High-pass Transfer Research Articles

Design of 2-D digital filters with rectangular passbands and stopbands

A modified version of a configuration proposed by K. Hirano and J.K. Aggarwal (1978) for the design of 2-D digital filters with rectangular stopbands is suggested, and sufficient conditions for its correct operation are derived. These conditions are used to show that the nine possible stopbands can be realized by using standard 1-D continuous low-pass, bandpass, or high-pass transfer functions that can be derived from classical analog-filter approximations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Generalized approximation techniques for selective linear-phase digital and nonreciprocal lumped filters

The paper presents expressions for low-pass digital filter transfer functions with finite-band approximation to constant amplitude and delay in the passband, together with an arbitrary number of transmission zeros at half the sampling frequency. The corresponding high-pass filter transfer functions can be obtained by a transformation. The available degrees of freedom can be divided arbitrarily between the passband and stopband responses. The functions are of the nonminimum-phase type, and the corresponding nonreciprocal analog (continuous) filters are also covered; these can be realized in standard active RC structures. The zero-bandwidth cases are obtained, either directly or as limiting cases of the finite-band ones. It is also indicated that there is an upper bound on the number of transmission zeros which may be introduced while maintaining the stability of the filter for a given degree. The technique represents the most comprehensive one available for the solution of the combined amplitude and phase approximation problem, and leads to a large family of stable transfer functions.

Transfer functions for switched-capacitor and wave digital filters

Closed-form expressions are presented for amplitude-oriented low-pass, high-pass, and bandpass sampled-data transfer functions suitable for realization as 1) switched-capacitor lossless discrete integrator (LDI) ladder filters, or 2) wave digital filters. Other types of realizations are also possible, such as those employing voltage inverter switches (VIS's), the recently introduced switched-capacitor "voltage wave" filters, and standard recursive digital realizations. The filters possess optimum equirippie (or maximally flat) passbands and monotonic stopbands with arbitrary selectivity. The low-pass and high-pass cases are derived from distributed passive prototype functions, but the more important bandpass functions are quite novel, appearing here for the first time.

A multi-output second-order digital filter without limit cycle oscillations

A multi-output second-order digital filter without zero-input, constant-input, and forced overflow oscillations is presented. The filter structure can be used for the simultaneous realization of low-pass, high-pass, band-pass, band-stop, all-pass, and general biquadratic transfer functions using two delays, four multipliers, and eleven adders.

A novel two-amplifier universal active switched-capacitor filter

A switched-capacitor (SC) filter circuit realizing low-pass (LP), high-pass (HP), and bandpass (BP) transfer functions is described. This circuit uses only two operational amplifiers (OAs) and is bottom-plate stray-insensitive.

Stability, dynamic range, and roundoff noise in a new second-order recursive digital filter

The limit cycle and roundoff noise behavior of a new second-order digital filter are examined. This digital filter is shown to be free from all constant input limit cycles if magnitude truncation and two's complement arithmetic are used. Low-pass, high-pass, and bandpass transfer functions can be readily obtained by using only two multipliers, two delay elements, and five adders. A closed-form expression of the normalized unit noise gain is derived and compared with the noise gains of other well-known second-order structures.

Universal multiple-output second-order digital filter

A universal, second-order, digital-filter structure is proposed, which realises simultaneously a lowpass, a highpass, a bandpass, a notch and allpass transfer function. The structure uses two unit-delays and four multipliers, and is quite attractive for VLSI implementation since a versatile universal chip can be fabricated, which can be used for the implementation of Butterworth, Chebyshev and elliptic digital filters as well as digital equalisers.

Electronically tunable analog active filters

Electronically tunable <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</tex> -active ladder filter transfer functions are realized by employing the four quadrant analogue multiplier as the basic nonlinear network element. All the frequency dependent branches of a conventional <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</tex> -active ladder structure realizations are simulated by means of impedance scaling networks. The scaling of these impedances allows the cutoff frequency of an elliptic low-pass or high-pass transfer function, of arbitrary order, to be varied by means of a tuning voltage. The method is strictly analogue and leads to practical filters that employ presently available integrated circuits; external timing signals or reference oscillators are not required in order to accomplish tuning.