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.

Development of active filter with series resonant circuit

Abstract: An active AC harmonic filter, composed of high-frequency inverters and a series-resonant LC circuit turned to the fundamental frequency, is proposed to solve harmonic distortion problems on distribution systems at lower cost and with higher efficiency. The design includes a voltage-source inverter for further decrease of the loss, a static-induction thyristor for instantaneous current response, control logic that takes into account the coupling circuit characteristics, and high-speed harmonic voltage detection to suppress overloading of the customer's LC filter. Operational experience with a prototype filter on a 6.6 kV system is presented, verifying reduction of the operating and improvement of the transient response. In particular, there is a sharp reduction of inverter rating and operating loss about one-third to one-fourth, compared to results for an active filter without a coupling circuit. >

A high-speed continuous-time bandpass VHF filter in MOS technology

Abstract: A very high frequency (VHF) second order bandpass filter has been developed. The filter is based on a minimal transistor-only all-MOS high-frequency generalized impedance converter (GIC) that simulates a passive RLC ladder. The filter poles are obtained using the internal lumped capacitances of the MOS transistor. Using this structure a very high frequency filter is obtained consuming a small chip area. The center frequency is controlled by an external bias current to the circuit. Using the GIC, a bandpass filter can be implemented in MOS technology with center frequencies in excess of 50 MHz. The filter is simulated for center frequencies of 47 MHz, 54 MHz and 63 MHz. >

Electronic switchable bandpass filter using PIN diodes for wireless low cost system-on-a-package applications

Abstract: A reconfigurable band-pass filter for wireless applications has been designed and demonstrated. The topology has been designed on Duroid, a low cost organic substrate intended for system-on-a-package (SOP) applications. The design achieves discrete bandwidth tuning by direct manipulation of its geometry and implements PIN diodes as switching elements. The filter was designed with a centre frequency of 5.8 GHz and a passband tunablity ratio of 2:1. Several tests such as one-tone power handling and two-tone intermodulation measurements were conducted to investigate the filter's response to different power signal levels as well as the level of signal distortion. The filter produced third-order intermodulation intercept points (IIP3s) greater than 46 dBm around the centre frequency for tones separated by 1 MHz. The resulting circuit presented here does not produce significant distortion and it is capable of handling signals with power levels greater than 2 W. The two distinct bandwidths produced by the filter were 10.12% with an insertion loss of 3.95 dB and 5.43% with an insertion loss of 4.73 dB. The physical size of the fabricated filter layout including the realisation of bias circuitry is comparable to the size of a conventional filter.

Ultrasonic wave generating apparatus with voltage-controlled filter

Abstract: The present invention deals with an ultrasonic wave generating apparatus with voltage controlled filter, comprising a phase comparator which detects a shifted value from a predetermined phase difference between a driving voltage or a driving current of an ultrasonic transducer and a vibratory velocity signal, and a voltage-controlled band-pass filter which is controlled by the output of the phase comparator and which is provided in a feedback loop from the vibratory velocity signal to an input of a driving amplifier of the ultrasonic transducer, wherein the oscillating frequency is changed while following the resonant frequency of the ultrasonic transducer, so that stable operation is materialized without developing abnormal oscillation in subresonant frequencies and permitting very small following error.

Digital $Q$ -Varying Notch IIR Filter With Transient Suppression

Abstract: In many measurement applications, it is required to have notch filters that simultaneously possess a very selective magnitude response (high quality factor Q) and a transient response of short duration. However, increasing the quality factor also increases the duration of the transient process in the filter after the action of the excitation. This paper presents a new concept of digital IIR notch filters, whose quality factor changes with time. Owing to a temporary change in the value of the quality factor, the transient can considerably be reduced. Simulations verifying the effectiveness of the proposed Q-varying IIR notch filter are presented and compared with the performance of the traditional Q-constant filter using ECG signals with unwanted sinusoidal interference as a study case.