A control circuit is disclosed for controlling operation of a radio frequency (RF) transistor. The control circuit has a first sub-circuit that accepts a reference voltage and a reference current. The control circuit has a second sub-circuit with a plurality of stacked transistors coupled between the first sub-circuit and ground, and a resistor ladder coupled between the first sub-circuit and an output port of the control circuit. The first sub-circuit provides the reference current to flow through the stacked transistors, and sets a total voltage drop across the stacked transistors equal to the reference voltage. The first sub-circuit also sets a total voltage drop across the resistor ladder equal to the reference voltage. Each rung of the resistor ladder is coupled to control an operating voltage of a stacked transistor, to cause each stacked transistor to operate with similar control conditions.

An apparatus includes a bypass circuit a resistor circuit and multiple staggered circuits. The bypass circuit may have a predetermined number of a plurality of transistors connected in series between an input node and an output node. The resistor circuit may have a given number of resistors connected in series between the input node and the output node. Adjoining pairs of the resistors may be connected at given nodes. The staggered circuits may be connected between the given nodes and either the input node or the output node. Each staggered circuit may have a respective number of the transistors connected in series. The bypass circuit, the resistor circuit and the staggered circuits may form part of a bridge attenuator.

In one aspect, a device includes a processor, an infrared (IR) detector accessible to the processor and that receives signals from a primary IR emitter on a hand-held device and a secondary IR emitter on the hand-held device, a projector accessible to the processor, a transceiver accessible to the processor, and storage accessible to the processor. The storage bears instructions executable by the processor to use a location of the secondary IR emitter as sensed by the IR detector and orientation data of the hand-held device received from the transceiver to extrapolate a handwriting projection reference. The instructions are also executable to use the handwriting projection reference to project handwriting onto a projected whiteboard.

Circuits and methods for eliminating or mitigating the amount of temperature-dependent variation in the relative attenuation of a multi-valued digital step attenuator (DSA) by using resistive components having temperature-dependent resistance values that compensate for or offset changes in the temperature-dependent ON resistance (R.sub.ON) of the switches within the DSA. In some embodiments, DSA attenuator cell switches are fabricated to have positive first-order resistance temperature (FORT) coefficients, while temperature-compensating series attenuation resistances are fabricated as a positive FORT coefficient resistor and temperature-compensating shunt resistances are fabricated as either a negative FORT coefficient resistor or a combination of a negative FORT coefficient resistor in parallel with a positive FORT coefficient resistor.

An attenuator having an impedance that is controllable by a first setpoint signal is coupled to a transmission line. A matching circuit having an impedance that is controllable by a second setpoint signal is also coupled to the transmission line. A transformer circuit block also coupled to the transmission line has a complex impedance. A control circuit sets the first and second setpoint signals so as to control a conjugate impedance relationship between the variable impedances presented by the attenuator and matching circuit relative to the complex impedance of the transformer circuit.

A programmable voltage variable attenuator (VVA) that enables selection among multiple analog, continuous attenuation ranges. Some embodiments include a dual-mode interface to enable digitally programming a DAC and provide the analog output to control the attenuation level of the VVA, or alternatively apply an externally provided analog voltage to directly control the VVA attenuation level. A VVA may be used in conjunction with a digital step attenuator (DSA). Some embodiments include circuitry for changing the VVA reference impedance. The attenuator architecture of the VVA includes one or more variable resistance shunt elements and/or series elements which may be a resistor and FET circuit controlled by a provided variable analog voltage. The multiple resistance element architecture may be implemented with stacked FET devices. Embodiments for the VVA may be based, for example, on T-type, Bridged-T type, Pi-type, L-pad type, reflection type, or balanced coupler type attenuators.

Digital step attenuator (DSA) and digital phase shifter (DPS) multi-stage circuit architectures that provide for high resolution. Embodiments use a dithering approach to weight bit positions to provide a much finer resolution than the lowest-valued individual stage. Bit position weights for stages are determined so as to enable selection of combinations of n bit positions that provide a desired total attenuation or phase shift range while allowing utilization of the large number of states (2.sup.n) available to produce fractional intermediate steps of attenuation or phase shift. The fractional intermediate steps have a resolution finer than the lowest-valued stage. Bit position weights may be determined using a weighting function, including weightings determined from a linear series, a geometric series, a harmonic series, or alternating variants of such series. In some embodiments, at least one bit position has a fixed value that is not determined by the bit position weighting function.

Attenuation circuitry for a wireless receiver system receives and attenuates an input signal. The attenuation circuitry includes an input pin, coil circuitry, capacitor network circuitry, and inverter circuitry. The input pin receives the input signal. The coil circuitry is electrically connected to the input pin, receives the input signal from the input pin, and outputs an adjusted signal from the input signal. The capacitor network circuitry is electrically connected to the coil circuitry. The capacitor network circuitry receives the adjusted signal from the coil circuitry, and outputs an attenuated signal from the adjusted signal. The inverter circuitry is electrically connected to the capacitor network circuitry. The inverter circuitry receives the attenuated signal and generates an output signal from the attenuated signal. The output signal is output from the attenuation circuitry via an output inductor.

A computing cable comprising a trace having a first impedance and an attenuator that includes a fixed resistor having a second resistance, a variable resistor having a first resistance, and a conductor having a second impedance. The combination of the first resistance, the second resistance, and the second impedance is based on the first impedance, wherein the first resistance is varied dynamically at runtime based on a control input.

Systems, methods, and devices are provided to efficiently share an antenna between multiple communication systems and allow for the communication systems to be simultaneously connected to the antenna with less attenuation and/or no fluctuation in signal strength. Communication circuitry may include an antenna that transmits and receives electromagnetic radiation. The communication circuitry may also include an antenna port that provides primary access to the antenna with a first attenuation via an antenna port input. Additionally, the communication circuitry may include a coupler attached to the antenna port. The coupler may provide secondary access to the antenna with a second attenuation.