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.

Quad-band bandpass filter design by embedding dual-band bandpass filter with dual-mode notch elements

Abstract: A quad-band bandpass filter of compact dimensions by embedding several dual-mode notch elements into a stub-type dual-band bandpass filter is presented, and the four passbands are achieved by splitting the two passbands of the dual-band bandpass filter with two notch bands generated by the dual-mode notch elements. A prototype filter with passbands located at 1.4–1.7, 2.1–2.3, 3.3–3.6 and 5.2–5.4 GHz is designed with the help of optimisation methods. Good agreement between simulations and measurements are achieved, demonstrating good features such as controllable and wide bandwidths, higher filter order, compact dimensions and high isolations.

A CMOS switched-current filter technique

Abstract: Basic design techniques and considerations for switched-current (SI) circuits are presented, and experimental results from integrated filters are given. By means of analogies to switched-capacitor circuits, a five-pole lowpass Chebyshev SI filter has been integrated in a 2- mu m N-well, double-metal CMOS technology. The average die area is about 200 mil/sup 2/ per SI pole. The current mirror gain factors were derived by means of signal flow-graph techniques starting with the RLC prototype. A doubly terminated five-pole Chebyshev filter was designed for a 0.1-dB ripple bandwidth of 5 kHz with a sampling frequency of 128 kHz. The measured response is shown. The noise floor is about 70 dB down with respect to the passband. A three-pole elliptic SI filter has also been integrated to illustrate the realization of transmission zeros with SI filter techniques. >

A GNSS interference identification using an adaptive cascading IIR notch filter

Abstract: A low-complexity time-domain approach for global navigation satellite systems is proposed to detect and identify single-tone, multi-tone, swept continuous wave interference (CWI) and band-limited white Gaussian noise (BLWN). An adaptive notch filter and adaptive cascading filter structure are employed to identify the type of interference signals. The number of the cascading stages is selected by comparing the total power in receiver bandpass, and after, passing the adaptive notch filter. For this reason, the proposed filter structure is more efficient in identifying and mitigating interference signals than the conventional filter structure. In addition, the automatic gain control gain is used to detect the existence of continuous wave interference. The performance of the interference detection and identification method is evaluated for the cases of GPS signal in the presence of single-tone, multi-tone, swept CWI and BLWN.

Differential Type Class-AB Second-Order Log-Domain Notch Filter

Abstract: In this paper, a new current-mode second-order differential type Class-AB log-domain notch filter is proposed. It is systematically designed using state-space synthesis method. The filter circuit is current-mode, Class-AB and differential type. In the circuit, the input and the output values, and dominant variables are all currents. Input and output currents are also differential signals. Only transistors and grounded capacitors are required to realize the filter circuit. Three cases of the second-order notch filter were obtained. The regular notch was obtained when omegan=omega0, the low-pass notch was obtained when omegan>omega0, and the high-pass notch was obtained when omegan>omega0. The center frequency, the notch frequency, the quality factor, and gain of the filter can be electronically tuned by changing external currents. Time and frequency-domain simulations are performed using PSPICE program for the filter to verify the theory and to show the performance of it. For this purpose, the filter is simulated by using idealized bipolar junction transistor models and AT&T CBIC-R (NR200N-2X NPN), (PR200N-2X PNP) type transistors.

A windowing approach for designing critically sampled nearly perfect-reconstruction cosine-modulated transmultiplexers and filter banks

Abstract: A very fast technique for designing nearly perfect-reconstruction (NPR) critically sampled cosine-modulated M-channel transmultiplexer (TMUX) and filter bank (FB) systems is proposed. This technique is based on using the windowing technique for designing the prototype filter so that its 3-dB cutoff frequency is located at /spl omega/=/spl pi//(2M). The motivation for this is the observation that if the prototype filter cascaded with itself is a 2Mth filter, then the resulting TMUX (in the case of an ideal channel being a pure delay) or FB system has approximately a perfect-reconstruction (PR) property. This implies that for this cascade the 6-dB cutoff point should be approximately located at /spl omega/=/spl pi//(2M), and, correspondingly, the 3-dB cutoff frequency of the prototype filter is located at this angular frequency. The main advantage of the proposed design scheme is that it significantly lowers the computational complexity when compared with other existing techniques proposed for designing critically sampled cosine-modulated TMUX or FB systems. The PR property is not achieved, but for the resulting TMUX (FB) systems, the intersymbol interference and crosstalk errors (the amplitude and alias errors) are small. Both of these errors are small enough in practical systems. Several examples are included illustrating these desired properties.