摘要:
A single transmission optical fiber is used to transmit RF signals of the same frequency but different polarization from a source to a polarization diversity receiver without introducing interference between the signals. The incoming signal of one polarization modulates a first laser transmitter operating at one wavelength, and the incoming signal of the other polarization modulates a second laser transmitter operating at a different, second wavelength. The two modulated optical beams are combined in an optical coupler whose output is connected to the transmission fiber leading to the polarization diversity receiver. At the receiver, a wavelength division multiplexing coupler is used to separate out the two modulated optical carriers. The two RF signals used to modulate the laser transmitters are separately recovered via photodiode detectors to provide inputs to the polarization diversity receiver.
摘要:
An optical heterodyne system provides the radiation source and beam scan control of a millimeter wave (MMW) array antenna. The heterodyne system is an optical feed system to produce the MMW by mixing the optical outputs from two lasers, distribute the signal source to an array of radiating elements through a Rotman lens and optical fibers, generate the differential phase shift for beam scan in the optical domain, change the beam direction by switching the input laser being used to illuminate the Rotman lens or by varying the frequency of one of the laser sources. The feed system includes a plurality n-1 lasers spaced along the transmit side of the lens, and a center laser disposed on the center axis of the transmit side. A l:n switch receives a command input to determine which of the n-1 lasers will operate. The beat frequency between the center laser operating frequency and that of the n-1 lasers is the MMW frequency. N optical receive elements are spaced along the output side of the Rotman lens and are connected to a corresponding photodetector by equal length optical fibers. The output of each photodetector is amplified and fed to a corresponding radiating element. The system also operates in a corresponding receive mode.
摘要:
Optoelectronic switching apparatus employing optoelectronic switching devices interconnected by optical media having different delay lengths and an multiport optical coupler. The optoelectronic switching apparatus provides for a multibit true-time-delay beamsteerer for beamsteering phased array antennas. The present invention combines two types of optoelectronic devices, lasers and photodiode switches, using an interconnected passive optical network comprising the optical fibers and the optical coupler. The switches, and input and output signal networks coupled to the respective switches, are controlled using a control signal generator. Using this scheme, any input can be independently selected and a signal can be routed to any output. Furthermore, the product of the total number of different interconnect paths (N.times.M) is provided which provides a greater number of delay lengths than is provided by using only one type of switch (i.e. laser (N) or photodiode (M)) alone. The present invention also provides for improved insertion loss while increasing the number of delay paths.
摘要:
A low-profile multi-band antenna module includes first and second antennas that transmit first and second radio frequency (RF) signals in a first and second RF band, respectively. A first RF multiplexer combines the first and second RF signals for transmission. The first antenna, second antenna, and first RF multiplexer are arranged on a panel. A transmission line communicates with the first RF multiplexer and transmits the first and second RF signals. A second RF multiplexer communicates with the transmission line and separates the first and second RF signals. At least one of the antennas communicates with an amplifier. The transmission line supplies direct current (DC) power to the amplifier. The first and second antenna are arranged on the panel in an orientation that minimizes electrical interference between the first and second antenna. A combination of the first and second antenna minimizes interference between the first and second RF band.
摘要:
A bidirectional optical fiber (12) amplifier suitable for use in a dual payout fiber-optic communication link (10) is disclosed herein. The inventive amplifier (12) is typically encasted in a shell or service loop, and is preferably connected between first and second optical fiber segments (18 and 20). The amplifier (12) includes a pump laser (102) for generating optical energy of a first wavelength. A wavelength selective optical coupler (82), in optical communication with the first fiber segment (18) and the pump laser (102), combines optical energy propagating through the first fiber segment (18) with the optical output of the pump laser (102). The amplifier (12) of the present invention further includes a doped optical fiber (114), optically connected between the wavelength selective optical coupler (82) and the second optical fiber segment (20), for amplifying optical energy within a predetermined wavelength spectrum passing therethrough. The inventive amplifier (12) may be advantageously employed within certain fiber-optic communication links in order to enhance optical signal strength.
摘要:
Fine single crystals of low-melting point materials are prepared by slowly withdrawing a glass crystal growth capillary tube containing the material from a heating apparatus which precisely maintains the molten material at a temperature just above its melting point. Temperature control of the molten material in the crystal growth tube, prior to solidification, is attained by enclosing the crystal growth tube in a temperature control tube containing the molten material being solidified. Preferably, the inside diameter of the temperature control tube is slightly larger than the outside diameter of the crystal growth tube, and both tubes reach into a reservoir of the molten material to be grown as a crystal, so that the molten material is drawn upwardly into the crystal growth tube and the space between the crystal growth tube and the temperature control tube by capillary action.
摘要:
A method of integrating a thin antenna module into a vehicle is disclosed. The thin antenna module comprises a high impedance surface with at least one antenna element disposed thereon. The method includes the steps of inserting the thin antenna module between a conductive layer and a dielectric layer located above a passenger compartment of said vehicle, and connecting at least one antenna element disposed on the high impedance surface to a receiver in said vehicle.
摘要:
Mixing and modulating methods are described for nonlinear optical amplifiers (30) which can generate intermodulation products of radio-frequency signals in an optical carrier signal (26) without the penalty of an optical conversion loss and without the need for radio-frequency mixers, electro-optic modulators and expensive polarization-maintaining optical fibers. The radio-frequency signals can be applied to either a bias port (36) or an optical input port (32) of the optical amplifier and are used to upconvert and downconvert signals in phased-array antenna and remote antenna embodiments of the invention.
摘要:
An antenna system includes a set of symmetrically located center-fed and segmented dipole antennas embedded on top of a frequency selective photonic bandgap crystal. A two-dimensional array of microelectromechanical (MEM) transmission line switches is incorporated into the dipole antennas to connect the segments thereof. An MEM switch is located at the intersection between any two adjacent segments of the antenna arm. The segments can be connected (disconnected) by operating the switch in the closed (open) position. Appropriate manipulation or programming of the MEM switches will change the radiation pattern, scanning properties and resonance frequency of the antenna array. In addition, an MEM switch is inserted into the crystal to occupy a lattice site in the 3-dimensional crystal lattice. The crystal will have a broadband stopgap if the MEM switch operates in the closed position (perfect symmetry of the crystal), and will produce a narrowband absorption line inside the stopgap if the MEM switch is in the open position, thereby permitting change in real time of the frequency response of the crystal.
摘要:
An apparatus and method for frequency translation of true time delay signals in a phased array radar system is provided. A local oscillator signal is true time delayed or modulo 2.pi. phase shifted and then mixed with a true time delay beamsteering signal from a true time delay circuit to produce a frequency translated transmit signal which is supplied to an antenna element. A receive signal received by an antenna element is mixed with a true time delayed or modulo 2.pi. phase shifted local oscillator signal to provide a frequency translated receive signal. The frequency translated receive signal can then be passed through a true time delay circuit and other subsequent processing circuitry. The frequency translation permits higher frequency transmit and receive signals to be used with lower frequency true time delay devices.