Superconducting spiral wide bandpass filters with wide upper stopband

Wide-band superconducting spiral bandpass filters have been successfully designed and tested. This extends the range of parameters that can be implemented using spirals. The shape of the spiral resonators was significantly modified to achieve the higher coupling coefficients required. A wide upper stopband was produced by using quarter-wave resonators for some of the spirals, and by shifting the second harmonic upwards for the others. One of the filters is eighth order with 1560-MHz center frequency and 27% bandwidth, and has an active area of only 9 mm/spl times/6 mm.     

Universal curves for bandpass filters

Universal curves are presented which permit the determination of bandpass poles when band-edge frequencies and low-pass poles are known. These curves are also useful for band-reject filters.     

Zolotarev bandpass filters

Zolotarev rational functions may be used in certain bandpass filter applications for which two narrower passbands are required. Coupled-resonator low-pass prototypes for narrow bandpass filters based on even- and odd-degree Zolotarev functions are synthesized using a transformed variable. Compared to other filters, those with Zolotarev responses have sharper skirt selectivity, resulting in lower passband distortion     

Inductorless bandpass filters

The technique of designing inductorless filters by replacing the inductors in conventional LC filters with gyrators and capacitors is considered for the special case of the high-quality channel bandpass filters used in multiplex telephony. One particular gyrator circuit, which has been found to be very satisfactory, using two operational amplifiers and four resistors, is analyzed in some detail. The difficulties of simulating floating inductors are discussed, and ways of designing filters to avoid the necessity of such simulations are proposed. The dynamic range of a filter is defined and the factors controlling it are described. Detailed measured results of two specific channel filter designs are included.     

Integrated bandpass filters

The letter presents some new results associated with one bandpass (b.p.) filter configuration of the integrated uniform R0-C0KR0 structure consisting of two rectangular resistive films, one having per-unit-length (p.u.l.) constant series resistance R0 and the other KR0 (where K is a dimensionless constant), separated from each other by a dielectric film having p.u.l. constant shunt capacitance C0. It is shown that the output voltage in the b.p. region may be made almost constant for the load fluctuations in the wide range R0 ? Rt < ? (where Rt = load resistance) by selecting K ? 0.3. The range of variation of Rt producing constant output voltage in the b.p. region is found to be narrower for increasing value of K.     

Two network-frequency transformations for bandpass filters

The two unsymmetrical stopbands of a general parameter bandpass filter can be interchanged by a simple network transformation. Another simple network transformation scales the bandwidth of a narrowband filter while preserving all its shape factors. Both transformations preserve the minimum-inductance property.     

Maximum Q factors for bandpass filters

The letter gives curves that relate the Q factors of the maximum Q pole of a bandpass filter to the normalised bandwidth of the filter.     

Multilevel monolithic inductors in silicon technology

Multilevel monolithic inductors implemented in standard BiCMOS technology are presented. Use of top metal layers shunted with vias provides Q values approaching 10 at 2.4 GHz and above 6 at 900 MHz for a 2 nH inductor. There is no modification to the conventional wiring metallurgy and no need for extra processing steps     

Lossless broad-band monolithic microwave active inductors

Lossless broadband microwave active inductors for general-purpose use in microwave circuits are proposed, and their characteristics are discussed. These active inductors are composed of a common-source cascode FET and a feedback FET, and operate in a wide frequency range with very low series resistance. Their low-loss characteristics are demonstrated by simulation and experimental results. A maximum Q factor of 65 is obtained. Theoretically, it can reach infinity. The inductance value can be controlled by an external voltage control     

Frequency-independent equivalent-circuit model for on-chip spiral inductors

A wide-band physical and scalable 2-/spl Pi/ equivalent circuit model for on-chip spiral inductors is developed. Based on physical derivation and circuit theory, closed-form formulas are generated to calculate the RLC circuit elements directly from the inductor layout. The 2-/spl Pi/ model accurately captures R(f) and L(f) characteristics beyond the self-resonant frequency. Using frequency-independent RLC elements, this new model is fully compatible with both ac and transient analysis. Verification with measurement data from a SiGe process demonstrates accurate performance prediction and excellent scalability for a wide range of inductor configurations.     

Maximum Q-factors for symmetrical bandpass filters

The letter presents curves for the estimation of the maximum pole Q-factors for geometrically symmetrical Butterworth. Cheby?shev and elliptic bandpass filters.     

Millimeter-wave tune-all bandpass filters

Distributed microelectromechanical varactors on a coplanar waveguide have been used to design a two- and four-pole bandpass tune-all filters. The two-pole initial bandwidth is 6.4% at 44.05 GHz with a mid-band insertion loss of 3.2 dB and with matching better than 15 dB. The four-pole initial bandwidth is 6.1% at 43.25 GHz with a mid-band insertion loss of 6.5 dB and with matching better than 10 dB. The use of microelectromechanical system bridges allows a continuous tuning for both center frequency and bandwidth. The varactors biasing network has been designed so that the center frequency and bandwidth can be tuned separately. The two-pole filter center frequency can be changed from 44.05 to 41.55 GHz (5.6% tuning range), while the bandwidth can be independently changed from 2.8 to 2.05 GHz. The four-pole filter center frequency can be changed from 43.25 to 40.95 GHz (5.3% tuning range) and the bandwidth can be changed from 2.65 to 1.9 GHz.     

Millimiter-wave stripline bandpass filters

The possibility to use thin (1 mm or less) pseudocombline structures of λ/2 resonators made of sections of symmetric transmission strip lines from a dielectric material with ε _r = 2.2 as millimeter-wave bandpass filters is shown. It is established that the relative bandwidth of such filters can reach FBW = 0.1. Designs of stripline pseudocombline filters with alternating signs of the coupling coefficients, which are characterized by improved selectivity due to the attenuation poles located on both sides of the passband, are proposed; the filters contain stepped-impedance “half-wave” resonators with a new feature. The results of the computer simulation of the frequency characteristics of the filters in the frequency band of 31–122 GHz and the comparison of them with the characteristics of other filters are presented.     

Realisability of bandpass filters

The traditional method of realising attenuation poles by resonant circuits is questioned. It is shown that, under some conditions, it is possible to depart from the conventional solution.     

Synthesis of direct-coupled-resonators bandpass filters for WDMsystems

A simple technique for the exact synthesis of selective bandpass filters for wavelength division multiplexing (WDM) systems is presented. The filters consist of direct-coupled ring resonators or cascaded Bragg gratings. The proposed technique permits the calculation of the physical dimensions of the optical structures given the desired frequency response of the filter in terms of bandwidth, free spectral range, out-of-band rejection, and frequency characteristic. The technique, explained in detail for Butterworth and Chebyshev frequency responses, is exact, uses closed-form formulae, and is physically well based. The resulting devices are very compact, have a high out-of-band attenuation, and are suitable for high-density integrated optics. Several filters for applications such as channel add-drop, channel selection, demultiplexing, multichannel filtering, and interleavers are designed, analyzed, and discussed in the paper     

New squared-magnitude function for digital bandpass filters

The skirt selectivities at the two ends of the passband of a usual digital bandpass filter may differ considerably if the passband is not symmetrically placed in the baseband. For such cases, a new magnitude function having better frequency characteristics is presented.     

Microwave SAW bandpass filters for spacecraft applications

Microwave SAW bandpass filters for spacecraft applications are described. Two SAW bandpass filters were designed and fabricated in the 1.5 GHz band using temperature-stable ST-cut quartz substrates. The SAW bandpass filters were then assembled in a SAW filter bank. One unique feature of the SAW filter bank is that a broader band is available merely by adding the outputs of SAW bandpass filters adjacent in the frequency domain. Measured electrical responses as well as results of a transmission experiment show satisfactory performance. Effects of the temperature and aging stability characteristics are investigated based on the measured and calculated responses     

Switched-capacitor high-Q bandpass filters for IF applications

Experimental results for a sixth-order switched-capacitor bandpass filter with a selectivity Q of 55 at a center frequency of 3.1 MHz are presented. A simple noise analysis of active bandpass filters composed of coupled identical resonators is introduced to explain the dynamic range reduction in high-Q active filters resulting from loose high-Q couplings between resonators. Theoretical predictions of noise in coupled resonator-type bandpass filters agree well with measured results. The prototype chip occupies 2 mm/SUP 2/ and dissipates 45 mW with a single 5-V supply.     

Improved and physics-based model for symmetrical spiral inductors

Recent growth in RF applications has increased the use of spiral inductors and thus demanded a more accurate model for such devices. In this paper, the authors focus on the model development of spiral inductors with symmetrical terminals, but the same approach can be applied readily to asymmetrical inductors. Relevant and important physics such as the current crowding in metal line, frequency-dependent permittivity in oxide, and overlap parasitics are accounted for. Experimental data and results calculated from the existing inductor models are included in support of the model development.     

Coupled-microstrip bandpass sine filters for broadbandcommunications systems

A bandpass microwave sine filter using coupled microstrip circuits is described. The filter contains three elements; a coupled line filter which creates the main lobe and zeros, a Butterworth filter to reduce out-of-band energy, and an isolation element. Results For a 2.35 GHz filter matched to a 110 MHz chip rate are shown