Low-cost Modulation Research Articles

A Low-Cost MEMS Missile-Borne Compound Rotation Modulation Scheme.

Rotation modulation (RM) has been widely used in navigation systems to significantly improve the navigation accuracy of inertial navigation systems (INSs). However, the traditional single-axis rotation modulation cannot achieve the modulation of all the constant errors in the three directions; thus, it is not suitable for application in highly dynamic environments due to requirements for high precision in missiles. Aiming at the problems of error accumulation and divergence in the direction of rotation axis existing in the traditional single-axis rotation modulation, a novel rotation scheme is proposed. Firstly, the error propagation principle of the new rotation modulation scheme is analyzed. Secondly, the condition of realizing the error modulation with constant error is discussed. Finally, the original rotation modulation navigation algorithm is optimized for the new rotation modulation scheme. The experiment and simulation results show that the new rotation scheme can effectively modulate the error divergence of roll angle and improve the accuracy of roll angle by two orders of magnitude.

Active controllable spin-selective terahertz asymmetric transmission based on all-silicon metasurfaces

A strong spin-selective asymmetric transmission metasurface usually relies on a multilayer metal frame or compound all-dielectric system. By contrast, an all-silicon metasurface has advantages of simple process, low cost, and easy optical modulation. However, there is little work to explore the spin-selective asymmetric transmission in terahertz band based on the all-silicon metasurface due to weak interaction between all-silicon materials and terahertz waves. Herein, we have achieved excellent spin-selective terahertz asymmetric transmission in the all-silicon metasurface by the ingenious chirality structure design, and the maximum circular dichroism can reach 0.4. Meanwhile, 1064 nm continuous wave optical pumping modulates the asymmetric transmission amplitude of the all-silicon metasurface to achieve circular dichroism switch between “On” and “Off.” We have also developed terahertz chiral imaging applications based on the all-silicon metasurface with spin-selective asymmetric transmission, and the chiral imaging with On and Off switching characteristics can be realized via optically active control.

A Novel Space Vector Modulation Scheme for a 10-Switch Converter

Three-level converters have drawn extensive attention due to their ability to deliver high-quality power. High semiconductor count is the main drawback of three-level converters. As a solution to this, a 10-switch converter is presented, that has advantages over both two- and three-level converters, simultaneously, plus it is applicable to a variety of power ranges. However, the switching pattern of 10-switch converter is not as simple as standard three-level converter due to lack of medium vectors. This paper presents a novel space vector modulation (SVM) for a 10-switch converter to reduce total harmonic distortion (THD) and common mode voltage (CMV) of this converter in comparison to prior carrier-based modulation methods. A simplified, low-cost modulation algorithm for the converter is proposed. The designed switching sequence has aimed at a low output THD and enhancement of DC bus voltage utilization. The performance of the proposed SVM is then compared to upgraded sinusoidal PWM. AC power quality and CMV of a 10-switch converter based on two modulation methods are investigated via simulation models. It was validated via simulation and experimental models that the proposed SVM utilized DC bus voltage more efficiently, generated remarkably less THD compared to other methods, and had a lower peak and rms CMV.

Design and Prototype Development of Quadrant Estimation Unit for Laser Beam Rider Guidance System

With the development of science and technology, precision-strike weapons are been considered to be important for winning victory and defending the country during war (or) attack. Laser guidance is one of the major methods to execute precision-strike in modern warfare. At present, the problems faced at the primary stage of Laser guidance has been solved with endeavors of countries. Several technical aspects of laser-beam riding guided system have been mature, such as atmosphere penetration of laser beam, clutter inhibition on ground, laser irradiator, encoding and decoding of laser beam. Further, laser beam quality, equal output power and atmospheric transmission properties are qualified for warfare situation. Riding guidance instrument is a crucial element of Laser-beam riding guided system and also in Radar-beam riding guiding system, and is also a essential element of airborne, vehicle-mounted and individual weapon. The optical system mainly consists of sighting module and laser-beam guided module. Photo detector (Quadrant detector) is the most important sensing device, and also the key to acquire the coordinate information of target space. Currently, in consideration of the 1064 nm of wavelength applied in all the semi-active laser guided weapons systems, lithium drifting silicon photodiode which is sensitive to 1064 nm of wavelength is used in photoelectric detector. Compared to Solid and gas laser, diode laser has many merits such as small volume, simple construction, light weight, long life, low cost and easy modulation.
 The present work includes the study of Various ATGM, their guidance mechanism, particularly laser beam rider guidance. Study has been carried to understand the composition and operating principle of Laser-beam riding guided system. The present work also deals with prototype development of quadrant estimation unit required for Laser beam rider guidance.

Physical vapor deposition of large-scale PbSe films and its applications in pulsed fiber lasers

Abstract Lead selenide (PbSe) is a new emerging semiconductor with layer-dependent bandgap that has attracted much interest due to its high infrared response and good environmental stability. We have prepared large-scale PbSe films with the area of 7 cm2 and thickness of 25 nm based on physical vapor deposition approach at 160°C. The PbSe films exhibit saturable absorption property at 1.55 μm and a polarization-sensitive saturable absorber is obtained by growing PbSe on D-shaped fiber. Single-pulse with the duration of 490 fs is generated at the pump of 12 mW and the mode-locking operation is maintained at the pump of 1500 mW, indicating the high damage threshold of the D-shaped fiber based saturable absorber. Two polarization-insensitive saturable absorbers are achieved by depositing PbSe on fiber facet and polyvinyl alcohol film, respectively. For fiber facet (polyvinyl alcohol film) based saturable absorber, the repetition rate of Q-switched pulses increases from 8.6 (16.3) kHz to 45.4 (59.2) kHz while the duration decreases from 7.92 (12) μs to 2.06 (3.12) μs by tuning the pump from 15 mW to 90 (60) mW. Such large-scale PbSe films possess features of low cost and high modulation ability, and can find important applications in infrared optical modulators and detectors.

Exploring multiamplitude voltage modulation to improve spectrum efficiency in low-complexity visible-light communication

Owing to the recent advancements in the Internet of Things (IoT), an increasing number of IoT devices have led to frequency crowding in wireless networks. The low-complexity visible light communication (VLC) system is a promising solution for indoor frequency-crowded wireless networks owing to the ubiquity of light-emitting diodes (LEDs) and readily deployable, low-cost modulation methods. However, due to the inherent limitations of LED materials and growth of data from IoT applications, low-complexity VLC systems can barely boost the data throughput without adding complex modulations and circuits. This study aims to design and implement a spectrum-efficient, low-complexity VLC system to improve data throughput with very little cost to support indoor IoT applications. This system uses multiamplitude voltage to transmit multiple bit streams simultaneously, making it a novel system. However, it is not trivial to achieve this goal as the varying voltage can cause the LEDs to flicker. Therefore, we further propose a voltage-to-current amplifier circuit, which effectively mitigates the effects of changes in the LEDs brightness upon human eyes. Finally, we evaluate the system under different speeds, distances, and angles. Extensive experiments demonstrate promising results from the viewpoint of spectrum efficiency, throughput, bit-error rate, and user perception.

A Radio Frequency Nonreciprocal Network Based on Switched Acoustic Delay Lines

This work demonstrates the first non-reciprocal network based on switched low-loss acoustic delay lines. The 4-port circulator is built upon a recently reported frequency-independent, programmable, non-reciprocal framework based on switched delay lines. The design space for such a system, including the origins of the insertion loss and harmonic responses, is theoretically investigated, illustrating that the key to better performance and low-cost modulation signal synthesis lies in a large delay. To implement a large delay, we resort to in-house fabricated low-loss, wide-band lithium niobate (LiNbO3) SH0 mode acoustic delay lines employing single-phase unidirectional transducers (SPUDT). The 4-port circulator, consisting of two switch modules and one delay line module, has been modularly designed, assembled, and tested. The design process employs time-domain full circuit simulation and the results match well with measurements. A 18.8 dB non-reciprocal contrast between insertion loss (IL = 6.6 dB) and isolation (25.4 dB) has been achieved over a fractional bandwidth of 8.8% at a center frequency 155 MHz, using a record low switching frequency of 877.19 kHz. The circulator also shows 25.9 dB suppression for the intra-modulated tone and 30 dBm for IIP3. Upon further development, such a system can potentially lead to future wide-band, low-loss chip-scale nonreciprocal RF systems with unprecedented programmability.

Low cost fast frequency switching driver for Acousto-Optic Modulators used in laser cooling

Abstract In many laser atom cooling experiments, Acousto-Optic Modulators (AOM) are used to modulate a laser beam frequency close to an electronic resonance of the atoms. Commercially available RF drivers for the AOMs tend to be expensive ($2k and above) and can also require supplementary equipment such as power supplies and amplifiers. This article presents a low cost, compact, re-configurable, and portable modulator driver system. This system can switch between two frequencies within a period of few hundreds of ns, while giving the user complete control over the frequency range and output power up to about 2 W. This fast switching allows to toggle a laser beam between two optical fibers which could be used for cooling, imaging, or optical pumping of the laser-cooled atoms.

FSK-Based Simultaneous Wireless Information and Power Transfer in Inductively Coupled Resonant Circuits Exploiting Frequency Splitting

Inductively coupled resonant circuits are affected by the so-called frequency splitting phenomenon at short distances. In the area of power electronics, tracking one of the peak frequencies is state-of-the-art. In the data transmission community, however, the frequency splitting effect is often ignored. Particularly, modulation schemes have not yet been adapted to the bifurcation phenomenon. We argue that binary frequency shift keying (2-ary FSK) is a low-cost modulation scheme which well matches the double-peak voltage transfer function H(s), particularly when the quality factor Q is large, whereas most other modulation schemes suffer from the small bandwidths of the peaks. Additionally, we show that a rectified version of 2-ary FSK coined rectified FSK (RFSK), is even more attractive from output power and implementation points of view. The analytical and numerical contributions include the efficiency factor, the impulse response, and the bit error performance. A low-cost noncoherent receiver is proposed. The theoretical examinations are supported by an experimental prototype.

Facile preparation of low-cost HKUST-1 with lattice vacancies and high-efficiency adsorption for uranium.

In this work, we prepared HKUST-1 and HKUST-1 with lattice vacancies (HLV) using benzoic acid (BA) as a low-cost modulator to replace part of the traditional trimesic acid ligand (H3BTC). The structure and morphology of the products were characterized by FTIR, XRD, SEM and XPS. The adsorption performance of the products for uranium from aqueous solutions was investigated. The results showed that the sorption of U(vi) on HKUST-1 and HLV agreed with the Langmuir isotherm model (RHKUST-12 = 0.9867 and RHLV2 = 0.9828) and the maximum adsorption capacity was 430.98 mg g−1 and 424.88 mg g−1, respectively. According to kinetics studies, the adsorption fitted better with a pseudo-second-order model (RHKUST-12 = 1.0000 and RHLV2 = 0.9978). The as-prepared adsorbents were used for the removal of uranium from real water samples as well. The results showed that HLV with lower cost is a promising adsorbent for uranium from aqueous solutions.

Impact of damping on high speed 850 nm VCSEL performance * * Project supported by the National Natural Science Foundation of China (Nos. 61335004, 61675046, 61505003), the Open Fund of IPOC2017B011 (BUPT).

High speed VCSELs are important optical devices in short-reach optical communication links and interconnects because of their low cost and high modulation speeds. In this paper, the impact of damping on the their static and dynamic characteristics is analyzed and demonstrated. Through the shallow corrosion of the top layer DBR, the VCSELs with different damping is designed and fabricated. With the increase of the surface etch depth from 0 to ~55 nm for 9 μm oxide-aperture VCSEL, the K factor related with the damping is reduced from 0.31 to 0.23 ns−1. When the etch depth of the VCSEL with 9 μm oxide-aperture is decreased to ~25 nm, output power is increased from 4.03 to 4.70 mW and small signal modulation bandwidth is also increased from 15.46 to 16.37 GHz. It shows that there is a tradeoff between damping and differential gain for improving modulation speed.

Polarization Gratings Spontaneously Formed from a Helical Twist‐Bend Nematic Phase

Spontaneous formation of polarization gratings by liquid crystalline phase made of bent dimeric molecules is reported. The grating is formed within the temperature range of the twist bend modulated nematic phase, NTB , without the necessity to pattern the cell surfaces, therefore the modulated nematic phase is a promising candidate for low-cost modulators and beam steering devices, the polarization properties of which depend on temperature. In addition, the study of the diffracted light properties turns out to be a sensitive measuring technique for determination of the 3D spatial variation of the optic axis in the cell.

Flexible Hybrid PAM2/4 for Fidelity Optimization in Digital Mobile Fronthaul

Four-level pulse amplitude modulation (PAM4) has been considered as a low-cost modulation format for capacity upgrade in digital mobile fronthaul; however, the bit error ratio increases due to the reduced Euclidean distance. In this letter, a novel scheme is proposed to suppress bit-error-induced error vector magnitude (EVM) distortion upon radio signal in PAM4-based fronthaul. The scheme is realized by pairing one high-order bit and one low-order bit onto one PAM4 symbol and setting a portion of low-order bits to “0.” As a result, sample bits with high priority are delivered by PAM2 symbols with small error probability, and sample bits with low priority are transmitted by PAM4 signal with high spectral efficiency. Without any modification of the hardware, the proportion between PAM2 and PAM4 can be flexibly adjusted according to the quality of optical link. Experiments validate that, under respective optimal PAM2/4 proportion, EVM of long term evolution-advanced like radio signal decreases by at least 20 dB, and up to 1024-quadratic-amplitude modulation can be supported.

Measurement-device-independent quantum communication with an untrusted source

Measurement-device-independent quantum key distribution (MDI-QKD) can provide enhanced security, as compared to traditional QKD, and it constitutes an important framework for a quantum network with an untrusted network server. Still, a key assumption in MDI-QKD is that the sources are trusted. We propose here a MDI quantum network with a single untrusted source. We have derived a complete proof of the unconditional security of MDI-QKD with an untrusted source. Using simulations, we have considered various real-life imperfections in its implementation, and the simulation results show that MDI-QKD with an untrusted source provides a key generation rate that is close to the rate of initial MDI-QKD in the asymptotic setting. Our work proves the feasibility of the realization of a quantum network. The network users need only low-cost modulation devices, and they can share both an expensive detector and a complicated laser provided by an untrusted network server.

DC-informative modulation for visible light communications under lighting constraints

Visible light communication employs low-cost intensity modulation and direct detection, where positive time-domain baseband signals are generated to drive LEDs through addition of a DC bias. However, the non-informative bias in this straightforward and easy-to-implement approach significantly reduces the system energy efficiency. In this article, new energy-efficient modulation schemes leveraging informative DC-bias are introduced. Under some lighting constraints, a convex optimization problem is formulated. Optimal constellations are constructed in either the time domain or frequency domain by compact sphere packing. Several DC-informative system architectures are then discussed. Finally, technical implementation challenges are investigated.

A Low Cost and High Quality Duty-Cycle Modulation Scheme and Applications

A Low Cost and High Quality Duty-Cycle Modulation Scheme and Applications

Acoustical phonon induced and polaron induced modulational amplification in polar semiconductors: a comparative study

The paper aims to comparatively study the amplification and excitation characteristics of polaron induced and acoustical phonon induced modulators. Based on the hydrodynamic model, an analytical investigation of frequency modulational interaction is made. An explicit expression for the growth rate and threshold electric field for the onset of the acoustic phonon driven and polaron driven instability is presented and analyzed analytically. We have numerically investigated the dependence of the threshold electric field for different values of the external parameters of a typical polar semiconductor (InSb) and have given a numerical estimation of the growth rate. We also found that the amplification coefficient in polaron induced modulation enhances by a factor of 10 as compared to acoustical phonon induced modulation; though polaron induced modulational instability occurs at a lower threshold than acoustical phonon induced modulational instability. The cyclotron frequency can be used as a control parameter to reduce thresholds and improve growth rates. These results could be important for understanding and improving the performance of modulators. It is hoped that a low cost modulator using the n-InSb–CO2 system can be fabricated as the outcome of this work.

Ultraviolet imprinting and aligned ink-jet printing for multilayer patterning of electro-optic polymer modulators

The present work demonstrates an electro-optic polymer-based Mach-Zehnder (MZ) modulator fabricated utilizing advanced ultraviolet (UV) imprinting and aligned ink-jet printing technologies for patterning and layer deposition. The bottom electrode layer is designed and directly ink-jet printed on the substrate to form the patterned layer. The waveguide structure is formed into a bottom cladding polymer using a transparent flexible mold-based UV imprinting method. All other layers can be ink-jet printed. The top electrode is aligned and printed over the MZ arm. The modulator demonstrates a V-pi of 8 V at 3 kHz. This technology shows great potential in minimizing the fabrication complexity and roll-to-roll compatibility for manufacturing low cost, lightweight, and conformal modulators at high throughput.

Free-Motion Beam Propagation Factor Measurement by Means of a Liquid Crystal Spatial Light Modulator

In contrast to the mechanical scanning procedure described in the standard ISO/DIS 11146, the use of electronically tunable focal length lenses has proved its capability for the measurement of the laser beam propagation factor (M2) without moving components. Here, we demonstrate a novel experimental implementation where we use a low-cost programmable liquid crystal spatial light modulator (SLM) for sequentially codifying a set of lenses with different focal lengths. The use of this kind of modulators introduces some benefits such as the possibility for high numerical aperture or local beam control of the phase of the lenses which allows for minimizing systematic errors originated by lens aberrations. The beamwidth, according to the second-order moment of the irradiance, is determined for each focal length by using a digital sensor at a fixed position with respect to the spatial light modulator. After fitting the measured data to the theoretical focusing behavior of a real laser beam, the beam propagation factor is obtained. We successfully validated the results in the laboratory where a full digital control of the measurement procedure without mechanical scanning was demonstrated.

Highly flexible MTF measurement system for tunable micro lenses

We present an efficient, low-cost modulation transfer function (MTF) measurement approach, optimized for characterization of tunable micro-lenses; the MTF may easily be measured at a variety of different focal lengths. The approach uses a conventional optical microscope with an optimized approach for lens illumination and the measurement results have been correlated with a commercial MTF measurement system. Measurements on fixed-focus and tunable micro-lenses were performed; for the latter, resolution for lenses with back focal length of 11 mm was 55 lines/mm, decreasing to 40 lines/mm for a back focal length of 4 mm. In general, it was seen that performance was better for lenses with longer focal lengths.