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.

Multiple mode RF power converter

Abstract: This disclosure relates to radio frequency (RF) power converters and methods of operating the same. In one embodiment, an RF power converter includes an RF switching converter, a low-drop out (LDO) regulation circuit, and an RF filter. The RF filter is coupled to receive a pulsed output voltage from the RF switching converter and a supply voltage from the LDO regulation circuit. The RF filter is operable to alternate between a first RF filter topology and a second RF filter topology. In the first RF filter topology, the RF filter is configured to convert the pulsed output voltage from a switching circuit into the supply voltage. The RF filter in the second RF filter topology is configured to filter the supply voltage from the LDO regulation circuit to reduce a ripple variation in a supply voltage level of the supply voltage. As such, the RF filter provides greater versatility.

A Complex Adaptive Notch Filter

Abstract: A complex adaptive notch filter is developed, for tracking single-sided (a.k.a. analytic or complex) tones immersed in background noise. A complex all-pass based realization is pursued which inherits useful properties from its real counterpart: independent tuning of the notch frequency and attenuation bandwidth, easy realization of the complementary band-pass filter, unbiased frequency estimation, and faster convergence and tracking than a gradient descent algorithm.

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.

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%.

Hybrid parallel active/passive filter system with dynamically variable inductance

Abstract: A parallel hybrid active filter system for harmonic compensation of large non-linear loads is provided. The hybrid filter includes a passive filter connected in series with an inverter that is controlled to produce a dynamically variable inductance at selected harmonic frequencies. The passive filter may include passive capacitive and inductive elements, or may include a power factor correction capacitor alone, with all the inductance for the hybrid filter provided by the active filter inverter. The active filter inverter is controlled to provide the dynamically variable inductance by a synchronous reference frame (SRF) based controller that generates active filter inverter voltage commands that are fed to a PWM or square wave modulated voltage source inverter (VSI). The SRF controller includes an inductance command generator that generates the inductance value necessary to provide harmonic compensation from measured three phase load and filter currents transformed into a two phase synchronous rotating reference frame. A single inverter may be controlled to implement variable inductances for compensation of multiple harmonic frequencies by superposition of active filter inverter voltage commands from multiple SRF controllers. The active filter inverter is also preferably controlled by a SRF based DC bus controller to provide for maintenance of a DC bus voltage providing power to the inverter without affecting the harmonic compensation of the hybrid filter.