Abstract: Microwave radiometers (MRs) and methods for detecting microwave emissions using an electro-optical receiver that incorporates a photonic integrated circuit are provided. The electro-optical receiver includes an electro-optic modulator that modulates received radio frequency signals onto an optical carrier signal supplied by a pump laser. The resulting upconverted signal, containing the full spectrum of the radio frequency signals, is divided into channels by an optical filter. Each of the channels is connected to a corresponding photodetector, which produces an electrical output having an amplitude that is proportional to the amplitude of the received optical signal. The components included in the photonic integrated circuit can be formed on a single substrate. In addition, the optical filter can filter the received full spectrum optical signal into a large number of channels (e.g. greater than 50).

Abstract: A stability monitoring system is described that provides an accurate, automated, and remote way of monitoring small movements over a large surface area without the need to pre-place reflective targets using a mobile SAR. The stability monitoring system allows the rapid, automated identification and measurement of small surface movements over a wide field of view from a safe standoff distance without the need for personnel working in hazardous zones. Using this data, authorities can more accurately identify hazard areas and efficiently allocate mitigation resources.

Abstract: An XDSL signal distribution system is provided having a regenerator unit located a predetermined distance from a central office XTU unit for extending the distribution reach of the system. The regenerator is arranged to decode the payload of transmitted XDSL signals into base digital data before repackaging and regeneration onto a twisted pair copper cable. This allows the regenerator to selectively reformat the XDSL signals into a desired protocol format suitable for either an ATM protocol layer, or direct transmission. In addition, the regenerator can retransmit the XDSL signals at a fixed or variable transmission rate to optimize data through-put or system reach.

Abstract: A stability monitoring system is described that provides an accurate, automated, and remote way of monitoring small movements over a large surface area without the need to pre-place reflective targets using a mobile SAR. The stability monitoring system allows the rapid, automated identification and measurement of small surface movements over a wide field of view from a safe standoff distance without the need for personnel working in hazardous zones. Using this data, authorities can more accurately identify hazard areas and efficiently allocate mitigation resources.

Abstract: Subscriber loop systems often contain bridged taps which may interfere with the transmission of DSL signals. The bridged tap creates at least one local minimum at a notch frequency in the frequency response of the subscriber loop within the frequency range of the DSL signals. Effects of the bridged tap on a subscriber loop are reduced by terminating the bridged tap with a bridged tap canceller. The bridged tap canceller has at least one filter element for each local minimum created by the bridged tap. Each filter element provides substantially complete reflection of DSL signals at the corresponding notch frequency.

Abstract: Subscriber loops often contain bridged taps which may interfere with the transmission of DSL signals. A bridged tap terminator provides high tap impedance for POTS signals, low insertion loss for DSL signals, and impedance matching for DSL signals when connected to the bridged tap.

Abstract: A test procedure for a VDSL distribution loop utilizes loop pre-qualification based on information stored in a network database in combination with field tests that are performed to confirm minimum performance capabilities of pre-qualified loops. During qualification, a VDSL test signal is sent on the loop, and SNR and bit error ratios are measured for desired upstream and downstream transmission rates. These measurements are compared to threshold values to verify performance of the loop for VDSL use. Thus, a cost effective test process is provided which allows accurate test data collection for sensitive VDSL distribution loops without the need for any pre-provisioning of the loop, and to allow for validation of the loop configuration database.

Abstract: An efficient, lightweight, broadband antenna, having high quality circular polarization capabilities, is disclosed for use in a variety of applications. In one embodiment, signals are fed to, or received by, an array of electromagnetically coupled patch pairs arranged in sequential rotation by an interconnect network which is coplanar with the coupling patches of the patch pairs. The interconnect network includes phase transmission line means, the lengths of which are preselected to provide the desired phase shifting among the coupling patches. The complexity of the array and the space required are thus reduced. In one described embodiment, two such arrays are employed, each having four patch pairs. The two arrays are arranged in sequential rotation to provide normalization of the circularly polarized transmitted or received beam. In another embodiment, a lightweight material having a dielectric constant less than about 1.

Abstract: A microstrip patch antenna structure is disclosed having increased bandwidth and reduced coupling while maintaining low profile capabilities. The structure includes a support member having an isolating recess in which an electromagnetically coupled patch pair of antenna elements is positioned, the upper element being substantially flush with the surface of the support member surrounding the recess. To enhance isolation of the elements, the recess walls and the support surface are preferably electrically conductive and connected to ground. Also preferably, the lower element is connected to a microstrip transmission line, coplanar with the lower element and suspended within an isolating channel through the support member. In one aspect of the invention, a transition means is interposed between the transmission line and a connector, which connects the support member to a transmitter/receiver, to permit relative rotation therebetween.

Abstract: The subject invention provides an improved conformal antenna array assembly having a strip conductor, a ground plane separated from and lying parallel to said strip conductor, said ground plane having a slot therein, said slot extending transverse to said strip conductor, a conductive planar element positioned across said slot and orthogonal to said ground plane, said conductive planar element having curved surfaces extending upwardly and outwardly from said slot. The strip conductor or microstrip and the slot-containing ground plane are separated by a dielectric material.

Abstract: A three resonator capacitively coupled microstrip antenna structure includes an inverted stacked array of elements with a lowermost driven element directly connected to a transmission line connector, and passive elements stacked above the driven element and separated from the driven element and from one another by dielectric layers. The dimensions, spacings and quality factors of the elements are chosen so that at least one, and possibly two elements are resonant at any given frequency within a desired frequency operating range. The resulting antenna structure offers very broad bandwidth at relatively low VSWR in a compact, rugged package. The manner in which parameters of the stacked antenna structure are specified to achieve desired VSWR bandwidth and radiation efficiency is also described.