Abstract:
A novel finite impulse response filter apparatus and method are disclosed. A multiplexed data stream composed of two or more data streams is provided as an input to a tapped delay line. Weight and sum operators are connected to the even or odd delay line taps and generate a filtered output. The filter operates on one data stream per cycle and generates a multiplexed output. In another form, odd weight and sum operators are connected to and odd taps and even weight and sum operators are connected to the odd taps generating two filtered outputs. The filter operates on both data streams in each cycle and generates two multiplexed outputs. A crossbar switch is disclosed for parsing the multiplexed outputs into the constituent filtered data streams. The filter stages may be cascaded.
Abstract:
An invalid reference detection circuit (10) is formed on a semiconductor chip having reference input terminals adapted for coupling to a reference source (12) external to the chip, a local reference source (14), and comparison circuit (15). The comparison circuit is responsive to the local reference source and a condition at the reference input terminals to detect an invalid condition at the reference input terminals and produce an output signal (17) indicative of the condition. The invalid condition at the reference input terminals may be an open circuit, a voltage across the reference input terminals being below a predetermined minimum or above a predetermined maximum, and/or short circuit. An analog/digital conversion system (8) is formed on a semiconductor chip together with the invalid reference detection circuit. The reference input terminals are adapted for coupling to the conversion circuitry.
Abstract:
A data transmission system including a telephone service subscriber loop utilized for transmission of data including telephone service signals; a splitter operable for splitting the subscriber loop into a first transmission path including a low pass filter which accommodates a continuation of telephone service signal transmissions along the subscriber loop and a second transmission path, said second transmission path including a capacitive element for attenuating the telephone service signals; and a digital subscriber loop transceiver coupled to the second transmission path for implementing high rate digital data transmission over the subscriber loop, the transceiver including a frontend processing circuit having a transmit path and a receive path, at least said receive path comprising a high pass filter for further attenuating said telephone service signals. The capacitive element in the second transmission path and the high pass filter in the receive path of the transceiver frontend operate in conjunction to maintain transhybrid loss.
Abstract:
A hysteresis circuit including first (88) and second (90) voltage reference circuits responsive to an input control signal ((VA) for providing first and second voltage levels connected in series to produce a higher voltage level; a first switching circuit (82), responsive to the voltage reference circuits to turn on and provide an output drive signal when the higher voltage is reached; a second switching circuit (84), responsive to the first switching circuit turning on, for removing one of the first and second voltage levels to produce a lower voltage level; the first switching circuit turning off in response to the input level control signal decreasing below the lower voltage level.
Abstract:
A semiconductor device having a semiconductor region including a material of a first predetermined conductivity type; an insulating layer (40) provided on the semiconductor region; a gate electrode (32, 34, 38) provided on the insulating layer, the gate electrode forming a potential well within the semiconductor region in response to a potential being applied thereto; and a diffusion (36) of highly doped material of a second predetermined conductivity type being positioned within the semiconductor region, and which is applied through an opening in the gate electrode and the insulating layer (40), the diffusion (36) being in direct ohmic contact with the potential well. The diffusion (36) can be either a n+ or p+ diffusion. The diffusion (36) accommodates a reduction in lateral time constants of charge redistribution within the potential well, direct sensing of the charge in the well, and injection and extraction of charge to and from the well.
Abstract:
A decimating PRML signal processor system (10) for processing a PRML data signal includes: an adaptive filter circuit (22) for receiving and for shaping the data signal; a gain control circuit (30), responsive to the adaptive filter circuit (22), for adjusting the gain of the data signal; a phase control circuit (32), responsive to the adaptive filter circuit (22), for adjusting the phase of the data signal; a clock circuit (40) for providing signals for driving each of the circuits; and a decimation controller (42) for reducing the rate of the clock signals to at least one of the circuits to decrease the power required to operate the system.
Abstract:
A gain control circuit (22) provides linear-in-decibel gain control for an RF signal variable gain amplifier (12). The gain control circuit (22) utilizes the transconductance characteristics of bipolar transistors to generate a logarithmic relationship betweena gain control current (IG) and an amplifier bias current (IC). The gain control circuit (22) comprises essentially a current mirror having two transistors (Q1, Q2) with a resistor (R1) coupled between the associated base terminals of the two transistors (Q1, Q2). A third transistor (Q3) and a resistor (R2) are also provided to absorb the gain control current (IG). The gain control current (IG) is applied to a base of a first one (Q1) of the two transistors and a voltage is thereby established across the resistor. This voltage subtracts from the base-emitter voltage of the second transistor (Q2) thereby producing a corresponding exponential reduction in the current through the second transistor (Q2). This current (IC) is provided to a gm stage (12), whose gain is linearly proportional to this current. Thus, a linear change in the gain control current (IG) produces an exponential change in the gainof the gm stage (12). Accordingly, a linear-in dB variable gain amplifier is achieved.
Abstract:
A method for fabricating a micromechanical device (48) and a semiconductor circuit (70) on a substrate (10) includes the steps of forming the micromechanical device (48) on a device area (58) of the substrate (10), the micromechanical device (48) being embedded in a sacrificial material (22, 34, 42), selectively depositing a planarization layer (54) on the substrate (10) in a circuit area (56) thereof, forming the semiconductor circuit (70) on the planarization layer (54) in the circuit area (56) and removing the sacrificial material (22, 34, 42) from the embedded micromechanical device (48). In a preferred embodiment, the planarization layer is an epitaxial silicon layer (54). A protective cap (98) may be formed over the micromechanical device (48), so that it is completely encapsulated and is thereby protected against particulate contamination.
Abstract:
A method and apparatus for providing a conductive plane (40) beneath a suspended microstructure. A conductive region is diffused into a substrate. A dielectric layer is added, covering the substrate, and then removed from a portion of the conductive region. A spacer layer is deposited over the dielectric and exposed conductive region. A polysilicon layer is deposited over the spacer layer, and formed into the shape of the suspended microstructure. After removal of the spacer layer, the suspended microstructure is left free to move above an exposed conductive plane (40). The conductive plane is driven to the same potential as the microstructure.
Abstract:
A method for providing a conductive ground plane beneath a suspended microstructure. A conductive region is diffused into a substrate. Two dielectric layers are added: first a thermal silicon dioxide layer and then a silicon nitride layer. A first mask is used to etch a ring partially through the silicon nitride layer. Then, a second mask is used to etch a hole through both dielectric layers in a region having a perimeter that extends between the inner and outer edges of the ring. This leaves the conductive region exposed in an area surrounded by a ring that has the silicon dioxide layer and a narrow silicon nitride layer. The ring is surrounded by an area in which the silicon dioxide and silicon nitride layers have not been reduced. A spacer silicon dioxide layer is deposited over the dielectric and then a polysilicon layer is deposited and formed into the shape of a suspended microstructure. When the spacer layer is etched away, the silicon dioxide under the narrow silicon nitride layer is removed, along with the narrow silicon nitride layer, leaving an exposed ground plane surrounded by a dielectric with minimal undercutting.