Abstract: A low power and high efficiency voltage-to-current (V/I) converter designed with few parts and having improved power supply rejection. The V/I converter may include an op-amp, a MOSFET, and a first and second voltage dividers. The first voltage divider circuit may include a first, second, third, and fourth resistors. A source terminal of the MOSFET may be connected to a junction of the third and fourth resistors and the fourth resistor may be connected to a positive supply rail. Also, an inverting input terminal of the op-amp may be coupled to a junction of the second and third resistors. Additionally, the second resistor may be coupled to the first resistor, which may be connected to an input terminal of the V/I converter. The V/I converter typically has very good DC rejection of the power supply because the first and second voltage dividers are designed to have the same ratios.

Abstract: A protection and voltage monitoring circuit that may provide the functionality of a diode without the typical large voltage drop and power dissipation. The protection and voltage monitoring circuit may include a first MOSFET, a second MOSFET, a first resistor, an input terminal, an output terminal, a diode, a BJT current source, and a voltage monitoring circuit. The BJT current source may limit a gate-to-source voltage of the two MOSFETs to a predetermined voltage that is less than a maximum allowed voltage by controlling a current flow through the first resistor to prevent damage to the MOSFETs. The voltage monitoring circuit may determine whether an external voltage is within an allowable range of voltages. If the external voltage is outside the predetermined voltage range, the voltage monitoring circuit turns off the BJT current source to block the external voltage from the output terminal of the protection and voltage monitoring circuit.

Abstract: A transportable powered wheelchair is provided which employs a variety of detachable modules to facilitate transport and storage. Further, the powered wheelchair may be readily disassembled/reassembled without the need for or use of tools. The powered wheelchair includes a power supply unit, a pair of primary drive wheels, a drive train subassembly rotatably mounting and independently driving one of the drive wheels. The powered wheelchair is further characterized by first and second main frame subassemblies each mounting one of the drive train subassemblies and detachably mounting the power supply unit therebetween. At least one cross member connects the main frame subassemblies and includes a detachable mount disposed intermediate the main frame subassemblies. The first and second main frame subassemblies and cross member, in combination, define a base or main frame assembly. Further, a seat is detachably mounted to the main frame assembly.

Abstract: An e-mail system that re-packages message attachments optimized for delivery to wireless handheld devices is described. The preferred embodiment provides an optimization of the e-mail deliveries to allow for the recipients to receive e-mail attachments at a time and in a size/format as desired. The preferred embodiment compares the size of attached images to the capabilities of the type of the recipient client device, and preempts delivery of the original format of those attachments if they are determined to be burdensome or overwhelming. In cases wherein these attachments would strain the capabilities of the recipient devices' wireless bandwidth and/or display features, the original attachments are removed from the messages and do not accompany the e-mail delivery. Any detached attachment is saved in a network media-sharing repository, and can be subsequently accessed via a link (e.g., URL) referencing that storage address.

Abstract: A system and method for reducing linearity errors in a delta-sigma converter. The linearity errors in the delta-sigma converter are modeled by generating a set of digital signals representative of an inputted sine wave. The set of digital signals are low-pass filtered and subjected to a fast Fourier transform algorithm to generate a frequency domain representation of the sine wave. Thereafter, a net linearity error spectrum is removed from the frequency domain representation and inverse Fourier transform back into the time domain. The filtered set of digital signals are also sorted into subsets of digital signals where each signal in a subset corresponds to a particular output of a delta-sigma modulator contained within the delta-sigma converter. A fast Fourier transform algorithm is applied to each of the filtered subsets of digital signals to generate a frequency domain representation thereof.

Abstract: A weather monitoring device includes a wind force receiving body supported by a support member and a wind velocity and direction measuring arrangement. The wind velocity and direction measuring arrangement, preferably includes strain gauges mounted upon the support member and measures the magnitude and direction of flex in the support caused by wind acting upon the wind receiving body. Wind direction and velocity are calculated from the flex measured in the support. The velocity and direction measuring arrangement also includes features to compensate for strain gauge offsets and temperature drift. Additionally, a rain monitoring arrangement may be included in the weather monitoring device to provide rain measurements in addition to the wind measurements. The rain monitoring arrangement includes a rain collection surface and a rain volume measuring device. The rain collection surface is completely contained within the wind force receiving body and directs water to the rain volume measuring device.

Abstract: A circuit for selecting an input to a signal processing network from among several switchable antenna units. Each antenna unit includes a winding which is connected to a common signal bus. The switchable antenna units may be placed in "on" or "off" states in response to a controller, such as a microprocessor. One terminal of each winding is connected to a transistor which causes the terminal to be in an open condition when the unit is unselected, attenuating any signal which might otherwise be transmitted to the signal bus. A second winding is inductively coupled to the first winding and is used to improve attenuation of unselected signals.