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.

Optimum Linear Filter for Speech Transmission

Abstract: A common speech‐communications problem is to maximize speech intelligibility over a noisy channel when the transmitter is peak‐power limited. An optimum linear solution is analytically derived, and consists of a speech‐processing filter in the transmitter. The degree of improvement due to use of the filter is derived for a number of bandwidths and signal‐to‐noise ratios. The filter was experimentally verified by articulation tests as the optimum linear configuration, and was significantly more intelligible than other filters that bounded it. Although the optimum filter depends on the noise spectrum, there is no significant difference between it and a noise‐invariant filter for white or speech‐shaped noise. The use of the filter is equivalent to raising the transmitter power between 1 and 10 dB, depending on the speech bandwidth and the signal‐to‐noise ratio.

Bandpass filter for a CATV converter

Abstract: A bandpass filter for a CATV converter is of the structure with a low-pass filter section with low-pass filters connected longitudinally in a plurality of stages and a high-pass filter section, and comprises a variable trap circuit including a varactor and an inductor, and another varactor connected to one of the capacitors belonging to the low-pass filter section. Capacitances of these varactors are controlled by a tuning voltage so as to eliminate the various problems which would occur in a double-balance mixer to be connected at a later stage in the CATV converter.

Filter and demodulation circuit

Abstract: A filter and demodulation circuit is proposed which, when used in a radio-frequency receiver, produces an increase in the sensitivity of the receiver. In the filter and demodulation circuit, the intermediate frequency is divided into at least two parallel channels (11, 12) at the input (10). Each channel contains a series circuit comprising a mixing and oscillator circuit (13, 15; 14, 16), a controllable IF filter (17, 18), a demodulator (19, 20) and a high-pass filter (21) or low-pass filter (22). One transmission channel essentially transmits the modulation frequencies of a first frequency range only and the other transmission channel transmits the modulation frequencies of a second frequency range. The AF voltage at the output of each transmission channel re-adjusts the IF filter of this channel and the oscillator circuit of the mixing and oscillator circuit of the other channel.

Filter with controlled offsets for active filter selectivity and DC offset control

Abstract: A filter is disclosed that actively controls one or more filter characteristics, such as the cut-off frequency of a selected filter pole, while minimizing the value of selected filter components such as the capacitor components. This helps improve the performance, reliability and yield of the filter. The filter rejects a selected frequency component or frequency band by actively providing an offset signal that effectively cancels the rejected frequency component or frequency band, while allowing the remaining frequency components or frequency bands to pass relatively freely to the output of the filter. The offset signal may also be used to actively reject a DC offset voltage or current from the input signal.

Design of compact bandpass filter with improved selectivity using source-load coupling

Abstract: A compact planar bandpass filter with improved selectivity using source-load coupling is proposed. The new filter consists of quarter-wavelength resonators and short-ended feedlines. An extra transmission zero is produced near the passband owing to the source-load coupling, which can improve the skirt-selectivity of the filter, and quarter-wavelength resonators are used to enhance the rejection level around the second harmonic. Both simulated and measured results with good agreement are presented.