Recursive algorithms for deriving bandpass or band-rejection filters from lowpass filters

Two recursive algorithms are presented for calculating the coefficients of a bandpass transfer function, given the lowpass prototype transfer function. In both cases, the method is general, valid for prototypes having both poles and zeros, and provides excellent accuracy. Moreover, it is shown that the coefficients of band-rejection filters can be derived by using either algorithm.<>     

Current-mode lowpass and bandpass filters using the operational amplifier pole

This paper proposes a circuit configuration for realizing current-mode lowpass and bandpass filters using the operational amplifier (op.-amp.) pole. The circuit simultaneously realizes lowpass and bandpass transfer functions using an op.-amp., three resistors and a capacitor. The effects of the paras tic poles (i.e. second and third poles) of the op.-amp. on the gain of a lowpass filter are also presented. Since the circuit uses the op.-amp. pole, it is suitable for high frequency operation.     

Voltage-mode highpass,bandpass and lowpass filters using two DDCCs

A new configuration for realizing voltage-mode highpass, bandpass and lowpass filters, simultaneously, using two differential difference current conveyors (DDCCs), two grounded capacitors and two grounded resistors is presented. The proposed circuit offers the following features: realization of highpass, bandpass and lowpass signals from the same configuration, no requirements for component matching conditions, the use of only grounded capacitors and resistors, high input impedance, low active and passive sensitivities and simpler configuration due to the use of only two DDCCs and four passive components.     

Current-mode highpass, bandpass and lowpass filters using the operational amplifier pole

The use of the Operational Amplifier (OA) pole has received much attention for its potential advantages of miniaturization, ease of design and high frequency performance. This paper proposes a novel circuit configuration for realizing current-mode filters using the OA pole. The circuit realizes simultaneously highpass, bandpass and lowpass transfer functions. Since the circuit uses the OA pole, it is suitable for high frequency operation.     

Sensitivity comparison of symmetric and asymmetric dual-mode bandpass filters

Sensitivity analysis of dual-mode filters shows: (a) approximately the same sensitivities for the symmetric and asymmetric realisations; (b) a trend that the further the physical cavity from the input/output ports, the higher is its sensitivity. These findings should help in the design of dual-mode filters for spacecraft application.     

High output impedance current-mode lowpass,bandpass and highpass filters using current controlled conveyors

Three new current-mode second-order filter configurations which employ one or two current controlled conveyors (CCCIIs) and three passive elements are presented. Each proposed filter can realize one of the bandpass, lowpass or highpass responses all at high impedance outputs. The proposed filters offer current-control of pole angular frequency ω_o without disturbing the parameter ω_o /Q. No component matching is required and all the passive and active sensitivities are low. PSPICE simulation results are given to confirm the theoretical analysis.     

Thin bandpass filters containing sections of symmetric strip transmission line

Thin (1-mm thick or thinner) combline bandpass filters based on sections of symmetric strip transmission lines and containing closely spaced (0.1–0.2 mm apart) stepped-impedance resonators are described. It has been found that, if these filters are made on high-permittivity ceramic substrates, their dimensions prove to be smaller than the dimensions of other ceramic-based filters. Various frequency characteristics of these filters—symmetric, with increased one-sided selectivity, and with a constant delay time—have been analyzed. The experimental results obtained for a 1-mm-thick bandpass filter with ? _r = 9.7 are in good agreement with the computer-simulation data.     

Fast synthesis of coupled-resonator filters

This letter proposes a new quickly converging technique for the synthesis of coupling matrix of cross-coupled resonator filters. The method formulates the synthesis as a nonlinear least squares problem involving the zeroes and poles of short circuit input and output admittances, as well as eigenvalues of the coupling matrix and its principal sub-matrices. The solution is found via a damped Levenberg-Marquardt method with analytically computed gradients. Numerical tests show that coupling matrices for high order pseudo-elliptical filters can be found in surprisingly few optimization steps.     

Variable lowpass wave-digital filters

The letter describes how the configurations and the coefficient values of a class of lowpass wave-digital filters realised in special-purpose hardware may be controlled by a microcomputer.     

Universal curves for bandpass filters

Universal curves are presented which permit the determination of bandpass poles when band-edge frequencies and low-pass poles are known. These curves are also useful for band-reject filters.     

Millimetre-wave low-loss finline lowpass filters

Millimetre-wave low-loss finline filters, with very sharp cutoff, consisting of a number of notches periodically spaced along the single-ridge finline are described. Measured pass-band insertion losses ranged 0.5 to 1 dB for Q-band (33 to 50 GHz) filters have been achieved. These results demonstrate the technological advance of millimetre-wave filters using finline integrated circuits.     

Novel microwave integrated lowpass filters

The procedure is described for synthesising Cauer Cheby?shev lowpass filters of the third order as rectangular microwave integrated structures. The synthesis procedure is based on a two-mode approximation and leads to structures with very small dimensions compared with the usual realisations of such type of filters. The experimental behaviour is shown to be quite satisfactory, particularly in the passband, where the filters show a better performance than the corresponding lowpass prototypes.     

Zolotarev bandpass filters

Zolotarev rational functions may be used in certain bandpass filter applications for which two narrower passbands are required. Coupled-resonator low-pass prototypes for narrow bandpass filters based on even- and odd-degree Zolotarev functions are synthesized using a transformed variable. Compared to other filters, those with Zolotarev responses have sharper skirt selectivity, resulting in lower passband distortion     

Interpolated narrowband lowpass FIR filters

The article describes a class of digital filters, called interpolated finite impulse response (IFIR) filters that can implement narrowband lowpass FIR filter designs with a significantly reduced computational workload relative to traditional FIR filters. Topics discussed include: optimum expansion factor choice, number of FIR filter taps estimation, IFIR filter performance modeling, passband ripple considerations, implementation, and filter design.     

Quadrature-modulation-type lowpass and highpass filters

Quadrature-modulation filters, introduced by the author four years ago, can be realised in two different configurations. It is shown that, in the transition bands of the `star?-structured filters, `unwanted? output frequency components (i.e. components not present at the input) are generated, but that, in `lattice-structured? filters, semiequivalent to the corresponding star configuration, such unwanted components are (or can be) suppressed.     

Inductorless bandpass filters

The technique of designing inductorless filters by replacing the inductors in conventional LC filters with gyrators and capacitors is considered for the special case of the high-quality channel bandpass filters used in multiplex telephony. One particular gyrator circuit, which has been found to be very satisfactory, using two operational amplifiers and four resistors, is analyzed in some detail. The difficulties of simulating floating inductors are discussed, and ways of designing filters to avoid the necessity of such simulations are proposed. The dynamic range of a filter is defined and the factors controlling it are described. Detailed measured results of two specific channel filter designs are included.     

Very longwavelength lowpass interference filters

The extension of metallic mesh interference filter techniques to wavelengths longer than 2000 μm is discussed. The problems associated with design considerations and removal of leaks is considered in some detail. Successful filters were produced with edges at 6.3 cm^?1 and 4.3 cm^?1. When used in series and with a specific optical system, good rejection of unwanted radiation was achieved.     

Integrated bandpass filters

The letter presents some new results associated with one bandpass (b.p.) filter configuration of the integrated uniform R0-C0KR0 structure consisting of two rectangular resistive films, one having per-unit-length (p.u.l.) constant series resistance R0 and the other KR0 (where K is a dimensionless constant), separated from each other by a dielectric film having p.u.l. constant shunt capacitance C0. It is shown that the output voltage in the b.p. region may be made almost constant for the load fluctuations in the wide range R0 ? Rt < ? (where Rt = load resistance) by selecting K ? 0.3. The range of variation of Rt producing constant output voltage in the b.p. region is found to be narrower for increasing value of K.     

Two network-frequency transformations for bandpass filters

The two unsymmetrical stopbands of a general parameter bandpass filter can be interchanged by a simple network transformation. Another simple network transformation scales the bandwidth of a narrowband filter while preserving all its shape factors. Both transformations preserve the minimum-inductance property.