87 results about "Stop band attenuation" patented technology

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.

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 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.

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 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 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).