Electrical Filter Research Articles

Freely tunable phase-locked dual-frequency microwave signal generation from injection-locked broadband optoelectronic oscillator

We propose and experimentally demonstrate an injection-locked broadband optoelectronic oscillator (OEO) to generate freely tunable phase-locked dual-frequency microwave signals. When two single-tone signals inside and outside the passband of the electrical broadband bandpass filter (BPF) are, respectively, injected into the OEO, a phase-locked dual-frequency microwave signal with ultra-low near-end side-mode spurs can be generated from the OEO cavity. Therefore, one frequency of the output signal is equal to the frequency of the injected signal within the BPF, and the other frequency is equal to the sum frequency or the differential frequency of two injected signals. By changing the frequencies of two injected signals, two frequencies of the generated dual-frequency microwave signal can be arbitrarily tuned over the passband of the BPF. In our experiment, freelytu nable phase-locked dual-frequency microwave signals within the frequency range of 8∼12 GHz can be generated, where the side-mode suppression ratios (SMSRs) are more than 90 dB during the frequency tuning.

Method for design and implementation of telecommunication devices for aircraft

This article highlights the importance of electrical filters in radio engineering devices, emphasizing their role in transmitting signals in the transparency band and suppressing signals in the stop band. We examined methods for designing frequency-selective circuits with lumped parameters, which, in general, are a complete field of radio engineering and allow the synthesis of devices of varying complexity. The focus of the article is the frequency region, where the distributed properties of the synthesized structures appear. The article also provides an overview of various methods for synthesizing ultra-high frequency (UHF) filters. It is emphasized that for low-pass filters a transition from a low-frequency prototype to a high-frequency representation is applied, which, despite the crudeness of the approach, provides satisfactory results that can be improved at the production stage. The article also discusses various methods for implementing bandpass filters on distributed elements, including the use of short-circuited and open-circuited stubs, as well as weak-coupled lines. In conclusion, the paper highlights the need to improve these methods to improve process accuracy and make filter designers more efficient in radio engineering.

Aerosol collection efficiency enhancement in HVAC systems through electrical field-Induced filter media polarization

Electrically enhanced media filters improve filtration efficiency in heating, ventilation, and air conditioning (HVAC) systems. Enhancement is accomplished by placing a uniquely formulated media material which can be polarized between arrays of wire electrodes. We explore the implementation of an electrically enhanced filtration system to both quantify the level of enhancement in filtration efficiency achievable in conditions representative of HVAC systems, and to determine the mechanism of collection enhancement. Measurements were carried out on a system comprised of a MERV 11 base filter, two arrays of upstream electrodes, and one array of downstream electrodes. Collection efficiency measurements reveal a strong dependency on the applied voltage across all examined face velocities. At a particle diameter of 0.3 μm, the collection efficiencies showed marked increases of 51.6%, 47.2%, and 30.7% from the zero-field level to a voltage of 10 kV at flow rates of 850, 1700, and 2550 m3 hr−1, respectively. Notably, this enhancement in collection efficiency is maintained even after particle loading on the filter. Charge state examinations revealed minimal changes in particle charge levels within the filter unit, demonstrating that the enhancement of filter performance is driven by dielectrophoretic motion and to a lesser extent electrophoretic motion.

All-optical, filter-free, image-reject, and fundamental/sub-harmonic downconverted RoF link

An all-optical, image-reject, and fundamental/sub-harmonic downconverted radio-over-fiber (RoF) link using a polarization-division multiplexing Mach–Zehnder modulator (PDM-MZM) and fiber-dispersion effect is proposed. At the remote antenna unit, the receiving radio frequency (RF) signal and the local oscillator (LO) signal are used to drive two sub-MZMs of the PDM-MZM. After a length of optical fiber transmission, at the central office, by using the fiber-dispersion effect and controlling the polarization controller to introduce an appropriate phase shift between the RF and LO sidebands, image rejection is achieved and power fading is avoided simultaneously. Because the scheme is a simple and all-optical system without electrical frequency-dependent devices or filters, it has a good image-reject capability over a large working frequency range. Besides, the downconverter in sub-harmonic mode can decrease frequency requirement of the LO signal. Experimental results indicate that in the fundamental and sub-harmonic downconverters, for a single-tone signal, IRRs are over 47 dB. Image rejection for the 100-Mbaud 16-QAM signal and demodulated desired IF signal with a good EVM of less than 7% are realized. The proposed structure can be applied in RoF systems and microwave and millimeter-wave receivers.

A High-Capacity Optical Metro Access Network: Efficiently Recovering Fiber Failures with Robust Switching and Centralized Optical Line Terminal.

This study proposes and presents a new central office (CO) for the optical metro access network (OMAN) with an affordable and distinctive switching system. The CO's foundation is built upon a novel optical multicarrier (OMC) generation technique. This technique provides numerous frequency carriers that are characterized by a high tone-to-noise ratio (TNR) of 40 dB and minimal amplitude excursions. The purpose is to accommodate multiple users at the optical network unit side in the optical metropolitan area network (OMAN). The OMC generation is achieved through a cascaded configuration involving a single phase and two Mach Zehnder modulators without incorporating optical or electrical amplifiers or filters. The proposed OMC is installed in the CO of the OMAN to support the 1.2 Tbps downlink and 600 Gbps uplink transmission, with practical bit error rate (BER) ranges from 10-3 to 10-13 for the downlink and 10-6 to 10-14 for the uplink transmission. Furthermore, in the OMAN's context, optical fiber failure is a main issue. Therefore, we have proposed a possible solution for ensuring uninterrupted communication without any disturbance in various scenarios of main optical fiber failures. This demonstrates how this novel CO can rapidly recover transmission failures through robust switching a and centralized OLT. The proposed system is intended to provide users with a reliable and affordable service while maintaining high-quality transmission rates.

Electrical Input Filters of Ganglion Cells in Wild Type and Degenerating rd10 Mouse Retina as a Template for Selective Electrical Stimulation.

Bionic vision systems are currently limited by indiscriminate activation of all retinal ganglion cells (RGCs)- despite the dozens of known RGC types which each encode a different visual message. Here, we use spike-triggered averaging to explore how electrical responsiveness varies across RGC types toward the goal of using this variation to create type-selective electrical stimuli. A battery of visual stimuli and a randomly distributed sequence of electrical pulses were delivered to healthy and degenerating (4-week-old rd10) mouse retinas. Ganglion cell spike trains were recorded during stimulation using a 60-channel microelectrode array. Hierarchical clustering divided the recorded RGC populations according to their visual and electrical response patterns. Novel electrical stimuli were presented to assess type-specific selectivity. In healthy retinas, responses fell into 35 visual patterns and 14 electrical patterns. In degenerating retinas, responses fell into 12 visual and 23 electrical patterns. Few correspondences between electrical and visual response patterns were found except for the known correspondence of ON visual type with upward deflecting electrical type and OFF cells with downward electrical profiles. Further refinement of the approach presented here may yet yield the elusive nuances necessary for type-selective stimulation. This study greatly deepens our understanding of electrical input filters in the context of detailed visual response characterization and includes the most complete examination yet of degenerating electrical input filters.

Compacted Care Beyond the Clinic: Designing and Implementing a Portable Dental Unit (PDU) for Remote and Mobile Services

For the sake of all those who need dental care in various places, this article presents the rationale for designing and implementing a portable dental unit and finding new and more modern ways to manufacture and evaluate it as well. This device gives priority to durability, portability of the device in different work environments, infection control, and safety. The basic components include, but are not limited to, the air pressure system, the water tank, the Arduino microcontroller to control and manage the pressure, the electrical valves and filters that are subject to international standards, the foot switch, and the device’s control panel. The handpiece assembly in this dental unit, which includes the electric motor handle, the triple syringe, the high-speed turbine, and the low-speed turbine, allows for a variety of dental treatments. The effectiveness of the dental unit was confirmed through its experiment by specialists at Al Noor University in May 2023. Dr. Al Qubais Al Assaf, who supervised the examination, confirmed the effectiveness of the unit in delivering water and compressed air, in addition to its successful design, the ease of carrying and transporting the device, and the ease of its installation, in addition to its durability and resistance to aging Infection and protective functions. Dr. Al-Assaf also spoke about the importance of the mobile dental unit to provide dental care in remote areas or in cases where individuals cannot reach scientific clinics.

Distortion managed directly modulated on-off keying signal transmission for 10 Gbps visible light communications using electrical filtration

Abstract In this research, a communication system that uses visible light as a carrier and is designed for high-throughput interior applications. In order to lower the overall system cost, this work uses intensity modulation at the transmitter and direct detection with electrical filtering at the receiver. Various low-pass filtration techniques (Gaussian, Butterworth, Bessel, and Chebyshev) have been proposed in his paper to mitigate the effect of channel distortion in visible light communication (VLC) systems. The achieved transmission range is up to 3 m in addition to the supported data rate of 10 Gbps with a bit error rate of less than 10−9. Simulations are carried out using optisystem software that includes PRBS OOK optical signal generation at LED output in the transmitter, VLC channel, and APD with LPF in the receiver.

High-precision temperature-compensated fiber Bragg grating axial strain sensing system based on a dual-loop optoelectronic oscillator with the enhanced Vernier effect.

A temperature-compensated fiber Bragg grating (FBG) axial strain sensor based on a two-dual-loop optoelectronic oscillator (OEO) with the enhanced Vernier effect is proposed and experimentally demonstrated. The sensing head consists of two cascaded FBGs, one of which acts as a sensing FBG to measure both the axial strain and temperature and the other as a reference FBG to detect temperature. Acting as the optical carrier, the reflected optical signal of the sensing head is divided into two paths with opposite dispersion coefficients and slightly different lengths to achieve an enhanced Vernier effect. After being divided by a wavelength division multiplexer, the optical signal launches into two electrical paths with different electrical bandpass filters (EBPFs) for frequency division multiplexing. The EBPF I selects the microwave signal generated by the sensing FBG, while the EBPF II selects the microwave signal generated by the reference FBG. Therefore, the axial strain and temperature can be recovered by recording the microwave frequency within EBPF I, and the temperature can be interrogated by tracking the microwave frequency within EBPF II. The axial strain applied on the sensing FBG can be distinguished by solving the cross-sensitivity matrix. The results show that the sensitivity of the dual-loop OEO is much greater than that of the single-loop OEO. The maximum measurement error for the axial strain is 0.112µε, and the maximum temperature compensation error is as low as 0.024°C in the dual-loop OEO, which is far less than that in the single-loop OEO. The enhanced Vernier effect not only improves the sensitivity, but also reduces the temperature compensation error.

A broadband integrated microwave photonic mixer based on balanced photodetection

An integrated microwave photonic mixer based on silicon photonic platforms is proposed, which consist of a dual-drive Mach–Zehnder modulator and a balanced photodetector. The modulated optical signals from microwave photonic links can be directly demodulated and down-converted to intermediate frequency (IF) signals by the photonic mixer. The converted signal is obtained by conducting off-chip subtraction of the outputs from the balanced photodetector, and subsequent filtering of the high frequency items by an electrical low-pass filter. Benefiting from balanced detection, the conversion gain of the IF signal is improved by 6 dB, and radio frequency leakage and common-mode noise are suppressed significantly. System-level simulations show that the frequency mixing system has a spurious-free dynamic range of 89 dB·Hz2/3, even with deteriorated linearity caused by the two cascaded modulators. The spur suppression ratio of the photonic mixer remains higher than 40 dB when the IF varies from 0.5 to 4 GHz. The electrical-electrical 3 dB bandwidth of frequency conversion is 11 GHz. The integrated frequency mixing approach is quite simple, requiring no extra optical filters or electrical 90° hybrid coupler, which makes the system more stable and with broader bandwidth so that it can meet the potential demand in practical applications.Graphical

A Photonics Approach for Microwave Waveform Generation Based on PM-IM Conversions Using Two Dual-Output Sagnac Interferometers

A photonics-assisted scheme for generating various microwave waveforms has been investigated in this paper. In the proposed scheme, two phase modulation to intensity modulation (PM-IM) conversions are realized using two cascaded Sagnac interferometers (SIs) to manipulate light in the optical domain. From the first SI, by adjusting the amplitude of the microwave signal and time delay of the tunable optical delay line (TODL), both half duty cycle square and full duty cycle triangular waveforms can be generated from the photodetector (PD) and balanced photodetection (BPD). Using the second SI and applying microwave signals with appropriate amplitudes and phases, as well as the BPD process, results in full duty cycle sawtooth and reversed sawtooth waveforms. Detailed theoretical analyses are presented and results are verified by simulations. In the simulations, square-, triangular- and sawtooth-shaped (or reversed sawtooth-shaped) waveforms are obtained successfully. To complete the simulation results, the effects of non-ideal microwave hybrid coupler and optical couplers on the performances of the proposed scheme have been studied and no destructive effects were observed. The proposed structure does not include any optical or electrical filters which result in a wide operational bandwidth.

Electro-optic power/signal quality optimization based on the interaction between electro-optic modulators and electrical filters

Abstract This paper clarifies the effects of electrical filters with electro-optic modulators variations on the power/signal quality optimization and minimum data error rates reduction. The electro-optic modulators that are namely Mach Zehnder modulator, absorption modulator measured, single-drive Mach Zehnder modulator measured, and electro-absorption modulator. In addition to the filters are employed low pass (LP) Gaussian filter, LP Bessel filter, LP Butterworth filter, and LP Chebyshev filter. The hybrid combination between these modulators at the Tx. and the filters at the Rx. side give the chance to set the best candidate combinations from these devices for the power and signal quality optimization.

Single-modulator Based Multi-Format Switchable Signal Generator Without Background Noise

A photonic multi-format background-free binarily modulated microwave signal generator using a single dual-polarization dual-parallel Mach–Zehnder modulator is proposed and demonstrated. The proposed generator features good reconfiguration and switchability. By simply adjusting the direct current biases of the modulator, amplitude shift keying (ASK), phase shift keying (PSK) and frequency-shift keying (FSK) microwave signals can be generated. Benefiting from the complementary intensity modulation, there is no residual baseband modulated signal in the generated binarily modulated signals. The system does not involve any optical or electrical filters, which ensures good tunability of the generator. By changing the frequency of the driven microwave carrier and bit rate of the electrical coded signal, the frequency and rate of the generated multi-format signals can be adjusted accordingly. The multi-format switchable signal generator has great potential in multi-functional communication and radar systems.

A Gap-Junction Mutation Reveals That Outer Hair Cell Extracellular Receptor Potentials Drive High-Frequency Cochlear Amplification.

Cochlear amplification enables the enormous dynamic range of hearing through amplifying cochlear responses to low- to moderate-level sounds and compressing them to loud sounds. Amplification is attributed to voltage-dependent electromotility of mechanosensory outer hair cells (OHCs) driven by changing voltages developed across their cell membranes. At low frequencies, these voltage changes are dominated by intracellular receptor potentials (RPs). However, OHC membranes have electrical low-pass filter properties that attenuate high-frequency RPs, which should potentially attenuate amplification of high-frequency cochlear responses and impede high-frequency hearing. We made in vivo intracellular and extracellular electrophysiological measurements from the organ of Corti of male and female mice of the CBA/J strain, with excellent high-frequency hearing, and from the CD-1 mouse strain, which has sensitive hearing below 12 kHz but loses high-frequency hearing within a few weeks postpartum. The CD-1 mouse strain was transfected with an A88V mutation of the connexin 30 gap-junction protein. By blocking the action of the GJ protein to reduce input resistance, the mutation increased the OHC extracellular RP (ERP) magnitude and rescued high-frequency hearing. However, by increasing the organ of Corti resistance, the mutation rescued high-frequency hearing through preserving the OHC extracellular RP (ERP) magnitude. We measured the voltage developed across the basolateral membranes of OHCs, which controls their electromotility, for low- to high-frequency sounds in male and female mice of the CD-1 strain that expressed the A88V mutation. We demonstrate that ERPs, not RPs, drive OHC motility and cochlear amplification at high frequencies because at high frequencies, ERPs are not frequency attenuated, exceed RPs in magnitude, and are appropriately timed to provide cochlear amplification.SIGNIFICANCE STATEMENT Cochlear amplification, which enables the enormous dynamic range of hearing, is attributed to voltage-dependent electromotility of the mechanosensory outer hair cells (OHCs) driven by sound-induced voltage changes across their membranes. OHC intracellular receptor potentials are electrically low-pass filtered, which should hinder high-frequency hearing. We measured the intracellular and extracellular voltages that control OHC electromotility in vivo in a mouse strain with impaired high-frequency hearing. A gap-junction mutation of the strain rescued high-frequency hearing, increased organ of Corti resistance, and preserved large OHC extracellular receptor potentials but reduced OHC intracellular receptor potentials and impaired low-frequency hearing. We concluded intracellular potentials drive OHC motility at low frequencies and extracellular receptor potentials drive OHC motility and cochlear amplification at high frequencies.

Active mode lock optoelectronic oscillator based on the simulated Brillouin scattering effect.

An active mode-locked optoelectronic oscillator (AML-OEO) based on the simulated Brillouin scattering (SBS) effect without an electrical filter is demonstrated here. By using phase modulation and SBS-based selective sideband amplification, the central frequency of the proposed SBS-AML-OEO is easily adjusted by simply changing the pump laser frequency instead of the filters. A microwave frequency comb signal with an adjustable central frequency and fixed bandwidth are generated by injecting a mode-locking external RF synchronizing with the free spectral ranging FSR. In addition, the harmonic SBS-AML-OEO is also achieved by harmonic signal injection. The proposed method reveals a simple solution to tune the central frequency and has the potential to be integrated on a chip since there is no structure changing in the scheme.

Simple microwave photonic downconversion channelizer based on multi-wavelength laser sources.

This work presents a simple microwave photonic downconversion channelizer based on multi-wavelength laser sources. The design of two laser diode (LD) arrays enables signal multiplexing and simultaneous multichannel downconversion processing, which provide stable, relatively flat, and strong multi-frequency combs. A proof-of-concept experiment was taken, showing that 14.375-17.75 GHz broadband radio frequency (RF) signals were successfully downconverted to the same intermediate frequency (IF) and were sliced into four subchannels with 875 MHz bandwidth showing excellent image rejection and channel uniformity, which agrees with the simulation results. The spurious free dynamic range (SFDR) of the proposed RF channelizer is 100dBHz2/3, the image rejection is over 28 dB, and the frequency measurement error is less than ±6MHz. Replacing optical filters with electrical filters, the proposed simple optoelectronic hybrid reconfigurable microwave photonic channelizer system acquits stable performance and high maturity and meets the application requirements, behaving with stupendous potential in fields such as radar, satellite communication, electronic warfare, and others.

Microwave Photonic Temperature Sensing Based on Fourier Domain Mode-Locked OEO and Temperature-to-Time Mapping

We report a novel temperature sensor based on a Fourier domain mode-locked optoelectronic oscillator (FDML OEO) and temperature-to-time mapping. In the proposed scheme, a narrow bandpass electrical filter is inserted into the FDML OEO cavity. The temperature information is mapped to the time interval of the output pulses due to the temperature-sensitive bidirectional scanning property of the FDML OEO. Compared with other OEO-based temperature sensors, the proposed scheme avoids the needs of wideband electrical spectrum analyzers, since the temperature-sensitive output pulses can be interrogated using a low-speed oscilloscope working under sub-Nyquist sampling condition. In the proof-of-concept experiment, a high sensitivity of 8.166 μs/°C and resolution of 0.03°C is achieved, demonstrating a good temperature sensing performance.

Polarization multiplexed active mode-locking optoelectronic oscillator for frequency tunable dual-band microwave pulse signals generation.

We propose and experimentally demonstrate a polarization multiplexed active mode-locking optoelectronic oscillator (AML-OEO) based on a single dual-polarization binary phase-shift keying (DP-BPSK) modulator for frequency tunable dual-band microwave pulse signal generation. In order to realize mode-locking, two single-tone signals whose frequency are integer multiple of the free spectrum range (FSR) of AML-OEO are applied as active modulation signals (AMSs) at the bias ports of the DP-BPSK modulator. By dividing the AML-OEO into two loops with polarization demultiplexing, both the carrier frequency and pulse repetition frequency (PRF) of the dual-band microwave pulses are independently adjustable. In the experiment, microwave pulses with different PRFs of 162.4 kHz, 324.8 kHz and 812 kHz are generated based on fundamental, second-order harmonic and fifth-order harmonic mode-locking, respectively. In addition, the carrier frequency tunability within 4∼10 GHz is verified by inserting a frequency tunable electrical filter. The phase noise of the generated pulse signal at 10 kHz offset is better than -125 dBc/Hz.

Characterizing ganglion cell types based on visual responses and electrical input filters in wild type and rd10 degenerated mouse retina

Characterizing ganglion cell types based on visual responses and electrical input filters in wild type and rd10 degenerated mouse retina

High-sensitivity optical fiber sensor based on a Fourier domain mode-locked optoelectronic oscillator

We propose and experimentally demonstrate an optical fiber sensor based on a Fourier domain mode-locked optoelectronic oscillator (FDML-OEO), which is achieved by synchronizing the period of the driving current of the laser with the round-trip time of the OEO loop. Pulsed microwave output can be obtained when a narrow-band electrical filter with the central frequency located within the frequency scanning range of the FDML-OEO is employed in the cavity. Thanks to the triangle waveform of the laser driving signal, two microwave pulses can be observed in one period. The wavelength shift of the phase-shift fiber Bragg grating (PS-FBG) in the cavity will produce a shift of the frequency scanning range, resulting in the pulse interval variation of the OEO output. The experimental results indicate that the pulse interval of the generated signal has a linear relationship with the notch wavelength shift of the PS-FBG. By applying fiber axial strain to the PS-FBG, we obtained a high strain measuring sensitivity of 0.817 μs/με. The sensor reveals the advantages of highly sensitive and easy demodulation, providing great potential for practical applications.