Abstract: A method of fabricating a self-aligned bipolar junction transistor in a semiconductor structure having a first layer of silicon carbide generally having a first conductivity type and a second layer of silicon carbide generally having a second conductivity type, opposite to the first conductivity type. The method comprises forming a pillar in the second silicon carbide layer, the pillar having a side wall and defining an adjacent horizontal surface on the second layer, forming a dielectric layer having a predetermined thickness on the second semiconductor layer, including the side wall and the horizontal surface. After formation of the dielectric layer, the dielectric layer on a portion of the horizontal surface adjacent the side wall is anisotropically etched while at least a portion of the dielectric layer remains on the side wall, thereby exposing a portion of the horizontal surface.
September 22, 1999
Date of Patent:
April 17, 2001
Cree Research, Inc.
Ranbir Singh, Anant K. Agarwal, Sei-Hyung Ryu
Abstract: A mobile telephone has a receiver, a transmitter, a microprocessor and an associated memory. The memory includes a first-in-first-out (FIFO) queue and a static buffer. An audio signal carried by the mobile telephone is digitized and provided to the microprocessor. The resulting digital signal is continuously written to the FIFO queue. In response to a first command from the mobile telephone user, the microprocessor causes the contents of the FIFO queue to be transferred to the static buffer. Upon a second command from the user, the contents of the buffer are converted to an analog signal and played back over the mobile telephone's speaker.
Abstract: An electronic device has a microprocessor operable in a plurality of modes including a memory update mode, a nonvolatile memory and a wireless communication interface for receiving data over a wireless communication channel. In one embodiment, the electronic device includes a wake-up or timer circuit for automatically placing the electronic device in a wireless memory update mode. Data received by said wireless communication interface is stored in the nonvolatile memory by the microprocessor in response to receipt of the data while the microprocessor is in memory update mode. A programming unit for transmitting update data has a microprocessor, a wireless communication interface and a memory containing update data. A communication path is established between the programming unit and the electronic device. A system for updating data stored in a nonvolatile memory of a plurality of electronic devices includes a programming unit and a plurality of electronic devices.
July 10, 1997
Date of Patent:
October 26, 1999
John Joseph Hayes, Jr., David Charles Hall
Abstract: An impedance matching circuit for a multi-band power amplifier has an input port for receiving RF signals from an amplifier, a first path for communicating RF signals in a first frequency band to a first output port, and at least one second path for communicating RF signals in a second frequency band to a second output port. The first path includes impedance matching circuitry for matching the impedance of the first output port and the input port in the first frequency band, and the second path includes impedance matching circuitry for matching the impedance of the second output port and the input port in the second frequency band. The first path contains circuitry which blocks RF signals in the second frequency band, and the second path contains circuitry which blocks RF signals in the first frequency band. A multiband power amplifier includes a multi-band amplifier coupled with an impedance matching circuit for a multiband power amplifier.
Abstract: An apparatus for charging a battery has a power supply terminal, a controllable power control switch coupled to said power supply terminal, a charging circuit having a charging terminal for connection to a terminal of the battery, and means for opening and closing the power control switch if a battery is disconnected or connected to the charging terminal, respectively. The means for opening and closing the power control switch may include an analog circuit, a digital circuit, a hybrid analog/digital circuit or a mechanical switch. A method of controlling a power control switch of a battery charging system is disclosed, comprising the steps of generating a reference voltage level, sensing the voltage level at the charging terminal, comparing the voltage level at the charging terminal to the reference voltage, and controlling the power control switch in response to the comparison of the reference voltage level and the voltage level at the charging terminal.
Abstract: A telephone has a receiver, a transmitter, a control interface, an audio processor and a microprocessor. The audio processor includes a digital signal processor, an input audio unit coupled to a microphone, an output audio unit coupled to a speaker, and a ring signal controller coupled to a transducer/ringer. When an incoming call is received, the audio processor samples the microphone input signal, which is indicative of ambient noise, and performs a spectral analysis of the ambient noise. The audio processor then sets the ring frequency and the ring volume responsive to the ambient noise spectrum and the ring volume control level set by the user.
Abstract: A voltage controlled oscillator has an active circuit, a resonant circuit coupled to the input node of the active circuit and an adjustable impedance circuit coupled to an output node of the active circuit. The impedance of the adjustable impedance circuit may be altered to tune the oscillation frequency of the oscillator. In one embodiment, the adjustable impedance circuit includes a varactor diode in series with a capacitor and means for varying the voltage across the varactor diode. An isolation circuit is coupled to an output node of the active circuit. In one embodiment, the isolation circuit is connected to a different output node than the adjustable impedance circuit is connected to.
Abstract: An apparatus for estimating channel tap coefficients of a communication channel is provided which calculates channel tap coefficient estimates as a function of a received sample stream corresponding to the channel whose channel taps are being estimated and as a function of at least one other received sample stream corresponding to another receive channel. The apparatus receives digital sample streams from a plurality of receive channels and an impairment correlation matrix containing impairment correlation information among multiple receive channels. In one embodiment, the apparatus includes a precombiner which forms linear combinations of initial error samples from a first received sample stream and a second received sample stream to generate refined error samples for generating channel tap coefficient estimates. In one embodiment, an impairment correlation estimator receives the complex samples and the channel tap coefficients and generates an impairment correlation matrix for multiple receive channels.
Abstract: An LCD has a layer of phosphorescent material which emits light at a predetermined frequency and intensity following stimulation by either ambient light or a backlight. In a preferred embodiment, a backlight LED is driven by low duty cycle voltage pulses which periodically refresh the phosphorescence of the phosphorescent layer. The phosphorescent layer may be provided by coating the rear polarizer of the LCD with a phosphor-based emulsion or by applying a thin film of phosphorescent material to the back of the LCD. In an embodiment of the invention, a transflective LCD has a layer of phosphorescent material disposed between a rear polarizer and a transflector.
Abstract: A speakerphone having echo suppression is provided. The speakerphone has an audio control system comprising a transmit path, a receive path, a pair of rectifiers for producing rectified signals indicative of the strength of the signals present on the receive path and the transmit path, respectively, and an analog-to-digital converter for generating digital samples of the rectified signals for further processing. The audio control system further includes a general use microprocessor. Samples of the rectified signals are taken periodically and processed to determine if the receive path or the transmit path should have control, or if the audio system should be in an idle state. If speech is detected on either channel, the samples are weighted depending on the current state of the audio system. The weighted samples are then analyzed to determine which path should have control.
Abstract: A telephone having a method and apparatus for increasing the intelligibility of the loudspeaker output and for echo cancellation. The telephone includes an intelligibility booster for processing a speech input signal to generate an intelligibility-enhanced signal. The intelligibility booster includes a reverberation signal path for generating a reverberation signal, a direct signal path for generating an attenuated direct signal corresponding to the input signal, and an adder for combining the reverberation signal and direct signal to generate the intelligibility-enhanced signal. The reverberation signal path includes an intelligibility-information emphasizer followed by a reverberation unit. In the preferred embodiment, the intelligibility information emphasizer is a high pass filter and/or compressor that generates an intelligibility-dense signal to generate the reverberation signal.
Abstract: An antenna coupler for coupling a portable radio to an auxiliary antenna to provide transmission and reception through the auxiliary antenna. The antenna coupler includes an outer tubular conductor and an inner tubular conductor coaxially disposed within the outer tubular conductor. An end cover having an antenna opening is secured to one end of the tubular conductors. The radio and auxiliary antenna are placed in a coupled position by inserting the on-board antenna into the inner tubular conductor. The coupled, on-board antenna and inner tubular conductor form a close-coupled transmission line with the antenna functioning as the central conductor and the inner tubular conductor functioning as an outer conductor of the transmission line. The inner tubular conductor is conductively connected to an impedance matching circuit and RF connector for providing impedance matching and interconnection with the auxiliary antenna.
Abstract: A cellular radiotelephone includes an antenna that is moveable between a first position and a second position. In the first position, the antenna is substantially parallel to the face of the radiotelephone thereby reducing the profile of the radiotelephone. Accordingly, the radiotelephone may be easier to store in a confined space such as a shirt pocket. In the second position, the antenna is canted away from the face of the radiotelephone thereby increasing the distance between the user's head and the antenna during use. Accordingly, the electromagnetic shielding caused by the user's head is reduced.