Showing papers on "Insertion loss published in 1997"

Planar microwave integrated phase-shifter design with high purity ferroelectric material

Abstract: Ferroelectric materials (FEM's) are very attractive because their dielectric constant can be modulated under the effect of an externally applied electric field perpendicular to the direction of propagation of a microwave signal. FEM may be particularly useful for the development of a new family of planar phase shifters which operate up to X-band. The use of FEM in the microwave frequency range has been limited in the past due to the high losses of these materials; tan /spl delta/=0.3 at 3 GHz is typical for commercial BaTiO/sub 3/ (BTO) and due to the high electric field necessary to bias the structure in order to obtain substantial dielectric constant change. In this paper, a significant reduction in material losses is demonstrated. This is achieved by using a new sol-gel technique to produce barium modified strontium titanium oxide [Ba/sub 1-x/Sr/sub x/TiO/sub 3/ (BST)], which has ferroelectric properties at room temperature. Also demonstrated is how the use of thin ceramics reduces the required bias voltage below 250 V, with almost no power consumption required to induce a change in the dielectric constant. A phase shift of 165/spl deg/ was obtained at 2.4 GHz, with an insertion loss below 3 dB by using a bias voltage of 250 V. Due to the planar geometry and light weight of the device, it can be fully integrated in planar microwave structures.

Design, fabrication, and characterization of form-birefringent multilayer polarizing beam splitter

Abstract: Polarizing beam splitters that use the anisotropic spectral reflectivity (ASR) characteristic of high-spatial-frequency multilayer binary gratings have been designed, fabricated, and characterized. Using the ASR effect with rigorous coupled-wave analysis, we design an optical element that is transparent for TM polarization and reflective for TE polarization at an arbitrary incidence angle and operational wavelength. The experiments with the fabricated element demonstrate a high efficiency (97), with polarization extinction ratios higher than 220:1 at a wavelength of 1.523 m over a 20 angular bandwidth by means of the ASR characteristics of the device. These ASR devices combine many useful characteristics, such as compactness, low insertion loss, high efficiency, and broad angular and spectral bandwidth operations.

Novel ferroelectric materials for phased array antennas

Abstract: Various composites of barium strontium titanium oxide (BSTO) combined with other nonelectrically active oxide ceramics have been formulated for application in phased array antennas. In general, the composites have adjustable electronic properties which can be tailored for use in phased array antennas and other phase shifting devices. The dielectric constant and the loss tangents have been reduced to enhance the overall impedance matching and thereby lowering the insertion loss of the device. In addition, the overall tunability, the change in the dielectric constant with applied voltage, is maintained at a sufficiently high level. In order to address a broad frequency range in the microwave region, the composites have been fabricated in bulk ceramic, thick film, and thin film form. This article discusses the processing, material characterization, and electronic properties of the composites in MHz and GHz frequencies.

Monolithically integrated switched capacitor bank using micro electro mechanical system (MEMS) technology

Abstract: A monolithically integrated switched capacitor bank using MEMS technology that is capable of handling GHz signal frequencies in both the RF and millimeter bands while maintaining precise digital selection of capacitor levels over a wide tuning range. Each MEMS switch includes a cantilever arm that is affixed to the substrate and extends over a ground line and a gapped signal line. An electrical contact is formed on the bottom of the cantilever arm positioned above and facing the gap in the signal line. A top electrode atop the cantilever arm forms a control capacitor structure above the ground line. A capacitor structure, preferably a MEMS capacitor suspended above the substrate at approximately the same height as the cantilever arm, is anchored to the substrate and connected in series with a MEMS switch. The MEMS switch is actuated by applying a voltage to the top electrode, which produces an electrostatic force that attracts the control capacitor structure toward the ground line, thereby causing the electrical contact to close the gap in the signal line and connect the MEMS capacitor structure between a pair of output terminals. The integrated MEMS switch-capacitor pairs have a large range between their on-state and off-state impedance, and thus exhibit superior isolation and insertion loss characteristics.

Silicon-on-insulator (SOI) phased-array wavelength multi/demultiplexer with extremely low-polarization sensitivity

Abstract: We demonstrate the first phased-array wavelength multiplexer fabricated in the silicon-on-insulator (SOI) waveguide technology. The four-channel wavelength division multiplexer (WDM) has a channel spacing of 1.9 nm centered at 1550-nm wavelength and a 3-dB channel bandwidth of 0.72 nm. The crosstalk to neighboring channels is less than -22 dB and the on-chip insertion loss is below 6 dB for all channels. The TE-TM shift is less than 0.04 nm which is the smallest attained without compensation techniques in any integrated optic technology.

(YBa2Cu3O7−δ,Au)/SrTiO3/LaAlO3 thin film conductor/ferroelectric coupled microstripline phase shifters for phased array applications

Abstract: We report on the design, fabrication, and testing of novel YBa2Cu3O7−δ/SrTiO3/LaAlO3 (YBCO/STO/LAO) and Au/SrTiO3/LaAlO3 (Au/STO/LAO) coupled microstrip line phase shifters (CMPS). These CMPS were tested at frequencies within the Ku and K bands (12–20 GHz), at temperatures from 24 to 77 K, and at dc voltages (Vdc) from zero to 350 V. A relative insertion phase shift (Δφ) of 390° was measured for an eight-element YBCO/STO/LAO CMPS at Vdc=350 V, 16 GHz, and 40 K. At 77 K, a Δφ ∼260° was obtained for the CMPS at the same bias and frequency. Both results correspond to an effective coupling length of 0.33 cm. At both temperatures, the phase shifter exhibits a figure of merit of ∼30°/dB. To our knowledge, these are the best results published so far at these frequencies where miniaturization, insertion loss, and phase delay are key considerations.

Fiber gratings in lasers and amplifiers

Abstract: The emergence of UV-written fiber gratings, both short and long period, as a reliable fiber technology has revolutionized the field of active fiber devices. The advantageous properties of spectral selectivity, low insertion loss, and component ruggedness have made devices possible that would not be viable without their use. The use of fiber gratings in conjunction with erbium-doped fiber amplifiers (EDFAs), fiber lasers, and with semiconductor diode lasers is reviewed.

A broadband uniplanar microstrip-to-CPS transition

Abstract: We report our recent investigation of a novel uniplanar transition between microstrip lines and coplanar strips (CPS) which is to be utilized in our velocity-matched distributed photodetector (VMDP). Both FDTD simulations and X-band experiments show broadband, low return loss performance of this newly proposed structure, with a measured 3 dB insertion loss bandwidth of 68 percent for the case of a balanced back-to-back microstrip-to-CPS transition.

Dielectric waveguide power combiner

Abstract: A transmission medium consists of a dielectric waveguide shielded by a metal guide. The guide is particularly suitable for providing low insertion loss, convenient transfer of power from one such transmission line to another and for the trouble free handling of high power levels at many hundreds of watts. This type of transmission medium may be used to provide low loss combination of power signals that is low loss, compact while containing the solid state power amplifying elements (MMICs) and capable of high power.

Optical wavelength multiplexer/demultiplexer

Abstract: Plurality of channel waveguides of an arrayed waveguide diffraction grating are arranged such that all of intervals thereof are not constant between each two adjacent channel waveguides at a first coupling portion for coupling an input slub waveguide and the arrayed waveguide diffraction grating and a second coupling portion for coupling an output slub waveguide and the arrayed waveguide diffraction grating. Further, the plurality of channel waveguides of the arrayed waveguide diffraction grating are arranged such that all of length differences thereof are not constant between each two adjacent channel waveguides. For example, one of the channel waveguides is deleted, so that a length difference of adjacent channel waveguides is determined to be larger than that of the other two adjacent waveguides. According to this structure, it is possible to provide an optical waveguide multiplexer/demultiplexer in which an insertion loss property becomes flat in all wavelength ranges and the insertion loss characteristics are not fluctuated by the fluctuation of the wavelength.

Optical device having low insertion loss

Abstract: An optical device 201, having one or more input waveguides 25 coupled to one side of a slab waveguide 20 and an array of output waveguides 26 coupled to an other side of the slab waveguide, is improved by including a transition region 22 immediately adjacent to the slab that operates to reduce insertion loss between the waveguide array 26 and the slab waveguide. The transition region includes a number of silica paths (a I . . . a n ) that intersect the waveguide array. The silica paths have widths W(a n ) that progressively decrease as they become further away from the slab waveguide. The silica paths are parallel to each other and perpendicular to the waveguide array. Disclosed embodiments include an M×N star coupler, a Dense Waveguide Division Multiplexer, and a 1×N power splitter. In each of these embodiments, insertion loss is substantially reduced over similar devices not employing such a transition region.

Switching circuit at high frequency with low insertion loss

Abstract: In a switching circuit, low insertion loss and enough isolation can be ensured at a desired frequency at the same time. An inductor is externally connected in parallel with the path between the drain and source of each of field-effect transistors built in a switching integrated circuit, and the inductor and the OFF capacitance of the field-effect transistor are made to generate parallel resonance. At this time, by suitably adjusting the inductance, low insertion loss and enough isolation are ensured at a desired frequency at the same time.

Polymeric arrayed-waveguide grating multiplexer with wide tuning range

Abstract: A 0.8 nm spacing polymeric arrayed-waveguide grating (AWG) multiplexer operating around 1550 nm is realised using a silicone resin waveguide. The AWG multiplexer has an insertion loss in the range 9-13 dB, a crosstalk of <-20 dB, and a polarisation-dependent wavelength shift of 0.35 nm. The transmission peak wavelength is tunable over 10 nm with a temperature change of 55/spl deg/C.

Micromechanical modulator having enhanced performance

Abstract: A modulator having low insertion and a broad operating bandwidth is disclosed. The modulator has a movable membrane that is spaced from a substrate. The reflectivity of the movable membrane, and the reflectivity of the subtrate/gap interface are unequal. In particular, relative to the membrane, the substrate has a lower reflectivity. Device finesse is dictated by the lower reflectivity "mirror," i.e., the substrate. The substrate configuration thus provides a broad operating bandwidth while the higher reflectivity membrane provides low insertion loss.

Optical add/drop multiplexer based on UV-written Bragg grating in a fused 100% coupler

Abstract: The authors report the first realisation of a simple and stable optical add/drop multiplexer based on a UV-written Bragg grating in the coupling region of a fused 100% coupler. Add/drop functions are demonstrated with a low insertion loss (<1 dB).

An electrically controlled Bragg reflector integrated in a rib silicon on insulator waveguide

Abstract: In this letter, we present a novel structure for light amplitude modulation based on a lateral p-i-n diode combined with a Bragg reflector which transforms the phase shift induced by the plasma dispersion effect in the intrinsic region of the diode into a voltage controlled variation of the reflectivity of the Bragg mirror. Numerical simulations show a modulation depth of 50% achieved in about 12 ns with a power dissipation of 4.0 mW and an insertion loss of 1.0 dB. The device is demonstrated to be very attractive in terms of power dissipation as compared to a Mach–Zehnder interferometer occupying the same area on chip.

Principles and performance of traveling-wave photodetector arrays

Abstract: Analog fiber-optic links are used in a variety of microwave applications, including cable-TV and cellular-telephone distribution, as well as antenna remoting. The RF insertion loss and output power obtainable from externally modulated links is primarily limited by photodetector optical-power handling capabilities. Using traveling-wave concepts similar to those in microwave distributed amplifiers, we demonstrate the principle of traveling-wave detector arrays (TWDAs) in which discrete photodiodes are embedded within an artificial transmission line. By feeding these detectors with suitably time-delayed optical signals, this arrangement coherently combines multiple RF photocurrents into a single output. This paper presents the theory, construction details, and results of two- and four-element TWDA's operating up into the Ku-band. We demonstrate a two-element TWDA yielding a 6-dB improvement in insertion loss and RF output power with 12 GHz of operating bandwidth, and a four-element TWDA yielding 12-dB improvement up to 18 GHz.

Fiber grating optical spectrum analyzer tap

Abstract: We demonstrate the first optical spectrum analyzer using a blazed and chirped fiber Bragg grating as the only wavelength dispersive element. A detector array demonstrates 14 nm bandwidth, 0.12 nm resolution, 35 dB dynamic range, and insertion loss less than 1 dB.

Reconfigurable add-drop multiplexer for optical communications systems

Abstract: In accordance with the invention, an optical multiplexer includes at least one reconfigurable add-drop unit that can add-drop one channel out of a large set by switching the light path through one of a set of fixed add-drop filters. Reconfiguration is done by switching from the add-drop filter path to a bypass path, changing to a different add-drop filter and then switching back. The phase delay of the bypass path is adjusted to maintain nearly maximum transmission during switching. The selection among add-drop filters is done by sliding an integrated optic chip with the set of add-drop filters between input and output waveguides. The reconfigurable add-drop multiplexer unit is latchable, passive between reconfigurations, and has low intrinsic insertion loss. Plural units in series can add/drop plural channels.

An experimental study of Love-wave acoustic sensors operating in liquids

Abstract: It has been shown that properly designed Love-wave acoustic sensors are very promising for sensing in gaseous and liquid environments because of their high sensitivity. Since Love-wave devices do not incur a radiative loss when used in a liquid, they have many potential applications in biosensing. We have successfully manufactured a range of 40 μm wavelength Love-wave devices based on SiO2/ST-quartz, with the SiO2 thickness ranging from 0 to 7.3 μm. The relationship of the mass-loading sensitivity to the thickness of the SiO2 layer has been obtained experimentally. High sensitivity (≥ 300 cm−2 g−1) is achieved at an SiO2 thickness between 3.5 and 6.5 μm. The Love-wave oscillators have operated efficiently in various liquids with excellent stability and low noise. In this paper, we report the experimental results for the devices operating in various liquids. The mass sensitivity, insertion loss, oscillation frequency stability, noise level, liquid viscous loading and acoustoelectric coupling have been studied. The influence of the thickness of the SiO2 layer on some of these properties has also been investigated.

A modified Chebyshev bandpass filter with attenuation poles in the stopband

Abstract: This paper describes a design method of a modified Chebyshev bandpass filter with attenuation poles in the stopband. The insertion of attenuation poles into resonators in the authors' bandpass-filter design is accomplished by connecting a lumped inductor or capacitor in series with a shunt-type coaxial transmission-line resonator. The inserted poles which are distributed over the stopband can be chosen such that the insertion loss of the filter has equiripple characteristic and maximum attenuation in the stopband with the given number of attenuation poles. The modified Chebyshev bandpass filter designed by this method can be effectively used in diplexer design.

Design of an electronically tunable microwave impedance transformer

Abstract: A new technique is introduced for designing continuously variable electronically tunable microwave impedance transformers that can be implemented using MIC or MMIC technology An S-band tunable transformer has been built and measurements demonstrate a circuit which can transform impedances from 50 /spl Omega/ to a range of 4-392 /spl Omega/ A typical transformation from 50 /spl Omega/ to 162 /spl Omega/ yields a measured 05 dB instantaneous bandwidth of 14-16%, tunable bandwidth of 18%, and insertion loss of 06-09 dB Applications for this novel technique include the design of electronically tunable wireless components, solid state power amplifiers, microstrip antennas, and microwave modulated laser transmit/receive systems

Fabrication of a side-polished fiber polarizer with a birefringent polymer overlay

Abstract: The fabrication of an in-line fiber polarizer consisting of a side-polished fiber (SPF) with a birefringent polymer thin-film overlay, polyvinyl carbazole, is described. Typical devices had <0.5-dB insertion loss and extinction ratios of ∼36 dB. A weakly coupled waveguide model that accurately describes these SPF–thin-film overlay devices and guides in their fabrication is also presented.

Silicon-on-insulator asymmetric optical switch based on total internal reflection

Abstract: Based on the large cross-section single-mode rib waveguide condition, total internal reflection (TIR) and the plasma dispersion effect, a silicon-on-insulator (SOI) asymmetric optical waveguide switch with transverse injection structure has been proposed and fabricated, in which the SOI technique utilizes silicon and silicon dioxide thermal bonding and back-polishing. The device performance is measured at a wavelength of 1.3 /spl mu/m. It shows that the extinction ratio and insertion loss are less than -18.1 and 6.3 dB, respectively, at an injection current of 60 mA. Response time is 110 ns.

Planar HTS structures for high-power applications in communication systems

Abstract: The use of rotational symmetric modes of superconductive disk (ring) resonators in order to increase the power handling capability of planar filters has been proposed. Several YBCO disk resonators on LaAlO3 and sapphire substrates have been measured as one- and two ports. The unloaded Q-factor of the resonators has been measured to be greater than 105 up to the oscillating power of 50 kW. Experimental results obtained show that a disk resonator can be used as a building block for low insertion loss, sharp skirt high-power planar filters at low GHz frequency range and temperatures of around 60 K.

Output power enhancement in optical fiber lasers

Abstract: An optical fiber used as the active amplifying medium in a fiber laser is arranged to have a high insertion loss at an undesired frequency, while retaining a low insertion loss at a desired lasing frequency. In one embodiment, loss at a Raman-shifted frequency is introduced by using an optical fiber which has multiple claddings with an index profile that includes an elevated index region located away from the core, but within the evanescent coupling region of the core. A distributed loss, which can be enhanced by bending, is produced at the Raman frequency which effectively raises the threshold at which Raman scattering occurs in the fiber and therefore results in a frequency-selective fiber. In another embodiment, an absorbing layer is placed around the core region. The absorbing layer is chosen to have a sharp absorption edge so that it absorbs highly at the Raman-shifted wavelength, but minimally at the desired lasing wavelength. In still another embodiment, the optical fiber is constructed with a core with long period gratings formed therein. The gratings are fabricated with a periodicity selected to provide a relatively high insertion loss at the Raman frequency while simultaneously providing a relatively low insertion loss at the lasing frequency. In accordance with yet another embodiment, a bend loss technique is used to suppress amplified spontaneous emission at an unwanted wavelength due to a competing atomic energy level system in a fiber laser.

Reduced height waveguide tuner for impedance matching

Abstract: A slotted line tuner, also capable of operation as a fully automated tuner, to provide arbitrary termination in high frequency waveguide media for use with frequencies of interest between 1 and 1000 GHz is disclosed. The electrical tuner is adapted to match the impedance of two waveguide media, or enhance or modify the characteristic impedance of a media relative to that of another one. The tuner utilizes a non-conductive rectangular bar vane made out of low loss, low dielectric constant material as the probe, with special gold plated areas, that is inserted through the slot of the line into a reduced height waveguide. The position and depth of this gradual probe penetration creates a continuously variable tuning of the complex impedance, ranging from a very low reflection state up to high reflection states together with an unlimited capability of phase change in its reflection. The non-conductive probe structure assures that the propagation of the coaxial guided wave modes, and especially the coaxial TEM mode, within the slot area are suppressed, thus eliminating a typical source of leakage. A series of slots is formed in the waveguide housing perpendicular to the main slotted line, to form a multi-choke filter that prevents the propagation of parallel plate modes within the slot area thus further reducing leakage and excessive insertion loss.

Synthesis and Design of Cascaded Trisection (CT) Dielectric Resonator Filters

Abstract: Synthesis of filters having asymmetric insertion loss poles as cross-coupled cascaded trisections (CT) of resonators is presented. The theory is applied to the design and realization of cellular PCS base station dielectric resonator filters with extremely demanding requirements on selectivity, out of band rejection and pass band insertion loss. Measured results are presented which demonstrates the validity and accuracy of the theory and design.

Laminated dielectric antenna duplexer and a dielectric filter

Abstract: A dielectric antenna duplexer used in a high frequency radio device such as a portable telephone, and a dielectric filter for forming the duplexer of the SIR (stepped impedance resonator) composed by cascade connection of first transmission lines having one end grounded and second transmission lines having one end open and lower in characteristic impedance than in the first transmission lines, first transmission lines and second transmission lines are individually coupled in electromagnetic field, thereby forming an antenna duplexer and a dielectric filter of small insertion loss, high bandwidth selectivity, excellent band pass characteristic, and low cost.

Digitally tunable optical filters using arrayed-waveguide grating (AWG) multiplexers and optical switches

Abstract: Two novel configurations for digitally tunable optical filters based on arrayed-waveguide grating (AWG) multiplexers are described in detail with emphasis on the connection of the AWG multiplexer and optical switches. Performance comparisons show that conventional configurations are disadvantaged by the switch size required and loss imbalance among the optical frequency-division-multiplexed (FDM) channels; the proposed configurations require only O(/spl radic/(N)) switch elements to select one of N FDM channels, and the loss imbalance is lower by up to 75% in decibel.