Tuners – With switching means – Capacitor only modified or substituted by switching
Reexamination Certificate
1999-07-15
2001-05-29
Lee, Benny (Department: 2817)
Tuners
With switching means
Capacitor only modified or substituted by switching
C334S084000, C333S174000, C455S180100
Reexamination Certificate
active
06239675
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to identification systems and more specifically to an identification system reader with multiplexed antennas.
BACKGROUND OF THE INVENTION
There is a great need for devices or apparatuses which make it possible to identify or detect objects in a contactless manner and over a certain distance. An additional desire exists to be able to change the data stored in, or operating characteristics of, such devices or apparatuses (i.e. “program” the devices or apparatuses).
It is, for example, desirable to request contactless identifications and over a certain distance identifications which are uniquely assigned to an object and which are stored in the device or apparatus so that, for example, the object may be identified. A determination may also be made as to whether or not a particular object exists within a given reading range. This concept can be used in a number of applications including security identification (e.g., security badges), inventory control, waste management, vehicle identification, and many others.
One such identification system is disclosed in U.S. Pat. No. 5,053,774 ('774) issued on Oct. 1, 1991 to Schuermann et al. In that arrangement, the transponder (or responder) unit includes an energy accumulator which stores the energy contained in an RF interrogation pulse, which is transmitted from a reader (or interrogator). The transponder includes circuitry which senses the termination of the reception of the RF interrogation pulse and the presence of a predetermined energy amount in the energy accumulator. The circuitry triggers the excitation of an RF carrier wave generator operating with the frequency contained in the RF interrogation pulse. A signal generated by the RF carrier wave generator can then be retransmitted back to the reader thereby conveying information stored within the transponder.
In some applications the reading repetition rate of a transponder will be slow and it is desirable couple a number of reading antennas to a single RF reader module. Therefore, there is presently a need for an identification reader with multiplexed antennas.
SUMMARY OF THE INVENTION
Other objects and advantages will be obvious, and will in part appear hereinafter and will be accomplished by the present invention which provides an identification reader with multiplexed antennas.
An electronic system is disclosed herein. The system includes circuitry for processing a signal and a plurality of antennas. A plurality of switches are also included. Each of the switches is coupled between the processing circuitry and a corresponding one of the antennas. Each of the switches includes first and second power MOSFETs where the source of the first MOSFET is coupled to the source of the second MOSFET. The system further includes circuitry for selecting of one of the plurality of switches to be on.
In one embodiment, a novel switch/driver circuit can be used to selectively couple a first node to a second node, e.g., to couple an antenna to a processing circuit. In this embodiment, a first power MOSFET with its drain coupled to the first node and a second power MOSFET transistor with its drain coupled to the second node comprise the switch. The source of the second MOSFET is coupled to the source of the first MOSFET, i.e., the MOSFETs are coupled antiserialy. A bipolar transistor has a base coupled to the gates of the first and second MOSFETS. A first diode is coupled to a high voltage node and a zener diode is coupled between the first diode and the emitter of the bipolar transistor. The circuit also includes a resistor coupled between the collector of the bipolar transistor and the first diode. In this circuit, a select signal is provided to the switch/driver circuit such that the switch/driver circuit is galvanically isolated from the select circuit.
In yet another embodiment, the present invention can be utilized to constitute a reader for an identification system comprising. This system will typically include interrogator processing circuitry which has first and second antenna nodes. A number of antennas are coupled to one of the antenna nodes. A switch is associated with each one of the antennas between the antenna and the interrogator processing circuitry. Each switch is driven by a driver circuit. Each driver circuit includes a supply node which is coupled to the second antenna node of the interrogator processing circuitry. Channel selection circuitry is provided to generate a select signal for each one of the driver circuits. The channel selection circuit is galvanically isolated from each of the driver circuits.
The antenna multiplexer of the present invention has a number of advantages. First, the antenna multiplexed used with the present invention can be the same as the standard antenna used with prior art systems. In effect, the antenna system can support receive as well as transmit functions to be multiplexed between the different antennas. This feature provides a significant advantage by multiplexing the transmit and receive functions as opposed to a receive-only antenna multiplexers.
Also, since standard antennas can be used, there is no change in the basic reading characteristic when multiplexing several antennas to a single interrogator. This is not the case when multiplexing special receive-only antennas to an interrogator.
The transit antenna multiplexer can also be implemented very easily since it is not necessary to change anything inside the interrogator. The transmit antenna multiplexer can just be plugged between the antennas and the interrogation circuit.
In addition, the number of multiplexed antennas can be expanded very easily and the number of channels are unlimited. For one additional channel only the driver/switch unit and one tuning matrix block (ie., set of jumpers) have to be added. (The channel selection circuit must be expanded only if all selection lines are already used up.) The tuning capacitors drive unit is unaffected by the number of multiplexed antennas.
REFERENCES:
patent: 3568112 (1971-03-01), Thomas
patent: 3573663 (1971-04-01), Huge et al.
patent: 3906405 (1975-09-01), Kommrusch
patent: 5065121 (1991-11-01), Gehadaksaz
patent: 886298 (1962-01-01), None
Brady III Wade James
Lee Benny
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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