87 results about "Stop band attenuation" patented technology

A system and method for broadband communications over power lines has a low-voltage transformer for the house connection unit and / or the electricity distribution inside the house. The system method allow for several parallel asynchronous data communications in different sub-channels with individual transmit power in each sub-channel. Sub-channel separation uses pass-band filters with high stop-band attenuation. High data rate in each sub-channel is achieved through the use of discrete wavelet multi-tone modulation. Coarse synchronization in each sub-channel and the optimization of the coefficients of the time-domain equalizer are carried out using a training sequence.

A system and a method are proposed for broadband communications over power lines comprising the area of the low-voltage transformer to the house connection unit and / or the electricity distribution inside the house. The new method allows for several parallel asynchronous data communications in different sub-channels with individual transmit power in each sub-channel. Sub-channel separation uses pass-band filters with high stop-band attenuation. High data rate in each sub-channel is achieved through the use of discrete wavelet multi-tone modulation. Coarse synchronization in each sub-channel and the optimization of the coefficients of the time-domain equalizer are carried out using a training sequence.

The invention relates to a method for designing a high-order finite impulse response digital filter, which comprises the following steps that: a neural network method is utilized and the amplitude-frequency response error sum of squares of a filter to be designed and an ideal filter serves as the calculation energy function of a neural network; the gradient descent learning algorithm is adopted to train the weight of the neural network to minimize the amplitude-frequency response error sum of squares of the filter to be designed and the ideal filter; when the neural network is stabilized, each parameter of the finite impulse response digital filter can be obtained and then the design of the finite impulse response digital filter is completed. The high-order finite impulse response digital filter designed by the method of the invention is characterized by small pass band fluctuation, large stop-band attenuation, controllable boundary frequency and high precision, etc., especially by that no matrix inversion algorithm is required to be carried out in the design, thus having fast operation speed, and the filter has broad application prospect in the engineering fields such as data transmission, high-precision televisions, radar and sonar systems and voice and image processing, etc.

The invention relates and discloses an interpolating digital filter device which is applied to a wireless medium range sensor network physical layer, comprising an interpolating digital filter module based on FIR (Finite impulse response filter) and an interpolating digital filter module based on CIC (Cascaded integrator-comb filter). The interpolating digital filter module based on FIR comprises a shift register time delay module, a multiplication module, a coefficient selector module, and an accumulator module. Wherein, the accumulator module comprises a register module and an adder module. The interpolating digital filter module based on CIC comprises a pectinate unit module, an interpolating unit module and an integral unit module. The invention is characterized in occupying less hardware resource, being applied to higher system clock rate, smaller passband ripple, more stopband attenuation and so on. The invention is applicable to a broadband wireless transceiver, in particular to a wireless broadband transmission system based on OFDM (Orthogonal Frequency Division Multiplexing) in the mobile environment.

A receiver portion includes a bandpass filter (e.g. SAW filter) that performs channel selection from an input signal having a plurality of channels, and an image cancellation circuit that is in parallel with the bandpass filter. The bandpass filter performs channel selection to select a desired channel that falls in a passband of the bandpass filter. Since the passband is typically a few channels wide, the image channel falls outside the passband and is attenuated by the stopband attenuation of the bandpass filter. The image cancellation circuit includes an attenuator and a phase shifter. The attenuator is configured to have the same attenuation as the stopband attenuation of the bandpass filter at the image channel frequency, and phase shifter is configured to provide a phase shift of approximately 180 degrees. Therefore, the image cancellation circuit has an output that is equal in amplitude, but opposite in phase, to that of the bandpass filter at the image channel frequency. A summer combines the output of the image cancellation circuit with the bandpass filter output to further suppress the image channel frequency over that achieved by the bandpass filter alone.

A method of tuning the stopband attenuation of an absorptive bandstop filter having at least a first and second resonator, where the first resonator includes a first tuning element that exhibits a first resonant frequency, the second resonator includes a second tuning element that exhibits a second resonant frequency, and the tuning elements are used to adjust the corresponding resonant frequencies, includes 1) adjusting the first resonant frequency using the first tuning element; and 2) adjusting the second resonant frequency using the second tuning element, such that both resonant frequencies are coordinated to obtain a selected stopband attenuation level and to thus realize a frequency-selective variable attenuator.

The present invention provides an unbalanced input and balanced output type SAW filter capable of obtaining stop-band attenuation approximately equivalent to that of an unbalanced input and unbalanced output type SAW filter. IDTs (12) (13) are respectively disposed on each side of a middle IDT (11). A comb electrode (11c) of the middle IDT (11) is connected with an input terminal (In) and other comb electrode (11b) is grounded. A comb electrode (12c) of the IDT (12) and a comb electrode (13b) of the IDT (13) are respectively connected with output terminals (Out 1) and (Out 2), and other comb electrode (12b) of the IDT (12) and other comb electrode (13c) of the IDT (13) are connected to each other and grounded. Electrode fingers (11a), (12a), (13a) of the middle IDT (11) and the side IDT (12), (13) are so arranged that adjacent electrode fingers of the middle IDT and the IDT on one side make a connection between terminals and the other adjacent electrode fingers of the middle IDT and the IDT on other side make a connection between a terminal and a ground.

The invention belongs to the field of software radio applications, and particularly relates to a non maximum extraction system integrated filter bank construction method based on DFT in a wide frequency band digital receiving and transmitting system, a voice signal processing system and a multi-carrier communication system. A frequency shift module is used for multiplying M to-be-integrated sub band baseband complex signals by a complex exponential modulation factor, and a signal spectrum distribution mode with the same bandwidth and central frequencies arranged at an equal interval is obtained; modulation data of M channels are subjected to a Fourier transform module, IDFT (Inverse Discrete Fourier Transform) is carried out on M sub channels, and data after transform are obtained; the data after IDFT are filtered, D-times interpolation is carried out, and data after M sub channel interpolation are obtained; and through a delay module and a summation module, a final target signal is obtained in an integrated mode. Better stop-band attenuation can be obtained, and the calculation amount and the hardware resource loss are reduced.

The invention relates to a compact micro-band resonant unit low-pass filter with low insertion loss and a wide stopband, which comprises a dielectric plate (1), a micro-band feed port (2), a micro-band feed line (3), low-resistance open-circuit stub lines (4), a crossed micro-band line (5) and gradually-changed trapezoidal resonant units (6), wherein the micro-band feed port (2), the micro-band feed line (3), the low-resistance open-circuit stub lines (4), the crossed micro-band line (5) and the gradually-changed trapezoidal resonant units (6) are positioned on the dielectric plate (1); the micro-band resonant units are respectively in left-and-right symmetrical structures and up-and-down symmetrical structures; the upper gradually-changed trapezoidal resonant unit (6) and the lower gradually-changed trapezoidal resonant unit (6) are connected by the crossed micro-band line (5) in the middle, wherein the left part of the crossed micro-band line (5) is connected with the micro-band feedline (3) through the low-resistance open-circuit stub lines (4), and the outer end of the micro-band feed line (3) is the micro-band feed port (2); and the characteristics of the upper gradually-changed trapezoidal resonant unit (6) and the lower gradually-changed trapezoidal resonant unit (6) are tuned by the left low-resistance open-circuit stub line (4) and the right low-resistance open-circuit stub line (4), and finally, the connection with the outside is realized through the micro-band feed port (2). The filter has good characteristics of low pass and stopband attenuation, and the designed CMRC metallic patch has small area and has the advantages of small volume, easy integration, and the like.

The invention discloses a novel microstrip band-reject filter with a C-shaped annular conduction band defect structure, which comprises a dielectric-slab of which the dielectric constant epsilon r is 2.65 and a ground plate which is arranged on the bottom surface of the dielectric-slab and is made of copper foils. The microstrip band-reject filter is characterized in that a copper conduction band arranged on the bottom surface of the dielectric-slab has two narrower ends and a wider middle part (belonging to a compensated microstrip line); and the middle part of the conduction band is etched with more than one C-shaped annular conduction band defect. The microstrip band-reject filter has the advantages of compact structure, convenient integration, high stopband attenuation, small passband ripple and wide stopband.

The present invention provides an unbalanced input and balanced output type SAW filter capable of obtaining stop-band attenuation approximately equivalent to that of an unbalanced input and unbalanced output type SAW filter. IDTs (12) (13) are respectively disposed on each side of a middle IDT (11). A comb electrode (11c) of the middle IDT (11) is connected with an input terminal (In) and other comb electrode (11b) is grounded. A comb electrode (12c) of the IDT (12) and a comb electrode (13b) of the IDT (13) are respectively connected with output terminals (Out 1) and (Out 2), and other comb electrode (12b) of the IDT (12) and other comb electrode (13c) of the IDT (13) are connected to each other and grounded. Electrode fingers (11a), (12a), (13a) of the middle IDT (11) and the side IDT (12), (13) are so arranged that adjacent electrode fingers of the middle IDT and the IDT on one side make a connection between terminals and the other adjacent electrode fingers of the middle IDT and the IDT on other side make a connection between a terminal and a ground.

The invention discloses a track signal filtering circuit which comprises a low-pass filtering unit and a high-pass filtering unit. Band-pass filtering and trapped wave processing are carried out by a band-pass filtering circuit formed by the low-pass filtering unit and the high-pass filtering unit on voltage signals from an induction coil, and the processed voltage signals are outputted to a processor to receive signal decoding processing. The maximum passing frequency of the low-pass filtering unit is 3125Hz, and the stop-band attenuation is greater than 40dB. The minimum passing frequency of the high-pass filtering unit is 400Hz, and the stop-band attenuation is greater than 40dB. The band-pass filtering circuit formed by the low-pass filtering unit and the high-pass filtering unit has a trapped wave suppressing effect on 50Hz signals and 150Hz signals, wherein the attenuation for the 50Hz signals is greater than 80dB, and the attenuation for the 150Hz signals is greater than 60dB. The track signal filtering circuit disclosed by the invention is simple in structure, not only can filter signals outside the bandwidth, but also can suppress interferences of power supply network single-frequency signals substantially.

Disclosed herein is a laminated filter with improved stop band attenuation, which is adopted in devices using a radio frequency, such as communication systems and / or broadcasting systems. The laminated filter forms cross capacitive coupling as feeding lines of input lead and / or output lead are coupled to a resonator pattern, and enhances an attenuation characteristic of stop band. Also, the laminated filter is minimized if feeding lines of the input lead and output lead are aligned in different layers, and the positions of the attenuation poles are easily controlled by adjusting the feeding line length.

The invention discloses a high-precision acceleration DAC (digital-to-analogue conversion) digital filter applicable to strapdown inertial navigation and relates to the field of data acquisition. The filter comprises a sampling comb filter, an FIR double-extraction compensation filter and an FIR quadruple-extraction compensation filter, wherein the sampling comb filter adopts an efficient down-sampling filter structure put forward by Hogenauer and is used for realizing high-rate underclocking; the FIR double-extraction compensation filter is generated through a fir2 function in the matlab, the function can design a multi-band random response curve phase FIR filter, the filter is mainly used for compensating the pre-stage CIC (cascaded integrator comb) filter with attenuation on band margins and realizing double extraction; the FIR quadruple-extraction compensation filter calculates coefficients of the optimal filter with the Parks-McClellan algorithm, and the filter is low in pass band ripple, narrow in transition band, large in stop band attenuation and high in filter order. The high-precision digital filter meets the strapdown inertial navigation system data sampling requirement.

The invention provides a heterogeneous filter bank filtering method based on a tree structure; the method comprises the following steps: using a dual-channel FIR quadrature mirror filter bank as a basic module, and employing the tree structure to build a heterogeneous filter bank; deriving reconstruction conditions of the whole tree structure heterogeneous filter bank, and resulting the whole system complete reconstruction conditions as to design a prototype filter satisfying specific conditions; using an iteration passband cut-off frequency to enable the designed prototype filter to satisfy reconstruction conditions. In a prototype filter special designing process, the method can employ a discrete weight square error criterion; compared with other methods, the criterion can better realize the passband flat characteristics and bigger stop band attenuation; the design scheme can effectively reduce the iteration complexity, can obtain bigger stop band attenuation and excellent system reconfiguration performance, thus providing important application values for a radar broadband channelization receiver and voice and picture signal processing.

In a method of digital communication where the transmitter includes a pulse-shaping filter and the receiver includes a plurality of corresponding matched filters, the pulse shaping filter is approximated to match a plurality of filters of the receiver for reducing the number of transmit shaping filters. The filter comprises a square-root raised cosine (SRRC) filter where the SRRC filter amplitude / phase response is approximated using a typical Parks-McClellan (remez) algorithm for designing linear phase FIR filters which, for a given set of input parameters, outputs a transmit filter coefficient set for the SRRC filter. The input parameters to the Parks-McClellan algorithm are chosen by iteration such that pass-band ripple, 3-dB point, and stop-band attenuation of the transmit filter meet or exceed specification requirements while the resulting transmit-receive filter pair ISI is minimized across a plurality of matched filter specifications.

The invention discloses a continuously adjustable double-band band elimination filter based on a surface acoustic wave resonator. The continuously adjustable double-band band elimination filter comprises two sections of input and output feeder lines, two same double-resonance filter units and a microstrip line for connecting the two units, wherein each filter unit is composed of two different single-port SAW resonators, a capacitor is arranged between the two resonators for coupling, two grounded inductors are connected to the two ends of a coupling capacitor in parallel, and two varactors andbiasing circuits of the varactors are connected to the joints of ports of the SAW resonators and the input and output feeder lines in parallel. The continuous dual-stop band bandwidth adjustability is realized by controlling the reverse bias voltage of the varactors. The invention provides a novel topological structure based on the surface acoustic wave resonator, which has the advantages of compact structure and simplicity and convenience in implementation. The surface acoustic wave resonator and lumped element hybrid design method is used, so that the working bandwidth is significantly wider than that of a traditional trapezoidal and lattice type SAW filter, and the filter has the characteristic of high stop band attenuation. Continuous adjustment of the bandwidth is realized, and the cost is low.

The invention belongs to the field of digital signal processing, and discloses a method for designing a finite impulse response digital low-pass filter. The method comprises the following steps: setting a frequency response function of an ideal low-pass filter; setting a frequency response function of an analog low-pass filter; setting a fitness function of a particle swarm algorithm; obtaining a position matrix of initial population particles and a velocity matrix of the initial population particles; obtaining the particle position corresponding to the minimum fitness function of each particle in an initial population and the particle position corresponding to the global minimum fitness function in the initial population; updating the velocity matrix, the position matrix, the particle position corresponding to the minimum fitness function of each particle, and the particle position corresponding to the global minimum fitness function; and obtaining the final analog low-pass filter according to the particle position corresponding to the global minimum fitness function. Thereby, the designed filter has a more flat passband and stronger stopband attenuation.

The invention relates to a low pass filter and a design method thereof. The design method comprises the following steps: S0, the index is determined according to the design input condition of the low pass filter; S1, the normalized value of out-of-band specified frequency of the low pass filter is calculated; S2, the section number is determined according to an equal-ripple filter stop-band attenuation characteristic diagram; S3, a model diagram of the low pass filter is created according to the section number; S4, normalized values of all elements are determined according to a normalized element numerical table of an equal-ripple low pass prototype filter; S5, actual values of all elements are calculated according to the normalized values. According to the low pass filter designed with the design method, both input impedance and output impedance are 50 omega, the low pass filter can be matched with a front end antenna and rear end receiving equipment conveniently, about no more than 1 dB of effect is caused to sensitivity of downstream equipment, and the typical value is no more than 0.5 dB. At the same time, the low pass filter adopts a symmetric circuit, input and output can be exchanged, and the use is convenient.

The invention discloses a minimization maximum design method for alternating DFT modulation filter banks. The requirement for oversampling of reconstructed characteristics and frequency characteristics of the DFT modulation filter banks is converted into a function relative to prototype filter coefficients, then a design problem of alternating the DFT modulation filter tanks is converted into a constrained optimization problem, and finally minimization maximum algorithm is adopted for obtaining the optimal coefficient of the prototype filter. An aliasing component compensation mode is introduced into the design of oversampling of the DFT modulation filter banks for the first time for controlling aliasing errors, so that aliasing errors are effectively constrained, the reconstruction performance is improved, and the high-aliasing problem caused by stopband attenuation is avoided.

The invention relates to a mode-mixing low-pass filter with cut-off frequency self-correction. The mode-mixing low-pass filter with the cut-off frequency self-correction comprises a mode-mixing low-pass filter, an annular oscillator and a frequency tuning module. The mode-mixing low-pass filter is formed by cascading two active RC double second-order filers; the annular oscillator comprises a NOR gate, a first inverter, a second inverter, resistors R5 and R6, and a adjustable capacitor array Ct; and the frequency tuning module comprises a first frequency counter, a second frequency counter, a comparator and an accumulator. According to the technical scheme provided by the invention, a full-difference four-order low-pass filter based on mixed application of filter response models obtains good in-band flatness while reaching a high-stop-band attenuation degree; the annular oscillator can realize an oscillation frequency adjustable function while eliminating metastable state points of the oscillator; and the frequency tuning module, through real-time monitoring and rapid automatic correction of the cut-off frequency of the filter, greatly inhibits the influences exerted by such fluctuations as the process, voltage, temperature and the like on the frequency response accuracy of the filter.

The invention discloses an electromagnetic band gap structure. The electromagnetic band gap structure comprises two groups of metal closed curves with different shapes, wherein all metal closed curves in each group have the same shape and different sizes; the two groups of metal closed curves sequentially surround each other from inside to outside in an overlapped mode; and the distance between the two adjacent metal closed curves in the same group is equal to the distance between the innermost metal closed curve in the group and a central point of an area which is surrounded by the innermost metal closed curve. The invention also discloses an electromagnetic band gap high-impedance substrate and a planar travelling wave tube with the electromagnetic band gap high-impedance substrate. The invention has the advantages that: stop-band bandwidth is large, stop-band attenuation is high, and the edge of a transmission curve is straight; a requirement of a slow wave structure for the surface wave suppression of a microwave frequency band can be well met, the coupling impedance of the slow wave structure is effectively improved, and the working bandwidth of the slow wave structure is increased; and a manufacturing process is simple, the transverse size of the conventional planar structure cannot be increased, and a magnetic field can be designed.

The invention belongs to the technical field of filters, and discloses an MTD filter group designing method based on frequency domain discrete sampling constraint convex optimization. The method comprises steps of setting radar working parameters, stop band attenuation of an MTD filter group, attenuation of a non-zero channel zero recessed opening, normalization frequency width of the non-zero channel zero recessed opening, the number N of channels; determining a pass band normalization frequency interval of the nth channel, the stop band normalization frequency interval, and the zero recessed opening normalization frequency interval; determining an optimization function of a filter coefficient of the nth channel; if the filter coefficient of the nth channel fails to meet a single-channel design requirement, changing the zero recessed opening normalization frequency interval and re-solving a filter coefficient; estimating the filter coefficients of the N channels; if the filter coefficients fail to meet an overall design requirement, adjusting the pass band normalization frequency interval of the non-zero channel. Thus, the an MTD filter group with the adjustable pass band frequency range can be obtained, the controllable stop band attenuation and the enough deep non-zero channel zero recessed opening can be obtained.

The invention discloses a small group delay crystal filter. An input circuit is connected with a resonance bridge and then connected with a crystal resonance element 12, passes through a widening circuit, then is sequentially connected with a crystal resonance element 34 and a resonance bridge, passes through a widening circuit, then is connected with a crystal resonance element 56, and finally is connected with an output circuit. By aid of the circuit connection mode, the small group delay crystal filter has the advantages of being good in performance, simple in structure, convenient to use, capable of being used in a temperature range of -55 DEG C to +85 DEG C, good in stability, small in pass band fluctuation, good in stop band attenuation and capable of improving digital sensitivity, and can be widely applied to mobile communication system products. In addition, the group delay index is smaller than 1.8 uS (centre frequency is + / -20k).

The present invention discloses a dual-band active filter having filtering response and positive pass-band gain. The dual-band active filter includes an input match unit for gain match of the dual-band active filter and for having a band-pass filtering response; a first gain stage electrically connected to the first input match unit for providing the flat gain of the dual-band active filter; an inter-stage unit electrically connected to the first gain stage for matching gain and for having a band-stop filter response; a second gain stage electrically connected to the inter stage unit for providing the flat gain of the dual-band active filter; and an output unit electrically connected to the second gain stage for matching the dual-band active filter and for having a low-pass filtering response. The dual-band active filter according to the present invention uses the cascade connection of multiple filter stages to have band-pass filtering response at two different frequency bands and obtain high stop-band attenuation by providing plural transmission zeros in the stop-band.

The invention discloses an FIR filter design method based on two-level optimization and a device thereof. The method comprises the steps of carrying out IDFT on a frequency sampling vector, thereby obtaining a transformed vector, and carrying out cyclic shift processing, thereby obtaining a shifted vector; selecting a common window with a length of N, carrying out convolution and normalization on the common window and a rectangular window, thereby obtaining a convolution window with the length of 2N-1; carrying out point multiplication on the shifted vector and the 2N-1 convolution window, thereby obtaining an FIR filter analysis coefficient; further optimizing the FIR filter analysis coefficient through utilization of an evolution strategy, obtaining a transition value and establishing the frequency sampling vector; and finding the globally optimum transition value, and further obtaining the final FIR filter coefficient. According to the method and the device, two-level optimization is applied; a high-performance FIR filter with small transmission curve passband ripples and high stopband attenuation is designed; the calculation complexity of an existing evolution optimization filter design method is reduced; and the design efficiency is improved.

A duplex radio transceiver, coupled to baseband circuitry and to an antenna, includes a receive chain, a transmit chain and a duplexer. The transmit chain includes filter components that attenuate signals originating from the transmit chain in a receive frequency band by a stop-band attenuation that is approximately equal to or greater than the stop-band attenuation of the duplexer in the receive band. Similarly, the receive chain includes filter components that attenuate signals in a transmit frequency band by a stop-band attenuation that is approximately equal to or greater than the stop-band attenuation of the duplexer in the transmit band. A bias control circuit senses a power level associated with radio signals in the transmit chain and adjusts an amplifier in the receive chain responsive to the power level.

The invention discloses a digital filter based on a distributed algorithm. The digital filter is formed by cascading a CIC filter, a CIC compensation filter and a half-band filter; an input signal issubjected to decimation filtering through a CIC filter, so that the working frequency of a high-speed system is reduced; then the signal is sent to the CIC compensation filter, the passband attenuation of the signal in the CIC compensation filter is compensated, the stop band attenuation is further increased, and the transition band width is reduced; and finally, after the signal passes through the half-band filter based on the distributed algorithm, the transition band is steeper, the stop band attenuation is reduced again, and a useful signal is output after the performance requirement of the digital filter is completely met. On the premise that all filter parameters reach the overall performance of the filter and meet the signal processing speed, hardware resource consumption is reducedto the maximum extent, and the area of an implementation circuit is reduced.

The invention discloses a microwave band-stop filter based on a tree-shaped micro-strip line structure, wherein the matrix is equipped with microwave band-stop filter components; the microwave band-stop filter components are characterized in that a plurality of root micro-strip lines are disposed on a straight-through micro-strip transmission line; that Grade One V-shaped branch micro-strip lines are respectively arranged on the upper end of the plurality of root micro-strip lines; that Grade Two V-shaped branch micro-strip lines are respectively disposed on two top ends of each Grade One V-shaped branch micro-strip line; Grade Three V-shaped branch micro-strip lines are respectively arranged on two top ends of the Grade Two V-shaped branch micro-strip lines; and signal is sent into end 1 and out of end 2. The band-stop filter of tree-shaped microwave micro-strip line structure has advantages of large stop-band bandwidth, high stop-band attenuation, simple structure, easy assembly, light weight, saving materials, easy manufacturing and integration and greatly reducing the cost and size of the product.