Butterworth filter

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

Development of integrated preamplifier for high-frequency ultrasonic transducers and low-power handheld receiver

Abstract: This paper describes the design of a front-end circuit consisting of an integrated preamplifier with a Sallen-Key Butterworth filter for very-high-frequency ultrasonic transducers and a low-power handheld receiver. This preamplifier was fabricated using a 0.18-μm 7WL SiGe bi-polar complementary metal oxide semiconductor (BiCMOS) process. The Sallen-Key filter is used to increase the voltage gain of the front-end circuit for high-frequency transducers which are generally low in sensitivity. The measured peak voltage gain of the frontend circuits for the BiCMOS preamplifier with the Sallen-Key filter was 41.28 dB at 100 MHz with a-6-dB bandwidth of 91%, and the dc power consumption of the BiCMOS preamplifier was 49.53 mW. The peak voltage gain of the front-end circuits for the CMOS preamplifier with the Sallen-Key filter was 39.52 dB at 100 MHz with a-6-dB bandwidth of 108%, and the dc power consumption of the CMOS preamplifier was 43.57 mW. Pulse-echo responses and wire phantom images with a single-element ultrasonic transducer have been acquired to demonstrate the performance of the front-end circuit.

Active polyphase filter with transconductor cross-coupling of filter sections

Abstract: The invention is an improved implementation of an active-RC polyphase band-pass filter with transconductor cross-coupling between filter sections. The polyphase filter has first to fourth inputs, first to fourth outputs, two filter sections, and a block of transconductor pairs. The four input signals to the polyphase filter succeed one another in phase by 90 degrees. The two filter sections have reactances comprised of active balanced operational amplifiers with matched capacitors in their feedback loops. The block of transconductor pairs is coupled between corresponding reactances of each filter. The transconductance of each transconductor pair is set as the product of a desired radian center frequency and the capacitance of the corresponding matched capacitors. In the preferred embodiment, the transconductors are Gm cells and the transconductance of at least one Gm cell is field adjustable. The filter sections of the preferred embodiment can be a pair of low-pass third-order active-RC gaussian filters or a pair of low-pass sixth-order active-RC gaussian filters.

Moving-average notch filter

Abstract: A moving-average notch filter with a well-defined phase characteristic for use in eliminating oscillation frequencies in a sound amplification system, wherein this moving-average filter is designed to have an output Y K in accordance with the system equation ##EQU1## where b 1 are the weighting coefficients, X K-i are input samples, and K is a constant. This filter may be designed to have a linear phase characteristic. In one embodiment, the location of the notch in the frequency response of the filter may be made to automatically track the drift of an acoustic oscillation frequency.

Switched-Capacitor Fractional-Step Butterworth Filter Design

Abstract: Switched-capacitor fractional-step filter design of low-pass filter prototypes with Butterworth characteristics is reported in this work for the first time. This is achieved using discrete-time integrators which implement both the bilinear and the Al-Alaoui s-to-z transformations. Filters of orders 1.2, 1.5 and 1.8 as well as 3.2, 3.5, and 3.8 are designed and verified using transistor-level simulations with Cadence on AMS $$0.35\,\upmu $$0.35μm CMOS process. Digital programmability of the fractional-step filters is also achieved.

Combined decimation/interpolation filter for ADC and DAC

Abstract: A COMBINED DECIMATION/INTERPOLATION FILTER FOR ADC AND DAC (analog-to-digital converter and digital-to-analog converter) provides a single filter which may be used both as a decimation filter and as an interpolation filter. It is simple and inexpensive. It gains simplicity and inexpensivenes by carefully selecting the tap weights of the filter, cascading multiple filters, time domain multiplexing the multiple filters into a single filter, and using adders instead of multipliers to provide the tap weights.