942 results about "Stopband" patented technology

A waveguide bandpass filter for use in microwave and millimeter-wave satellite communications equipment is presented. The filter is based on a substrate integrated waveguide (SIW) having several cascaded oversized SIW cavities. The filter is implemented in a printed circuit board (PCB) or a ceramic substrate using arrays of standard metalized via holes to define the perimeters of the SIW cavities. Transmission lines of a microstrip line, a stripline or coplanar waveguide are used as input and output feeds. The transmission lines have coupling slots for improved stopband performance. The filter can be easily integrated with planar circuits for microwave and millimeter wave applications.

A light emitting device comprises a novel low-loss array of conductive vias embedded in a dielectric multilayer stack, to act as an electrically-conductive, low-loss, high-reflectivity reflector layer (CVMR). In one example the CVMR stack is employed between a reflective metal bottom contact and a p-GaN semiconductor flip chip layer. The CVMR stack comprises at least (3) layers with at least (2) differing dielectric constants. The conductive vias are arranged such that localised and propagating surface plasmons associated with the structure reside within the electromagnetic stopband of the CVMR stack, which in turn inhibits trapped LED modes coupling into these plasmonic modes, thereby increasing the overall reflectivity of the CVM R. This technique improves optical light extraction and provides a vertical conduction path for optimal current spreading in a semiconductor light emitting device. A light emitting module and method of manufacture are also described.

To solve the existing problems in distributed Bragg reflectors (DBR) used in the prior art, the present invention provides a fabrication method of group III nitride based distributed Bragg reflectors (DBR) for vertical cavity surface emitting lasers (VCSELs), which suppresses the generation of cracks, and a distributed Bragg reflector with high reflectivity, broad stopband, and adaptability to optical devices such as vertical cavity surface emitting lasers, micro-cavity light emitting diodes, resonance cavity light emitting diodes and photodetectors.

Electromagnetic Bandgap (EBG) structures are embedded between adjacent power planes in a multi-layer PCB to decrease the emanation of Electromagnetic radiation induced by power buses, signal layers, as well as to suppress the switching noise. EBG stages with different stop bands are cascaded to create rejection over a wider frequency region. The cascading can be performed in series, or may be formed in a variety of arrangements such as a checkerboard design or concentric ribbons positioned along the perimeter of the PCB. Each EBG stage is composed of conductive patches and via posts extending from each patch, which are positioned at a predetermined distance from each other. By surrounding the source of the noise with EBG stages, a sufficient suppression of electromagnetic noise over specific frequency bands of interest is achieved.

A device contains at least one wavelength-tunable multilayer interference reflector controlled by an applied voltage and at least one cavity. The stopband edge wavelength of the wavelength-tunable multilayer interference reflector is preferably electrooptically tuned using the quantum confined Stark effect in the vicinity of the cavity mode (or a composite cavity mode), resulting in a modulated transmittance of the multilayer interference reflector. A light-emitting medium is preferably introduced in the cavity or in one of the cavities permitting the optoelectronic device to work as an intensity-modulated light-emitting diode or diode laser by applying an injection current. The device preferably contains at least three electric contacts to apply forward or reverse bias and may operate as a vertical cavity surface emitting light-emitter or modulator or as an edge-emitting light emitter or modulator. Using a multilayer interference reflector containing tunable section allows also obtaining a wavelength-tunable laser or a wavelength-tunable resonant cavity photodetector in the case where the optical field profile in the active cavity or cavities is affected by the stopband wavelength shift. Adding additional modulator sections enables applications in semiconductor optical amplifiers, frequency converters or lock-in optical amplifiers.

An absorptive bandstop filter includes at least two frequency-dependent networks, one of which constitutes a bandpass filter, that form at least two forward signal paths between an input port and an output port and whose transmission magnitude and phase characteristics are selected to provide a relative stopband bandwidth that is substantially independent of the maximum attenuation within the stopband and/or in which the maximum attenuation within the stopband is substantially independent of the unloaded quality factor of the resonators. The constituent network characteristics can also be selected to provide low reflection in the stopband as well as in the passband. The absorptive bandstop filter can be electrically tunable and can substantially maintain its attenuation characteristics over a broad frequency tuning range.

A method of constructing a band-stop filter comprises designing a band-stop filter including a signal transmission path, resonant elements disposed along the signal transmission path, and non-resonant elements coupling the resonant elements together to form a stopband having transmission zeroes corresponding to respective frequencies of the resonant elements. The method further comprises changing the order in which the resonant elements are disposed along the signal transmission path to create different filter solutions, computing a performance parameter for each filter solution, comparing the performance parameters to each other, selecting one of the filter solutions based on this comparison, and constructing the band-stop filter using the selected filter solution. Another RF band-stop filter comprises resonant elements coupled together to form a stopband, wherein at least two of the resonant elements have third order IMD components different from each other, such that the IMD components are asymmetrical about the stopband.

In a tunable duplexer combining a tunable filter with a canceler, calibration for optimizing passband characteristics and stop band characteristics is accelerated, and the deterioration of performance due to variations is highly accurately compensated. The tunable filter is calibrated to acquire isolation characteristics, and then coarse calibration and fine calibration are performed on the canceler. In coarse calibration, the use band of the tunable filter is set to a suppression band, and the isolation characteristics of the canceler are acquired. An amplitude, a phase, and a bias voltage are adjusted based on a result of comparison with the acquired isolation characteristics of the tunable filter for determining an approximate convergence. Fine calibration is further performed, and the optimum point is determined in a narrow range near the convergence.

It has been difficult to provide a band elimination filter having characteristics of a high attenuation within a desired stop band and a low loss over wide frequency bands higher and lower than the stop band. A band elimination filter includes: a plurality of acoustic wave resonators as an acoustic resonator each having one end grounded; and a transmission line to which the other end of each of the plurality of acoustic wave resonators as an acoustic resonator is connected, in which at least some of the other ends are coupled to the transmission line at predetermined intervals, and at least one inductor is provided on transmission line in all or some of the predetermined intervals.

The present invention provides a straightforward and robust synthetic process for producing a chromatographic column with eluent-sensitive light diffracting properties based on an inherent photonic band structure and a chromatographic device using the chromatographic column. The present invention provides chromatographic devices employing a chromatographic column which in one embodiment is a photonic colloidal crystal which includes an assembly of colloidal microspheres assembled into a highly ordered array within a housing such as a tube with the highly ordered array being a photonic crystal along the length of the crystal, and a second embodiment which is an inverse construct of the first embodiment, where solid microspheres making up the photonic colloidal crystal chromatographic column are replaced with spherical voids or void spaces subsequent to infiltration of a material of selected refractive index. The photonic band structures of the first type of column made with colloidal particles and the second type of column made by inverting the first type of column may include a photonic band gap, a fundamental stop-band, higher stop-bands, or combinations thereof.

Thermochromic filters use combinations of absorptive, reflective, thermoabsorptive, and thermoreflective elements covering different portions of the solar spectrum, to achieve different levels of energy savings, throw, shading, visible light transmission, and comfort. Embodiments include stopband filters in the near-infrared spectrum.

In an adaptive clutter filter for spectral Doppler imaging using an ultrasound system, the stopband center frequency and/or bandwidth of the clutter filter are effectively adjusted on a short time scale to better eliminate moving clutter while allowing low velocity bloodflow signals to pass through.

Provided are, among other things, systems, apparatuses, methods and techniques for converting a continuous-time, continuously variable signal into a sampled and quantized signal. One such apparatus includes an input line for accepting an input signal that is continuous in time and continuously variable, multiple processing branches coupled to the input line, and an adder coupled to outputs of the processing branches, with each of the processing branches including a bandpass noise-shaping circuit, a sampling/quantization circuit coupled to an output of the bandpass noise-shaping circuit, a digital bandpass filter coupled to an output of the sampling/quantization circuit, and a line coupling an output of the sampling/quantization converter circuit back into the bandpass noise-shaping circuit. A center frequency of the digital bandpass filter in each processing branch corresponds to a stopband region in a quantization noise transfer function for the bandpass noise-shaping circuit in the same processing branch.

Methods for sample rate conversion are provided that use a polynomial interpolator with minimax stopband attenuation. A method for sample rate conversion of an input signal is provided that uses a time-varying polyphase filter having a discrete polyphase index m. Another method for sample rate conversion of an input signal is provided that uses a time-varying polyphase filter having a continuous polyphase index τ. In these methods, an output time index is mapped to an input sample index and the polyphase index, the polynomial coefficients of a polyphase filter are computed using the polyphase index, and the polyphase filter is applied to an input sample at the input sample index to generate the output sample at the output time index.

An electronic device includes a main circuit connected between an input terminal and an output terminal, and an auxiliary circuit connected in parallel to the main circuit between the input terminal and the output terminal. The main circuit includes a filter having a first passband and a stopband. The auxiliary circuit has a passing characteristic that allows a signal having a frequency in a certain frequency band inside the stopband to pass through the auxiliary circuit. The main circuit is configured to output a main signal in response to an input signal. The auxiliary circuit is configured to output an auxiliary signal in response to the input signal. The main signal and the auxiliary signal contain phase components opposite to each other in the certain frequency band inside the stopband. This electronic device has an attenuation amount in the stopband.

The present disclosure provides a duplexer for separating a transmit signal and a receive signal. The duplexer comprises a transmit filter, a receive filter and an analogue quadrature splitter, a first filtering element and a second filtering element. By choosing the first filtering element and the second filtering element substantially identical, it is possible to transform filtering characteristics of the first and second filtering element such that stop bands are substantially transformed into an effective pass band, and vice versa. The analogue quadrature splitter is adapted to increase an attenuation of the transmit signals outside the transmit band, such as in the receive band. Therefore out-of-band emissions by the transmitter will be substantially reduced. The present disclosure further provides a method for separating a transmit signal and a receive signal, and computer program products for the manufacture for carrying out the method of separating transmit signals and receive signals.

The invention belongs to the technical field of avionics and relate to a module and a method for acquiring and processing a vibration signal of the rotating component of a helicopter. The module comprises a sensor interface circuit, a programmable amplifier, an anti-aliasing filter, an A/D converting circuit, and a FPGA which are successively connected. The method comprises steps of using a vibration sensor to input the vibration signal into the sensor interface circuit in order to convert the vibration signal into a voltage signal, and passing the voltage signal through a high-pass filter in the sensor interface circuit in order to filter a DC component in the voltage signal. Compared with a CPU-controlled A/D converting manner, a FPGA-controlled A/D converting manner increases sampling frequency and sampling realtimeness. By using anti-aliasing filtering technology, the order and the cut-off frequency of the filter can be set flexibly; the stop band descending slope of the filter is increased; and a signal anti-interference capability is enhanced.

A method for designing Wavelets for communications and radar which combines requirements for Wavelets and finite impulse response FIR filters including no excess bandwidth, linear performance metrics for passband, stopband, quadrature mirror filter QMF properties, intersymbol interference, and adjacent channel interference, polystatic filter design requirements, and non-linear metrics for bandwidth efficient modulation BEM and synthetic aperture radar SAR. Demonstrated linear design methodology finds the best design coordinates to minimize the weighted sum of the contributing least-squares LS error metrics for the respective performance requirements. Design coordinates are mapped into the optimum FIR symbol time response. Harmonic design coordinates provide multi-resolution properties and enable a single design to generate Wavelets for arbitrary parameters which include dilation, down-sampling, up-sampling, time translation, frequency translation, sample rate, symbol rate, symbol length, and set of design harmonics. Non-linear applications introduce additional constraints. Performance examples are linear communications, BEM, and SAR.

An optical filter is provided, including a first plurality and second plurality of alternating first and second material layers, where the first plurality of layers is at a first angle to incident light and has a cut-on edge, and the second plurality of layers is at a second angle to the incident light and a cut-off edge; where polarization splitting of the first plurality of layers at the cut-on edge and polarization splitting of the second plurality of layers at the cut-off edge do not exceed approximately 1 percent for any first and second angle between approximately 0 and 40 degrees; and the s-stopband wavelength of the second plurality of layers is approximately less than or equal to the cut-on edge wavelength, which is less than the cut-off edge wavelength, which is approximately less than or equal to the s-stopband wavelength of the first plurality of layers.

The invention discloses a velocity-deception-jamming-resistant phase encoding method for a cognitive radar, belongs to the technical field of radar jamming resistance, and particularly relates to a radar jamming-resistant waveform design technology. According to the method, relevant parameters of a target and jamming are extracted from prior information acquired by the cognitive radar, a stop band is arranged close to each real target Doppler according to a real target Doppler estimated value, a stop band is arranged at the same position as a constant-mode encoding sequence configured in advanced, and an optimal pulse-to-pulse phase encoding transmission waveform is designed according to the criterion that the spectrum energy of a coded signal in the stop band, thereby effectively inhibiting velocity deception jamming in a multi-target and multi-jamming scene, increasing the signal-to-jamming ratio of each real target, and realizing the effect of correct detection of a plurality of real targets.

A SAW device includes an IDT which is provided on the principal surface of a quartz crystal substrate having Euler angles (−1.5°≦φ≦1.5°, 117°≦θ≦142°, |ψ|≠90°×n (where n=0, 1, 2, 3)) and excites a Rayleigh wave (wavelength: λ) in a stopband upper end mode. Inter-electrode-finger grooves are recessed between electrode fingers of the IDT. An IDT line occupancy η and an inter-electrode-finger groove depth G satisfy a predetermined relationship in terms of the wavelength λ, such that the SAW device has a frequency-temperature characteristic of a cubic curve having an inflection point between a maximum value and a minimum value in an operation temperature range. The inflection point is adjustable to a desired temperature or a desired temperature range depending on the IDT line occupancy η within an operation temperature range.