Delay Device Research Articles

Development of High Precision Thermo-Anemometer

An improved system of thermo-anemometer was developed. Temperature compensator was designed based on more accurate equations. Assumptions in the temperature compensation equation were minimized to make minute adjustment in each part of the circuit. An improved corrector circuit reduced the error of the velocity signal to be less than ±1% up to about 120°C. A new digital delay device was designed. Deviations from the specification of delay device could be adjusted by employing an automatic amplitude and mean voltage adjuster. Consequently, it can regenerate the original velocity waveform quite accurately, free from wave deformation and electrical noise up to 6kHz. Calibration time was reduced. The present device can obtain higher correlation terms in the thermal flow fields more accurately.

Investigation on Microwave Negative Group Delay Circuit

In this article, a fundamental analytical approach and experimental verification of a radio frequency active circuit capable of exhibiting negative group delay at microwave wavelengths are presented. By using the S-parameter theory, basic properties and characteristics of the negative group delay circuit under study are established. To highlight the functionality principle of this innovative circuit, time-domain investigations based on ultra-wide-band pulse signal tests are performed. Then, the mechanism of propagating output signal envelopes in time advance compared to the input is demonstrated. To validate this concept, a prototype of a negative group delay device was designed, fabricated, and tested. Experimental results in good agreement with theory and simulation were obtained. In the frequency domain, a negative group delay of about −2.5 ns with amplification of 2 dB was measured at around 622 MHz. Due to this negative group delay effect, envelope advance of about −1.5 ns was observed by considering a pulse signal with a half-height full-width of 10 ns, which modulates a sine carrier with a frequency of 622 MHz. The negative group delay topology presented is potentially useful for the compensation of radio frequency/microwave signal delays.

정지궤도 위성통신 환경모의를 위한 100 MHz 대역폭의 위성링크 시뮬레이터 개발

The transponder simulator designed to simulate the transponder of military satellite communication systems in the geostationary orbit is required to have time delay function, because of 250 ms delay time, when a radio wave transmits the distance of 36,000 km in free space. But, it is very difficult to develop 250 ms time delay device in the transponder simulator of 100 MHz bandwidth, due to unstable operation of FPGA, loss of memory data for the high speed rate signal processing. Up to date, bandwidth of the time delay device is limited to 45 MHz bandwidth. To solve this problem, we propose the new time delay techniques up to 100 MHz bandwidth without data loss. Proposed techniques are the low speed down scaling and high speed up scaling methods to read and write the external memory, and the matrix structure design of FPGA memory to treat data as high speed rate. We developed the satellite link simulator in 100 MHz bandwidth using the proposed new time delay techniques, implemented to the transponder simulator and verified the function of 265 ms time delay device in 100 MHz bandwidth.

Hardware Demonstration of Extremely Compact Optical True Time Delay Device for Wideband Electronically Steered Antennas

An optical true time delay device is demonstrated that is capable of supporting 112 antennas with 81 different delays (>; 6 bits) in a volume 16 × 5 × 4 including the box with electronics. It uses a free-space design based on the White cell, and alignment is made simple, fast, and robust by the use of slow-tool diamond turning of many optics on a single substrate. Pointing accuracy of the 12 objective mirrors is better than 10 μrad, and surface roughness is ≈ 45 nm RMS. Delays vary from 0 to 25 ns in 312.5 ps increments. Short delays are implemented using delay rods of high refractive index, and long delays using folded mirror trains. Total insertion loss from fiber to detector was 7.82 dB for the no-delay path, and 10.22 dB for the longest lens train. A three-state tip-style MEMS micromirror array is used to select among the delays, with tilt angles ±1.4° plus flat, and switching time <; 100 μs for the entire array. An InP wideband optical combiner photodetector array converts the optical signal to RF with 20 GHz bandwidth. The unit survived temperature cycling 0 to 50 C and random vibration on three axes (9.84 g RMS) with no degradation of signal.

Polymer waveguide delay device using right-angle X junctions

A four-channels polymer waveguide delay device is demonstrated and fabricated using direct ultra-violet photolithography process. The device is composed of right-angle junctions and bending waveguide. The optimized structural properties of the device and fabrication procedures are demonstrated. The loss of bending waveguides and right-angle X junction is calculated. The near-infrared field guided-mode patterns of the devices are obtained. Each incoming radio-frequency signal can be independently received. Measured delays are 0, 60.9, 121.9, and 182.9 ps. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26050

Analysis and Development of the Experimental Apparatus of the Laser-Induced Plasma Spectrum

This paper mostly summarizes experimental device of laser-induced plasma and taking pictures of plasma plume. The progress in the experimental study on laser-induced plasma was discussed. The experimental apparatus include the laser、delay device; The system of the plasma radiation gathered and radiation received were reviewed. In addition, photos of plasma plume were discussed; at last, dynamic process of laser-induced plasma plume explosion was discussed.

Circuit For Eliminating Abnormal Sound

A circuit for eliminating abnormal sound includes a video/audio processor, a D/A converter, a front-stage mute circuit, a changing delay device, a front-stage amplifier, a back-stage amplifier, a back-stage mute circuit, and a micro control unit. The circuit is mounted in a display device connected to a DVD player. When DVD player plays the video/audio signal having HDMI standard, the display device will generate an abnormal sound (pop voice or declining voice) during performing an operation such as pause, stop or play. Therefore, this circuit uses the changing delay device, the micro control unit, and the mute circuit to filter out the noise for providing a better outputting quality.

True Time Delay Photonic Circuit Based on Perfluorpolymer Waveguides

A high-performance 4-bit optical true time delay device is realized on a perfluoropolymer integrated optic platform. The integrated waveguide circuit is based on athermal arrayed wavegide grating with monolithically integrated delay lines in a wavelength-selective recirculating loop configuration. The device provides precise delay length control (i.e., 1 m) over 16 channels with 40-ps incremental time delays. The device offers athermal operation over the 0°C-50°C range with a maximum insertion loss of 6.8 dB and a polarization shift of 0.4 nm. This compact device (20 × 32 × 3 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) promises applications in code-division multiple access and phased arrayed antenna systems, where the large channel counts with high resolution delay length controls and small footprints are required.

Electro-Optic Delay Devices With Double Feedback

We analytically and numerically study the effect of an additional feedback in the semiconductor laser used to pump optoelectronic delay devices. We show that this additional feedback renders the system into chaotic regime for a broader parameter range and also induces a stronger chaotic behavior. We study the synchronization of this system as function of the parameter mismatch and show its capability for encoded message transmission.

Improved Dielectric Properties of Low-Temperature-Sintered (Ba,Sr)TiO3-Based Ceramics by Ge Substitution

Multilayer microwave dielectric materials with low sintering temperature are required for microwave phase shifters, filters, and true-time delay devices. We investigated the sintering and dielectric properties of (Ba0.6Sr0.4)(Ti1-xGex)O3 (BSTG; 0.05≤x≤0.3) ceramics. As the Ge concentration was increased, the lattice constant of BSTG ceramics decreased, and Ba2Ge2TiO8, which is the liquid phase at low temperature, was formed. Ba2Ge2TiO8 liquid phase may increase the sintering density. The effect of Ge substitution is the decrease in the sintering temperature from over 1400 to 1150 °C in BST system ferroelectric ceramics. With increasing Ge concentration, the dielectric constant decreased from 2190 to 530, and the dielectric loss decreased up to 0.001 (at 1 MHz) with sintering at 1150 °C for 2 h. When Ge was substituted at 0.05 and 0.1 mol of Ti in the BST at 1150 °C, the dielectric constant, dielectric loss, tunability, Curie temperature, and figure of merit were 2184 and 1529, 0.002 and 0.001, 27 and 23%, -11 and -18 °C, and 135 and 230, respectively. These compositions show microwave dielectric properties comparable to those of (Ba0.5Sr0.5)TiO3 ferroelectrics, which are the important materials for tunable devices such as varactors, phase shifters, and frequency agile filters.

UWB time‐domain antennas beam scanning

AbstractUltra‐wideband (UWB) antenna is indispensable in impulse radar that transmits and receives short electromagnetic pulse signals and preserves the waveform well. Phased array antenna systems cannot meet the demand of the system. Optical true‐time delay techniques open the possibility of ultra‐wide bandwidth antenna systems, while at the same time meeting the stringent weight and size requirements. Continuously tunable true‐time delay techniques can provide continuous beam scanning. With advanced optoelectronic technique, fast wavelength tuning speed is possible. To detect and track moving‐target [Bi and Ren, Prog Electomagn Res 87 (2008), 15–41)], UWB time‐domain antenna array beam scanning is studied in this article. First, the theory of time‐domain antenna array scanning is analyzed, some useful conclusions are achieved. Then, an experiment system of UWB time‐domain antenna array scanning is built, which includes an antenna array, fiber‐optic true‐time delay device, and other equipments. Finally, the theoretical and experimental results combined to are made to validate the theory of UWB time‐domain antenna array beam scanning. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1110–1112, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25102

Modeling and Testing for Small-Scale Time Delay Device Based on Magnetorheological Fluid

Because of magnetorheological (MR) dampers’ mechanical simplicity, high dynamic range, low power requirements, large force capacity and robustness, they are the most promising devices for structural vibration control. But this paper uses MR dampers’ damp characteristics to complete a function of short time delay, and the damper’s volume is smaller than the other dampers that have been applied for commercial uses. This paper discusses two types of structures for time delay, gap structure time delay device and holes structure time delay device. In order to estimate the two kinds of devices’ delay time, mathematical modeling and experimental testing are built in this paper. From the test results, we know that holes structure does not always implement theoretical delay time, but the gap structure can complete the time delay function satisfactory. For judging whether the time delay device can work normally under different circumstance, the time delay device with gap structure is tested in a change temperature field from -40 °C to 55 °C.

Periodic optical delay line based on a tilted parabolic generatrix helicoid reflective mirror

We report the design and testing of a novel linear scanning periodic optical delay line (ODL) by use of a helicoid reflective mirror based on a tilted parabolic generatrix that was driven by an electrical motor for a periodic change in the optical path length of the reflected light beam. The divergence and pulse front distortion of the optical beam reflected by the helicoid reflective mirror were simulated based on differential geometry. With a round-trip pass arrangement, a scanning range of delay time as large as 100 ps was obtained by spinning the helicoid reflective mirror with a pitch distance of 7.5 mm. This periodic ODL was used in an optical second-harmonic generation autocorrelator to test the linearity and temporal resolution in comparison with the autocorrelation signal obtained using an ODL structured with a motorized linear translation stage. Experiments demonstrate that our helicoid optical delay device may provide exceptional performance for optical interference, high-resolution terahertz time-domain spectroscopy, and general optical pump-probe experiments.

Real-time all-optical performance monitoring using optical bit-shape correlation

A new optical performance monitoring technique of an optical link in real time is experimentally demonstrated. Rather than comparing bit streams or analyzing eye diagrams, we use a novel optical correlator to compare the shapes of the individual received bits to a standard. The all-optical correlator outputs a pulse whose strength directly measures the degradation of the bit during transmission. Results are produced within three bit periods in real time instead of requiring statistical analysis of long data streams. The correlator is based on a simplified White cell-based true-time delay device.

Irregular Polyomino-Shaped Subarrays for Space-Based Active Arrays

This paper presents new results showing the application of polyomino-based subarrays to limited field of view and wideband, wide-angle scanning. This technology can reduce the number of phase controls in arrays used for limited sector coverage or the number of time delay devices for wideband radar or communications, and so can reduce the cost of space-based active arrays. We concentrate on the wideband application. Results are presented by comparing the gain and peak sidelobe results of irregular polyomino subarray-based arrays with those of rectangular subarrays. It is shown that using irregular polyomino subarrays can result in a major decrease in sidelobes while presenting, in most cases, only a few tenths of a dB gain reduction compared to rectangular subarrays.

Information theoretic framework for the analysis of a slow-light delay device

We present a framework for the information theoretic analysis of slow-light devices. We employ a model in which the device input is a binary-valued data sequence and the device output is considered within a window of finite duration. We use the mutual information between these two quantities to measure information content. This approach enables the information theoretic definitions of delay and throughput. We use our new framework to analyze a delay device based on stimulated Brillouin scattering (SBS) and find good agreement with previous SBS delay bounds.

Photonic Generation of Phase-Coded Millimeter-Wave Signal Using a Polarization Modulator

A novel approach to generating phase-coded millimeter-wave (mm-wave) signal in the optical domain is proposed. In the proposed system, a radio frequency signal is applied to a Mach-Zehnder modulator that is biased at the minimum transmission point to generate two optical sidebands with suppressed carrier. A differential group delay device is utilized to rotate the polarization states of the optical sidebands to ensure they are orthogonally polarized. The two sidebands are then sent to a polarization modulator (PolM), with their polarization directions aligned with the two principal axes of the PolM, to achieve phase coding. A 33-GHz mm-wave signal that is phase coded by an 8.28 Gb/s digital sequence is experimentally demonstrated. The approach has potential applications in mm-wave pulse compression radar and wireless communications.

Optimal pump profile designs for broadband SBS slow-light systems

We describe a methodology for designing the optimal gain profiles for gain-based, tunable, broadband, slow-light pulse delay devices based on stimulated Brillouin scattering. Optimal gain profiles are obtained under system constraints such as distortion, total pump power, and maximum gain. The delay performance of three candidate systems: Gaussian noise pump broadened (GNPB), optimal gain-only, and optimal gain+absorption are studied using Gaussian and super-Gaussian pulses. For the same pulse bandwidth, we find that the optimal gain+absorption medium improves the delay performance by 2.1 times the GNPB medium delay and 1.3 times the optimal gain-only medium delay for Gaussian pulses. For the super-Gaussian pulses the optimal gain-only medium provides a fractional pulse delay 1.8 times the GNPB medium delay.

A Novel Composite Method for Ultra-Wideband Doublet Pulses Generation

A novel composite approach to generate ultra-wideband (UWB) doublet pulses in optical domain through an electrical Gaussian pulse is proposed and demonstrated in this letter. Two pulses with reversed polarity generated by polarization modulation are fed into a differential group delay device and a semiconductor optical amplifier (SOA) wherein the optical pulse profile is modified. Doublet pulses are obtained after optical-electrical detection due to gain saturation and recovery mechanism in the SOA. The fractional bandwidth of doublet pulses exceeds 180%, fulfilling the UWB requirements.

Maximizing the opening of eye diagrams for slow-light systems

We present a data-fidelity metric for quantifying distortion in slow-light optical pulse delay devices. We demonstrate the utility of this metric by applying it to the performance optimization of gain-based slow-light delay systems for Gaussian and super-Gaussian pulses. Symmetric Lorentzian double-line and triple-line gain systems are optimized and achieve maximum delay of 1.5 and 1.7 times the single-line gain system delay, respectively. The resulting double-line gain system design is qualitatively similar to the double-line gain system designed with a previous metric, but is tuned specifically to constrain data fidelity.