Showing papers on "Waveguide filter published in 1991"

Miniature dual mode microstrip filters

Abstract: A new generation of planar dual mode filters is introduced which offers significant size, weight, and cost advantages over previous designs. All currently used elliptic function, self-equalized, etc. filter designs can be implemented in microstrip using this new concept. The proposed filter structures are ideally suited for implementation using high-temperature superconductors. Basic dual mode resonator and filter structures are discussed, and experimental data for proof-of-concept filters implemented using both normal and superconducting microstrip are presented. Superconducting realizations of this class of filters may be used to replace bulkier, heavier filters currently used for satellite communications. >

Tunable microwave and millimeter-wave band-pass filters

Abstract: The authors present an overview of tunable microwave and millimeter-wave bandpass filters realized in different technologies. Some general design principles are described. Recent progress in the performance of various tunable filters is reported. The authors survey magnetically tunable filters (ferrimagnetic resonance filters, magnetostatic-wave filters, evanescent waveguide filters, E-plane printed circuit filters), electronically tunable filters, and mechanically tunable filters. The typical performance parameters are summarized. This comparison shown that none of these devices can simultaneously satisfy all requirements for perfect tunable filters. For microwave systems where multioctave tuning is essential, a YIG filter is an obvious choice. In systems where the requirement of high power handling capability combined with low insertion loss, predominates, mechanically tunable filters and magnetically tunable E-plane filters are recommended. If the tuning speed is a crucial requirement, varactor-tuned filters or E-plane filters with ferrite toroids are devices of choice. For millimeter-wave design, the most promising structures are ferrimagnetic resonance filters utilizing hexagonal ferrite resonators or, up to 60 GHz, magnetically tunable E-plane printed circuit filters. >

Theoretical and experimental characterization of coplanar waveguide discontinuities for filter applications

Abstract: A full-wave analysis of shielded coplanar waveguide (CPW) two-port discontinuities based on the solution of an appropriate surface integral equation in the space domain is presented. Frequency-dependent scattering parameters for open-end and short-end CPW stubs are computed using this method. The numerically derived results are compared with measurements performed in the frequency range 5-25 GHz and show very good agreement. From the scattering parameters, lumped-element equivalent circuits have been derived to model the discontinuities. The inductors and capacitors of these models have been represented by closed-form equations, as functions of the stub length, to compute the circuit element values for these discontinuities. >

All-fiber filter for efficient dispersion compensation.

Abstract: A dispersive filter is proposed that is based on the coupling, with a chirped periodic perturbation, of two copropagating waveguide modes that have different group velocities. Numerical calculations show that a nearly constant dispersion can be obtained over the filter bandwidth. Pulse recompression by a factor of 10 or more is possible. The filter could be made with photoinduced refractive-index gratings in optical filters.

Electronically switchable and tunable coplanar waveguide-slotline band-pass filters

Abstract: A coplanar waveguide (CPW)-slotline bandpass filter is described. The circuit allows planar integration of active and passive semiconductor devices both in series and in shunt. A microstrip-to-slotline transition designed to test the filter is also described. Two of the transitions exhibit an insertion loss of less than 1.0 dB over the 2.0-4.0-GHz range. A three-section CPW-slotline bandpass filter demonstrates an insertion loss of less than 0.2 dB over the passband centered at 2.9 GHz. A three-section CPW-slotline switchable bandpass filter integrated with three p-i-n diodes is discussed. It has a 0.7-dB insertion loss in the passband when the p-i-n diodes are off and a 25.0-dB isolation across the entire band when the p-i-n diodes are on. A three-section CPW-slotline varactor-tunable filter integrated with three varactor diodes is presented, showing a 2.0-dB insertion loss and over 20% electronic tuning range. Simple transmission line circuit models are used to optimize the design. >

A two-step synthesis of broadband ridged waveguide bandpass filters with improved performances

Abstract: A quarter-wave broadband ridged waveguide bandpass filter with improved attenuation has been designed and realized. The two-step synthesis uses an equivalent network whose parameters are obtained with a multimodal variation approach that characterizes the discontinuities involved in the structure. It is shown that the frequency behavior of the filter is determined at this step by the chosen filter prototype. The structure is optimized taking into account all side effects (higher order modes, dispersion) and the rectangular to ridged waveguide transformer. Predicted data are compared with measured data and good agreement is observed. It is shown how the use of lambda /4 resonators improves the attenuation in the upper stop-band and reduces the filter volume, which is important in on-board satellite telecommunication systems. >

Vertically coupled InGaAsP/InP buried rib waveguide filter

Abstract: We report the first demonstration of narrowband (<17 A full width at half maximum) wavelength selective grating‐assisted coupling between vertically stacked buried rib InGaAsP/InP channel waveguides These vertically coupled channel waveguides form the basis both of integrable filters essential to photonic circuits such as amplifier/filter and demultiplexer/detector circuits as well as a general approach to vertical integration of photonic circuits

High-speed optical signal processing potential of grating-coupled waveguide filters

Abstract: The application of grating-coupled waveguides to spread spectrum fiber-optic communications systems is described. It is first shown that such a device can act as its own matched filter for impulsive excitation, which allows its use as an encoder and decoder of ultrashort pulses. This is true even in the case of strong coupling, although considerable pulse distortion occurs. A typical performance that might be expected from existing technology is then outlined, and a number of numerical examples are presented to illustrate typical signal processing operations.

Design and performance of a high-T/sub c/ superconductor coplanar waveguide filter

Abstract: The design of a coplanar waveguide low-pass filter made of YBa/sub 2/Cu/sub 3/O/sub 7- delta / (YBCO) on an LaAlO/sub 3/ substrate is described. Measurements were incorporated into simple models for microwave CAD analysis to develop a final design. The patterned and packaged coplanar waveguide low-pass filter of YBCO, with dimensions suited for integrated circuits, exhibited measured insertion losses when cooled in liquid nitrogen superior to those of a similarly cooled thin-film copper filter throughout the 0 to 9.5 GHz passband. Coplanar waveguide models for use with thin-film normal metal (with thickness either greater or less than the skin depth) and YBCO are discussed and used to compare the losses of the measured YBCO and copper circuits. >

800 MHz High Power Bandpass Filter using TM Dual Mode Dielectric Resonators

Abstract: A novel high power bandpass filter using TM110 dual mode dielectric resonators was developed. TM110 dual mode is achieved with dielectric resonators physically coupled in an asymmetrically orthogonal manner and these arrayed resonators are constructed in monoblock and have high unloaded Q. By assembling these resonators, an 800 MHz high power bandpass filter was realized. Specific features achieved with this new filter are, center frequency of 840 MHz, band width of 40 MHz, and insertion loss of 0.4 dB. Physical size is 80×90×180 mm. Volume is less than 30% of conventional type high power bandpass filter using cavity resonators. This filter is useful as an antenna filter for cellular base stations.

Coupling for dual-mode resonators and waveguide filter

Abstract: Dual-mode resonators are coupled together to form a highly selective bandpass filter by means of a short section of waveguide. The short sections have cutoff frequencies beyond the passband of the filter. The coupling is adjustable over a wide range by means of adjustable screws. The coupling means is applicable to both empty cavities and dielectric-resonator-loaded cavities.

Superconducting millimeter-wave E-plane filters

Abstract: The authors report on the measured performance of a three-pole E-plane filter constructed from high-T/sub c/ superconducting bulk materials at 34.5 GHz. Experimental results are presented for the insertion loss and return loss of the filter at 77 K. The problems associated with the use of bulk materials at the millimeter-wave range are addressed. Other possible superconducting waveguide filter configurations are proposed. While the experimental results are taken at low input power level, the current distribution inside the filter structure is calculated, and the power handling capability of the superconducting filter is discussed. >

Microwave filter with a wide spurious-free band-stop response

Abstract: The present invention is directed to reducing the number of components required to minimize intermodulation distortion within the wide transmission frequency band used by a satellite communications repeater system. In particular, at least two TM010 mode cavity is cascaded to a plurality of TE113 mode cavities to form a narrow band-pass, wide band-stop filter for receiving and outputting channel signals to the multiplexer manifold of a satellite repeater. The filter thus constructed realizes the narrow band-pass response required in microwave communications, while eliminating the spurious resonance frequencies normally eliminated by additional filter components. In this manner, the size and weight considerations of the satellite system are improved without loss in performance.

Microstrip spur-line broad-band band-stop filter

Abstract: This invention discloses a band-stop filter, which has multiple sections of non-uniform and unbalanced microstrip transmission line. Such a structure can optimize the characteristics and maximize the matching frequency range. The total length of the filter can be reduced to a half of that of a conventional filter, and the insertion loss in the pass-band is reduced to a third of that of a conventional filter. Besides, this invention suggests a structure which does not require the inward etching of the microstrip line. Instead, the microstrip line itself is used directly as the building element of a spur-line filter. Thus, the tolerance in fabrication can be greatly relaxed without effecting the required characteristics.

Method of interference reduction for frequency multiplexed optical fiber communication

Abstract: A fiber-optic bandpass filter comprising a resonant cavity formed in an optical waveguide is coupled to a fiber-optic bus which carries a large number of frequency multiplexed channels. The fiber-optic bandpass filter is selected to be one-half the modulation wavelength of the desired center frequency within a range of frequencies carried on the same transmission. The creation of a resonant cavity at the desired center frequency provides a filter which reduces the intensity of signals at surrounding frequencies so that an overall reduced output power is provided, resulting in less cross-talk between a large number of frequency multiplexed signals which, unfiltered, would all have equal power. The filter is broad enough that many adjacent channels are not significantly attenuated. The optical waveguide of which the filter is formed may be in the form of an optical fiber segment or a planar waveguide.

Backward-wave suppression in a very wide-band helix travelling-wave tube using a slow waveguide filter

Abstract: In octave bandwidth travelling-wave tubes (TWT), employing helical slow-wave circuits, suppression of the backward-wave, which produces an unwanted oscillation just above the highest frequency of the normal operating band, is usually achieved by means of ‘lossy serpentine resonators’ deposited on the helix support rods This technique is wholly satisfactory when the power levels involved are modest However, when significant power levels are required, these deposited resonators are insufficiently robust and an alternative procedure is required This paper describes an external slow-waveguide filter which extracts the backward-wave oscillation (BWO) energy in the output section of a travelling-wave tube through an array of apertures in the helix shield

Microstrip design laboratory

Abstract: Design concepts, fabrication, measurements, and optimization of a microstrip filter, directional coupler, and amplifier are presented. The microstrip circuit implementation is simple and easily alterable for optimization. Results from an undergraduate laboratory course are presented which show reasonable agreement with design parameters, and the optimization process adds to the educational experience. >

High-dielectric constant stripline band-pass filters

Abstract: High-dielectric constant (K=38) stripline was employed to realize selective bandpass filters. Seven-pole, gap-coupled filters centered at 6.0 and 8.0 GHz were designed for 140-MHz 3-dB bandwidths. The unloaded Q, choice of operating impedance, and the role played by higher order modes has been both analytically and experimentally considered. It has been found that experiment and theory are in good agreement, and allow the present results to be used in predicting performance levels for use in future designs. Miniaturization of high-performance filters has been demonstrated. Such filters are expected to find application in frequency multiplexers as well as in individual circuits, particularly with MMIC (microwave monolithic integrated circuit)-based systems. >

Mirror-folded polarization-independent wavelength filter

Abstract: A 1.55- mu m polarization-independent optical bandpass filter with a 3-dB bandwidth of 6 AA and a tuning range of at least 100 AA is demonstrated. The photonic circuit of the filter consists of a waveguide TE-TM mode splitter, two parallel electrooptic TE-to-TM, TM-to-TE mode converters as the wavelength selective element, and a reflective mirror at the far end of the crystal. The circuit can be viewed as a mirror-folded version of the polarization-independent filter. It is shown that by passing the light two times through the narrowband mode converters, the filter bandwidth can be reduced by about a factor of two compared to a conventional single-pass filter of the same length. A novel tunable mode converter structure is also demonstrated that allows coherent in-phase mode conversion during the two passes through the mirror-folded filter. >

Superconductive waveguide filter

Abstract: Filter apparatus comprises at least one superconductive element 13 within a waveguide 12 and forming at least part of a resonant structure. This gives a low loss filter with a uniform passband. A plurality of superconductive elements 13-16 may be provided and by controlling the state of the elements so that they are either superconductive or non-superconductive it is possible to control the filter characteristics after assembly or during operation of the filter.

The rigorous CAD of aperture-coupled T-junction bandstop-filters, E-plane circuit elliptic-function filters, and diplexers

Abstract: The rigorous computer-aided design (CAD) of waveguide bandstop filters, elliptic-function E-plane integrated circuit filters with additional bandstop cavities, and high-return-loss E-plane T-junction diplexers with iris matching elements is introduced. Based on the general rectangular waveguide T-junction key building block modal S-matrix, the design takes into account both the finite thickness of all coupling elements and the higher order mode interaction at all step discontinuities. The theory is verified by measurements. >

High frequency ladder type piezo-electric filter with differently poled series and parallel resonators

Abstract: A ladder type piezo-electric filter comprising series piezo-electric resonators and parallel piezo-electric resonators having improved second harmonic mode, high resonance response and anti-resonance impedance near 1-7 MHz, for use in communication applications requiring filter shaving resonator dimensions less than 5 mm and operating frequencies in excess of 455 kHz.

The simplified real frequency method applied to the active filters synthesis

Abstract: A direct method for the design of active filters using the simplified real frequency technique is presented. This method bypasses the analytic theory and yields the maximum flat transducer power gain possible. An example for low-pass filters is given. The example involves an active filter over the band 1-5 GHz, with a transmission zero at 5.6 GHz. >

Selectivity-improved e-plane filter for millimetre-wave applications

Abstract: Measurements on a Ka-band selectivity-improved E-plane filter prototype are compared with computed predictions and are found to be in excellent agreement. The measured insertion loss is 1.55 dB, and the bandwidth is 180 MHz centred at 32.8 GHz. These prototype measurements confirm that this design has the potential for significantly improving the performance of filter components in the millimetre-wave frequency range.

Characterization of microstrip open end in the structure of a parallel-coupled stripline resonator filter

Abstract: An accurate characterization of the stripline open end in the parallel-coupled microstrip filter configuration is described. The method of analysis is based on a two-port resonance technique where the spectral-domain approach is used as a full-wave analysis. Even- and odd-mode edge effects are characterized separately by solving transcendental equations. Calculated results are used for the design of certain filters. Experimental results show excellent filter performances. >

Multiple‐quantum‐well nonlinear waveguide grating device

Abstract: We report on the preliminary experimental demonstration of a multiple‐quantum‐well waveguide grating element. Due to optical nonlinearities in a multiple‐quantum‐well layer incorporated into the structure, the out‐coupling angle of the grating is varied by the intensity of light in a guided mode. Experiments with GaAs‐based planar as well as rib waveguide samples confirmed theoretical predictions. Changes in the coupling angle obtained are on the order of minutes. The demonstrated principle can be employed in fine tuning of the coupling angle, fine focusing of the output beam, or as a nonlinear beam‐steering method for dispersion measurements.

Analysis and design of a novel microwave active filter

Abstract: The theory and design of a novel microwave active bandpass filter structure using a combination of microstrip line resonators and FETs are described. The resulting filter not only compensates for losses but also produces positive gain. It has superior performance regarding harmonic bands compared with an end-coupled filter structure using the same number of resonators. A 350-MHz bandwidth bandpass filter in the S-band region was designed and fabricated to verify the described technique and to investigate the effects of parasitic and feedback elements of the active devices on the filter performance. The measured results are in good agreement with the predicted results. >

HTSC microstrip UHF filter at 2 GHz

Abstract: HTSC planar high Q resonators can be used to realize microstrip filters. These filters have a low insertion loss and a sharp slope. The size of the substrates of 10 mm*10 mm leads to a low frequency limit of about 2 GHz for a two-pole filter. At 77 K the measured on-chip insertion loss of a two-pole Butterworth bandpass filter with 3% relative bandwidth is less than 0.2 dB. The complete filter including housing and coaxial connectors has an insertion loss of 0.4 dB. Improving the structuring process and reoptimizing the filter design will improve the filter characteristic. Particular low-loss bonded contacts instead of silver paint between the coaxial microstrip transition will decrease the insertion loss of the filter. Outer dimensions of the filter housing with coaxial connectors are 34 mm*30 mm* 20 mm. Waveguide filters with comparable filter characteristics will be approximately 100 times larger in volume than planar HTSC filters and they are useless for a planar system with active and passive components on a single board.

Agile microwave filter having at least one ferrite resonator

Abstract: An agile microwave filter tunable by ferrite is constituted as a filter having dielectric confinement resonators and as a result comprises an evanescent mode waveguide and resonant cylinders placed in the waveguide. In addition, the cylinders are made of ferrite and means are provided for applying an adjustable magnetic field thereto, thereby enabling the center frequency of the filter to be shifted.

Tunable microwave filter

Abstract: Ferrite-tuneable agile microwave filter. It is built as a filter with resonators with dielectric confinement, and therefore comprises an evanescent-mode guide (2) and resonant cylinders (15, 16) placed in this guide. Furthermore, means (11A, 11B, 17) are provided for applying an adjustable magnetic field (H1, H2) to these cylinders (15, 16), which have the feature of being made of ferrite, in order to shift the central frequency of this filter.