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.

Harmonic Voltage Reduction Using a Series Active Filter Under Different Load Conditions

Abstract: This paper proposes a series active filter using a simple control technique. The series active filter is applied as a controlled voltage source contrary to its common usage as variable impedance. It reduces the terminal harmonic voltages, supplying linear or even nonlinear loads with a good quality voltage waveform. The operation principle, control strategy, and theoretical analysis of the active filter are presented. These aspects were proven by the results of numerical simulations. Experimental results of the series active filter demonstrated its good performance under different load conditions

An LTCC balanced-to-unbalanced extracted-pole bandpass filter with complex load

Abstract: In this paper, the fundamental characteristics of a novel third-order RF balanced-to-unbalanced filter, namely, a balun filter, for integrated RF module applications are presented. This center-tapped transformer-based new device works concurrently as a balun, an extracted-pole bandpass filter, and a matching network. As coupled resonant tanks are employed to perform the balun type of operation, traditional coupled-resonator filter theory can thus be used to design and analyze such a new device. Moreover, an extracted-pole technique is used not only for creating a transmission zero, but also provides a capability to match the filter with a complex load. In addition to providing a simple design procedure for the device, its working mechanism is also revealed mathematically. Specifically, return-loss sensitivity with respect to each resonator admittance and complex load matching capability are discussed in details. This balun filter has been implemented in a multilayered low-temperature co-fired ceramic substrate, demonstrating its promising potentials in miniaturized RF front-end modules. Experimental measurements are also presented to validate the theory and computer simulations.

Switchless Tunable Bandstop-to-All-Pass Reconfigurable Filter

Abstract: The theory of a new type of bandstop-to-all-pass reconfigurable filter is developed in this work. A bandstop filter structure with both source-to-load and inter-resonator coupling is implemented. The synthesis equations are manipulated such that the signals in the filter's resonators and source-to-load transmission line can be made to constructively or destructively interfere at the output port through tuning of the resonant frequency of the filter's resonators. The relationship between resonator quality factor, filter bandwidth, and the all-pass response state is shown for the first time. The theory is proven through fabrication of a bandstop-to-all-pass filter with resonator unloaded quality factors greater than 500. Measured results show that the filter can continuously tune from insertion loss of 2.1 dB in the all-pass state to insertion loss of 69 dB in the bandstop state at the center frequency of the filter. Analog tuning of the attenuation level is also shown. The capability to switch from an all-pass to a variable-attenuation bandstop response enables a spectrally aware system to operate over wide bandwidths when interference levels are low and to dynamically add bandstop responses when interference affects its performance or signal equalization is required.

Electronically tunable current-mode second-order universal filter using minimum elements

Abstract: A new electronically tunable universal filter with single-input, triple-output employing only four elements (two capacitors and two negative-type second generation current controlled conveyors (CCCII)) is proposed. The proposed filter realises three basic filter functions simultaneously: lowpass, highpass and bandpass. The validity of the proposed filter is verified through PSPICE simulations.

Dual-band filter network

Abstract: A dual band filter network for a radio communication apparatus is provided. The network has an antenna (212) for receiving and transmitting signals from a first frequency band and a second frequency band. The network has a first duplex pair (202) including a first transmit filter (204) including a first passband and stopband. The first duplex pair (202) also includes a second receive filter (206). The first filter (204) presents a consistent phase in the second passband due to the wide frequency separation between the first filter (204) and the second filter (206). The network has a second duplex pair (202') with similar characteristics as the first duplex pair (202). The network also has a switching circuitry (210) controlled by a switch control voltage (214) for selecting the appropriate filter circuitry. The network can be provided in a small sized, low cost package that also offers improved insertion loss performance.