The present invention is generally directed to a system for monitoring a variety of environmental and/or other conditions within a defined remotely located region. In one aspect, a system is configured to monitor utility meters (613) in a defined area. The system is implemented by using a plurality of wireless transmitters (614), each integrated into a sensor (612) adapted to monitor a particular data input. The system also includes a plurality of transceivers (221) that are dispersed throughout the region at defined locations. The system uses a local gateway (210) to translate and transfer information from the transmitters to a dedicated computer (260) on a network (230). The dedicated computer collects, compiles and stores the data for retrieval upon client demand across the network. The computer further includes means for evaluating the received information and identifying an appropriate control signal to be applied at a designated actuator.

System and method for monitoring and controlling remote devices

This article reviews the history, the present status and possible future developments of HgCdTe ternary alloy for infrared (IR) detector applications. HgCdTe IR detectors have been intensively developed since the first synthesis of this material in 1958. This article summarizes the fundamental properties of this versatile narrow gap semiconductor, and relates the material properties to its successful applications as an IR photoconductive and photovoltaic detector material. An emphasis is put on key developments in the crystal growth and their influence on device evolution. Competitive technologies to HgCdTe ternary alloy are also presented. Recent advances of backside illuminated HgCdTe heterojunction photodiodes have enabled a third generation of multispectral instruments for remote sensing applications and have led to the practicality of multiband IR focal plane array technology. Finally, evaluation of HgCdTe for room temperature long wavelength IR applications is presented. (Some figures in this article are in colour only in the electronic version)

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HgCdTe infrared detector material: history, status and outlook

A wireless network, which includes a wireless router client operable to broadcast data packets to at least one wireless server and one additional wireless client. Each client and server includes programs for determining optimum routes between them. The client also includes a program for determining if a received data packet is not addressed to it and if the packet has been sent via a new optimal route unknown to the client, and for notifying the respective server of such a new optimal route.

Wireless network system and method for providing same

Several research groups have been actively pursuing antimonide-based electronic devices in recent years. The advantage of narrow-bandgap Sb-based devices over conventional GaAs- or InP-based devices is the attainment of high-frequency operation with much lower power consumption. This paper will review the progress on three antimonide-based electronic devices: high electron mobility transistors (HEMTs), resonant tunneling diodes (RTDs), and heterojunction bipolar transistors (HBTs). Progress on the HEMT includes the demonstration of Ka- and W-band low-noise amplifier circuits that operate at less than one-third the power of similar InP-based circuits. The RTDs exhibit excellent figures of merit but, like their InP- and GaAs-based counterparts, are waiting for a viable commercial application. Several approaches are being investigated for HBTs, with circuits reported using InAs and InGaAs bases.

Antimonide-based compound semiconductors for electronic devices: A review

An emergency message system provides a system and method for generating and transmitting emergency messages. In one embodiment, the emergency message system employs a transceiver network with a plurality transceivers coupled to monitoring devices residing at a plurality of customer premises. Control room operators receive an emergency message from an identifiable transceiver. The transceiver, identified by an identification code, indicates a location and the nature of the emergency condition so that the control operators may request appropriate emergency assistance.

System and method for transmitting an emergency message over an integrated wireless network

InSb enhancement‐mode, metal‐insulator‐semiconductor, field‐effect transistors with 1 μm gate lengths have been fabricated. When operated at room temperature with less than 0.5 V applied between the source and drain, the transistors have a static dynamic range in excess of 20 dB, a cut‐off frequency (fT) of 14 GHz and a transconductance, at 1 GHz, of 230 mS mm−1. Analysis of the parasitic capacitances indicates an intrinsic fT of about 90 GHz. The static electron mobility in the channel is 2×104 cm2 V−1 s−1, so a carrier velocity of about 3.7×107 cm s−1 should be attained. This leads to a predicted frequency response of 84 GHz, in reasonable agreement with the intrinsic microwave data.

Uncooled high‐speed InSb field‐effect transistors

We have analyzed the various noise processes occurring in photon infrared detectors operating at room temperature and show that background-limited performance for photon detectors is potentially achievable at room temperature over the 3–13 μm band even in restricted fields of view. We discuss practical embodiments in which this might be realized and give quantitative estimates of the material properties required to achieve this performance. A critical feature to achieve the highest performance is that devices within an array should not be radiatively coupled to each other.

Towards background-limited, room-temperature, infrared photon detectors in the 3–13 μm wavelength range

Using heterostructures of InSb/In1−xAlxSb, grown by molecular beam epitaxy, diodes have been fabricated which emit at room temperature with a peak wavelength in the range 55–58 μm and an internal efficiency of 02%

Uncooled InSb/In1−xAlxSb mid‐infrared emitter

InSb and related narrow‐gap alloys have many potential applications in addition to the conventional one of infrared detection, provided that ambient temperature operation can be achieved We report experimental results on multilayer InSb/In1−xAlxSb structures utilizing minority‐carrier exclusion and extraction At room temperature, diodes have R0A values several orders higher than homostructure InSb devices Negative differential resistance associated with Auger suppression is observed under reverse bias Enhancement‐mode metal‐insulator‐semiconductor field‐effect transistors have near classical output characteristics at 294 K, with a typical transconductance of 34 mS/mm and dynamic range of 23 dB

Ambient temperature diodes and field‐effect transistors in InSb/In1−xAlxSb

Long wavelength diodes in CdxHg1−xTe show large deviations from ideality in their reverse characteristics The excess currents are attributed in many published papers on band to band tunneling at high reverse bias and to trap assisted tunneling at low reverse bias Measurements of photocurrent multiplication, current–voltage characteristics, and noise have been made on long wavelength loophole diodes to determine the breakdown mechanism This has produced strong evidence that the reverse characteristics of good quality diodes of this type are limited by impact ionization At higher biases, there is evidence of an additional breakdown mechanism, probably tunneling

C. T. Elliott

Papers

Uncooled high‐speed InSb field‐effect transistors

Towards background-limited, room-temperature, infrared photon detectors in the 3–13 μm wavelength range

Uncooled InSb/In1−xAlxSb mid‐infrared emitter

Ambient temperature diodes and field‐effect transistors in InSb/In1−xAlxSb

Reverse breakdown in long wavelength lateral collection CdxHg1−xTe diodes