Voltage-controlled filter

About: Voltage-controlled filter is a research topic. Over the lifetime, 5514 publications have been published within this topic receiving 70872 citations. The topic is also known as: VCF.

An adaptive analog continuous-time CMOS biquadratic filter

Abstract: An adaptive analog continuous-time biquadratic filter is realized in a 2- mu m digital CMOS process for operation at 300 kHz. The biquad implements the notch, bandpass, and lowpass transfer functions. The update method is based on a LMS algorithm which adapts the notch frequency to minimize the power at the notch filter output. Applications include FM demodulators (linear and frequency shift keying), clock extractors, and frequency acquisition aids for phase-locked loops and Costas loops. Measured results from experimental prototypes are presented. >

A 600 kHz electrically-coupled MEMS bandpass filter

Abstract: This paper presents a 600 kHz MEMS bandpass filter implemented using electrical coupling of single crystal silicon HARPSS micromechanical resonators. Passive and active filter synthesis approaches based on electrical coupling of capacitive MEMS resonators are introduced and discussed. A third order passive bandpass filter at the center frequency of 600 kHz with a bandwidth of 125 Hz, a stopband rejection of 48 dB, and a 20 dB-shape-factor of 2.1 is demonstrated. A quality factor (Q) enhancement technique based on active electrical cascading of the resonators is also presented. A 3-stage active cascade at 600 kHz demonstrated a 2/spl times/ increase in the effective Q.

User interface for the control of an audio spectrum filter processor

Abstract: A user interface control apparatus is disclosed for the control of electronic filter parameters of audio spectrum equalizers, crossovers, and other filter processors. The user interface apparatus comprises five pushbutton keys arranged in a specific cross-shaped pattern. This single arrangement of control keys provides a common user interface control apparatus which can be used to control one or more filter types. Depression of particular keys, or particular combinations of keys can be made to electronically control multiple filter parameters, some simultaneously, and for different filter types depending on the filter type for which the invention is applied. The unique arrangement of the invention's pushbutton keys facilitates an intuitive operation of the various parameters for bell, notch, shelf, and pass-band audio filter types with a minimal number of control elements and minimal control area. The filter parameters of a bell filter that can be controlled include center frequency, amplitude, and bandwidth. The filter parameters of a notch filter that can be controlled include center frequency and bandwidth. The filter parameters of a shelf filter that can be controlled include transition frequency, shelf amplitude, and transition slope. The filter parameters of a pass-band filter that can be controlled include corner frequency, pass-band amplitude, and filter slope. Additionally, the unique arrangement of keys facilitates intuitive control of some filter parameters at two rates of continuous change. Also, the user interface allows control of a graphic equalizer, where the selection of a particular bell filter, or “band”, can be scanned at two different rates. Finally, the user interface allows the control of the corner frequencies of two adjacent pass-band filters simultaneously, such as in a crossover processor, so as to preserve the combined response of the two filters over the overlapping region.

Dual-band bandpass filter using stub loaded resonators with multiple transmission zeros

Abstract: A dual-band bandpass filter using both an open stub-loaded resonator (OSLR) and a short stub-loaded resonator (SSLR) is presented. The use of SSLR has the advantage that a transmission zero can be flexibly controlled by tuning the length of the short stub, which can be employed as a new but convenient way to create transmission zeros in front of passbands in filter design. By further introducing a two-order planar transversal filter structure using the OSLR as well as the source-load coupling, a dual-band filter is implemented with four transmission zeros and exhibits high skirt selectivity based on the simulated result. Two passbands with center frequencies of 2.45 GHz and 3.5 GHz are achieved with compact size of about 0.18λ × 0.12λ at 2.45 GHz.

A Wide Tuning Range $G_{m}$ – $C$ Continuous-Time Analog Filter

Abstract: A CMOS operational transconductance amplifier (OTA) for low-power and wide tuning range filter application is proposed in this paper. The OTA can work from the weak inversion region to the strong inversion region to maximize the transconductance tuning range. The transconductance can be tuned by changing its bias current. A fifth-order Elliptic low-pass filter implemented with the OTAs was integrated by TSMC 0.18-mum CMOS process. The filter can operate with the cutoff frequency of 250 Hz to 1 MHz. The wide tuning range filter would be suitable for multi-mode applications, especially under the consideration of saving chip areas. The third-order inter-modulation (IM3) of -40 dB was measured over the tuning range with two tone input signals. The power consumption is 0.8 mW at 1-MHz cutoff frequency and 1.8-V supply voltage with the active area less than 0.3 mm2