Sideband Ratio Research Articles

MZM–SOA based RoF system for 30-tuple millimeter-wave generation

Abstract In this paper, we have reported radio over fiber system with 30-tuple millimeter-wave generation using dual parallel Mach–Zehnder modulator and semiconductor optical amplifier. The optimum choice of Mach–Zehnder modulator parameters has resulted into generation of signal lightwave and pump signal with frequency separation of 10f RF. Four wave mixing effect in semiconductor optical amplifier results into 30-tuple millimeter-wave signal. The proposed scheme is applicable to radio over fiber system with multiple base stations. The multiple number of frequencies such as 50 GHZ, 100 GHz, and 150 GHz have been generated using 5 GHz radio frequency only. NRZ data at 2.5 Gbps was modulated and successfully transmitted via optical fiber. The impact of injection current on the sideband ratio and BER is investigated. The proposed scheme confirms quality reception of demodulated signal at a transmission distance of 20 km.

Temperature drift suppression for micro‐electro‐mechanical system gyroscope based on vibrational‐displacement control with harmonic amplitude ratio

AbstractMicro‐electro‐mechanical system gyroscope detection output is susceptible to drift due to ambient temperature variations. Furthermore, the drive‐mode vibration amplitude is affected by the signal pickup circuit and structural parameters, which significantly influence the temperature drift of the bias and scale factor (SF). This study proposes a vibration amplitude control method based on harmonic amplitude sideband‐ratio (SBR), namely SBR‐AGC, which characterizes the vibration amplitude using the harmonic amplitude ratio of the vibrational electrical signal. The constancy of vibration amplitude is maintained via closed‐loop control to suppress bias and SF temperature drift. The experimental results on cobweb‐like disk resonator gyroscope reveal that the temperature coefficient of bias in the SBR‐AGC mode lies within −20 to 60°C and decreases by 36%, and the temperature coefficient of the SF lies within −10 to 50°C and decreases by 49.7%. Therefore, the environmental adaptability of the gyroscope is effectively improved.

Simulation of Friction Fault of Lightly Loaded Flywheel Bearing Cage and Its Fault Characteristics.

Because of the operating environment and load, the main fault form of flywheel bearing is the friction fault between the cage and the rolling elements, which often lead to an increase in the friction torque of the bearing and even to the failure of the flywheel. However, due to the complex mechanism of the friction fault, the characteristic frequencies often used to indicate cage failure are not obvious, which makes it difficult to monitor and quantitatively judge such faults. Therefore, this paper studies the mechanism of the friction fault of the flywheel bearing cage and establishes its fault feature identification method. Firstly, the basic dynamic model of the bearing is established in this paper, and the friction between the cage and the rolling elements is simulated by the variable stiffness. The influence law of the bearing vibration response reveals the relationship between the periodic fluctuation of cage-rolling element friction failure and the bearing load. After analyzing the envelope spectrum of the vibration data, it was found that when a friction fault occurred between the cage and the rolling element, the rotation frequency component of the cage modulated the rotational frequency component of the rolling element, that is, the side frequency components appeared on both sides of the characteristic frequency of the rolling element (with the characteristic frequency of the cage as the interval). In addition, the modulation frequency components of the cage and rolling element changed with the severity of the fault. Then, a modulation sideband ratio method based on envelope spectrum was proposed to qualitatively diagnose the severity of the cage-rolling element friction faults. Finally, the effectiveness of the presented method was verified by experiments.

Silicon Photonic-Based Integrated Microwave Photonic Reconfigurable Mixer, Phase Shifter, and Frequency Doubler

An integrated microwave photonic (IMWP) reconfigurable mixer, phase shifter, and frequency doubler based on the silicon photonics platform is proposed and theoretically investigated in this paper. The proposed structure consists of a novel dual-drive Mach–Zehnder modulator (DDMZM) placed in parallel with an electro-optic phase modulator (PM). The novel DDMZM is a bias-free modulator that has advantages over conventional MZMs, such as bias-free operation and tunable optical-to-carrier sideband ratio (OCSR). The proposed novel structure can be configured as an IMWP phase tunable mixer or IMWP double-balanced mixer by properly adjusting optical wavelength and choosing the proper radio frequency (RF) hybrid coupler. Besides, the proposed IMWP reconfigurable mixer has the ability to perform up-converting, down-converting, RF frequency doubling, and phase shifting. The proposed structure is theoretically analyzed and is verified by simulations.

High Modulation Efficiency and Dynamic Range Optical Single Sideband Modulation Without Gain Penalty in Nonlinear Distortion Suppression

The optical single sideband (OSSB) modulation with tunable optical carrier to sideband ratio (OCSR) is a promising and popular technique in wideband analog signal transmission and microwave signal processing, which can improve modulation efficiency and combat the fiber chromatic dispersion. However, in all reported schemes for achieving OSSB modulation with tunable OCSR, the spurious free dynamic ranges (SFDR) of the systems are all limited by the third-order intermodulation distortion (IMD3). In this paper, our object is to improve the SFDR and suppress the IMD3 in a novel OSSB modulation with tunable OCSR. The proposed system consists of a primary channel and a secondary channel. In primary channel, an OSSB modulation with tunable OCSR is implemented. In secondary channel, the optical carrier and first-order sidebands are perfectly cancelled out, which can suppress the IMD3 without gain penalty at the same received optical power. In this way, a large-SFDR OSSB modulation with tunable OCSR is realized. Experimental results exhibit that the IMD3 gets effective cancellations without gain penalty under unchanged total received power, and the output microwave signal power obtains about 11-dB improvement by optimizing the OCSR. A greatly increased SFDR of over 128 dBHz4/5 is achieved in the proposed system.

Stabilizing Electro-Optic Modulation Depth With Carrier to Sideband Ratio by Intermediate Optical Beatings

Electro-optic modulation with a constant modulation depth plays important roles in quantum metrology, microwave photonics, and optical precision measurement and sensing, etc. To compensate the continuous drift of the half-wave voltage and maintain the modulation depth, we incidentally generated a reference laser to make intermedia optical beatings with the carrier and +1st sideband, and tightly locked the carrier to sideband ratio by extracting the relative microwave power of those intermedia beat signals using a home-made electronic control module. Experiments of the short-term test for locking bandwidth, the anti-jamming capability, and the long-term stability were demonstrated. As is verified that, the locking bandwidth was estimated up to tens of kHz, and the anti-jamming capability was confirmed despite of a strong hair-dryer agitation. The long-term stability for the modulation depth stabilization showed that the peak-to-peak relative stability for 150-minute was 5.67 × 10−6, and the Allan deviation reached a minimum of 2.19 × 10−7 at an averaging time of 400 s, which is improved by more than four orders of magnitude compared with the open-loop regime. We believe the reported method as well as the designed module is versatile and potential to precision measurement and sensing applications badly requiring a stable modulation depth, such as atom interferometry, optical interferometry and lidar detection.

Photodetector optic power optimization to increase the gain on sub-octave microwave photonic link / Optimização da potência óptica do fotodetector para aumentar o ganho na ligação fotónica de microondas sub-octave

An investigation of the optic spectral components beating at the photodetector to recover the RF signal at the output of a sub-octave microwave photonic link is presented, by a theoretical and experimental approach. It is demonstrated the best efficiency is achieved when the carrier to sideband ratio (CSR) is 0 dB at a low bias voltage condition on Mach-Zehnder (MZM) intensity modulator. A RF power link gain improvement of 9.7 dB is demonstrated for a same photodetector incident optic power, compared with a link operating at quadrature bias voltage condition on the MZM.

Integrated Direct Single Sideband Modulation Utilizing Sideband Amplification Injection Locking Effect Based on Multi-Section Mutual Injection DFB Laser

An integrated single sideband (SSB) modulation method benefitting from the sideband amplification injection locking (SAIL) effect for radio-over-fiber (ROF) link is proposed and experimentally demonstrated, which is based on an integrated multi-section mutual injection (IMSMI) DFB laser. The IMSMI-DFB laser, which overcomes the drawbacks of using discrete devices, simplifies the whole structure. The SAIL effect, which is regulated by the input RF power and bias current of IMSMI-DFB laser, promises a good pathway for adjusting and controlling the modulation frequency, optical carrier to sideband ratio (OCSR), and sideband suppression ratio (SSR), meanwhile, provides high gain in the link. The characteristics of SAIL effect are investigated. The OCSR can be optimized to 0 dB, the SSR is over 26 dB, and the transmission link gain improves over 20 dB from 16 GHz to 26 GHz. The ROF transmission experiments demonstrate that the power fading introduced by fiber dispersion is dramatically eliminated, and the error vector magnitudes (EVMs) of the received 20 MSymbol/s 32 QAM signals at frequencies from17 GHz to 22.3 GHz after 50 km fiber transmission are below 4.8%. This work provides an effective way to realize integrated direct SSB modulation with outstanding features for ROF link.

A ROF system based on 18-tuple frequency millimeter wave generation using external modulator and SOA

In this paper, we have reported a radio-over-fiber (ROF) system with 18-tuple frequency optical millimeter-wave using external modulator and four-wave mixing (FWM) in semiconductor optical amplifier (SOA). Signal lightwave and pump with frequency interval of 6fRF are generated by adjusting the parameters of the Mach-Zehnder modulator (MZM). After FWM in SOA and filtering, 18-tuple frequency millimeter-wave signal is generated. Based on the proposed scheme, a 90 GHz optical millimeter-wave is generated only using 5 GHz RF by numerical simulation. The simulation results show that our proposed scheme can provide 20 km single-mode fiber (SMF) transmission. In addition, the impact of SOA’s current on the sideband ratio (SR) and the system performance are also studied.

High Power Efficiency and Dynamic Range Analog Photonic Link with Suppressed Dispersion-Induced Power Fading

An analog photonic link (APL) based on a dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM) is proposed and experimentally demonstrated. The proposed APL can suppress the nonlinearity of modulator, compensate the power fading induced by dispersion (PFID), and improve the power efficiency of link, leading to large dynamic range. The PFID and the nonlinearity are suppressed by adjusting the phase of optical carrier (OC) and polarization controller (PC), respectively. In addition, by optimizing the optical carrier to sideband ratio (OCSR) in the DP-DPMZM, the output RF power and the power efficiency of link can be significantly improved while the total optical power received by the photodetector (PD) remains constant. An experiments are performed to demonstrate the feasibility of the APL. The results show that an spurious free dynamic range (SFDR) of 103.2 dB·Hz4/5 for 13.73 GHz is achieved after compensating PFID and nonlinearity, which is 32 dB higher than that of a conventional double sideband (DSB) assisted APL. After OCSR optimizing, the output RF power achieves 13-dB improvement, and the SFDR is further raised to 114.1 dB·Hz4/5.

Optimization of quantitative time-resolved 3D (4D) digital subtraction angiography in a porcine liver model

BackgroundTime-resolved three-dimensional digital subtraction angiography (4D-DSA) can be used to quantify blood velocity. Contrast pulsatility, a major discriminant on 4D-DSA, is yet to be optimized. We investigated the effects of different imaging and injection parameters on sideband ratio (SBR), a measure of contrast pulsatile strength, within the hepatic vasculature of an in vivo porcine model.MethodsFifty-nine hepatic 4D-DSA procedures were performed in three female domestic swine (mean weight 54 kg). Contrast injections were performed in the common hepatic artery with different combinations of imaging duration (6 s or 12 s), injection rates (from 1.0 to 2.5 mL/s), contrast concentration (50% or 100%), and catheter size (4 Fr or 5 Fr). Reflux was recorded. SBR and vessel cross-sectional areas were calculated in 289 arterial segments. Multiple linear mixed-effects models were estimated to determine the effects of parameters on SBR and cross-sectional vessel area.ResultsTwelve-second acquisitions yielded a SBR higher than 6 s (p < 0.001). No significant differences in SBR were seen between different catheter sizes (p = 0.063) or contrast concentration (p = 0.907). For higher injection rates (2.5 mL/s), SBR was lower (p = 0.007) and cross-sectional area was higher (p < 0.001). Reflux of contrast does not significantly affect SBR (p = 0.087).ConclusionsThe strength of contrast pulsatility used for flow quantitation with 4D-DSA can be increased by adjusting injection rates and using longer acquisition times. Reduction of contrast concentration to 50% is feasible and reflux of contrast does not significantly hinder contrast pulsatility.

Wideband and Dispersion Immune Microwave Photonic Phase Shifter With Tunable Optical Carrier to Sideband Ratio

A wideband microwave photonic phase shifter (MPPS) based on a dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM) is proposed and experimentally demonstrated. The proposed system has the features of chromatic dispersion (CD) immunity and tunable optical carrier to sideband ratio (OCSR), which can realize long fiber transmission distance with improved power efficiency. It is realized by carrier suppress double sideband (CS-DSB) plus optical carrier (OC) modulation at two orthogonal polarization states. The phases of output RF signals can be tuned continuously and independently by controlling the phases of the OCs. The experiment results show that the continuous 360° phase shifts of output RF signal over 5–25 GHz are both realized in the cases of back-to-back and fiber transmission. No CD-induced power fading and phase severe shaking of the RF signals appear after the dispersion compensating fiber (DCF) of −331 ps/nm at 1545 nm transmission. By optimizing the OCSR of the system, the output RF power efficiency of the proposed scheme realizes significantly improvement when input RF powers and output optical powers are both fixed. The possibility of generating frequency doubling signal is also verified.

Optimizing the Quality of 4D-DSA Temporal Information.

Quantification of blood flow using a 4D-DSA would be useful in the diagnosis and treatment of cerebrovascular diseases. A protocol optimizing identification of density variations in the time-density curves of a 4D-DSA has not been defined. Our purpose was to determine the contrast injection protocol most likely to result in the optimal pulsatility signal strength. Two 3D-printed patient-specific models were used and connected to a pulsatile pump and flow system, which delivered 250-260 mL/min to the model. Contrast medium (Isovue, 370 mg I/mL, 75% dilution) was injected through a 6F catheter positioned upstream from the inlet of the model. 4D-DSA acquisitions were performed for the following injection rates: 1.5, 2.0, 2.5, 3.0 and 3.5 mL/s for 8 seconds. To determine pulsatility, we analyzed the time-density curve at the inlets using the oscillation amplitude and a previously described numeric metric, the sideband ratio. Vascular geometry from 4D-DSA reconstructions was compared with ground truth and micro-CT measurements of the model. Dimensionless numbers that characterize hemodynamics, Reynolds and Craya-Curtet, were calculated for each injection rate. The strongest pulsatility signal occurred with the 2.5 mL/s injections. The largest oscillation amplitudes were found with 2.0- and 2.5-mL/s injections. Geometric accuracy was best preserved with injection rates of >1.5 mL/s. An injection rate of 2.5 mL/s provided the strongest pulsatility signal in the 4D-DSA time-density curve. Geometric accuracy was best preserved with injection rates above 1.5 mL/s. These results may be useful in future in vivo studies of blood flow quantification.

Low-Power RF Signal Detection Using a High-Gain Tunable OEO Based on Equivalent Phase Modulation

A novel photonic method for low power radio-frequency (RF) signal detection by a tunable optoelectronic oscillator (OEO) with high gain based on equivalent phase modulation (EPM) is proposed and experimentally demonstrated. A dual-parallel Mach-Zehnder modulator is utilized to generate the EPM signal with a controllable optical carrier to sideband ratio, by which the gain to the RF signal by the OEO loop can be enhanced. A phase-shifted fiber Bragg grating (PS-FBG) with a narrow-band notch in its reflection band implements the phase modulation to intensity modulation conversion by removing one sideband of the EPM signal. The gain and noise performance of the detection system are theoretically analyzed and simulated. In the experiment, the maximum gain of 10.4 dB is obtained at 8 GHz, and the detection sensitivity for RF signals from 2 to 18 GHz are within the range of −87.7 to −84.3 dBm by using the developed detection system. Compared to normal phase modulation based scheme, the EPM-based system offers 9.1 dB higher gain. Utility of the proposed approach for detecting modulated RF signal is also investigated and an optimization scheme is discussed.

Continuously tunable orthogonally polarized RF optical single sideband generator based on micro-ring resonators

We demonstrate a continuously RF tunable orthogonally polarized optical single sideband (OP-OSSB) generator based on dual cascaded micro-ring resonators (MRRs). By splitting the input double sideband signal into an orthogonally polarized carrier and lower sideband via TE- and TM-polarized MRRs, an OP-OSSB signal is generated. A large tuning range of the optical carrier to sideband ratio of up to 57.3 dB is achieved by adjusting the polarization angle of the input light. The operation RF frequency of the OP-OSSB generator can be continuously tuned with a 21.4 GHz range via independent thermal control of the two MRRs. Our device represents a competitive approach towards OP-OSSB generation with wideband tunable RF operation, and is promising for photonic RF signal transmission and processing in radar and communication systems.

A Quadrature Single Side-Band Mixer with Passive Negative Resistance in Software-Defined Frequency Synthesizer.

Software-defined radio (SDR) is a good solution for complying with the existing and incoming protocols for emerging wireless sensor networks (WSN) and internet of things (IoT) applications. The frequency synthesizer in a SDR tranceiver usually consists of a phase locked loop (PLL) and a post synthesizer. The PLL is the narrow band signal source and the post synthesizer generates wideband outputs by mixing and dividing. Compared with a frequency synthesizer utilizing the wideband PLL, this synthesizer features relatively constant loop parameters and mitigates the requirement for the oscillator. In this paper, a quadrature single side-band (QSSB) mixer with the proposed passive negative resistance (PNR) for frequency mixing in a post synthesizer is presented. The PNR is achieved by biasing the Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFET) of the cross-coupled pair at the deep-triode region periodically and incorporates an inductor and a cap-array as the mixer load. Compared with the traditional single side-band mixers utilizing Inductor-Capacitor (LC) resonant loads or quality factor enhanced (Q-enhanced) LC resonant loads, which suffer from a selectivity versus working range trade-off, the mixer employing the proposed loading structure provides not only a wide operating range, but also a superior image side-band rejection ratio (ISRR). Moreover, the oscillating risk in conventional mixers adopting Q-enhanced LC resonant loads is eliminated. A wideband frequency synthesizer employing the proposed mixer was implemented in a TSMC 0.18 µm CMOS process and the mixer performed ISRR of 40–57 dB and 30–57 dB across 2.5–3 GHz and 2.3–3.2 GHz, respectively. The power consumption of the QSSB mixer, including buffer, is 18 mA from a 1.8 V supply and the active area is 0.445 mm2. The measurement results provide validation that the proposed QSSB mixer is suitable for wideband software-defined frequency synthesizers and other frequency generating systems.

Measuring blood velocity using 4D-DSA: A feasibility study.

Four-dimensional (4D) DSA reconstruction provides three-dimensional (3D) time-resolved visualization of contrast bolus passage through arterial vasculature in the interventional setting. The purpose of this study was to evaluate the feasibility of using these data in measuring blood velocity and flow. The pulsatile signals in the time concentration curves (TCCs) measured at different points along a vessel are markers of the movement of a contrast bolus and thus of blood flow. When combined with the spatial content, that is, geometry of the vasculature, this information then provides the data required to determine blood velocity. A Fourier-based algorithm was used to identify and follow the pulsatility signal. A Side Band Ratio (SBR) metric was used to reduce uncertainty in identifying the pulsatility in regions where the signal was weak. We tested this method using 4D-DSA reconstructions from vascular phantoms as well as from human studies. In five studies using 3D printed patient-specific cerebrovascular phantoms, velocities calculated from the 4D-DSAs were found to be within 10% of velocities measured with a flow meter. Calculated velocity and flow values from three human studies were within the range of those reported in the literature. 4D-DSA provides temporal and spatial information about blood flow and vascular geometry. This information is obtained using conventional rotational angiographic systems. In this small feasibility study, these data allowed calculations of velocity values that correlated well with measured values. The availability of velocity and blood flow information in the interventional setting would support a more quantitative approach to diagnosis, treatment planning and post-treatment evaluations of a variety of cerebrovascular diseases.

Simulation study for the Stratospheric Inferred Winds (SIW) sub-millimeter limb sounder

Abstract. Stratospheric Inferred Winds (SIW) is a Swedish mini sub-millimeter limb sounder selected for the 2nd InnoSat platform, with launch planned for around 2022. It is intended to fill the altitude gap between 30 and 70 km in atmospheric wind measurements and also aims at pursuing the limb observations of temperature and key atmospheric constituents between 10 and 90 km when current satellite missions will probably come to an end. Line-of-sight winds are retrieved from the Doppler shift of molecular emission lines introduced by the wind field. Observations will be performed with two antennas pointing toward the limb in perpendicular directions in order to reconstruct the 2-D horizontal wind vector. Each antenna has a vertical field of view (FOV) of 5 km. The chosen spectral band, near 655 GHz, contains a dense group of strong O3 lines suitable for exploiting the small amount of wind information in stratospheric spectra. Using both sidebands of the heterodyne receiver, a large number of chemical species will be measured, including O3 isotopologues, H2O, HDO, HCl, ClO, N2O, HNO3, NO, NO2, HCN, CH3CN and HO2. This paper presents a simulation study that assesses measurement performance. The line-of-sight winds are retrieved between 30 and 90 km with the best sensitivity between 35 and 70 km, where the precision (1σ) is 5–10 m s−1 for a single scan. Similar performance can be obtained during day and night conditions except in the lower mesosphere, where the photo-dissociation of O3 in daytime reduces the sensitivity by 50 % near 70 km. Profiles of O3, H2O and temperature are retrieved with high precision up to 50 km ( &lt; 1 %, &lt; 2 %, 1 K, respectively). Systematic errors due to uncertainties in spectroscopic parameters, in the radiometer sideband ratio and in the radiance calibration process are investigated. A large wind retrieval bias of 10–30 m s−1 between 30 and 40 km could be induced by the air-broadening parameter uncertainties of O3 lines. This highlights the need for good knowledge of these parameters and for studying methods to mitigate the retrieval bias.

A novel method to realize optical single sideband modulation with tunable optical carrier to sideband ratio

AbstractAn optical single sideband (OSSB) modulation method with tunable optical carrier to sideband ratio (OCSR) is proposed and experimentally demonstrated based on a dual‐polarization Mach–Zehnder modulator (DPol‐MZM). An orthogonally polarized double sideband (DSB) signal output from the DPol‐MZM is filtered out the carrier and one sideband utilizing an optical bandpass filter (OBPF). Then the orthogonally polarized OSSB signal is transformed into a linear polarized OSSB signal by a polarizer (Pol). By changing the polarization direction of the Pol utilizing a polarization controller (PC), the tunable OCSR can be achieved. In the demonstrated experiments, an OSSB modulation is implemented over the wide microwave frequency range of 5–30 GHz. The OCSR is tuned from −30 dB to infinity. The proposed OSSB modulation method is advantageous in many respects as large tunable OCSR range, wide operation bandwidth, and simple structure.

Analog Photonic Link With Tunable Optical Carrier to Sideband Ratio and Balanced Detection

Optical carrier to sideband ratio (CSR) optimization and balanced detection are two effective techniques to improve the performance of an analogy photonic link (APL). Here, we proposed an APL where tunable optical CSR and balanced detection can both be implemented. A single integrated polarization division multiplexing Mach–Zehnder modulator (PDM-MZM) is used to generate a polarization multiplexed signal containing an optical carrier and two radio frequency modulated sidebands, and the optical CSR can be tuned from –15 to 15 dB by simply adjusting the direct current bias of the modulator. By optimizing the optical CSR in the proposed link, the link gain and noise figure (NF) are improved by 12 and 6.8 dB compared with conventional quadrature biased link. In addition, after balanced detection in the proposed link, the link gain, NF, third-order spurious free dynamic range (SFDR), and especially the second-order SFDR are further improved.