A Method for Reducing Ocean Wave-Induced Magnetic Noises in Shallow-Water MT Data Using a Complex Adaptive Filter

In shallow-water areas,the marine magnetotelluric(MT)method faces a challenge in the investigation of seabed conductivity structures due to electrical and magnetic noises induced by ocean waves,which seriously contaminate MT data.Ocean waves can affect electric and magnetic fields to different extents.In general,their influence on magnetic fields is considerably greater than that on electric fields.In this paper,a complex adaptive filter is adopted to reduce wave-induced magnetic noises in the frequency domain.The processing results of synthetic and measured MT data indicate that the proposed method can effectively reduce wave-induced magnetic noises and provide reliable apparent resistivity and phase data.

Design of complex FIR filters with arbitrary magnitude and group delay responses

To design approximately linear-phase complex coefficient finite impulse response （FIR） digital filters with arbitrary magnitude and group delay responses, a novel neural network approach is studied. The approach is based on a batch back-propagation neural network algorithm by directly minimizing the real magnitude error and phase error from the linear-phase to obtain the filter＇s coefficients. The approach can deal with both the real and complex coefficient FIR digital filters design problems. The main advantage of the proposed design method is the significant reduction in the group delay error. The effectiveness of the proposed method is illustrated with two optimal design examples.

Theoretical convergence analysis of complex Gaussian kernel LMS algorithm

With the vigorous expansion of nonlinear adaptive filtering with real-valued kernel functions,its counterpart complex kernel adaptive filtering algorithms were also sequentially proposed to solve the complex-valued nonlinear problems arising in almost all real-world applications.This paper firstly presents two schemes of the complex Gaussian kernel-based adaptive filtering algorithms to illustrate their respective characteristics.Then the theoretical convergence behavior of the complex Gaussian kernel least mean square（LMS） algorithm is studied by using the fixed dictionary strategy.The simulation results demonstrate that the theoretical curves predicted by the derived analytical models consistently coincide with the Monte Carlo simulation results in both transient and steady-state stages for two introduced complex Gaussian kernel LMS algonthms using non-circular complex data.The analytical models are able to be regard as a theoretical tool evaluating ability and allow to compare with mean square error（MSE） performance among of complex kernel LMS（KLMS） methods according to the specified kernel bandwidth and the length of dictionary.

Measurement Sensitivity and Estimation Error in Distribution System State Estimation using Augmented Complex Kalman Filter

Distribution state estimation(DSE)is an essential part of an active distribution network with high level of distributed energy resources.The challenges of accurate DSE with limited measurement data is a well-known problem.In practice,the operation and usability of DSE depend on not only the estimation accuracy but also the ability to predict error variance.This paper investigates the application of error covariance in DSE by using the augmented complex Kalman filter(ACKF).The Kalman filter method inherently provides state error covariance prediction.It can be utilized to accurately infer the error covariance of other parameters and provide a method to determine optimal measurement locations based on the sensitivity of error covariance to measurement noise covariance.This paper also proposes a generalized formulation of ACKF to allow scalar measurements to be incorporated into the complex-valued estimator.The proposed method is simulated by using modified IEEE 34-bus and IEEE 123-bus test feeders,and randomly generates the load data of complex-valued Wiener process.The ACKF method is compared with an equivalent formulation using the traditional weighted least squares(WLS)method and iterated extended Kalman filter(IEKF)method,which shows improved accuracy and computation performance.

A CMOS G_m-C complex filter with on-chip automatic tuning for wireless sensor network application

A Gm-C complex filter with on-chip automatic tuning for wireless sensor networks is designed and implemented using 0.18 μm CMOS process. This filter is synthesized from a low-pass 5th-order Chebyshev RLC ladder filter prototype by means of capacitors and fully balanced transconductors. A conventional phase-locked loop is used to realize the on-chip automatic tuning for both center frequency and bandwidth control. The filter is centered at 2 MHz with a bandwidth of 2.4 MHz. The measured results show that the filter provides more than 45 dB image rejection while the ripple in the pass-band is less than 1.2 dB. The complete filter including on-chip tuning circuit consumes 4.9 mA with 1.8 V single supply voltage.

A dual-mode complex filter for GNSS receivers with frequency tuning

A fifth/seventh order dual-mode OTA-C complex filter for global navigation satellite system receivers is implemented in a 0.18μm CMOS process.This filter can be configured as the narrow mode of a 4.4 MHz bandwidth center at 4.1 MHz or the wide mode of a 22 MHz bandwidth center at 15.42 MHz.A fully differential OTA with source degeneration is used to provide sufficient linearity.Furthermore,a ring CCO based frequency tuning scheme is proposed to reduce frequency variation.The measured results show that in narrow-band mode the image rejection ratio（IMRR）is 35 dB,the filter dissipates 0.8 mA from the 1.8 V power supply,and the out-of-band rejection is 50 dB at 6 MHz offset.In wide-band mode,IMRR is 28 dB and the filter dissipates 3.2 mA.The frequency tuning error is less than±2%.

A reconfigurable complex band-pass filter with improved passive compensation

This paper presents a 5th-order Chebyshev-I active RC complex filter for multi-mode multi-band global navigation satellite systems （GNSS） RF receivers. An improved passive compensation technique is used to cancel the excess phase lag of the integrators, thus ensuring the in-band flatness of the frequency response over various ambient conditions. The filter has a programmable gain from 0 to 42 dB with a 6 dB step, a tunable center fre- quency at either 6.4 MHz or 16 MHz, and a bandwidth from 2 to 20 MHz with less than 3% frequency uncertainty. Implemented in a 0.18μm CMOS process, the whole filter consumes 7.8 mA from a 1.8 V supply voltage and occupies a die area of 0.4 mm2.

A CMOS G_m-C complex filter with a reconfigurable center and cutoff frequencies in low-IF WiMAX receivers

This paper presents a reconfigurable fifth-order complex Gm-C filter for different data rates in low-IF WiMAX applications.The design procedure and linearized measures to realize the complex filter are described.In order to achieve the reconfigurability of bandwidth window,the center frequency and the cutoff frequency filter are adjusted simultaneously by changing capacitor values while keeping transconductors unchanged.Also,the filter integrates an on-chip automatic frequency tuning circuit based on a PLL.Experimental results show that it has an IRR of 32 dB,a THD of -43 dB,and an input-referred noise of 21μVrms.The chip is fabricated in 0.13μm CMOS process,occupies 0.7×1 mm2,and consumes 4.8 mA current from a 1.2 V power supply.

A pseudo differential Gm-C complex filter with frequency tuning for IEEE802.15.4 applications

This paper presents a CMOS G;-C complex filter for a low-IF receiver of the IEEE802.15.4 standard.A pseudo differential OTA with reconfigurable common mode feedback and common mode feed-forward is proposed as well as the frequency tuning method based on a relaxation oscillator.A detailed analysis of non-ideality of the OTA and the frequency tuning method is elaborated.The analysis and measurement results have shown that the center frequency of the complex filter could be tuned accurately.The chip was fabricated in a standard 0.35μm CMOS process,with a single 3.3 V power supply.The filter consumes 2.1 mA current,has a measured in-band group delay ripple of less than 0.16μs and an IRR larger than 28 dB at 2 MHz apart,which could meet the requirements of the IEEE802.15.4 standard.

Microwave photonic notch filter with complex coefficient based on four wave mixing

A microwave photonic notch filter with a complex coefficient is proposed and demonstrated based on four wave mixing(FWM). FWM effect of two single-frequency laser beams occurs in a highly nonlinear fiber(HNLF), and multi-wavelength optical signals are generated and used to generate the multi-tap of microwave photonic filter(MPF). The complex coefficient is generated by using a Fourier-domain optical processor(FD-OP) to control the amplitude and phase of the optical carrier and phase modulation sidebands. The results show that this filter can be changed from bandpass filter to notch filter by controlling the FD-OP. The center frequency of the notch filter can be continuously tuned from 5.853 GHz to 29.311 GHz with free spectral range(FSR) of 11.729 GHz. The shape of the frequency response keeps unchanged when the phase is tuned.

A BFSK and OOK IF demodulation circuit with 2.8 μs settling time and re-configurable image rejection functions for MICS/BCC applications

A BFSK and OOK IF base-band circuit is provided to implement the low-IF RF receivers for a dualband MICS/BCC network controller. In order to transfer the massive vital data immediately, the IF circuit is comprised of the fast-settling feed-forward programmable gain amplifier（PGA）, a Gm-C complex filter, the fixed gain amplifier（FGA） and a 4-input ＂quadratic sum＂ demodulator. A novel auto-switched coarse gain-setting method is adopted in the PGA to enhance the reaction speed and narrow the output signal range. Also the PGA does not suffer the same stability constraint as open-loop topologies. The complex filter fulfills the function of image rejection,in which the center frequency and bandwidth can be adjusted individually. The FGA is used to ameliorate the linearity and the ＇quadratic sum＇ demodulator can reduce the overall power consumption. The designed IF circuit is fabricated with SMIC 0.18 μm CMOS process. The chip area is about 5.36 mm^2. Measurement results are given to verify the design goals.

Design of a high linearity and high gain accuracy analog baseband circuit for DAB receiver

An analog baseband circuit of high linearity and high gain accuracy for a digital audio broadcasting receiver is implemented in a 0.18-μm RFCMOS process.The circuit comprises a 3rd-order active-RC complex filter（CF） and a programmable gain amplifier（PGA）.An automatic tuning circuit is also designed to tune the CF＇s pass band.Instead of the class-A fully differential operational amplifier（FDOPA） adopted in the conventional CF and PGA design,a class-AB FDOPA is specially employed in this circuit to achieve a higher linearity and gain accuracy for its large current swing capability with lower static current consumption.In the PGA circuit,a novel DC offset cancellation technique based on the MOS resistor is introduced to reduce the settling time significantly.A reformative switching network is proposed,which can eliminate the switch resistor＇s influence on the gain accuracy of the PGA.The measurement result shows the gain range of the circuit is 10-50 dB with a 1-dB step size,and the gain accuracy is less than ±0.3 dB.The OIP3 is 23.3 dBm at the gain of 10 dB.Simulation results show that the settling time is reduced from 100 to 1 ms.The image band rejection is about 40 dB.It only draws 4.5 mA current from a 1.8 V supply voltage.

A Control Strategy of Frequency Self-adaptation Without Phase-locked Loop for VSC-HVDC

A control strategy of frequency self-adaptation without phase-locked loop(PLL)underαβstationary reference frame(αβ-SRF)for a VSC-HVDC system is presented to improve the operational performance of the system under severe harmonic distortion conditions.The control strategy helps to eliminate the cross-coupling under dq synchronous reference frame(dq-SRF),and is achieved through two key technologies:1)positive phase sequence(PPS)and negative phase sequence(NPS)fundamental components are extracted from the AC grid voltage with an improved multiple complex coefficient filter(IMCF),and 2)grid instantaneous frequency is rapidly and precisely tracked using a frequency self-adaptation tracking algorithm(FATA)without PLL.The proposed strategy is applied to a point-to-point VSCHVDC system and validated by means of simulations.The results are compared to those with the traditional vector control strategy under dq-SRF.Simulation results illustrate that the proposed strategy results in better system performance than that with the traditional strategy in terms of harmonic suppression under normal and severe operating conditions of the AC system.

Fingerprint Core Location Algorithm Based on Sliding Window

In order to improve the efficiency of the fingerprint core location algorithm, a fingerprint core location method using sliding window on the basis of core location algorithm with the complex filter was proposed. The local region of the fingerprint image was extracted by a fixed-size window sliding in the region of the fingerprint image, and the selected local region by window as the calculation object is used to detect the core. The experiment results show that the method cannot only effectively detect fingerprint core, but also improve the efficiency of the detection algorithm comparing with the global fingerprint core location detection algorithm.

A low power 2.4 GHz transceiver for ZigBee applications

This paper presents a low power 2.4 GHz transceiver for ZigBee applications.This transceiver adopts low power system architecture with a low-IF receiver and a direct-conversion transmitter.The receiver consists of a new low noise amplifier（LNA） with a noise cancellation function,a new inverter-based variable gain complex filter （VGCF） for image rejection,a passive quadrature mixer,and a decibel linear programmable gain amplifier（PGA）. The transmitter adopts a quadrature mixer and a class-B mode variable gain power amplifier（PA） to reduce power consumption.This transceiver is implemented in 0.18μm CMOS technology.The receiver achieves—95 dBm of sensitivity,28 dBc of image rejection,and -8 dBm of third-order input intercept point（IIP3）.The transmitter can deliver a maximum of＋3 dBm output power with PA efficiency of 30%.The whole chip area is less than 4.32 mm^2. It only consumes 12.63 mW in receiving mode and 14.22 mW in transmitting mode,respectively.