Abstract: A system and method for achieving, while using a laser and optical fibers, high signal-to-noise ratio. In particular, the system splits an incoming main light signal into two orthogonal polarization states, which then propagate through an optical circuit before recombining. The use of appropriate path differences ensures that the system is immune from the conversion of mode partition noise to intensity noise arising from the interference between parasitic light waves which traveled through the system in undesired polarization states.

Abstract: A method is provided for equalizing an amplitude modulated compatible digital broadcasting signal which includes an amplitude modulated radio frequency signal having a first frequency spectrum, the amplitude modulated radio frequency signal having a first carrier modulated by an analog program signal, a plurality of digitally modulated carrier signals positioned within a bandwidth which encompasses the first frequency spectrum, a first group of the digitally modulated carrier signals including complementary signals and lying within the first frequency spectrum, and second and third groups of the digitally modulated carrier signals including non-complementary signals and lying outside of the first frequency spectrum.

Abstract: A system and method for transmitting digital information through a medium such as atmospheric free-space includes a transmitter which generates a signal based on a basis set of mutually orthogonal, spectrally-shaped, sequences of substantially equal length and having predetermined autocorrelation values. The sequences may resemble noise in at least some of their characteristics. The orthogonality or cross-correlation characteristics, the autocorrelation characteristics and the resemblance to noise are due to features derived from sequences of pseudo-random numbers which themselves resemble noise in at least some of their characteristics. The waveform set based on the sequences is modulated digitally. The modulated set may be summed together along with a wideband reference signal of reduced amplitude and optionally an FM analog signal to form a composite signal which is broadcast typically through free space to at least one receiver.

Abstract: A tunable delay line includes an input, an output, a first conductor electrically coupled to the input and the output, a ground conductor, and a voltage tunable dielectric layer positioned between the first conductor and the ground conductor. DC blocks and impedance matching sections are connected between the first conductor and the input and output. Additional layers of tunable dielectric material and additional conductors can be positioned in parallel with the voltage tunable layer.

Abstract: A method is provided for transmitting control information in a digital audio broadcasting system. The method comprises the steps of transmitting a plurality of control bits in each of a plurality of control frames, wherein a first sequence of the control bits represents a transmission mode, and a second sequence of the control bits represents a control data synchronization word. The plurality of control bits can further include a third sequence of bits representative of an interleaver synchronization word. A method performed in a radio receiver for determining transmission mode and synchronization for a digital audio broadcasting signal is also provided. The method comprises the steps of receiving a plurality of interleaver frames containing digital information, wherein each of the interleaver frames includes a plurality of control frames.

Abstract: A method for transmission of data in a digital audio broadcasting system includes the steps of providing a plurality of orthogonal frequency division multiplexed sub-carriers, with the sub-carriers including data sub-carriers and reference sub-carriers, and modulating the data sub-carriers with a digital signal representative of information to be transmitted. The reference sub-carriers are modulated with a sequence of timing bits, wherein the sequence of timing bits includes an unambiguous block synchronization word, and the number of bits comprising the block synchronization word is less than one half of the number of bits in said timing sequence. Then the orthogonal frequency division multiplexed sub-carriers are transmitted. Receivers that differentially detect the block synchronization word and use the block synchronization word to coherently detect the digital signal representative of information to be transmitted are also included.

Abstract: The system for recovering symbol timing offset and carrier frequency error from an orthogonal frequency division multiplexed (OFDM) signal includes a receiver circuit for receiving an OFDM modulated signal representing a series of OFDM symbols, and providing a received signal to an output thereof. A peak development circuit is included for developing a signal having a plurality of signal peaks representing symbol boundary positions for each received OFDM symbol, where each of the signal peaks is developed responsive to an amplitude and phase correspondence produced between the leading and trailing portions of each of the received OFDM symbols. The system includes a circuit for enhancing the signal peak detectability, which includes a circuit for additively superimposing and then filtering the signal peaks, to produce an enhanced signal peak having an improved signal-to-noise ratio.

Abstract: This invention provides a phased array antenna comprising an input, a feed network electronically coupled to the input, a plurality of radiating elements, a plurality of continuously voltage tunable phase shifters for receiving signals from the feed network and providing phase shifts for the signals prior to transmitting the signals to the radiating elements, and a controller for controlling the phase shift provided by the phase shifters. The phased array antennas can be configured to produce beams that can be scanned in one dimension (one-dimensional) or two dimensions (two-dimensional) by using continuously adjustable phase shifters that are based on low cost, low loss voltage-tunable dielectric materials.

Abstract: A voltage tunable dielectric varactor includes a substrate having a low dielectric constant and having generally planar surface, a tunable ferroelectric layer positioned on the generally planar surface of the substrate, and first and second electrodes positioned on a surface of the tunable ferroelectric layer opposite the generally planar surface of the substrate. The first and second electrodes are separated to form a gap therebetween. The varactor includes an input for receiving a radio frequency signal and an output for delivering the radio frequency signal. A bias voltage applied to the electrodes changes the capacitance of the varactor between the input and output thereof. Phase shifters and filters that include the varactor are also described.

Abstract: A method of estimating SNR for a plurality of carriers modulated with digital information, wherein the digital information includes data baud and training baud, comprising the steps of: receiving the plurality of carriers; determining a first SNR for the data baud; determining a second SNR for the training baud; comparing at least one of the first and second SNRs to predetermined selection criteria; and selecting one of the first and said second SNRs based on the comparison step. In the preferred embodiment, the carriers are processed to produce an equalizer output for each of the carriers, and the equalizer output is processed to produce a symbol decision for each of the carriers. The equalizer output is subtracted from the symbol decision when a data baud is received to produce a first difference value, and the first difference value is squared to produce a first signal to noise estimate.

Abstract: An optical data storage system 100 utilizes optical fibers 102 for transfer of information to and from storage media 107. The storage media 107 comprises magneto-optical storage disks. The optical fibers 102 are low-birefringence optical fibers. As compared to the prior art, a polarization state conveyed by the optical fiber 102 is accurately reproduced with reduced noise.

Abstract: An electronic filter includes a substrate, a ground conductor, an input, an output, a first microstrip line positioned on the substrate and electrically coupled to the input and the output, and a first tunable dielectric varactor electrically connected between the microstrip line and the ground conductor. The input preferably includes a second microstrip line positioned on the substrate and including a portion lying parallel to the first microstrip line. The output preferable includes a third microstrip line positioned on the substrate and including a portion lying parallel to the first microstrip line. The first microstrip line includes a first end and a second end, the first end being open circuited and the varactor being connected between the second end and the ground conductor. The filter further includes a bias voltage circuit including a high impedance line, a radial stub extending from the high impedance line, and a patch connected to the high impedance line for connection to a DC source.

Abstract: A method for digital audio broadcasting comprises the steps of providing a plurality of bits of digital information to be transmitted, interleaving the bits of digital information into a plurality of partitions, forward error correcting the bits of digital information using a combination of pragmatic trellis code modulation and complementary punctured code, and transmitting the bits of digital information. The partitions include a main partition, a backup partition, an upper partition, and a lower partition, wherein the upper partition and lower partition are non-overlapping. The main partition overlaps both of the upper and lower partitions and the backup partition overlaps both of the upper and lower partitions. The interleaved bits comprise a core interleaver and an enhancement interleaver.

Abstract: The present invention relates to electronically tunable dielectric materials which have favorable properties for many applications, including the area of radio frequency (RF) engineering and design. The electronically tunable materials include an electronically tunable dielectric phase such as barium strontium titanate in combination with a metal silicate phase such as Mg2SiO4. The electronically tunable materials may be provided in bulk, thin film and thick film forms for use in devices such as phased array antennas, tunable filters and the like.

Abstract: An enclosure for use in a cable management system includes an outer shell having a generally rectangular shape and defining an interior space. The outer shell includes a bottom wall and a sidewall, with the sidewall defining a sidewall opening for access to the interior space. The bottom wall includes a curved portion adjacent to a first edge. A tray positioned within the interior of the enclosure includes a curved portion positioned adjacent to a first edge of the tray. The first edge of the bottom wall and the first edge of the tray are positioned adjacent to each other such that the curved portion of the bottom wall and the curved portion of the tray together form a first radius control structure positioned adjacent to the sidewall opening.

Abstract: A system for combining AM and FM transmissions. In-band, on-channel, FM Digital Audio Broadcast (IBOC FM-DAB) allows simultaneous transmission of DAB and FM over existing FM allocations without interfering with conventional analog FM signals. The utility of existing FM spectrum allocations is therefore enhanced.

Abstract: A lithography method combines both high gap resolution and high processing speed. An electron beam sensitive resist is applied to a substrate, followed by a photoresist. The undesired portions of the photoresist are removed through photolithography. An electron beam flood exposure or oxygen ashing is used to remove those portions of the electron beam sensitive resist not protected by the photoresist. An optical flood is used to remove the remaining photoresist. Electron beam lithography is then used to define narrow gaps within the remaining electron beam sensitive resist.

Abstract: A method is provided for operating a duplexer including a first tunable bandpass filter, a second tunable bandpass filter and means for coupling the first bandpass filter and the second bandpass filter to an antenna. The method comprises the steps of tuning the first tunable bandpass filter to provide a passband corresponding to an assigned transmit frequency, and tuning the second tunable bandpass filter to provide a passband offset from an assigned receive frequency, when the duplexer is operated in a transmit mode. When the duplexer is operated in a receive mode, the first tunable bandpass filter is tuned to provide a passband offset from an assigned transmit frequency and the second tunable bandpass filter is tuned to provide a passband corresponding to the assigned receive frequency.

Abstract: A method for AM in-band-on-channel (IBOC) digital audio broadcasting (DAB) uses a center channel signal in a central frequency band of an AM radio channel, the center channel signal is modulated by first and second versions of the program material to be transmitted. Sub-carriers in a upper and lower sidebands of the AM radio channel are modulated with addition digitally encoded portions of the program material. The upper sideband lies within a frequency band extending from about +5 k Hz to about +10 kHz from a center frequency of the radio channel and the lower sideband lying within a frequency band extending from about −5 k Hz to about −10 kHz from the center frequency of the radio channel. The center channel signal the upper and lower sideband sub-carriers are transmitted to receivers.

Abstract: A method of demodulation and equalization is used to process an amplitude modulated compatible digital broadcasting signal including an amplitude modulated radio frequency signal having a first carrier modulated by an analog program signal in a first frequency spectrum, a plurality of digitally modulated carrier signals positioned within a bandwidth which encompasses the first frequency spectrum, a first group of the digitally modulated carrier signals including complementary carrier signals and lying within the first frequency spectrum, and second and third groups of the digitally modulated carrier signals including non-complementary carrier signals and lying outside of the first frequency spectrum.