Telecommunications – Transmitter and receiver at separate stations – Distortion – noise – or other interference prevention,...
Reexamination Certificate
1998-12-23
2001-08-21
Downs, Robert W. (Department: 2765)
Telecommunications
Transmitter and receiver at separate stations
Distortion, noise, or other interference prevention,...
C455S501000
Reexamination Certificate
active
06278863
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns a system for exchanging data between a portable payment terminal and a stationary base terminal which is capable of being in communication with a payment center. The invention finds one particularly advantageous application in the field of electronic transactions effected by means of an electronic memory card operable with a portable payment terminal.
BACKGROUND OF THE INVENTION
At present many transactions are conducted, especially in stores and restaurants, in electronic form using a memory card, known as a bank card, incorporating a microprocessor in a semiconductor chip. The memory card is inserted into the card reader of a portable payment terminal which can exchange transactional data with a stationary base terminal which is capable of being in communication with a payment center, usually via the public switched telephone network. The payment center processes the transactions transmitted to it and can grant or refuse a requested authorization.
The prior art includes systems for exchanging data between portable payment terminals and stationary base terminals in which a portable terminal and the associated base terminal each includes a central unit and a radio transmit-receive module. The central unit of the portable terminal is able to generate binary messages to be transmitted to the base terminal, with the messages including the amount of the transaction, the identity of the customer and the identity of the trader, for example. The messages are transmitted to the base terminal by radio via the radio transmit-receive module of the portable terminal. The base terminal can transmit binary messages to the portable terminal using its radio transmit-receive module, for example, to authorize or to cancel a transaction.
The above prior art data exchange systems operate in the following manner, but it must be understood that the roles of the portable terminal and the base terminal are totally symmetrical. During transmission, the central unit and the radio transmit-receive module of whichever terminal is transmitting operate simultaneously in the sense that the data received from the central unit is transmitted to the receiving terminal by the transmit-receive module as and when it arrives. Switching in the central unit during the generation of binary messages causes electromagnetic interference at the transmit-receive module, in particular at the antenna, thereby producing noise in the transmit band. However, in this case such interference has only a slight effect on the signal being transmitted given that the signal is amplified to a relatively high level.
During reception, on the other hand, operation of the central unit of the receiving terminal to read the binary messages as they are received by the radio transmit-receive module causes a relatively higher level of interference because the signal received can be at a low level, in particular when there is a relatively great distance between the portable terminal and the base terminal. The noise generated by the central unit of the receiving terminal then renders the signal from the transmitting terminal virtually unusable, and this limits the range of the system.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to prevent any interference in operation between the central unit and the transmit-receive module so as to provide a maximum signal-to-noise ratio of the signal transmitted or received by the module.
In accordance with one aspect of the present invention, the portable payment terminal and/or the stationary base terminal includes means for storing the binary messages and means for deactivating the central unit such that the radio transmit-receive module is operable only when the central unit is deactivated.
Accordingly the central unit and the transmit-receive module operate sequentially rather than simultaneously and the module is no longer subject to interference generated by the central unit. The signal-to-noise ratio of the transmit-receive module is significantly improved, especially when receiving, with the advantage of enabling the system arranged in accordance with the invention to operate with a greater distance between the portable terminal and the base terminal.
In one advantageous embodiment of the data exchange system in accordance with the invention, the binary messages are written into the storage means at a transmission speed higher than the transmission speed of the radio link between the portable payment terminal and the stationary base terminal. This minimizes the increase in the transmission time between the two central units due to the fact that the central units and the transmit-receive modules operate sequentially rather than simultaneously.
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Downs Robert W.
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Kanof Pedro
Schlumberger Systemes
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