High-selectivity Bandpass Research Articles

A simple method to design a compact and high performance wideband filter

AbstractIn this letter, a simple method to design a compact and high performance dual hooks wideband filter with open stubs is presented. By combining the coupled line section with two tapped open stubs, a wideband filter with wide stopband and very high passband selectivity is realized. This filter at center frequency f0 of 5.3 GHz has presented very good measured characteristics, including 3‐dB fractional bandwidth of 85%, very low insertion loss of −0.5 ± 0.3 dB, wide stopband from 8 to 15 GHz, and very high selectivity near the passband edge. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 822–824, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22268

High selective stepped-impedance dual-band bandpass filter

A high selective stepped-impedance dual-band bandpass filter is presented. The filter has a feature of two tunable passbands over a wide frequency range and compact size. A multi-coupling scheme is introduced so that two finite transmission zeros are generated between the two passbands to achieve a high out-of-band rejection. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1964–1966, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21831

Hybrid narrow-band tunable bandpass filter based on varactor loaded electromagnetic-bandgap coplanar waveguides

A varactor-loaded resonator inserted between two Bragg reflectors has been implemented to design high-selectivity tunable bandpass filters. First, a mechanical tuning method is demonstrated. A varactor tunable bandpass filter is then implemented at 9 GHz, yielding good agreement between computational and experimental results. The tuning range reaches 3.5% with a loaded quality factor Q/sub L/=40, a maximum insertion loss of 4.75 dB, and a return loss exceeding 20 dB. The theory is carefully explained, showing the importance of the parameters of the Bragg reflectors and of the resonator, in particular, the effect of diode-case parasitics and varactor position with respect to the resonator. A large-signal experimental analysis is done, showing a maximum allowable input power of a few dBm. Finally, possible filter improvements are discussed, and simulations with a microelectromechanical systems varactor are shown.

Reduced‐size wideband microstrip bandpass filter with low loss and high selectivity

AbstractA reduced‐size low‐loss high‐selectivity wideband microstrip bandpass filter is proposed using three λg/4 short‐circuited stubs and folded λg/2 connecting lines between them. The filter has 2n − 1 poles within the passband, whereas it consists of only n resonators. The 3‐dB bandwidth of the filter is about 92% at 2.1 GHz. The insertion loss is around 0.8 dB within the passband. The filter is verified by both simulation and measurement. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 147–148, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20751

New microstrip diplexers using open-loop ring resonators with two transmission zeros

This paper presents a diplexer with good isolation constructed by two high-selectivity bandpass filters. The high-selectivity filter is designed by an asymmetrically fed structure that shows two transmission zeros next to the passband of the filter. By using a simple equation, the locations of the transmission zeros are designed at the passbands of the filters in order to filter out unwanted signals and obtain good isolation for the diplexer. The insertion loss of the diplexer is less than 2.2 dB and the isolation is greater than 41 dB. This high-performance diplexer can be used in many wireless communication systems. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 396–398, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20647

Low-loss and high-selectivity bandpass filter with harmonic suppression and piezoelectric transducer tuning

A low-loss and high-selectivity bandpass filter with harmonic suppression and piezoelectric transducer (PET) tuning is presented. At the 3.5 GHz passband, the insertion loss is 1.48 dB, and the transmission zeros at 3.05 and 4.08 GHz have rejection of 55 dB. The rejection at the 7 GHz second harmonic is 50 dB. A PET tunes the bandstop sections to obtain a tunable suppression (>45 dB) around the second harmonic from 5.35 to 7.8 GHz.

High-Selectivity Switched-Capacitor Bandpass Filter with Quasi-Continuous Quality Factor Tunability

This paper describes the design and implementation of a second-order switched-capacitor (SC) bandpass (BP) filter with very wide quality factor (Q) programmability range. The filter selectivity is digitally programmed by varying the effective sampling frequency of an SC branch, without modifying any capacitor value. The proposed approach allows a quasi-continuous Q-factor tunability avoiding, in principle, the inherent quantization error associated to any traditional programming technique. Automatic Q-factor tuning is performed by using a scheme based on an amplitude-locking loop approach. Experimental results obtained from a 0.8-µm CMOS integrated prototype demonstrate the versatility of the proposed technique for high-Q SC BP filters.

A high-selectivity switched-capacitor bandpass filter

A high-selectivity switched-capacitor bandpass filter is presented. The filter center frequency is 100 kHz with a -3 dB bandwidth of 980 Hz (i.e., with a quality factor Q/spl sim/100). This has been implemented with a 12th-order transfer function whose poles are placed at only two frequencies. This choice has been used in the integrated circuit realization. In fact, the transfer function has been implemented using the cascade of six biquad cells of only two types. For the available 20 samples, the center frequency mean-value error is lower than 0.2%, and the Q mean-value error is lower than 0.2% as well. The filter is realized in a not-recent BiCMOS technology (L/sub NMOS/=4 /spl mu/m, L/sub PMOS/=3 /spl mu/m). The same performance (opamp, switches, and overall filter) can be easily obtained with a standard scaled-down (0.35 /spl mu/m, for instance) CMOS technology. In this direction, an evaluation of the area and power consumption of the circuit as implemented in a standard 0.35-/spl mu/m CMOS technology is finally given.

A 10.7-MHz BiCMOS high-Q double-sampled SC bandpass filter

A fundamental block in telecommunication systems is the high-selectivity bandpass filter centered at the intermediate frequency (IF). In this paper, a BiCMOS high-Q (Q=29) 10.7-MHz switched-capacitor (SC) bandpass filter to be used in the FM receiver channel has been developed. The filter uses low-gain large-bandwidth opamps. The opamp finite gain effects have been compensated using an SC integrator suited for high-Q filters. The particular SC finite-gain compensation scheme allows the implementation of double sampling to relax opamp bandwidth requirements. To reduce total output noise, noisy T-cell networks (often used in other cases) have been avoided. The resulting large capacitors (the largest capacitor is 8.5 pF) are driven by a Class AB output buffer. In a 1.2-/spl mu/m BiCMOS technology, the filter prototype has an area of about 1.6 mm/sup 2/ and a power consumption of 17 mW. The in-band noise density is 380 nV//spl radic/Hz, and the dynamic range is about 68 dB for a 3% IM.

GaAs integrated RC active filters with high-selectivity bandpass and low-selectivity bandstop responses

This paper presents bandpass and bandstop second-order RC active filters integrated on GaAs and operating above 1 GHz. In particular, high-selectivity bandpass filters have been investigated and two structures are proposed. These structures combine high selectivity and low sensitivity more easily than classical filters when only low-gain elements are available, and they may therefore also be useful at high frequencies. The quality factor of the proposed GaAs implementations of these structures can be tuned up to 50 typically when low-accuracy tuning biases are used.

Fine-structure of energy spectra of velocity fluctuations in the transition region of a two-dimensional wake

Measurements of the fine-structure of the energy spectrum of the velocity fluctuations were made in the transition region of a two-dimensional wake. Line and continuous spectra were determined separately with a high-selectivity band-pass filter. The transition was initiated by an external sinusoidal sound. The sound-induced periodic fluctuation and the natural random fluctuation in the wake were added and a system of line and continuous spectra was formed. Higher harmonics of the periodic component were produced by the nonlinear interaction. As a result of the interaction between discrete and continuous components, a continuous spectrum was generated at low wavenumbers. A simple model for the interaction is proposed. The evolution of the spectrum is explained by three fundamental rules concerning the nonlinear interaction between spectral components: (i) the growth of a spectral component is suppressed by the presence of another strong component, (ii) mutual interaction is more effective when the amplitudes of interacting components are closer, and (iii) a stronger interaction takes place between components of closer wavenumbers. The randomization of the regular fluctuation is properly expressed as the growth of the ‘randomness factor’, the ratio of the energy of the random components to the total fluctuation energy.