Abstract: The present invention provides sensitivity enhancement for a single antenna RFID interrogating device by separately coupling a nulling signal formed using a portion of a transmit signal into a receiver. The phase and amplitude of nulling signal can be adjusted so that the nulling signal cancels that a reflected transmit signal from the antenna, resulting in the small backscattered signal from the distant RFID tag to be more easily detected, and improving the sensitivity of the RFID receiver.

Abstract: The embodiments of the present invention include a bias circuit for a power-amplifying device, which receives and amplifies an input RF signal having a series of RF cycles within a modulation envelop. The bias circuit compensates odd-order distortion processes by detecting the power in the input signal and providing a dynamic adjustment to a bias stimulus for the power-amplifying device within a time scale of the modulation envelope.

Abstract: An RFID reader accessible thorough a personal computer and includes a PC card interface and a controller both operating according to clock signals from a crystal oscillator. The RFID reader further includes a linearized power amplifier modulator in a transmit path, a receive chain capable of demodulating either class_1 or class _0 signals from RFID tags, and an integrated switching device for selecting one of a plurality of antenna for transmitting or receiving RF signals.

Abstract: The present invention provides an ESD protection device or structure that exploits the high conductivity of a heavily doped heterojunction base of a standard SiGe bipolar junction transistor (BJT) cell. This improved ESD protection scheme further uses the combination of trench isolation and buried subcollector layer of the SiGe BJT to confine ESD current, minimizing parasitic substrate leakage and achieving large forward voltages while imposing minimal parasitic capacitive loads on a protected active device. Since the ESD protection structure is formed from conventional SiGe BJT transistor cells through modification of the contact metallization, it can be fabricated in an available SiGe BiCMOS fabrication process without additional processing steps, and characterization data already available for the SiGe BJTs can be used to model the performance of the ESD protection devices.

Abstract: A radio frequency identification (RFID) system includes a plurality of RFID tags addressable by a tag reader, with each tag comprising a RF antenna, an integrated circuit including a memory for identification data and coupled to the antenna, the integrated circuit being configured to have a first antenna load impedance when accessed by the tag reader and a second higher load impedance after access by tag reader whereby the tag switches to a low scattering state for a finite period of time to reduce scattering of signals from the tag reader.

Abstract: An RFID reader accessible thorough a personal computer and includes a PC card interface and a controller both operating according to clock signals from a crystal oscillator. The RFID reader further includes a linearized power amplifier modulator in a transmit path, a receive chain capable of demodulating EPCglobal Class_1 and Class_0 signals from RFID tags, and an integrated switching device for selecting one of a plurality of antenna for transmitting or receiving RF signals.

Abstract: The present invention includes a balanced compact antenna, conforming to the envelope restrictions appropriate to a PC-card form factor, with maximum radiation intensity along a long axis of the card. The inventive antenna configuration employs an inductive shorting bar to match an “M”-shaped bent dipole antenna to a differential feed. The combination of horizontal cross-members and large vertical downward legs ensures radiation predominantly in a broadside direction while keeping the dimensions of the antenna sufficiently compact to fit within the PC-card envelope.

Abstract: The safe-operating area (SOA) in a heterojunction bipolar transistor (HBT) is improved by providing a collector region in the transistor having a graded (uniformly or stepped) doping between the base region and the underlying subcollector region with the collector doping being lower near the base and higher near the subcollector and with the collector doping being less than the doping of the subcollector. The non-uniformly doped collector reduces Kirk effect induced breakdown when collector current increases.

Abstract: The invention relates to a method and apparatus for digital communications that provides high data rate wireless connections with bandwidth efficiency. The creation of multiple channels (that share the same time-frequency region) between the transmitter and the receiver is achieved by sampling the wavefield space with respect to the spatial domain. The wavefield space is the space spanned by the channel parameters that characterize the multipath fading environment. At the transmitter, symbols are simultaneously modulated and transmitted using signals that occupy the same frequency portion of the spectrum, but are distinguishable because different is their position in the wavefield space. The received signals are optimally processed to extract the digital information. The optimum demodulator estimates the wavefield space parameters without any training sequence or signal and performs optimum separation of the different signals to obtain the multiple streams.

Abstract: A microwave broadside coupled balun integral in a multi-layer printed wiring board formed by broadside coupled conductors embedded in the multi-layer printed wiring board. The balun may be used to form components which are integrated into the multi-layer printed wiring board, such as a microwave mixer formed by two of said broadside coupled baluns embedded in a multi-layer printed wiring board and connected to a diode ring quad.