共查询到20条相似文献,搜索用时 437 毫秒
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An adaptive analog continuous-time biquadratic filter is realized in a 2-μm digital CMOS process for operation at 300 kHz. The biquad implements the notch, bandpass and low-pass transfer functions. The only parameter adapted is the resonant frequency of the biquad, which is identical to the notch frequency and the bandpass center frequency. The update method is based on a least-means-square algorithm which adapts the notch frequency to minimize the power at the notch filter output. The actual update is modified to reduce the circuit complexity to one biquad and one correlator. When the filter is tracking a sinusoid, this update generates a ripple-free gradient that decreases tracking error. Applications include phase-frequency detectors, FM demodulators (linear and frequency shift keying), clock extractors, and frequency acquisition aids for phase-locked loops and Costas loops. Measured results from experimental prototypes are presented. Nonidealities of an all-analog implementation are discussed, along with suggestions to improve performance 相似文献
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Time-varying AR modeling and adaptive IIR notch filter for anti-jamming DSSS receiver 总被引:1,自引:0,他引:1
Using Time-Varying AR (TVAR) model and adaptive notch filter is a new method for the non-stationary jammer suppression in
Direct Sequence Spread Spectrum (DSSS). The performance of TVAR model for Instantaneous Frequency (IF) estimation will be
affected by some factors such as basis functions. Focusing on this problem, the optimal basis function of TVAR model for the
IF estimation of the LFM signal is obtained in this paper. Besides the depth and width of notching, the phase properties of
notch filter affect the Signal-to-Interference plus-Noise Ratio (SINR) of correlation output to the narrowband jammer suppression
in DSSS, in response to the problem the closed solution of correlation output SINR improvement has been derived when a single
frequency jammer passes through direct IIR notch filter, and its performance has been compared with those of five coefficient
FIR filters. Later, a novel method for LFM jammer suppression based on Fourier basis TVAR model and direct IIR notch filter
is proposed. The simulation results show the effectiveness of the proposed method. 相似文献
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G. Y. Luo 《International Journal of Communication Systems》2012,25(5):598-615
Spread spectrum signal transmitted by wireless channel for location tracking can be severely corrupted by noise due to external disturbances. Narrowband noise is the most effective interference that can make measurement signal undetected. However, the current methods for narrowband interference (NBI) suppression are either very time‐consuming or add distortion to the signal received. In this paper, an adaptive Gaussian wavelet filter with optimal time–frequency localization and variable notch depth is proposed to suppress a large number of NBIs with additive white Gaussian noise and pulsed noise that interfere with the spread spectrum communication system. The filtering of both continuous and time‐varying NBIs with fast resampling is performed in conjunction with the fast Fourier transform‐based correlation for peak detection, and is computationally efficient for real‐time operation of signal detection. The performance of the adaptive filter has been evaluated by experiments employing a reliable noise detector. Experimental results demonstrate that the proposed wavelet filter isolates the signals from the NBI in accordance with the corrupted frequency contents while preserving the desired spread spectrum signal, and improves signal to noise ratio for peak detection leading to higher accuracy of timing measurement for real‐time wireless location. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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一种应用于限制零极点位置复数陷波器的迭代算法 总被引:1,自引:0,他引:1
基于最小均方误差准则(MMSE),本文推导出了一种修改限制零极点位置的一阶复数陷波器权值迭代算法,并进而提出了一种新的可应用于矩阵型高阶陷波器的自适应权值修改算法,该高阶陷波器由一阶陷波器作为陷波单元构成。该迭代算法直接修改陷波器权值的指数,因而在算法迭代过程中能够将高阶复数陷波器的极点始终限制在单位圆内,从而保证了陷波器的稳定工作。仿真结果表明,采用该算法的一阶和高阶复数陷波器工作稳定,对输入陷波器的宽带信号损伤小,且能快速跟踪和有效抑制其中的强单/多频信号。 相似文献
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The optical scanner is one of the most important components in free-space optical communications,airborne and space-based lidars,adaptive optics,and so on.The performance of an optical scanner is frequently limited by the presence of mechanical resonances.This paper presents an analog notch filter with adjustable function to reject the mechanical resonances of the optical scanner.First of all,the structure and work principle of the piezoelectric optical scanner are introduced.Furthermore,the frequency sweep method based on virtual instruments is used to gain the natural frequency of the piezoelectric optical scanner.Then,the notch filters in series are used to reduce the oscillation of the scanner at the resonance frequencies.A variety of scanning experiments were carried out.After the introduction of the notch filter,the non-linearity was reduced to±1.1% from ±2.1%.The linearity performance was greatly improved. 相似文献
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在多模谐振器的基础上,设计了一种新型的具有双陷波特性的超宽带滤波器。该滤波器在十字形谐振器的基础上加载了一对阶跃阻抗谐振器及两组短路反耦合线结构。设计得到的滤波器尺寸紧凑,且可实现滤波器谐振频率及陷波点的独立可控。测试可得滤波器的通频带为1.8~12.1 GHz,3 dB相对带宽为148%,通带内插入损耗小于1 dB,两个陷波点频率分别位于5.15 GHz和6.98 GHz。结果表明,该超宽带滤波器能有效地抑制WLAN频段和C波段卫星信号的干扰,与仿真结果吻合良好。 相似文献
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We have proposed a cost-effective sub-terahertz (THz) continuous wave (CW) generation scheme based on a usual double sideband-suppressed carrier (DSB-SC) scheme. The usual DSB-SC scheme, which consists of a discrete optical source, an optical intensity modulator (OIM), a local oscillator (LO), an optical notch filter, and an erbium doped fiber amplifier (EDFA), is one of well-known photonic-based sub-THz CW generation schemes. As the discrete optical source of the usual DSB-SC scheme is eliminated and an optical feedback loop is incorporated with the usual DSB-SC scheme, our proposed scheme is constructed to decrease implementation costs. Without an optical input, the output of the pump laser of the DC-biased EDFA is inserted to the optical notch filter. Reflected lightwaves with fiber bragg grating wavelengths of the optical notch filter is fed back to the input of the OIM through the optical feedback loop, which is composed of a circulator and a 90:10-coupler. DSB-SC lightwaves have been made by modulating feedbacked lightwaves on the OIM with the frequency of the LO. A sub-THz CW is generated by photomixing them. To verify feasibility of our proposed scheme, we generated and characterized a 120 GHz CW. The measurement results were also compared to those of the usual DSB-SC scheme. Based on our measurement results, we found that characteristics of the generated 120 GHz CW using our proposed scheme are comparable to those using the usual DSB-SC scheme. Consequently, our proposed scheme can be helpful to make a cost-effective sub-THz CW generator based on photonics. 相似文献
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邸珩烨 《智能计算机与应用》2016,(2):100-103
无线电扩频通信受到多径分量噪声的干扰,导致通信信道均衡性不好,抗干扰能力不强,误码率较高。需要进行噪声干扰抑制,改善无线电扩频通信质量。提出一种基于自适应级联陷波和码间干扰抑制的无线电扩频通信优化技术。构建无线电扩频通信系统传输结构模型,采用自适应陷波器对无线电扩频通信中的多径分量噪声进行有效抑制,降低了进入信号通频带内的干扰功率,提高解调器的输出信噪比和信干比。采用扩展后的序列去调制载波,将信号搬移到载频上,实现信道均衡,提高抗干扰能力。仿真结果表明,该算法能有效降低无线电扩频通信的误比特率,抗干扰性较强,提高通信质量。 相似文献
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为实现滤波器设计小型化,降低带通滤波器的高次谐波干扰,结合传统的1/4波长谐振器结构,采用在谐振器微带线上添加开路线的方法,降低高次谐振频点处的插入损耗,消减谐波影响。相比于半波谐振器,1/4波长谐振器能有效地减小滤波器尺寸,此外开路线的添加除具有消减高次谐波作用,同时还能降低基频谐振点,促进设计小型化。通过仿真软件对该方案的验证及网络分析仪的实物测试表明,此方案具有良好效果,能广泛应用于窄带通滤波器小型化及谐波抑制。 相似文献
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Xiao Li Yong Zhang Oupeng Li Yan Sun Haiyan Lu Wei Cheng Ruimin Xu 《Journal of Infrared, Millimeter and Terahertz Waves》2017,38(2):166-175
In this paper, a novel design of frequency tripler monolithic microwave integrated circuit (MMIC) using complementary split-ring resonator (CSRR) is proposed based on 0.5-μm InP DHBT process. The CSRR-loaded microstrip structure is integrated in the tripler as a part of impedance matching network to suppress the fundamental harmonic, and another frequency tripler based on conventional band-pass filter is presented for comparison. The frequency tripler based on CSRR-loaded microstrip generates an output power between ?8 and ?4 dBm from 228 to 255 GHz when the input power is 6 dBm. The suppression of fundamental harmonic is better than 20 dBc at 77–82 GHz input frequency within only 0.15?×?0.15 mm2 chip area of the CSRR structure on the ground layer. Compared with the frequency tripler based on band-pass filter, the tripler using CSRR-loaded microstrip obtains a similar suppression level of unwanted harmonics and higher conversion gain within a much smaller chip area. To our best knowledge, it is the first time that CSRR is used for harmonic suppression of frequency multiplier at such high frequency band. 相似文献
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《Mechatronics》2014,24(6):632-639
A new method to design notch filters for MIMO motion control systems with flexible mechanical structures is proposed. The method involves so-called directional notch filters that work only in the direction of the targeted resonant mode. As a result, only one SISO notch filter is required per mode to suppress a resonance throughout the MIMO system. Compared to the conventional approach where a notch filter is placed and tuned in each of the separate control loops, the new approach reduces the order of the controller significantly and facilitates the design process. The directional notch filter is computed using either the input or output mode shapes of the system. A new numerical optimization method to obtain these mode shapes from frequency response data is described. Experiments on a flexible beam setup demonstrate the feasibility of the proposed method in practice. 相似文献
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为实现滤波器设计小型化,降低带通滤波器的高次谐波干扰,本文结合传统的1/4波长谐振器结构,采用在谐振器微带线上添加开路线的方法,降低高次谐振频点处的插入损耗,消减谐波影响。相比半波谐振器,1/4波长谐振器能有效地减小滤波器尺寸,此外开路线的添加除具有消减高次谐波作用,同时还能降低基频谐振点,促进设计小型化。通过仿真软件对该方案的验证及网络分析仪的实物测试表明,此方案具有良好效果,能广泛应用于窄带通滤波器小型化及谐波抑制。 相似文献
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Investigates adaptive digital notch filters for the elimination of powerline noise from biomedical signals. Since the distribution of the frequency variation of the powerline noise may or may not be centered at 60 Hz. Three different adaptive digital notch filters are considered. For the first case, an adaptive FIR second-order digital notch filter is designed to track the center frequency variation. For the second case, the zeroes of an adaptive IIR second-order digital notch filter are fixed on the unit circle and the poles are adapted to find an optimum bandwidth to eliminate the noise to a pre-defined attenuation level. In the third case, both the poles and zeroes of the adaptive IIR second-order filter are adapted to track the center frequency variation within an optimum bandwidth. The adaptive process is considerably simplified by designing the notch filters by pole-zero placement on the unit circle using some suggested rules. A constrained least mean-squared algorithm is used for the adaptive process. To evaluate their performance, the three adaptive notch filters are applied to a powerline noise sample and to a noisy EEG as an illustration of a biomedical signal 相似文献
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The stability issue in adaptive notch filters is investigated from a structural viewpoint. A new adaptive algorithm for direct frequency estimation is developed using a constrained pole-zero notch filter. The basic characteristic of this algorithm is that the notch filter is realised in a cascade form, with each stage implemented in a normal realisation. A simplified version of the gradient signals is derived, which makes the algorithm very efficient. It is shown that this proposed adaptive notch filter is bounded-input-bounded-output stable. Numerical examples with simulations, where the proposed algorithm performs well in terms of convergence and guaranteed stability, are given to support the theoretical results 相似文献