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.

Integrated circuit tuner with broad tuning range

Abstract: An integrated front end filter for a tuner provides an array of from several to a multitude of passbands, each for passing at least one but less than all channels designated in a band of frequencies. Each passband is exclusively selectable. The integrated front end filter can include at least one active filter unit with an active reactance element in either of fixed and variable filter configurations and a decoder coupled to said at least one active filter unit and being responsive to a control signal for selecting a one of the passbands. In one example, a multitude of active filter units of fixed filter configuration provide the multitude of passbands. In another example, a plurality of data corresponds to a like plurality of selectable passbands in combination with a filter element of the variable filter configuration. Each data is stored at a predetermined location and reproduced in response to a corresponding control data signal from a tuner controller. Each data characterizes one of the plurality of passbands. The filter element is switchable from one passband to another in response to the control data signal. Lower power dissipation and lesser requirements of an on-following integrated circuitry tuner permit a reduction of “off chip” connections and cost.

Adjustable bandwidth optical filter

Abstract: THE OPTICAL APPARATUS USED IN A TELEVISION SYSTEM, FOR EXAMPLE, INCLUDES A SERIES ARRANGEMENT OF THREE BIREFRINGENT ELEMENTS OF DIFFERENT THICKNESS INTERSPERSED WITH TWO QUARTER WAVE DELAY ELEMENTS TO CONSTITUTE AN OPTICAL FILTER. THE FILTER IS PLACED IN THE LIGHT PATH BETWEEN AN OBJECT AND THE IMAGE FORMED AT THE PHOTOSENSITIVE ELEMENT OF A CAMERA TUBE. THE SPATIAL FREQUENCY BANDWIDTH OF THE LIGHT PASSING THROUGH THE FILTER IS CONTROLLABLE IN ONE OR MORE DIRECTIONS AND IN THE SAME OR DIFFERENT AMOUNTS IN A PLURALITY OF DIFFERENT DIRECTIONS BY SUITABLE DIMENSIONING OF THE BIREFRINGENT ELEMENTS AND/OR BY APPROPRIATE ROTATIONAL POSITIONING OF THE ENTIRE FILTER ABOUT THE OPTICAL AXIS.

A Three-Pole 1.2–2.6-GHz RF MEMS Tunable Notch Filter With 40-dB Rejection and Bandwidth Control

Abstract: This paper presents a high-performance three-pole tunable notch filter with frequency and bandwidth control. The filter is implemented using suspended-stripline resonators and planar 3-bit RF MEMS capacitive networks. A tuning range of 1.1-2.7 GHz with a 40-dB rejection bandwidth of 115±25 MHz is demonstrated with a passband insertion loss <; 0.8 dB. A 40-dB rejection bandwidth of 26-126 and 24-200 MHz is demonstrated at 1.6 and 2.0 GHz, respectively. The filter introduces no noticeable distortion of wideband code-division multiple-access (WCDMA) waveforms with a power of 25 dBm at frequencies corresponding to the 30-40 dB nulls and at the - 3-dB and - 6-dB passband frequencies. At the - 0.5-dB passband frequency, the filter can handle up to 30 dBm of WCDMA power with no measurable distortion. To our knowledge, this filter represents state-of-the-art tuning performance and power handling for planar notch filter designs. The application areas are in wideband cognitive radios with high interference levels.

Enhanced control of grid-connected inverters with non-linear inductor in LCL filter

Abstract: In grid-connected inverters, utilisation of an appropriate output filter is vital to improve power quality. However, the filter, which comprises of capacitor and inductor(s), should be cost effective. In this study, an LCL filter with non-linear inverter-side inductor is used to reduce the filter volume and cost. In order to harness the undesirable non-linear behaviour of the LCL filter's inductor, a new control scheme based on proportional-resonant controller is proposed. The control strategy is based on combinational feedback of inverter-side and grid-side currents, with online adaptive estimation of non-linear inductor. With this scheme, the harmonic compensators’ gains can be reduced, while stability margins and dynamic response are improved. Therefore, while a cost-effective filter is used at the inverter output, acceptable total harmonic distortion is achieved. Experimental tests based on a 7 kW digital signal processor controlled prototype inverter are provided to verify the proposed control strategy for grid-connected inverters with LCL output filter benefiting from low-cost non-linear inductor.