Butterworth filter

About: Butterworth filter is a research topic. Over the lifetime, 6187 publications have been published within this topic receiving 69070 citations.

Diplexer for television tuning systems

Abstract: A diplexer comprises a first frequency selective filter coupled between its first input terminal and a circuit point, a second frequency selective filter coupled between the circuit point and its output terminal, and third frequency selective filter coupled between its second input terminal and the circuit point. The first filter selects frequencies higher than a first frequency and the second filter selects frequencies lower than a second frequency which is higher than the first frequency. The third filter selects frequencies lower than a third frequency which is lower than the first frequency. In a television receiver, the first and second filters serve as a bandpass filter for the UHF band, and the third filter passes the VHF and CATV bands.

Decimation filtering apparatus and method

Abstract: A decimation filtering apparatus using interpolated second order polynomials compensates for a droop caused by a CIC (Cascaded Integrator-Comb) filter (51). The decimation filter includes a CIC decimation filter (51) for decimation filtering the sampling signal to downconvert a sampling signal; an ISOP filter (53) for monotanically increasing an output of the CIC decimation filter (51) to compensate for a passband droop caused by the CIC decimation filter (51); a multistage halfband filter (55) including at least one modified halfband filter for 1/2 decimating a signal output from the ISOP filter (53), the multistage halfband filter (55) decimating the signal output from the ISOP filter (53) to downconvert the signal; and a programmable FIR (Finite Impulse Response) filter (57) for compensating for a passband droop of a signal output from the multistage halfband filter (55).

Band-pass filter circuit

Abstract: A band-pass filter circuit comprising a band-pass filter for removing noise modulation components from an input signal comprising a carrier sine wave, a phase detector for detecting a phase difference between input and output signals of the band-pass filter, a loop filter supplied with the output from the phase detector, and automatic control means for effecting control by the output from the loop filter so that a difference between the frequency of the input sine wave and the center frequency of the band-pass filter is reduced to zero. For carrier recovery in a burst mode, the loop filter is selected for each particular case so that high-speed pulling-in is possible even if a narrow-band filter is employed as the band-pass filter for the removal of noise components. Also, high-speed and high-precision pulling-in is achieved when many bursts of different frequencies are applied in one frame period. Further, when common and individual frequency variations occur at the same time, high-speed pulling-in is also achieved for each burst.

A New Class of Low-Loss High-Linearity Electronically Reconfigurable Microwave Filter

Abstract: A novel electronically reconfigurable microwave bandpass filter based on a switched delay-line approach is presented. In contrast to conventional tunable filters, the approach enables the lossy and nonlinear switching elements to be used as part of the coupling elements rather than within the resonators. Therefore, the filter distinguishes itself through its ability to provide a wide tuning bandwidth with low passband loss and high linearity. Theoretical analysis of the approach is presented in this paper. The feasibility of the approach has been experimentally verified with microstrip circuit prototypes. The filter produced a maximum passband loss of 1.7 dB and a third-order intercept point of >32 dBm with 35% tuning bandwidth.

A Widely-Tunable, Reconfigurable CMOS Analog Baseband IC for Software-Defined Radio

Abstract: This paper describes a reconfigurable analog baseband (ABB) for a software-defined radio (SDR). A wide variety of filter characteristics needed for SDR can be obtained by a reconfigurable filter based on a newly developed duty-cycle controlled discrete-time transconductor. The ABB, implemented in a 90 nm CMOS process, provides second- and fourth-order Butterworth, Chebyshev, and elliptic responses with bandwidths from 400 kHz to 30 MHz. The chip draws only 12 mA and achieves a P1dB of +7 dBm with a 1.0 V supply. The input-referred integrated in-band noise is 0.31 mVrms and the die area is as small as 0.57 mm2.