Low-cost Continuous Wave Research Articles

Signal processing implementation of low-cost target speed detection of CW radar using FPGA

The low-cost Continuous Wave (CW) radar architecture for object speed detection is presented in this research. An FPGA (Field-Programmable Gate Array) processor is utilized to implement the CW radar dependably and optimally. The suggested approach uses a bank of filters made expressly to extract velocity information from radar signals to compute the target velocity. Depending on the needs of the particular application, the acquired data has either undergone additional processing or been presented in an approachable manner. The implemented design is checked in real-time with a chip scope, functionally simulated, and then inspected with lab instruments to compare all simulated and implemented outcomes. Numerous applications, such as industrial automation, surveillance, and automotive systems, where accurate velocity detection is crucial and low-cost design is required, could benefit from this concept.

Terahertz Quasi-Time Domain Spectroscopy using a 808nm multimode diode laser

We report on a terahertz quasi-time domain spectroscopy (QTDS) system based on a low-cost continuous wave multimode diode laser. Commercially available low-temperature grown gallium arsenide (LT-GaAs) based photoconductive antennas (PCAs) with spiral and dipole configurations were used as emitter and detector, respectively. Terahertz pulses spaced at approximately 55 ps with a bandwidth of 400 GHz were obtained. Parametric measurements of the terahertz peak-to-peak intensity were performed by varying the injection current and temperature while maintaining incident laser power. The highest peak-to-peak intensity was obtained at 170mA injection current and 20° C temperature settings. The change in the THz peak-to-peak intensity is attributed to the mode hopping characteristics of the device which in turn, is dependent on injection current and temperature.

VitRad: A low-cost continuous wave Doppler radar system with 3D-printed horn antennas for human vital sign detection

In this study, a low-cost continuous wave (CW) radar system with 3D-printed high-gain horn antennas called VitRad is proposed for human vital sign detection. The CW radar consists of 3D-printed high-gain horn antennas, commercially available low-cost surface-mounting devices, and monolithic ICs. The CW radar system operates at a frequency band of 5.8 GHz, and the backscattered I/Q data are collected using a digital storage oscilloscope (DSO). The data is processed on MATLAB to determine vital sign information such as respiratory and heartbeat rates. It is demonstrated that the proposed CW radar system for vital-sign monitoring can effectively measure respiratory and heartbeat rates.

Portable continuous wave Doppler ultrasound for primary healthcare in South Africa: can the EUnetHTA Core Model guide evaluation before technology adoption?

BackgroundThis study had a threefold aim: to test the value of stakeholder involvement in HTA to reduce evidence gaps and interpret findings; and to assess a medical device by applying the EUnetHTA Core Model (CM) in South Africa and thus ultimately provide a first overview of evidence for potential widespread adoption of the technology in a primary health care (PHC) setting. Used in primary healthcare setting for obstetric use, the technology under assessment is a low-cost continuous wave Doppler ultrasound (DUS).MethodsThe scoping of the assessment was defined by involving policy makers in selecting the domains and corresponding questions relevant to the ultrasound and its use. Additionally, hospital managers were invited to respond to dichotomous questions on the criteria for procurement. To substantiate evidence obtained from an initial literature review, different stakeholders were identified and consulted. The evidence generated fromall steps was used to populate the high-ranked assessment elements of the CM.ResultsThe HTA on continuous-wave DUS incorporated the evidence on organizational, ethical, and social value of its use together with effectiveness, safety, and cost-effectiveness of the technology. The domains on “health problem” and “safety” had a higher rank than the rest of the nine domains. Unexplained fetal mortality is the largest single contributor to perinatal deaths in South Africa. Pregnant women in PHC setting were examined using a continuous-wave DUS, after their routine antenatal visit. The healthcare professionals interviewed, indicated the benefit in the use of continuous-wave DUS in the PHC setting and the need for training.ConclusionsCollection and generation of evidence based on the HTA CM and the chosen decision criteria provided a generalized but structured guidance on the methodology. Several questions were not applicable for the technology and the context of its use and elimination of those that are inappropriate for the African context, resulted in a pragmatic solution. Engaging and consulting local stakeholders was imperative to understand the context, reduce evidence gaps, and address the uncertainties in the evidence, ultimately paving the way for technology adoption. Given the ongoing studies and the evolving evidence base, the potential of this technology should be reassessed.

Noncontact Measurement of River Surface Velocity and Discharge Estimation With a Low-Cost Doppler Radar Sensor

River discharge is an important variable to measure in order to predict droughts and flood occurrences. Once the cross-sectional geometry of the river is known, discharge can be inferred from water level and surface flow velocity measurements. Since river discharges are of particular interest during extreme weather events, when river sites cannot be safely accessed, noncontact sensing technologies are particularly appealing. To this purpose, this work proposes a prototype of a low-cost continuous wave (CW) Doppler radar sensor, which is able to monitor the surface flow velocity of rivers. The prototype is tested at two gauged sites in central Italy, along the Tiber River. The surface flow velocity distribution across the river is monitored by means of the analysis of received Doppler signal. The surface velocity statistics are then extracted using a novel algorithm that is optimized to run on a microprocessor platform with minimal computing power (ArduinoUNO). In particular, the radar measurements are used to initialize a 2-D entropy-based velocity model (EVM) that is able to estimate river discharges in any flow condition. Finally, the results concerning the observed discharge provided by the EVM prove to be comparable with those obtained with more expensive commercial solutions. The results are important since the described methodology can be extended to small-size Doppler radar sensors onboard unmanned aerial vehicles (UAVs), the latter providing a method for mapping surface velocity of rivers.

Optical Coherence Tomography/Angiography-Guided Tumor Ablation With a Continuous-Wave Laser Diode

Laser ablation can be an effective modality for treatment, but it is complicated to apply continuous-wave (CW) light sources for laser ablation because of the unpredictable photothermal damage. In this study, an integrated theranostic system combining a low-cost CW laser diode with optical coherence tomography (OCT)/angiography (OCTA) was utilized for the in vivo ablation of tumor tissues. To examine the effect of laser exposure on tissue scattering characteristics, the OCT backscattering intensities of non-ablated and ablated tissues were analyzed, and the effect on the skin microvasculature produced by laser ablation was quantitatively evaluated. Moreover, the integrated system and the proposed method were implemented for the treatment of skin tumor on the mouse model. The obtained results indicate that the developed laser ablation system can effectively remove tumor tissues with controllable photodamage under OCT/OCTA guidance and that the system cost may be significantly reduced by using the CW laser diode.

Deposition of Fine Linewidth Silver Layer using a Modified Laser-induced Forward Transfer Technique

This paper reports the deposition of a metal line using a multilayer stack and laser-induced forward transfer (LIFT) using a low cost continuous wave blue laser with a wavelength of 450 nm. The donor structure was composed of a light-to-heat (LTH) layer, a release layer, and a transfer layer in series. Amorphous silicon as the LTH layer absorbs photon energy and converts it to heat. A release layer was melted so that a silver transfer layer would be transferred to the receiver substrate. The transferred silver layer showed reasonable physical and electrical characteristics. A low cost fine linewidth metal layer could be achieved using this modified LIFT technique and blue laser.

Direct Silver Micro Circuit Patterning on Transparent Polyethylene Terephthalate Film Using Laser-Induced Photothermochemical Synthesis

This study presents a new and improved approach to the rapid and green fabrication of highly conductive microscale silver structures on low-cost transparent polyethylene terephthalate (PET) flexible substrate. In this new laser direct synthesis and pattering (LDSP) process, silver microstructures are simultaneously synthesized and laid down in a predetermined pattern using a low power continuous wave (CW) laser. The silver ion processing solution, which is transparent and reactive, contains a red azo dye as the absorbing material. The silver pattern is formed by photothermochemical reduction of the silver ions induced by the focused CW laser beam. In this improved LDSP process, the non-toxic additive in the transparent ionic solution absorbs energy from a low cost CW visible laser without the need for the introduction of any hazardous chemical process. Tests were carried out to determine the durability of the conductive patterns, and numerical analyses of the thermal and fluid transport were performed to investigate the morphology of the deposited patterns. This technology is an advanced method for preparing micro-scale circuitry on an inexpensive, flexible, and transparent polymer substrate that is fast, environmentally benign, and shows potential for Roll-to-Roll manufacture.

Additive and Photochemical Manufacturing of Copper.

In recent years, 3D printing technologies have been extensively developed, enabling rapid prototyping from a conceptual design to an actual product. However, additive manufacturing of metals in the existing technologies is still cost-intensive and time-consuming. Herein a novel platform for low-cost additive manufacturing is introduced by simultaneously combining the laser-induced forward transfer (LIFT) method with photochemical reaction. Using acrylonitrile butadiene styrene (ABS) polymer as the sacrificial layer, sufficient ejection momentum can be generated in the LIFT method. A low-cost continuous wave (CW) laser diode at 405 nm was utilized and proved to be able to transfer the photochemically synthesized copper onto the target substrate. The wavelength-dependent photochemical behaviour in the LIFT method was verified and characterized by both theoretical and experimental studies compared to 1064 nm fiber laser. The conductivity of the synthesized copper patterns could be enhanced using post electroless plating while retaining the designed pattern shapes. Prototypes of electronic circuits were accordingly built and demonstrated for powering up LEDs. Apart from pristine PDMS materials with low surface energies, the proposed method can simultaneously perform laser-induced forward transfer and photochemical synthesis of metals, starting from their metal oxide forms, onto various target substrates such as polyimide, glass and thermoplastics.

Structural, morphological and mechanical properties of laser-irradiated copper using continuous wave diode laser

ABSTRACTLaser irradiation effects on morphological, structural and mechanical properties of copper are explored. The targets are exposed by employing low-cost continuous wave (CW) laser (wavelength of 532 nm) in air. The surface morphology, structural and mechanical modification of irradiated targets was investigated by scanning electron microscopy (SEM) (Fei, Quanta 250), an X-ray diffractrometer (XRD) (DMAX III ARigaku, Japan) and a Vickers hardness tester, respectively. The SEM analysis revealed the exfoliation sputtering, electronic sputtering, thermal stresses and cracks. The grain size, dislocation line density, relative intensity and d-spacing of irradiated metals were studied by XRD. Micro hardness is found to increase with the increase in time of laser irradiation, in accordance with the Vickers hardness tester. This work provides a cost-effective, user-friendly and easy-to-handle study of several properties of irradiated targets with good results.

Microscopic coherent Raman imaging using low-cost continuous wave lasers

Significant effort is devoted to improving the instrumentation for stimulated Raman scattering (SRS) microscopy, which plays an important role in non-invasive biomedical optical imaging by providing a chemically specific contrast without relying on fluorescent markers. In this work we employ low-cost continuous wave lasers to achieve highly sensitive SRS imaging suitable for future application in biology, medicine and materials science. We perform microscopic imaging of dimethyl sulfoxide using two independent, commonly used lasers: a diode pumped, intracavity doubled 532 nm laser and a He–Ne laser operating at 632.8 nm. We further demonstrate that SRS imaging using cw laser sources (cwSRS) is advantageous over pulsed laser based SRS, as it eliminates the possibility of sample damage due to exposure to high-intensity light radiation, while substantially reducing the cost and complexity of the setup and keeping a sub-micron spatial resolution.

Compact cw Terahertz Spectrometer Pumped at 1.5 μm Wavelength

A compact and low-cost continuous wave terahertz spectrometer operating at an optical wavelength of 1.5 μm is presented. The spectrometer employs high power distributed feedback (DFB) laser diodes in integrated “butterfly” packages. No further optical amplification of the beating signal is required. An integrated photodiode antenna with an output power of 5 μW at 500 GHz is used as efficient terahertz emitter. Employing low-temperature grown (LT-) InGaAs/InAlAs photoconductive receivers as coherent detectors, SNR values of the terahertz power up to 75 dB are attained at an integration time of 300 ms. Accurate characterization of the thermal tuning behavior of the DFBs and precise thermal control yield an absolute accuracy of 1 GHz and a resolution of better than 5 MHz, without any on-line monitoring of the optical frequency. Due to the high frequency resolution no delay line is needed to vary the terahertz phase.

편광 및 위상 부정합을 이용한 광혼합을 통하여 발생된 서브 밀리미터파 대역 연속파의 위상 잡음 특성 개선

본 논문에서는 광혼합 방식으로 서브 밀리미터 및 테라헤츠 대역 연속파 신호를 발생시키는 기법 중 가장 널리 사용되는 광반송파가 억제된 양측 대역 발생 방식(Double Sideband-Suppressed Carrier: DSB-SC)을 이용하여 발생된 연속파(Continuous Wave: CW) 신호의 위상 잡음 개선을 위하여 광신호의 편광과 위상 제어 기법을 제안하고 실험적으로 증명하였다. 광신호의 편광 및 위상 제어 기법은 일반적인 DSB-SC 신호와 DSB-SC 신호에 포함된 광반송파와 동일한 파장과 위상차를 가지며, 광반송파의 편광 성분 중 하나의 편광 성분만을 갖도록 편광제어된 광신호를 결합하여 광혼합하는 방법이다. 실험 및 측정 결과, 서브 밀리미터파 대역 CW 신호의 크기는 1.5 dB 증가하였으며, 위상 잡음 특성은 약 3 dB@10 kHz offset frequency 개선됨을 확인하였다. 따라서 본 논문의 결과는 광신호의 위상 및 편광 성분 제어만으로 광반송파를 효과적으로 억제하여 서브 밀리미터 및 테라헤르츠 대역 CW 신호의 특성을 개선함으로써 광혼합 방법을 이용한 밀리미터파 및 테라헤르츠파 대역 CW 신호 발생기의 저가화를 위한 기본적인 데이터로서 활용 가치가 높다. In this paper, we have proposed and experimentally performed a polarization and phase control method of an optical signal which has same wavelength with the optical carrier to improve phase characteristics of a continuous wave(CW) generated by the double sideband-suppressed carrier(DSB-SC) as one of the famous photomixing technique for making sub-millimeter and terahertz waves. A polarization and phase controlled optical signal has been coupled with the general DSB-SC on an optical coupler. The output of the optical coupler is then photomixed by a photomixer. From our analysis and measurement results, we have found that the amplitude of the generated sub-mm and terahertz CW signal is higher 1.5 dB and the phase noise is lower about 3 dB@10 kHz offset frequency than the general DSBSC. Consequently, since our proposed method has improved the amplitude and phase noise of CW signals in the sub-mm and terahertz bands, it can be helpful results to make low cost CW generator in sub-millimeter and subterahertz bands.

Experimental investigation of continuous-wave supercontinuum ring laser composed of clad-pumped Er/Yb codoped fiber and highly-nonlinear optical fiber

We experimentally demonstrate a practical benefit of our proposed continuous-wave (CW) supercontinuum (SC) generating ring laser scheme in terms of low-cost device implementation and then investigate its output intensity noise property, as a further study to our previous paper of Ref. [J.H. Lee, Y. Takushima, K. Kikuchi, Opt. Lett. 30 (2005) 2599]. First, we implement a practical and low-cost CW SC laser using a double clad Er/Yb codoped fiber and a highly nonlinear dispersion-shifted fiber (HNL-DSF). Unlike the scheme in Ref. [J.H. Lee, Y. Takushima, K. Kikuchi, Opt. Lett. 30 (2005) 2599] the gain medium of an Er/Yb fiber is clad-pumped by low quality multimode pump LDs to underline the fact that our proposed scheme does not require any high power single-mode laser pump. A SC of a bandwidth larger than 470nm is readily achieved. Next, we measure relative-intensity-noise (RIN) of the generated SC and compare it with that of a pumped Er/Yb fiber ASE. The SC laser is found to have a much higher RIN than the ASE due to the nonlinear amplification of quantum fluctuations both in the seed light oscillation and in the Raman scattering process.

Frequency-shifted Mach-Zehnder interferometer for locating multiple weak reflections along a fiber link

We propose and demonstrate a novel technique for measuring fiber lengths and locating multiple weak reflections along the fiber using a low-cost continuous wave source, a folded Mach-Zehnder interferometer (MZI), and a frequency shifter. By sweeping the frequency of the shifter, which is located in one path of the MZI, the optical length of the test fiber can be determined precisely from the interference pattern constructed by the reflected signals from the fiber end. Experimentally, for fibers shorter than 10 km, the standard deviations are less than 1 mm. Furthermore, by incorporating lock-in detection and fast Fourier transform techniques, both the locations and the reflectance of multiple reflection sites along one fiber can be resolved with a spatial resolution of about 5 m and a sensitivity better than -67dB. This could be a powerful interrogating technique for optical fiber sensor arrays.

Intensity‐modulated diode laser radar using frequency‐modulation/continuous‐wave ranging techniques

Barry L. StannWilliam C. RuffZoltan G. SztankayDepartment of the ArmyArmy Research LaboratoryAMSRL-SE-EP2800 Powder Mill RoadAdelphi, Maryland 20783-1145E-mail: stann@arl.milAbstract. This paper treats a practical adaptation of frequency modula-tion (FM) radar ranging principles to an incoherent laser radar (ladar). Inthe simplest sense, the ladar’s laser transmitter output is amplitude-modulated with a radio-frequency subcarrier, which itself is linearlyfrequency-modulated. The subcarrier signal may have a start frequencyin the tens to low hundreds of megahertz and a stop frequency in thehundreds of megahertz to low gigahertz. The difference between thestart and stop frequency, DF, is chosen to establish the desired rangeresolution DR according to the usual equation from FM radar theory,DR5c/2 DF, where cis the velocity of light. The target-reflected light isincoherently detected with a photodiode and converted into a voltagewaveform. This waveform is then mixed with an undelayed sample of theoriginal modulation waveform. The output of the mixer is processed toremove ‘‘self-clutter’’ that is commonly generated in FM ranging systemsand obscures the true target signals. The clutter-free waveform is thenprocessed coherently using the discrete Fourier transform to recovertarget amplitude and range. A breadboard of the ladar architecture wasdeveloped around a 100-mW GaAlAs diode laser operating at 817 nm.Imagery and range responses obtained show that the theoretical rangeresolution of 0.25 m was attained for a DFof 600 MHz. Embodiments ofthis ladar are likely to be practical and economical for both military andcommercial applications because low-cost continuous wave (cw) laserdiodes are used, coherent optical mixing is not required, and the post-mixing processor bandwidth is low.