Abstract: The present invention provides a system and method of use for recovering data from an area. The data are gathered with at least one sensor converting the data to a digital packet. The packet is processed as encoded data and the encoded data is stored as a data frame. A reader transmits a signal to a plurality of the sensors and replicates the signal. Each sensor produces a reflected signal in response to the transmit signal and assigns a modulation frequency to the reflected signal. The reader receives the reflected signal. The reader separates frequency components of the reflected signal into upper and lower sidebands and separates the sidebands into data channels. The reader outputs the encoded data by processing the data channels. The reader decodes the encoded data to retrieve the data packet and the environmental data.

Abstract: An electromagnetic radiation interface is provided that is suitable for use with radio wave frequencies. A surface is provided with a plurality of electrically conductive bristles. A corresponding plurality of termination sections are provided so that each bristle is terminated with a termination section. The termination section may comprise one or more different termination packages for operating on received electromagnetic radiation and/or producing desired reflections and transmissions. In one embodiment, switches and termination packages may be implemented within integrated circuits wherein the switches may be utilized to switch between different termination packages. The termination packages may include selected fixed reactances and/or modulators designed to produce desired reflections, e.g., Doppler effects to make it appear the surface of the interface is moving a speed different than the actual speed.

Abstract: A plurality of remotely readable sensor apparatus and reader systems for collecting data frames from all apparatus within the reader field of view. Each sensor apparatus converts one or more environmental observable into information signals, converts the information signals into digital data and appends other discriminating digital data as desired to form a digital data frame. The state of a diode, connected to an antenna with the digital data frame, is modulated and a timing apparatus controls the digital-data-frame start times. The modulated states of the diode connected to a sensor-apparatus antenna are chosen so the angle of the antenna reflection coefficient is modulated between two values separated by approximately 180 degrees, so a carrier signal received by the antenna effects a bi-phase modulated signal containing the digital data frame that is reflected by the sensor-apparatus antenna toward the reader receiver antenna.

Abstract: A waterway shield system comprises a plurality of autonomous underwater nodes wherein each underwater node comprises acoustic detectors which may comprise horizontal and/or vertical acoustic arrays which may be directly mounted thereto or extend outwardly therefrom. Each underwater node comprises an acoustic modem for transmitting high resolution acoustic data to a gateway node that provides a connection to a surface system and a network of other underwater nodes in other waterways. The data from the underwater nodes may be utilized to produce acoustic attribute data for hulls of ships in the waterways. An acoustic database is provided that compiles the predetermined acoustic attribute data for a variety of ships and other entities thereby providing previously stored identifying means. The acoustic database is utilized in conjunction with one or more databases of other physical attributes of ships or other objects to thereby provide an automated identification process.

Abstract: A system and method are provided to measure relatively short distances between one or more moveable objects and with respect to an environment. The transponders may be affixed to other moveable objects and/or may be affixed in position within the environment. The transponders detect the query signal and respond with an acoustic response signal. A synchronized clock system establishes common timing between the transponders and the moveable objects such that the start time at which the acoustic response signal is sent is known. The moveable object detects a receipt time when the acoustic response signal is received. Knowing the start time and the receipt time, a transit time for the acoustic signal can be determined whereby a separation vector may be calculated. The system may be used to determine and transmit a table that contains the relative positions of all moveable objects in the environment.

Abstract: A system and method are provided to measure relatively short distances between one or more moveable objects and with respect to an environment. The transponders may be affixed to other moveable objects and/or may be affixed in position within the environment. The transponders detect the query signal and respond with an acoustic response signal. A synchronized clock system establishes common timing between the transponders and the moveable objects such that the start time at which the acoustic response signal is sent is known. The moveable object detects a receipt time when the acoustic response signal is received. Knowing the start time and the receipt time, a transit time for the acoustic signal can be determined whereby a separation vector may be calculated. The system may be used to determine and transmit a table that contains the relative positions of all moveable objects in the environment.

Abstract: An antenna apparatus (and corresponding innate method) comprises an array of antenna elements each having a phase center. An “observable signal” that contains a low-frequency component and a high-frequency component is generated. The high-frequency component is summed with the signal received by each antenna element near its phase center, forming a plurality of sum signals. These are fed into a signal processing arrangement that processes these signals with the low frequency component of the observable signal, including analog to digital conversion to (i) remove the high frequency component of the observable signal, (ii) normalize the effects of the signal transfer characteristics on the digital sum signals, (iii) synchronously re-sample the digital sum signals, and (iv) differentially time-reference each digital sum signal to the phase center of the corresponding antenna element. The thusly, processed digital signals are combined into a single composite signal.

Abstract: A communication system having a communication network, such network having a plurality of communication paths interconnected at various nodes of the network. A plurality of subscriber units is adapted to exchange information through the network. A computer is provided having a processor and a memory, such memory being adapted to store programs to enable the processor to control the information exchange among the plurality of subscriber units. The memory stores an operating system and at least one applications program, the operating system being adapted to manage interfacing between the application program and the system. One of the application programs enables the processor to convert a modulation format of one of the subscriber units into another information transmission protocol of the network.

Abstract: A circularly polarized microwave radio antenna which is constructed so that its phase center can be very easily and very accurately positioned with respect to a marker point over which the antenna is placed is disclosed. The antenna includes a ground plane, antenna elements in a common plane parallel thereto and supported by a perpendicular center post, separate feed lines for each element and a combining network all positioned symmetrically about an axial bore in the center post so that the phase center of the antenna is on the axis of the center post at the intersection with the upper surface of the ground plane. A graduated rod may be positioned in the bore to align the antenna with the marker point.

Abstract: A method and apparatus for monitoring the resonant frequency and absorption level at resonance of an absorption type resonant cavity which involves providing a voltage controlled oscillator, applying to the control input of the voltage controlled oscillator a control signal having a main component V.sub.m and a dither component V.sub.d, splitting the output signal from the voltage controlled oscillator into a portion directed along a test path and a portion directed along a reference path, the reference path including an attenuator controlled by a voltage signal V.sub.k, directing the signal in the test path through the resonant cavity, splitting the signal emerging from the resonant cavity into a portion directed along a frequency detection path and a portion directed along a level detecting path, using the signal directed along the frequency detection path for generating a signal for changing the amplitude of V.sub.

Abstract: A practice for moisture measurement wherein a transmission means is utilized in conjunction with a circuit means connected in shunt with the transmission means and adapted to receive a material to be tested such that the driving point impedance of the circuit means is dependent upon the moisture content of the material.

Abstract: A circuit for mixing first and second rf signals to produce an output signal containing a beat frequency comprises a pair of switches each of which has a four diode bridge controlled by the first rf signal. The first rf signal is coupled to a balanced current divider with common mode signal rejection. Load resistors coupled to the bridges provide matched termination of the first rf signal irrespective of the conductive state of the bridges. The value of the resistors and the characteristic impedance of the drive circuit is related to the characteristics of the diodes utilized to maximize the dynamic range of the mixer. Circuitry is provided for coupling all diodes of each bridge in series with respect to the average dc component of the first rf signal and to properly terminate the average dc component. The two diode bridges are conductive and non-conductive in opposing half cycles of the first rf signal.

Abstract: A circuit for mixing first and second rf signals to produce an output signal containing a beat frequency comprises a pair of switches each of which has a four diode bridge controlled by the first rf signal. The first rf signal is coupled to a balanced current divider with common mode signal rejection. Load resistors coupled to the bridges provide matched termination of the first rf signal irrespective of the conductive state of the bridges. The value of the resistors and the characteristic impedance of the drive circuit is related to the characteristics of the diodes utilized to maximize the dynamic range of the mixer. Circuitry is provided for coupling all diodes of each bridge in series with respect to the average dc component of the first rf signal and to properly terminate the average dc component. The two diode bridges are conductive and nonconductive in opposing half cycles of the first rf signal.