescribed communications protocol. The system transmitter requires no local oscillator and is only active during actual communication, so that its current drain is not a significant factor in total battery life. Also, the receiver is active for only a small fraction of time. The need for large, complex and expensive filters is minimized by using a single IF band-pass filter in active form or passively in the form of a low cost ceramic filter such as those used in inexpensive transistor radios. The digital transmitter and receiver portions of the system are implemented by low cost, and ultra low power CMOS logic.
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Citations
22 Claims
- 1. A communication system comprising a transmitter exclusive of an up-conversion local oscillator that is operative to transmit an RF signal modulated with a baseband signal as on-off keyed (OOK) modulation and one of frequency shift keyed (FSK) and pulse position/width modulation (PPM/PWM), and a receiver that is operative to receive and demodulate said RF signal and recover information contained therein.
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14. A method of conveying information between first and second devices, comprising the steps of:
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(a) encoding an information signal as one of a baseband frequency shift keyed (FSK) modulated signal and a pulse position/width modulation (PPM/PWM) signal; and
(b) transmitting from said first device an on-off keyed (OOK) modulated RF signal that is modulated with said one of said baseband frequency shift keyed (FSK) and pulse position/width modulation (PPM/PWM) signals representative of information encoded in step (a). - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
(c) at said second device, receiving and demodulating said OOK modulated RF signal that has been modulated with said one of frequency shift keyed (FSK) and pulse position/width modulation (PPM/PWM), and recovering said information.
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16. A method according to claim 14, wherein said OOK RF signal is modulated with FSK modulation representative of said information.
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17. A method according to claim 14, wherein said OOK RF signal is modulated with PPM/PWM modulation representative of said information.
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18. A method according to claim 14, wherein step (b) comprises transmitting first and second OOK pulse waveforms having respectively different frequencies, one above and one below an IF center frequency.
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19. A method according to claim 15, wherein step (c) comprises receiving said OOK modulated RF signal by way of a narrow band antenna, coupling the output of said narrow band antenna to an AM detector, filtering a pulse train derived by said AM detector through a band-pass filter having a center frequency matched to the OOK transmission rate, coupling said band-pass filter being to a received signal strength indicator circuit, the output of which is compared with a prescribed signal level threshold, to controllably gate a received signal waveform, to prevent potentially false data from being coupled to digital processing circuitry, and recover said information.
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20. A method according to claim 19, wherein step (c) further comprises coupling a received signal to an FSK receiver having an FM discriminator circuit and a digital tone detector that is operative to validate received OOK data, and digital FSK processing circuitry that is operative to integrate the received data validated by said received signal strength indicator circuit and digital tone detector circuit, and to store validated recovered data to system memory.
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21. A method according to claim 17, wherein step (b) comprises transmitting transmitter first and second OOK PPM/PWM waveforms of the same IF center frequency, and shifted in phase by respectively different first and second phase shift amounts, encoded in step (a) in accordance with first and second logical states of said information.
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22. A method according to claim 21, further including the step (c) of, at said second device, receiving and demodulating, by PPM/PWM digital processing circuitry, said OOK modulated RF signal that has been modulated with said one of frequency shift keyed (FSK) and pulse position/width modulation (PPM/PWM), and recovering said information.
Specification