Universal three input and one output current-mode filter withoutexternal passive elements

A new current-mode universal filter is proposed. The filter uses only operational amplifiers and operational transconductance amplifiers (OTAs) and can realise lowpass, highpass, bandpass, notch and allpass responses without changing circuit topology. The parameters ω₀, ω₀/Q₀, and the gain can be electronically tuned by adjusting the bias currents of the OTAs. The proposed circuit has low sensitivity     

采用单个四端浮地零器的电压模式滤波器

文中提出了电压模式单ＦＴＦＮ滤波器新通用电路结构，它能实现二阶低通、高通、带通、全通（陷波）和一阶低通、高通、全通滤波功能。给出了二阶带通和一阶低通的ＰＳＰＩＣＥ仿真频响，进一步证实了理论分析的正确性，各滤波电路的增益与极点角频率（或品质因素）独立可调，且有低的无源灵敏度。     

Novel approach to the design of I/Q demodulation filters

A novel filter design approach to digital I/Q demodulation is proposed. Two possible realisations are presented using this approach. The first one is based on the highpass filter method which is suitable for B⩽f₀ and while the other realisation is based on the lowpass filter method suitable for B⩽f₀, where B and f ₀ are the IF signal bandwidth and the IF frequency, respectively. Both new realisations maintain the advantages of an earlier lowpass approach such as zero DC offset, matched channel frequency responses, and good performance over a wide bandwidth. At the same time, the new highpass filter realisation method possesses higher computational efficiency than other wideband approaches reported in the literature     

A new method for the design of IIR filters with flat magnitude response

This paper presents a new direct design of infinite-impulse response (IIR) filters with a flat magnitude response in both passband and stopband (Butterworth filters). The design specifications are passband and stopband frequencies and passband droop and stopband attenuation. The approach is based on an allpass filter with flatness at frequency points /spl omega/=0 and /spl omega/=/spl pi/. Depending on the parity of the IIR filter order, the allpass filter is either real or complex. However, in both cases, the resulting IIR filter is real.     

New current-mode current-controlled universal filter with single input and three outputs

In this study, a new current-mode current-controlled universal filter with single input and three outputs is presented. The proposed circuit uses single-output current controlled conveyors (CCCIIs) and can simultaneously realize lowpass, bandpass and highpass filter functions all at high impedance outputs. Realization of notch and allpass responses does not require additional active elements. The circuit enjoys independent current-control of the parameters ω₀ and ω₀/Q without disturbing the gains of the lowpass, bandpass and highpass filters. Both its active and passive sensitivities are low.     

The equivalent circuit model in solid-state electronics—III Conduction and displacement currents

The equilibrium and nonequilibrium equivalent circuits of a single and a multiple energy level recombination centers were developed in parts I and II. This paper extends the analysis to include the nonequilibrium case arising from a d.c. steady state conduction current in the semiconductor structure. Application is made to minority carrier small signal transport in both homogeneous and heterogeneous semiconductors at low steady state levels (P « N in n-type sample). Samples containing p-n junctions are not included but the effect of static, built-in electric field on the signal propagation is considered. In an extrinsic sample, it is shown that the nonequilibrium equivalent circuit is identical to the equilibrium case for considering carrier trapping, recombination and generation at the defect or impurity centers if the recombination conductances and capacitances are defined in terms of the steady-state carrier concentrations. The conditions on the properties of the imperfection centers and the frequency range in which trapping, recombination or generation event dominates at the centers are discussed in detail. It is shown that the effective small-signal minority carrier lifetime, τ_p in n-type semiconductor, is a complex variable due to the charge storage or trapping effect at the centers. In addition, τ_p is positional dependent due to the spatial variation of the steady state carrier concentrations. The small-signal lifetime, τ_p, is substantially different from the steady state lifetime τ_pSS which is commonly used in high-frequency, lumped-model device analysis. For strongly extrinsic samples with low concentration of recombination centers, the usual approximation, τ_p τ_pSS τ_p0 = 1/c_pN_TT, is valid. The lump model approximation to a specimen of length W is rigorously derived for minority carrier transport. It is shown that the commonly used stored-charge lump model is valid only at low frequency and zero recombination when the sample is geometrically divided into two or more lumps. For finite recombination, the effective length of each lump is shorter than at zero recombination and the sum of the length of each lump is less than the physical length of the sample.     

Cascadable current-mode single CCII biquads

A new configuration for the realisation of current-mode single-CCII-biquad (SCB) filters with high output impedance is presented. It can synthesise lowpass, bandpass, highpass, notch, and allpass filtering functions with a single CCII connected to five passive RC one-port elements. The quality factor, Q, and the central frequency, omega /sub 0/, of the proposed SCBs are insensitive to the current tracking error of the CCII. These SCBs have the advantages of low passive sensitivities and independently adjustable omega /sub 0/ or Q.<>     

A novel mixed-mode current-conveyor-based filter

A new mixed-mode biquad circuit is presented. The circuit uses six single-output plus-type second-generation current-conveyors (CCII+s), a single dual-output CCII+, two grounded capacitors, eight resistors, at least two of them permanently grounded, and can realize lowpass, highpass, bandpass, notch, lowpass notch, highpass notch and allpass responses from the same topology. The circuit can be driven by voltage or current and its output can be voltage or current. The parameters ω₀ and ω₀/Q ₀ enjoy independent electronic tunability. Simulation results are included.     

On the Statistics of the Sum of Squared Complex Gaussian Random Variables

In this letter, we derive new results for the statistics of the complex random variable z=^DeltaSigma_n=1 ^N x _n ²=z ₁+jz _Q = re ^jphi where {x _n} is a set of mutually independent complex-valued Gaussian random variables with arbitrary means and equal variances. Each random variable x _n is assumed to have independent real and imaginary components with equal variance for all n. Expressions are derived for the joint probability density function (pdf) of (z ₁,z _Q), for the joint pdf of (r,phi) and also for the marginal pdf of the modulus r. An useful Fourier series expansion for the pdf of the phase phi is also derived. As an application of the results, a theoretical performance analysis of the well-known nondata-aided Viterbi and Viterbi feedforward carrier phase estimator operating with BPSK signals is presented. In particular, the expressions for the exact pdf, variance, and equivocation probability of the carrier phase estimates are derived.     

A versatile current-mode biquad using operational amplifiers

A versatile current-mode biquadratic filter using three operational amplifiers and nine passive elements is proposed. By suitably choosing the output branch, lowpass, bandpass, highpass, bandstop and allpass transfer functions are realized simultaneously without changing the circuit configuration and elements. Two circuits, one is for low frequency application and the other for high frequency, are proposed. The center frequency, quality factor and gain constants of the circuit can be tuned independently. Simulated results show that the circuits work successfully.     

New Universal Filter with One Input and Five Outputs Using Current-Feedback Amplifiers

A new universal voltage-mode second-order filter circuit is presented. The circuit uses five current-feedback operational amplifiers, two grounded capacitors three grounded resistors and three floating resistors. The circuit can realize all the standard filter functions; lowpass, highpass, bandpass, notch and allpass, without changing the passive elements. The proposed circuit enjoys independent grounded-resistance-control of the natural frequency and the bandwidth, low output impedances, high input impedance as well as low active and passive sensitivities.     

一种新颖的电压模式通用二阶CCII滤波器设计

提出了一种基于电流传送器的电压模式通用二阶滤波器电路。该电路由三个电流传送器（CCII＋／-）、两个电容、三个电阻构成，它能实现二阶低通、带通、高通、陷波、全通滤波函数。分析了该电路的电压传输函数及电路参数，并用PSPICE对该电路进行了仿真，仿真结果表明，该电路设计正确，电路结构简单，所用元器件少。     

Voltage-mode multifunction filter using one current feedback amplifier and one voltage follower

A universal voltage-mode second-order filter with three inputs and one output employing one current feedback amplifier, one voltage follower, two capacitors and two resistors is presented. It offers the following features: realization of allpass, notch, highpass, bandpass and lowpass signals from the same configuration, no requirements for component-matching conditions, orthogonal control of natural frequency and bandwidth, low active and passive sensitivities, minimum active and passive components and cascadability.     

MOCCII电流模式二阶滤波器的系统设计

本文提出一种MOCCⅡ电流模式二阶滤波器的一般电路模型和设计理论。根据该电路模型和理论可以产生多种滤波器结构。每一种结构可以实现低通、带通、高通、带阻及全通滤波器或其中的多种滤波器。所有滤波器的无源元件均接地，且具有很低的灵敏度。最后对所产生的滤波器进行了PSPICE模拟。     

High input impedance voltage-mode lowpass, bandpass and highpassfilter using current-feedback amplifiers

A new configuration for realising high input impedance lowpass, bandpass and highpass filters simultaneously by using three current-feedback amplifiers, three grounded capacitors, three grounded resistors and one floating resistor is presented. The proposed circuit offers the following features: realisation of lowpass, bandpass and highpass signals from the same configuration, no requirements for component matching conditions, orthogonal control of ω₀ and Q, the use of grounded capacitors, low active and passive sensitivities and low output impedance     

Three-band biorthogonal interpolating complex wavelets with stopband suppression via lifting scheme

Wavelet research has primarily focused on real-valued wavelet bases. However, the complex filterbanks provide much convenience for complex signal processing. For example, in radar and sonar signal processing, the complex signals from the I/Q receiver can be efficiently processed with complex filterbanks rather than real filterbanks. Specifically, the positive and negative Doppler frequencies imply different physical content in the moving target detector (MTD) and moving target identification (MTI); therefore, it is significant to design complex multiband filterbanks that can partition positive and negative frequencies into different subbands. We design two novel families of three-band biorthogonal interpolating complex filterbanks and wavelets by using the three-band lifting scheme. Unlike the traditional three-band filterbanks, the novel complex filterbank is composed of three channels, including the lowpass channel, the positive highpass channel whose passband distributes in the positive frequency region, and the negative highpass channel in the negative frequency region. Such a filterbank/wavelet naturally provides the ability to extract positive frequency components and negative frequency components from complex signals. Moreover, a novel set of design constraints are introduced to manipulate the stopband characteristic of highpass filters and are referred to as stopband suppression, which strengthens the traditional constraints of vanishing moments. Finally, a numerical method is given to further lower stopband sidelobes.     

Cascadable Current-Mode Biquads

New procedures are presented that yield cascadable, opamp based current-mode biquads from voltage-mode biquads without the use of voltage-mode to current-mode transformations. The opamps in the resulting current-mode circuits can be replaced by current-mode devices, such as current conveyors, producing circuits that are fully current-mode. The procedures are applied to several multi-opamp voltage-mode circuits to achieve current-mode lowpass, highpass, bandpass, notch, and allpass filters. The procedures are also applied to a single opamp circuit. Experimental results are given.     

Selective Digital Filters with Linear Phase

A method for synthesis of digital bandpass and bandstop filters obtained by parallel connection of two allpass networks, is considered. A procedure is based on allpass network linear phase approximation at three levels in mini-max sense, which enables obtaining of selectivedigital filters in form of elliptic filters with linear phase in both passband and stopband.     

Conditions at a p-n junction in the presence of collected current

An abrupt p-n junction, such as occurs at the collector junction of an n-p-n transistor, is considered. The ratio of n- to p-region conductivity is taken to be very high, so that the transition region is restricted almost entirely to the p-region. The electron density distribution n within the transition region is investigated as a function of the applied reverse bias V_c, and of the minority carrier electron current density J which is injected into the transition region from the neutral p-region. It is shown that significant departures occur from the conventional solutions in which the presence of current is neglected. In particular, the electron density n_c at the plane of injection and the transition region thickness w_t, used as collector boundary conditions in the analysis of transistor operation, are shown to be current-dependent.

Two cases are considered. In Case I, applicable to transistors with an epitaxial layer in the base region below the collector, the electron velocity is assumed much less than the limiting drift velocity. For low injection level, where the minority carrier density n is everywhere less than the equilibrium majority carrier density p_p, the transition region is essentially a depletion region and the injected electrons move in an electric field determined uniquely by the applied voltage. It is shown that n_c ∝ J and w_t ∝ V_c^1/2. For high injection level, when n p_p, the transition region is essentially an accumulation region, and conditions of space-charge-limited current flow are established for which n_c ∝ J^2/3 and . The low-level injection results are primarily of interest as analytical extensions of the classical treatment. The high-level injection results are also relevant to the treatment of the dielectric diode.

In Case II, applicable to most alloy and diffused-base transistors, the electron velocity is assumed equal to the limiting drift velocity throughout the transition region. Mobile carrier depletion at low injection again gives way to accumulation at high injection. The functional relationships remain as for Case I at low injection, but become at high injection.

Semi-quantitative and detailed quantitative treatments are developed, and normalized graphs of the minority carrier density as a function of distance within the transition region are given for various junction voltages and injected currents.     

Universal active current filters using single second-generation current conveyor

Two novel universal active current filters, one of which has multiple outputs and the other of which has a single output and high output impedance, employing a single negative second-generation current conveyor, three position-fixed capacitors and four/five position-fixed resistors are proposed. The proposed networks with the advantages of low passive sensitivities can obtain second-order lowpass, bandpass, highpass, notch and allpass current signals by adjusting the magnitudes of a grounded resistor and a grounded capacitor provided that another resistor is separable. The resonance angular frequency and quality factor are insensitive to the current tracking error of the nonideal CCII.<>