Communications: electrical – Continuously variable indicating – Via radiant energy beam
Reexamination Certificate
1999-05-17
2001-01-30
Horabik, Michael (Department: 2735)
Communications: electrical
Continuously variable indicating
Via radiant energy beam
C340S870020, C340S870180, C370S210000, C375S327000, C455S334000
Reexamination Certificate
active
06181258
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a data transmission system, and more particularly to a data transmission system for utility metering.
The development and commercialization of various utility products, such as electricity, water, and gas have contributed to dramatic advances in living standards. In allocating usage bills, utility companies typically gauge consumption using meters and bill their customers accordingly. Traditionally, at the end of a reporting period, a utility employee physically inspects and records each customer's meter readout dials which reflect usage. The recorded data is eventually entered into an accounting system for billing purposes. This process is labor intensive and duplicative. Moreover, the meter reading process may be disrupted by unplanned nuisances such as dogs and inclement weather. Further, this process cannot provide time-of-day metering so that the utility company can charge for the utility product as a function of load factors.
To overcome these inefficiencies, remote meter reading systems have been developed which automatically capture consumption data from the field. In situations which cannot afford dedicated lines or connections to the plain old telephone service (POTS), wireless meter reading systems have been deployed. Typically, such a wireless meter reading system includes a base station which transmits on one frequency to a remote station, which in turn may relay the transmission to other remote stations. The base station also receives data from the remote stations on the same or related frequency. The wireless transmission of data between the base and remote stations is determined by the licensing rules of a government regulatory authority such as the Federal Communications Commission (FCC) in the United States or the Radio-Communications Authority (RA) in the United Kingdom (UK).
Generally, the authority grants licenses to operate radio transmitters that have to operate within a limited frequency spectrum. For instance, in the UK, a spectrum between 183.5 MHZ and 184.5 MHZ is reserved for metering applications. The band is in turn divided into eight 25 kHz channels and four 200 kHz channels. Similar frequency allocations are also enforced in various other countries which reserve a band of frequencies for various applications such as meter data collection.
Due to the limited frequency spectrum, data transmission needs to be within a narrow range such as within about 100 kHz of a predesignated transmission frequency. Since the wireless meter reading system deploys many more transmitters than receivers in forwarding usage statistics to a utility company's central location, each transmitter needs to be made as economically as possible. Typically, the most expensive component in the transmitter is a quartz crystal resonator which controls the transmission frequency.
The resonators use crystals made of quartz in the frequency generation process. Due to the cost of the crystal, it is desirable to use the least possible expensive grade of crystal. However, low grade crystals tend to be more sensitive to ambient and operating temperature variations. Further, over time, the frequency generated by low grade crystals tend to drift. As such, the use of low grade, inexpensive crystals tends to reduce the accuracy of the transmitter's operating frequency. Further, other components associated with the frequency generation process are also subject to aging. For instance, as capacitors age, variations in their capacitive values may cause a frequency variation in a ±10% range.
Thus, the use of inexpensive components may cause the transmission frequency to vary out of alignment during operation as the components heat up. Further, over time, the transmission frequency may drift out of alignment due to aging. If the frequency variations are significant, the components associated with the frequency generation process need to be replaced or aligned so that the base station and the remote stations can communicate with each other in the designated frequency range. Such replacement or alignment operations are cost prohibitive and for many applications, not practicable. Alternatively, higher grade, but more expensive crystals could be used.
SUMMARY
A receiver which is capable of receiving in parallel data transmitted at arbitrary frequencies within a radio channel includes: a radio frequency (RF) front end to convert an RF signal to a digitized signal; a Fast Fourier Transform (FFT) generator coupled to the RF front-end to separate the digitized signal into a plurality of sub-channels; a bank of phase locked loops (PLLs) coupled to the FFT generator, each PLL operating on a sub-channel with a sub-channel center; and a flag detector coupled to the bank of PLLs to detect variations from the sub-channel center and to recover the usage data transmitted from the end-point.
Implementations of the invention include one or more of the following. The receiver has a second RF front end coupled to the FFT generator to convert a diversity RF signal to an intermediate frequency and to digitize the intermediate frequency. A multiplexer can be coupled to the RF front ends. A decimator can be coupled to the RF front-end and the FFT generator, and a mixer can be coupled to the decimator. The FFT generator can produce a stream of values representing a plurality of band pass filters. Data can be transferred at a bit rate and wherein each band pass filter has a center which is spaced by one half the bit rate. Each sub-channel can have a bin frequency, and wherein the flag detector determines a difference between the PLL frequency and the bin frequency. Where each bin spacing separates one bin from an adjacent bin, the flag detector can correlate the digitized signals of each sub-channel against a first flag sequence if the difference is less than the bin spacing. The flag detector can also correlate the digitized signals of each sub-channel against a second flag sequence if the difference is greater than the bin spacing.
In another aspect, a remote data collection system for collecting usage data from an end-point includes a monitoring module coupled to the end-point, the monitoring module having a wireless transmitter to transmit the usage data and a remote receiver coupled to the wireless transmitter. The receiver has a radio frequency (RF) front end to convert an RF signal to a digitized signal; a Fast Fourier Transform (FFT) generator coupled to the RF front-end to separate the digitized signal into a plurality of sub-channels; a bank of phase locked loops (PLLs) coupled to the FFT generator, each PLL operating on a sub-channel with a sub-channel center; and a flag detector coupled to the bank of PLLs to detect variations from the sub-channel center and to recover the usage data transmitted by the end-point.
Advantages of the invention include one or more of the following. The meter data transmission system is reliable in the field and free of transmission variations induced by aging and temperature variations. Repeatability is enhanced as the system does not depend on component tolerance. The system requires virtually no calibration or alignment with respect to its operating frequency. The system is robust to minor frequency variations and requires less time and effort to manufacture as well as to install in the field. The system has a low power consumption. Certain additional functionality may be programmed using the system's processor and memory without requiring additional circuitry.
REFERENCES:
patent: 4322842 (1982-03-01), Martinez
patent: 4477809 (1984-10-01), Bose
patent: 4977612 (1990-12-01), Wilson
patent: 5179569 (1993-01-01), Sawyer
patent: 5553094 (1996-09-01), Johnson et al.
patent: 5604768 (1997-02-01), Fulton
patent: 5710720 (1998-01-01), Algrain et al.
patent: 5768693 (1998-06-01), Wong
patent: 5790615 (1998-08-01), Beale et al.
“65 MSPS Digital Receive Signal Processor,” Analog Devices, downloaded from www.analog.com/pdf/preview, Apr. 28, 1999, 1 pg.
Product Page:AD6600 Ad6620, downloaded from www.
Irving Clive Russell
Luxford Gregory Vincent
Summers Andrew Gordon
CellNet Data Systems, Inc.
Edwards, Jr. Timothy
Fish & Richardson P.C.
Horabik Michael
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