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.

Half-Mode Substrate Integrated Waveguide (HMSIW) Filters and its Application to Tunable Filters

Abstract: —In this paper, novel bandpass filter and tunable bandpass filter are designed based on half-mode substrate integrated waveguide (HMSIW) embedded with complementary resonators Various passband characteristics are observed, and lumped equivalent circuit analysis models are developed The configuration of the proposed bandpass filter is an open structure, and it is easy to load the active devices and build the bias/control networks on the signal plane The tunable bandpass filter is presented based on the proposed novel bandpass filter loaded with semiconductor varactor diodes, and it has good spurious suppression characteristics and excellent out of band rejection The prototype with overall size of 159 mm × 302 mm × 05 mm was designed and fabricated so as to validate the new structure The measured central frequency is 1538 GHz and 1718 GHz, and the insertion loss is 51 dB and 33 dB, at 0 V and 30 V, respectively

High-speed tunable microwave photonic notch filter based on phase modulator incorporated Lyot filter

Abstract: A high-speed tunable microwave photonic notch filter with ultrahigh rejection ratio is presented, which is achieved by semiconductor optical amplifier (SOA)-based single-sideband modulation and optical spectral filtering with a phase modulator-incorporated Lyot (PM-Lyot) filter. By varying the birefringence of the phase modulator through electro-optic effect, electrically tuning of the microwave photonic notch filter is experimentally achieved at tens of gigahertz speed. The use of SOA-polarizer based single-sideband modulation scheme provides good sideband suppression over a wide frequency range, resulting in an ultrahigh rejection ratio of the microwave photonic notch filter. Stable filter spectrum with bandstop rejection ratio over 60 dB is observed over a frequency tuning range from 1.8 to 10 GHz. Compare with standard interferometric notch filter, narrower bandwidth and sharper notch profile are achieved with the unique PM-Lyot filter, resulting in better filter selectivity. Moreover, bandwidth tuning is also achieved through polarization adjustment inside the PM-Lyot filter, that the 10-dB filter bandwidth is tuned from 0.81 to 1.85 GHz.

Filter device for suppressing harmonics in radio frequency signals when dual frequencies exist

Abstract: The present invention relates to a power amplifier device (10), switchable for at least two separate basic frequency bands, for radio frequency signals with effective suppression of harmonics, where harmonics, corresponding to a first basic frequency band, can be permitted to overlap the frequency range of at least one second basic frequency band The power amplifier device (10) comprises a power amplifier (1) and an impedance matching circuit (2), switchable by means of a PIN-diode, which provides a load impedance adapted to each individual basic frequency band Furthermore, the power amplifier device comprises a filter device (3) comprising a fixed low-pass filter (3b) and a switchable filter (3b) acting as an engageable and disengageable notch filter, which comprises at least one reversible PIN-diode This switchable filter (3a) allows to pass, in a first mode, signals in the first basic frequency band and suppresses at the same time at least one order of harmonics corresponding to this basic frequency band In a second mode, the second basic frequency band is transmitted without appreciable losses, and harmonics are suppressed by the fixed low-pass filter (3a)

Compact planar and vialess composite low-pass filters using folded stepped-impedance resonator on liquid-Crystal-polymer substrate

Abstract: A compact composite low-pass filter, designed by the image parameter method and semilumped component approach, will be described and results for cutoff frequency ranging from C- to V-band will be presented. This composite design combines four filter sections and the presence of a strong attenuation pole near the cutoff frequency provides an extremely sharp attenuation response, while ensuring good matching properties in the passband, making this filter design very attractive for harmonic spurious response suppression or diplexing. The lumped-element schematic of the filter has been implemented using a combination of a stepped-impedance filter and folded stepped-impedance resonators. The overall folded layout has been optimized using full-wave simulation and occupies an ultra-compact area of only 5/spl times/5 mm/sup 2/ for a C-band filter. Measured results exhibit rejection of the attenuated pole greater than 40 dB. Similar filter designs have been realized for C- and V-bands. These filters have been fabricated on a liquid-crystal-polymer substrate demonstrating a high performance, ultra-compact, and very low-cost solution for RF and millimeter-wave applications.

Control strategies of active filters in the context of power conditioning

Abstract: Active power filters have been intensively explored in the past decade Various topologies and control schemes have been documented aiming at reducing the cost and improving the performance of the compensation system Hybrid active filters inherit the efficiency of passive filters and the improved performance of active filters, and thus constitute a viable improved approach for harmonic compensation In this paper a parallel hybrid filter is studied for current harmonic compensation The hybrid filter is formed by a single tuned LC filter per phase and a small-rated power three-phase active filter, which are directly connected in series without any matching transformer The required rating of the active filter is much smaller than a conventional standalone active filter would be No additional switching-ripple filter is required for the hybrid filter because the LC filter functions not only as a harmonic filter but also as a switching-ripple filter around 10 kHz Simulation results and experimental results obtained in laboratory confirmed the validity and effectiveness of the control