Abstract: A high gain input stage for a radio frequency transponder uses an amplifier for increasing a magnitude of an input signal. A DC bias circuit is used for controlling the operation of the amplifier. A resonant circuit is coupled between the amplifier and the DC bias circuit. The resonant circuit is used for receiving a signal generated by an electromagnetic field and for generating the input signal which is amplified by the amplifier. The resonant circuit has an inductor which is used to bias the amplifier thereby removing the need for a decoupling capacitor between the tuned circuit and the DC biasing of the amplifier. Multiple transponder inputs may be implemented in a single integrated circuit package.

Abstract: A remote control system for opening and closing a barrier, such as a garage door, includes an RF receiver and a plurality of RF transmitters. The transmitters and receiver include circuitry programmed to provide transmission of encrypted code signals each time the transmitters are used and employing a code hopping method which prevents unauthorized signal interception or code “grabbing”. The system is operated in a code learning mode for the receiver by momentarily actuating a receiver learn mode button for receiving each transmitter identification code and a secret decryption key for that transmitter with the system automatically returning to the operate mode. Each transmitter identification and secret key code signal is automatically and randomly stored in an available and unused memory in the receiver circuitry.

Abstract: A remote control system for opening and closing a barrier, such as a garage door, includes an RF receiver and a plurality of RF transmitters. The transmitters and receiver include circuitry programmed to provide transmission of encrypted code signals each time the transmitters are used and employing a code hopping method which prevents unauthorized signal interception or code “grabbing”. The system is operated in a code learning mode for the receiver by momentarily actuating a receiver learn mode button for receiving each transmitter identification code and a secret decryption key for that transmitter with the system automatically returning to the operate mode. Each transmitter identification and secret key code signal is automatically and randomly stored in an available and unused memory in the receiver circuitry.

Abstract: A high gain input stage for a radio frequency transponder uses an amplifier for increasing a magnitude of an input signal. A DC bias circuit is used for controlling the operation of the amplifier. A resonant circuit is coupled between the amplifier and the DC bias circuit. The resonant circuit is used for receiving a signal generated by an electromagnetic field and for generating the input signal which is amplified by the amplifier. The resonant circuit has an inductor which is used to bias the amplifier thereby removing the need for a decoupling capacitor between the tuned circuit and the DC biasing of the amplifier. Multiple transponder inputs may be implemented in a single integrated circuit package.

Abstract: A radio frequency transponder device in an integrated circuit package requires only one dedicated pin for connection to a parallel resonant tuned circuit for receiving a remote signal. The one dedicated pin has a capacitor which blocks direct current (DC) flow and allows independent DC biasing of a radio frequency amplifier for increased signal amplification gain. Another package pin used for common power or ground connections supplies the second connection to the resonant tuned circuit. Multiple transponder inputs may be implemented in a single integrated circuit package using only one dedicated pin per input plus one common pin which may be used for another purpose, such as a power or a ground connection.

Abstract: A system and method for identifying tags with a reader, wherein the tags have unique tag identification codes, having a transmitter of a wake-up signal from the reader to a tag within a field of the reader; a transmitter of a signal corresponding to an initial portion of the tag identification code from the tag to the reader; a transmitter of an initial acknowledgement signal responsive to the signal corresponding to the initial portion of the tag identification code; and a recorder in the reader of an initial portion of a tag confirmation code corresponding to the initial acknowledgement signal. The system send and acknowledges subsequent portions of the identification codes from the tags. If a tag does not receive an acknowledgement of its code, the tag becomes inactive. The system continues until only one tag remains active and transmits its entire code for acknowledgement. This tag is selected.

Abstract: A signal discriminator for preventing activation by undesired signals of low power transponder circuits in a keyless entry system. These undesired signals may be noise or interfering signals. An asymmetrical low pass filter is used to determine the presence of a desired signal having a defined length of time. The asymmetrical filter has a longer charge time then discharge time, thereby being adapted to quickly discharge upon the loss of a signal. Signal duration verification is further used to determine if the desired signal is of a correct time duration.

Abstract: An electronic system, comprising a digital processor and an EEPROM, has circuit logic and program software or firmware for determining if a programming voltage level is sufficient for reliably programming the EEPROM. A charge pump is enabled and generates a voltage used for programming of the EEPROM. The enabled charge pump thereby loads a battery power supply. In addition, a test load may be connected to the output of the charge pump to simulate the EEPROM load during a programming operation to the EEPROM. The charge pump output voltage is measured to determine if at least a desired voltage value is obtained. Once the charge pump voltage level has been pre-qualified for the desired voltage value, an actual programming operation to the EEPROM may be performed. If the voltage level does not reach the desired value then a programming operation is inhibited and the electronic system may alarm or shut down operation.

Abstract: A remote control system for opening and closing a barrier, such as a garage door, includes an RF receiver and a plurality of RF transmitters. The transmitters and receiver include circuitry programmed to provide transmission of encrypted code signals each time the transmitters are used and employing a code hopping method which prevents unauthorized signal interception or code "grabbing". The system is operated in a code learning mode for the receiver by momentarily actuating a receiver learn mode button for receiving each transmitter identification code and a secret decryption key for that transmitter with the system automatically returning to the operate mode. Each transmitter identification and secret key code signal is automatically and randomly stored in an available and unused memory in the receiver circuitry.