Butterworth filter

About: Butterworth filter is a research topic. Over the lifetime, 6187 publications have been published within this topic receiving 69070 citations.

Unified active filter biquad structures

Abstract: The authors present a new biquad filter model based on nullators, norators, current mirrors and passive R (resistor) and C (capacitor) elements. Two implementations derived from the new biquad filter model by using second generation current-controlled conveyors (CCCIIs) and operational transconductance amplifiers (OTAs) are also proposed. The two biquad implementations are capable of achieving five important filter performance parameters simultaneously and without trade-offs, including universal filtering, minimum components count and independent control of ωo and ωo/Q. This is unlike recently reported filter structures which make certain trade-offs that emphasise some parameters at the cost of others. Simulation results are included confirming the theoretical prediction.

Input and Output Cross-Coupled Wideband Bandpass Filter

Abstract: A new wideband bandpass filter configuration with input-output cross-coupling is investigated. The new filter is based on a transmission line filter with short-circuited stubs. In order to allow the filter to exhibit high selectivity filtering characteristic and to enhance the group delay with only a few resonators, cross-coupling between the input and output feed lines is introduced. As a result, new symmetrical pairs of transmission zeros are generated at the lower and upper stopbands, leading to a quasi-elliptic function response that improves the passband and out-of-band performances. A general circuit model for the proposed filter is presented and a demonstrator with approximately 48% ripple bandwidth at a midband frequency of 3 GHz is developed. The design is successfully realized in theory and verified by full-wave electromagnetic simulation and the experiment, where excellent agreement is obtained.

Active Filter Design Techniques

Abstract: Publisher Summary The simplest design of a bandpass filter is the connection of a high pass filter and a low pass filter in series, which is commonly done in wideband filter applications. Thus, a first order high pass filter and a first order low pass provide a second order bandpass, while a second order high pass filter and a second order low pass result in a fourth order bandpass response. In comparison to wideband filters, narrowband filters of higher order consist of cascaded second order bandpass filters that use the Sallen–Key or the multiple feedback topology. A filter with an even order number consists of second order stages only, while filters with an odd order number include an additional first order stage at the beginning. For low pass filter design, the higher the corner frequency of a partial filter, the higher is its Q. Therefore, to avoid the saturation of the individual stages, the filters need to be placed in the order of rising Q values. To design the first stage of a third order unity gain Bessel low pass filter, assuming the same values for fC and C1, requires a different value for R1. When operating at unity gain, the noninverting amplifier reduces to a voltage follower, thus inherently providing superior gain accuracy. High pass filters use the same two topologies as the low pass filters: Sallen–Key and multiple feedback. The only difference is that the positions of the resistors and the capacitors have changed. As with the low pass filters, higher order high pass filters are designed by cascading first order and second order filter stages. The filter coefficients are the same ones used for the low pass filter design.

Frequency spectrum based low-area low-power parallel FIR filter design

Abstract: Parallel (or block) FIR digital filters can be used either for high-speed or low-power (with reduced supply voltage) applications. Traditional parallel filter implementations cause linear increase in the hardware cost with respect to the block size. Recently, an efficient parallel FIR filter implementation technique requiring a less-than linear increase in the hardware cost was proposed. This paper makes two contributions. First, the filter spectrum characteristics are exploited to select the best fast filter structures. Second, a novel block filter quantization algorithm is introduced. Using filter benchmarks, it is shown that the use of the appropriate fast FIR filter structures and the proposed quantization scheme can result in reduction in the number of binary adders up to 20%.

2 GHz $rm Q$ -Enhanced Active Filter With Low Passband Distortion and High Dynamic Range

Abstract: A tunable Q-enhanced filter with low passband distortion is presented. The Q of the on-chip spiral inductors that form the filter resonators is enhanced by using a cross-coupled differential pair which is degenerated by a second LC tank. This technique allows for frequency dependent compensation of inductor losses and ensures that the Q-enhanced LC resonators have a frequency behaviour close to the ideal in the passband of the filter. The circuit allows DC voltage control of Q-enhancement. The filter centered at 2.0 GHz with a 130 MHz bandwidth is tunable in frequency by 3%, exhibits a -6.6 dBm 1-dB compression point and a 15 dB noise figure while consuming 17 mW of DC power. The circuit was fabricated in 0.18-mum CMOS and the performance was verified experimentally