Abstract: An RFID system using encoded digital information utilizing pulsed linear frequency modulation (LFM). The LFM waveform is sent from an24 aircraft or satellite and is received by a transponder. The LFM waveform is demodulated using both, an AM and an FM receiver. The demodulated data is compared to preprogrammed criteria tables, and after validation is decoded and utilized. Algorithms in the transponder are used to determine the frequency deviation and for calculating the direction of the slope of the LFM input signal. The valid RF signal is stored in a delay element, encoded with the transponder data using phase modulation (PM), and frequency modulation (FM). The tag transmission is synchronized to the input LFM waveform. The transmit/receive chopping signal prevents unwanted oscillations and is capable of randomization.

Abstract: An RFID system using encoded digital information utilizing pulsed linear frequency modulation (LFM). The LFM waveform is sent from an aircraft or satellite and is received by a transponder. The LFM waveform is demodulated using both, an AM and an FM receiver. The demodulated data is compared to preprogrammed criteria tables, and after validation is decoded and utilized. Algorithms in the transponder are used to determine the frequency deviation and for calculating the direction of the slope of the LFM input signal. The valid RF signal is stored in a delay element, encoded with the transponder data using phase modulation (PM), and frequency modulation (FM). The tag transmission is synchronized to the input LFM waveform. The transmit/receive chopping signal prevents unwanted oscillations and is capable of randomization.

Abstract: A method of communicating to a RF tag having a low power mode and a scan mode with a radar and an interrogator. The method comprises the steps of alternating the RF tag between the low power mode and the scan mode and then transmitting a wake-up call to the RF tag with the radar. Next, the wake-up call is received from the radar by the RF tag when the RF tag is in the scan mode. Once the wake-up call has been received, the radar will transmit a downlink message to the RF tag. Upon receipt of the downlink message, the RF tag will send an uplinked message to the radar. After the uplink message has been sent to the radar, the RF tag will return to the low power mode. By alternating the RF tag between the low power mode and the scan mode, the power consumption of the RF tag is greatly reduced thereby increasing the battery life thereof.

Abstract: A PCMCIA modem card which is connectable a host computer and utilizes an integrated, extendable antenna for wireless transmission and reception, is provided with a circuit board. The circuit board is provided with a cavity interior. The cavity extends to a first end of the circuit board. The modem card is further provided with communications circuitry which is formed on the circuit board. The modem card is further provided with an antenna structure which is in electrical communication with the communications circuitry. The antenna structure is translatable from a first position wherein the antenna structure is substantially disposed within the cavity and a second position wherein the antenna structure is extended from the cavity.

Abstract: A balanced battery charger maintains a balanced charge upon a plurality of battery cells which are connected in series with one another. The balanced battery changer has a monitoring circuit for determining when an imbalance between the charge upon the battery cells occurs and a charging/discharging circuit for selectively charging and discharging at least a selected one of the battery cells so as to generally balance the charge upon the battery cells. Balancing the charge upon the battery cells substantially enhances the life thereof.

Abstract: A method is disclosed for controlling operation of a battery powered modem to implement power conservation by adaptive modem sleep. The method comprises detecting the presence of a periodic network timing signal and detecting transition of the modem processor to a processing ready condition, wherein received RF signals can be processed. A processor ready signal is generated in response to detection of the processing ready condition and compared in time to occurrence of the network timing signal. A sleep error signal is generated which represents the interval between occurrence of the network timing signal and the processor ready signal. A modem is then directed into a sleep mode for periods of time sufficient to reduce the sleep error signal to be within a predetermined error budget.