Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1998-10-28
2001-12-25
Legree, Tracy (Department: 2681)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S212000, C455S218000, C455S266000, C455S260000, C455S258000, C455S334000, C455S339000, C455S326000, C379S106010, C331SDIG002, C331S004000
Reexamination Certificate
active
06334060
ABSTRACT:
The invention relates to a circuit and method for overcoming the disadvantages of interchannel-interference and cross-talk which can occur between transmitters and receivers.
The invention provides wireless anti-jamming and selective address low frequency telemetry for data transmission offering a high degree of immunization against interchannel-interference and cross-talk. The invention makes use of wireless low frequency (split-frequency for channel separation) telemetry in order to convey information between a transmitter and a receiver. In particular, the invention has applications with respect to heart rate chest belt transmitters which communicate with receivers which can be either of a wrist-watch type, a belt-clip type, or as part of a fitness monitor mounted on a particular piece of fitness equipment. Of course, it will be understood that the invention could also be used with respect to any communication application which may suffer from interchannel-interference and cross-talk between transmitters and receivers.
It is known in health club settings, where the fitness or exercise machines, such as treadmills, are placed close to one another, or when a number of individuals exercising using the heart rate transmitter are within each others wireless receiving vicinity, that a certain amount of interchannel-interference and cross-talk may occur which jeopardizes the accuracy between the transmitter and the receiver. These problems are overcome according to the present invention.
According to the present invention, a wide-band, low frequency transmitter and receiver system termed a “multi-channel system” is provided for digital telemetry and features high selectivity, high sensitivity, safeguards against in-channel noise and the capability of scanning/multiplexing multiple stations. The multi-channel system is available not only for wide-band applications, but also for narrow-band applications such as with respect to the known heart rate monitors discussed above.
At radio frequencies wherein the transmission bandwidth is not very critically limited, i.e., on the order of hundreds-of MHz to the GHz range, the use of frequency division multiplexing (FDM) has been used with respect to coaxial cable links, radio links, and satellite links. However, at low frequencies, the transmission bandwidth limitation becomes a major concern. For example, a power line cable has a transmission band with typically only around 1 MHz. As such, frequency division multiplexing and filtering become increasingly difficult. The present invention is designed specifically for such low frequency telemetry systems wherein the available bandwidth is at a premium.
According to the present invention, the multi-channel system makes use of coherent detection (having a high selectivity-typical channel separation of approximately a few hundred Hz), quadrature detection (also having a high sensitivity), a matching filter to average out noise, and a system clock which is software steerable for scanning/multiplexing. Advantageously, the multi-channel system is useful for data transmission over inductive, infrared, sonic and cable links. By providing enhanced electrical noise immunity, the multi-channel system is suitable for industrial applications wherein noise sources are present.
Example of Split-frecuency Telemetry Approach
One approach against interchannel-interference is by using the method of providing a separate frequency for each channel.
1. Channel allocation
Considering the available bandwidth and possibly the level of cross-talk, nine (9) discrete frequencies are designated with the following channel numbers for communication.
Channel number
0
1
2
3
4
5
6
7
8
Frequency (Khz)
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
Channel 0 (2.8 Khz) is reserved for a so-called “Proximity down-loading” identification ID exchange protocol use.
2. Proximity down-loading
During a channel number initialization routine, the transmitter decides upon a channel for subsequent cardiac data transmission through a random number generator. This “official channel number” is passed on to the receiver by “near field” Proximity down-loading, that is, by bringing the receiver close to the transmitter. The transmitted code has the following format.
<START>
<CHANNEL #>
<CHANNEL #>
<STOP>
1 bit
3 bits
3 bits
1 bit
The receiver, after checking the twice received channel number, will “beep” to acknowledge a successful ID transfer. Thereafter, that channel/frequency will be the communication channel between the agreed transmitter/receiver pair.
Should interchannel-interference be encountered, the ID transfer routine can be activated by Proximity down-loading for a new ID (channel #).
3. Coherent detection
Split-frequency uses one out of the nine possible communicating frequencies: 2.8 Khz, 3.0 Khz, 3.2 Khz, 3.4 Khz, 3.6 Khz, 3.8 Khz, 4.0 Khz, 4.2 Khz and 4.4 Khz to separate among different channels for different users.
The transmitter and the receiver have to acknowledge an agreed channel (frequency) for their cardiac data transmission by the “Proximity down-loading” mechanism during the ID initialization routine.
Such a narrow band system calls for coherent detection that requires a replica of the transmitter carrier (reference signal) to be re-generated at the receiver.
The above requirement can be realized by a microprocessor programmable oscillator at the transmitter (master oscillator) generating one out of the nine possible carrier frequencies for amplitude shift keying modulation during data transmission.
The corresponding receiver, acknowledged with the channel # for communication through the ID initialization routine at 2.8 Khz (default) has its on-board microprocessor programmable oscillator (slave oscillator) steered to the same (reference) frequency for coherent detection.
General illustrations of the split-frecuency, multi-channel, transmitter and receiver systems, as well as a prototypical circuit implementation, are described below in the drawings.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
REFERENCES:
patent: 4503401 (1985-03-01), Kriyakos et al.
patent: 4847617 (1989-07-01), Silvian
patent: 5367555 (1994-11-01), Isoyama
patent: 5488631 (1996-01-01), Gold et al.
patent: 5748104 (1998-05-01), Argyroudis et al.
patent: 5774555 (1998-06-01), Lee et al.
patent: 6047170 (2000-04-01), Paulsen et al.
Sham Ka Yiu
Wong Philip Lim-Kong
Acumen Inc.
Crowell & Moring LLP
Legree Tracy
LandOfFree
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