dB Attenuation Research Articles

Direct creation of three-dimensional photonic crystals by a top-down approach

Three-dimensional (3D) photonic crystals can block photons in any direction and are expected to make possible their ultimate control. However, creating 3D crystals without any unintentional defects over large areas at optical wavelengths has been challenging. For example, opal-based crystals inevitably contain unintentional defects, it is difficult to increase the sizes of micro-manipulated crystals over approximately 6 microm and producing stacked 3D crystals with thin 2D layers requires complicated and time-consuming processes. So far, these difficulties have hindered 3D photonic-crystal research. Here, we demonstrate a novel top-down approach to creating 3D crystals that overcomes these difficulties and significantly simplifies the process. We have developed a double-angled deep-etching method, which enables the direct creation of 3D woodpile crystals in single-crystalline silicon. A strong photonic bandgap effect with >20 dB attenuation in all directions has been achieved. Furthermore, bonding a light emitter onto or between 3D crystals created in this way has been shown to enhance or suppress spontaneous emission.

Design of coplanar waveguide elliptic low pass filters

This article proposes three design topologies of coplanar waveguide elliptic low pass filters. The design procedure is simple and explained in detail for the first topology. Numerical results are provided using the commercially available simulation softwares IE3D and HFSS to show the validity of the design with very good agreement. The proposed filters yield less than 0.1 dB attenuation in the passband (0–2 GHz), with a controllable slope of the transition between passband and stopband. The width of the rejection band is increased by simple filter cascading resulting in a passband to stopband ratio of up to 1:6. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.

Noniterative Permittivity Extraction of Lossy Liquid Materials From Reflection Asymmetric Amplitude-Only Microwave Measurements

A very promising amplitude-only microwave method is proposed to noniteratively determine the complex permittivity of lossy materials, which possess at least 10 dB attenuation. It utilizes reflection-only measurements, which in some instances increases the performance of the determination since the accuracy of transmission measurements significantly decreases for high-loss materials. The method is very feasible for industrial-based applications since the implementation of the method requires very simple microwave components or inexpensive microwave instruments. However, the method requires different reflection-only measurements, which in turn necessitates elaborate preparation of the sample holder.

A 1024-QAM Analog Front-End for Broadband Powerline Communication Up to 60 MHz

A high performance analog front-end (AFE) for broadband powerline communication between 1.6 and 60 MHz is presented. The frequency division multiplexing AFE supports optimum channel selection, avoids disturbing RF signals and allows co-existence with other users of the spectrum. The direct-conversion receiver operates linearly up to a + 18 dBm input level. Tunable low-pass filters, integrated into the receive path, support a wide class of service requirements by channel bandwidth selection. The dynamic range is 99.5 dB for 2 MHz channels, and 90.5 dB for 16 MHz channels. Error vector magnitude measurements are presented for a single-carrier 1024-QAM and a 1024-carrier 64-QAM signal as function of frequency and channel attenuation. For 1024-QAM, the error vector magnitude (EVM) is below or equal to 1.2% rms up to 60 dB of attenuation, whereas the 1024-carrier 64-QAM performs well up to 80 dB of attenuation. The presented chip was fabricated in a 0.25 mum SiGe BiCMOS process, and the measured power consumption from a single 2.5 V supply is 668 mW.

Filled and unfilled temperature-dependent epoxy resin blends for lossy transducer substrates

In the context of our ongoing investigation of low-cost 2-dimensional (2-D) arrays, we studied the temperature- dependent acoustic properties of epoxy blends that could serve as an acoustically lossy backing material in compact 2-D array-based devices. This material should be capable of being machined during array manufacture, while also providing adequate signal attenuation to mitigate backing block reverberation artifacts. The acoustic impedance and attenuation of 5 unfilled epoxy blends and 2 filled epoxy blends - tungsten and fiberglass fillers - were analyzed across a 35 degrees C temperature range in 5 degrees C increments. Unfilled epoxy materials possessed an approximately linear variation of impedance and sigmoidal variation of attenuation properties over the range of temperatures of interest. An intermediate epoxy blend was fitted to a quadratic trend line with R(2) values of 0.94 and 0.99 for attenuation and impedance, respectively. It was observed that a fiberglass filler induces a strong quadratic trend in the impedance data with temperature, which results in increased error in the characterization of attenuation and impedance. The tungsten-filled epoxy was not susceptible to such problems because a different method of fabrication was required. At body temperature, the tungsten-filled epoxy could provide a 44 dB attenuation of the round-trip backing block echo in our application, in which the center frequency is 5 MHz and the backing material is 1.1 mm thick. This is an 11 dB increase in attenuation compared with the fiberglass-filled epoxy in the context of our application. This work provides motivation for exploring the use of custom-made tungsten-filled epoxy materials as a substitute PCB-based substrate to provide electrical signal interconnect.

A new 5th-order differential type class-AB log-domain elliptic lowpass filter for video frequency applications

This paper proposes a new current-mode 5th-order differential type class-AB log-domain elliptic lowpass filter for video frequency applications. The design is based on the state-space synthesis method. The proposed filter has 5.75 MHz cut-off frequency with maximum 0.177 dB passband ripple and attenuation greater than 40 dB at 7.88 MHz. Only BJTs and grounded capacitors were used, and operated with single power supply of 2.5 V. Since the parameters of proposed filter are tunable, it is easy to control of cut-off frequency. This adjustment is accomplished by changing external currents. SPICE simulations are given to confirm the theoretical analysis. For this purpose, the filter is simulated by using both idealized BJT models and AT&T CBIC-U2 type transistors.

A compact ultra‐wideband band‐pass filter with defected ground structure

AbstractIn this article, a compact ultra‐wideband (UWB) band‐pass filter (BPF) with improved upper‐stopband is presented. In this design, a novel multiple‐mode resonator (MMR) with two symmetrical loading stubs and three dumbbell‐shaped defected ground structures (DGS) on the back of the filter improve the harmonic‐suppression characteristic of conventional BPF. Combining these two structures, a new UWB BPF is fabricated and measured. Measured results show that the proposed BPF has wide bandwidth from 3.0 to 10.7 GHz, and the insertion loss of the BPF is less than 1.0 dB in this band. A wide stop‐band bandwidth with 20 dB attenuation from 12 GHz up to 20 GHz is achieved. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 979–981, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24234

Frequency Selective Surface Designed Using Electric Resonant Structures in Terahertz Frequency Bands

Electric resonant structures are primary unit cells to construct single negative permittivity metamaterials, which are also widely used in the design of novel microwave components. In this paper, the relative equivalent circuit model is first studied, the resonant characteristics of such structure is analyzed, the factors effected on the distribution of zero and pole transmission points are presented, based on which a realizable way to design filters with narrow transition-band from stop-band to pass-band is elicited. Then, a frequency selective surface (FSS) is designed with –3.9 dB attenuation in 40 GHz near the working frequency of 0.7 THz. The S parameters are also compared with those of a conventional electric resonant structure, from which we observe that the later has larger size besides wider transition bandwidth. On the other hand, the novel FSS can increase the utilization factor of frequency spectrum. In order to further decrease the transition bandwidth, three layers of the FSS structures are arrayed. By tuning the distance between each two layers, much narrower bandwidth is easily achieved which can be reached to 10 GHz.

An Improved Microstrip Open-Loop Resonator Bandpass Filter with DGSS for WLAN Application

This paper presents a novel harmonic-suppressed microstrip open-loop resonator bandpass filter with the different transmission line characteristic impedance of the feed line and open-loop resonator for wireless local area network (WLAN) application. To improve the stopband rejection of the filter, the dumbbell-shape defected ground structure (DGS) are applied under the feed lines to suppress the harmonics and the equivalent parameters extraction formulations of double-dumbell-shaped DGSs are the first to proposed. The bandpass filter with center frequency of 2.44 GHz were designed and fabricated on a TLX substrate with thickness of 1 mm and dielectric constant of 2.55. Measurement results show the filter has a wide stopband characteristic with 30 dB attenuation up to 7.5 GHz and only has an –1.23 dB insertion loss while it is a little larger than the conventional one. The measured results are in good agreement with the simulated results. It can be widely used for WLAN application.

Compact Ultra-Wideband Bandpass Filter Using Dual-Line Coupling Structure

This letter presents a novel compact ultra-wideband (UWB) microstrip bandpass filter with spurious response suppression. A dual-mode ring resonator is constituted to allocate its first two resonant frequencies in the UWB band, and the dual-line parallel-coupled structure is used in this compact UWB filter, which is expected to achieve much tighter coupling degree. Simulated and measured results are found in good agreement with each other, showing a wide passband from 4.9 to 10.9 GHz, 15 dB return loss bandwidth of about 5 GHz, minimum insertion loss of 0.49 dB at 7.3 GHz, and wide upper stopband with more than 20 dB attenuation up to 20 GHz.

Ultra-wideband bandpass filter using hybrid quasi-lumped elements and defected ground structure

A compact planar microstrip ultra-wideband (UWB) bandpass filter is presented. The proposed UWB filter is realised by cascading a highpass filter (HPF) and a lowpass filter (LPF). Additional U-slot defected ground structure is adopted to improve the attenuation performance in the stop band. The HPF consists of inter-digital capacitors and a short-circuited stub. The LPF achieved by a hybrid microstrip and four backside slots on the ground plane is equivalent to a typical 9-pole stepped-impedance LPF. Combining these two structures, a new UWB bandpass filter is fabricated and measured. Measured results show that the proposed bandpass filter has a wide bandwidth from 3.1 to 11 GHz, and insertion loss is less than 1.2 dB over the most central passband. It also achieves a wide stop band with 20 dB attenuation up to 20 GHz.

Membrane covered duct lining for high-frequency noise attenuation: Prediction using a Chebyshev collocation method

A spectral method of Chebyshev collocation with domain decomposition is introduced for linear interaction between sound and structure in a duct lined with flexible walls backed by cavities with or without a porous material. The spectral convergence is validated by a one-dimensional problem with a closed-form analytical solution, and is then extended to the two-dimensional configuration and compared favorably against a previous method based on the Fourier-Galerkin procedure and a finite element modeling. The nonlocal, exact Dirichlet-to-Neumann boundary condition is embedded in the domain decomposition scheme without imposing extra computational burden. The scheme is applied to the problem of high-frequency sound absorption by duct lining, which is normally ineffective when the wavelength is comparable with or shorter than the duct height. When a tensioned membrane covers the lining, however, it scatters the incident plane wave into higher-order modes, which then penetrate the duct lining more easily and get dissipated. For the frequency range of f=0.3-3 studied here, f=0.5 being the first cut-on frequency of the central duct, the membrane cover is found to offer an additional 0.9 dB attenuation per unit axial distance equal to half of the duct height.

An all-optical scheme of signed digit binary addition based on optical non-linear material

We propose a new integrated method which covers addition of any two signed digit numbers in all-optical domain. To implement this scheme we have exploited some photo-refractive characters of optical non-linear materials, which may experience 0.1–0.2 dB attenuation loss as silica is used as non-linear medium. Moreover, the attenuation loss may be reduced to 0.001 dB/m if we consider the use of slow light at 1.56 μm.

Edge and Data Adaptive Equalization of Serial-Link Transceivers

Limited channel bandwidth introduces inter-symbol interference (ISI) at both data and edge samples. In addition to the ISI at data samples, ISI at the edge samples (edge ISI) increases the bit error rate (BER) by degrading on the eye diagram and increasing the jitter of the clock and data recovery (CDR). This work proposes a forward FIR equalizer and a decision-feedback equalizer (DFE) that compensate for both data and edge samples. To adapt both the data and edge equalizers, a modified LMS adaptation algorithm is introduced to achieve convergence. A transmitter and receiver are implemented in 0.13 mum and 0.18 mum technologies respectively. The edge ISI is improved by 20% and the jitter is improved by 10% in measurement. The link operates over a 120 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">''</sup> FR4 channel with 24 dB attenuation at Nyquist frequency, and the BER is below 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-14</sup> at 3.6 Gb/s.

An ultra‐wide stopband low‐pass filter using dual reverse U‐shaped DGS

AbstractOn the basis of the characteristics of defected ground structures (DGSs), a low‐pass filter (LPF) with a sharp rejection and an ultra‐wide stopband is constructed. The proposed LPF comprises of a dual reverse U‐shaped DGS along with two H‐shaped patterns on the ground plane and a microstrip line on the top layer. The attenuations are 2 and 32.8 dB at 3.7 and 3.85 GHz, respectively. The maximum attenuation rate is 205 dB/GHz. The proposed LPF achieves an ultra‐wide stopband with overall 20 dB attenuation from 3.75 GHz up to 20 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2780–2783, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23843

Active control of ultrasonic hearing in frogs

Vertebrates can modulate the sound levels entering their inner ears in the face of intense external sound or during their own vocalizations. Middle ear muscle contractions restrain the motion of the middle ear ossicles, attenuating the transmission of low-frequency sound and thereby protecting the hair cells in the inner ear. Here we show that the Chinese concave-eared torrent frog, Odorrana tormota, can tune its ears dynamically by closing its normally open Eustachian tubes. Contrary to the belief that the middle ear in frogs permanently communicates with the mouth, O. tormota can close this connection by contraction of the submaxillary and petrohyoid muscles, drastically reducing the air volume behind the eardrums. Mathematical modeling and laser Doppler vibrometry revealed that the reduction of this air volume increases the middle ear impedance, resulting in an up to 20 dB gain in eardrum vibration at high frequencies (10-32 kHz) and 26 dB attenuation at low frequencies (3-10 kHz). Eustachian tube closure was observed in the field during calling and swallowing. Besides a potential role in protecting the inner ear from intense low-frequency sound and high buccal air pressure during calling, this previously unrecognized vertebrate mechanism may unmask the high-frequency calls of this species from the low-frequency stream noise which dominates the environment. This mechanism also protects the thin tympanic membranes from injury during swallowing of live arthropod prey.

Reflective attenuator for high-energy laser measurements

A high-energy laser attenuator in the range of 250 mJ (20 ns pulse width, 10 Hz repetition rate, 1064 nm wavelength) is described. The optical elements that constitute the attenuator are mirrors with relatively low reflectance, oriented at a 45 degrees angle of incidence. By combining three pairs of mirrors, the incoming radiation is collinear and has the same polarization orientation as the exit. We present damage testing and polarization-dependent reflectance measurements for 1064 nm laser light at 45 degrees angle of incidence for molybdenum, silicon carbide, and copper mirrors. A six element, 74 times (18 dB) attenuator is presented as an example.

High-dynamic-range hybrid analog–digital control broadband optical spectral processor using micromirror and acousto-optic devices

For the first time, to the best of our knowledge, the design and demonstration of a programmable spectral filtering processor is presented that simultaneously engages the power of an analog-mode optical device such as an acousto-optic tunable filter and a digital-mode optical device such as the digital micromirror device. The demonstrated processor allows a high 50 dB attenuation dynamic range across the chosen 1530-1565 nm (~C band). The hybrid analog-digital spectral control mechanism enables the processor to operate with greater versatility when compared to analog- or digital-only processor designs. Such a processor can be useful both as a test instrument in biomedical applications and as an equalizer in fiber communication networks.

Proof of the existence of large complete band gaps in high frequency silicon phononic crystal plates

We show, for the first time, the evidence of the existence of large phononic band gaps (PBGs) in two‐dimensional phononic crystal (PC) plates formed by etching a hexagonal (honeycomb) array of air holes through a free standing plate of silicon (Si). A CMOS compatible fabrication process is used on a Si on insulator (SOI) substrate to realize the PC devices. More than 30 dB attenuation is observed for eight periods of the hexagonal lattice PC at high frequency region, i.e. 133 MHz with a band gap to mid gap ratio of 25%. We show that the experimental results agree very well with the theoretical predictions for the PBG. This result opens a new direction in the implementation of high frequency practical PC structures for a variety of applications especially wireless communication, and sensing.

Compact cross‐coupled hairpin filter design using ceramic substrates

AbstractCross‐coupled hairpin filter design using electrical‐coupling with asymmetric feed on ceramics was reported. The band‐pass filters are designed at center frequency of 2.0 (GHz) with bandwidth of 10%. In addition, this article presents an analytical technique for positioning the locations of two transmission zeros for a microstrip band‐pass filters. The band‐pass filter uses two resonators with two transmission zeros to obtain lower insertion loss than a conventional cross‐coupled microstrip filter. Also, by using high Q, high permittivity dielectric materials as substrates, the filters demonstrate high selectivity, compact size, and can be used in many wireless communication systems. A bandwidth of 10% with −0.75 dB insertion loss and −34 dB attenuation was achieved with chip size of 2.5 × 0.85 cm2. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1795–1800, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23505