Frequency Modulation Transmitter Research Articles

Suppression of Nonlinear Optical Effects in DWDM-PON by Frequency Modulation Non-Coherent Detection

We propose a simple and cost-effective method, using a direct frequency modulation (FM) and noncoherent detection (NCD) scheme, to suppress the nonlinear optical effects in dense wavelength division multiplexed (DWDM) optical communication. The FM transmitter comprises a directly modulated distributed feedback laser and a saturable semiconductor optical amplifier. In the NCD receiver, an optical slope filter as the FM to intensity modulation (IM) signal convertor is placed before a conventional photodetector. Because the FM signal has more evenly distributed optical power, bit-pattern-dependent nonlinear effects are consequently suppressed. After analyzing the nonlinear effects in the FM-NCD system and traditional IM direct detection (IM-DD) system, we found that the minimum achievable BER of the proposed FM-NCD scheme is 40 dB smaller. Moreover, a 2 Tbps (10 Gb/s × 200 channels) capacity was achieved by the FM-NCD system in 100 km DWDM passive optical networks (PONs), which is twice the capacity of the IM-DD system (10 Gb/s × 100 channels) under the same condition. These results indicate that WDM-PONs with the cost-effective FM-NCD scheme are strong candidates for future broad access networks and show great potential for the combination of optical access and metro networks for future generations of PONs.

FM Transmitter using Proteus 8

FM (Frequency Modulation) signal transmitter is a small device that can be used to transmit Frequency Modulation signal over short range. It also protects signal from interference and unwanted signals. Audio signal/voice signal is modulated into radio frequency carrier, new radio frequency signal moves up and down in frequency. This document consists of most simple and economical technique for building a FM transmitter using basic electronic component like resistor, inductor, capacitor etc. The FM transmitter receives human voice signal through microphone. It further amplifies it, and modulates over carrier and finally gets transmitted to it. Frequency modulation transmitter has many merits over the (AM) Amplitude modulation. It protects the signal from interference and unwanted signal that is noise. It provides high Signal to Noise than Amplitude modulation. Overview of frequency modulation (FM) is the frequency of radio wave which is less endangered to the noise than AM. Frequency modulation are indigenous to reduce the noise which enhances the quality of radio reception.

Suppression of Mode Partition Noise in FP Laser by Frequency Modulation Non-Coherent Detection

We propose a frequency modulation (FM) non-coherent detection (NCD) scheme, attempting to suppress the mode partition noise (MPN) in fiber-optic communication systems with the Fabry-Perot (FP) semiconductor laser as the light source. The system comprises a FM transmitter with a directly modulated FP laser and a semiconductor optical amplifier, standard single mode fiber, and a NCD receiver with an optical slope filter as the FM to intensity modulation (IM) signal convertor placed in front of a conventional photodetector. In this configuration, the MPN is converted into a random frequency deviation by the transmitter and is reduced by the slope filter after fiber transmission. The FM signal is therefore less noisy after being converted back into the IM signal. With optimized parameter selections, our simulation result shows that the FM-NCD system allows a direct transmission span of 40 km for the 10 Gbps signal at 1577 nm, and 120 km for the 25 Gbps signal at 1310 nm, respectively, as opposed to a span of only 3 km and 10 km achievable by a conventional FP laser driven IM direct detection (DD) system for the corresponding signals at the corresponding wavelengths. Remarkably, our simulation result also shows that the performance of the FM-NCD system even surpasses that of a directly modulated distributed feedback laser driven IM-DD system, in which the maximum span is around 15 km and 60 km for 10 Gbps and 25 Gbps signals at 1577 nm and 1310 nm, respectively.

Frequency-Dependent Spatial Coherence in Conventional and Chirp Transmissions.

The development of adaptive imaging techniques is contingent on the accurate and repeatable characterization of ultrasonic image quality. Adaptive transmit frequency selection, filtering, and frequency compounding all offer the ability to improve target conspicuity by balancing the effects of imaging resolution, the signal-to-clutter ratio, and speckle texture, but these strategies rely on the ability to capture image quality at each desired frequency. We investigate the use of broadband linear frequency-modulated transmissions, also known as chirps, to expedite the interrogation of frequency-dependent tissue spatial coherence for real-time implementations of frequency-based adaptive imaging strategies. Chirp-collected measurements of coherence are compared to those acquired by individually transmitted conventional pulses over a range of fundamental and harmonic frequencies, in order to evaluate the ability of chirps to recreate conventionally acquired coherence. Simulation and measurements in a uniform phantom free of acoustic clutter indicate that chirps replicate not only the mean coherence in a region-of-interest but also the distribution of coherence values over frequency. Results from acquisitions in porcine abdominal and human liver models show that prediction accuracy improves with chirp length. Chirps are also able to predict frequency-dependent decreases in coherence in both porcine abdominal and human liver models for fundamental and pulse inversion harmonic imaging. This work indicates that the use of chirps is a viable strategy to improve the efficiency of variable frequency coherence mapping, thus presenting an avenue for real-time implementations for frequency-based adaptive strategies.

Perancangan Trainer Komunikasi Receiver Frequency Modulation sebagai Media Pembelajaran untuk Teknik Elektro

On a Frequency Modulation (FM) receiver there is an interference caused which is usually due to the distance and strong signal from the FM transmitter carried to the FM receiver device. The system used PLL (Phase Loocked Loop) system on the oscillator. An oscillator is an electronic device that produces a voltage signal output. The use of oscillators as the carrier of the signal and the message signal produces waves with a certain frequency value, and has a frequency shift of 56,25KHz. The output of the FM receiver is a signal containing of the FM transmitter in the 88MHz-108MHz range. The signals received from the transmitter are short audio and sine signals, so they can be analyzed based on their waves in oscilloscopes and matlab experiments. In this trainer, there are tuners, IF amplifier, multiplexer demodulator, and digital counter frequency. The IC used is LA1260, LA3361, LB3500, LC7265. The result of making an FM receiver trainer get a satisfaction value of the practical test 80,12% based on aspects of media appearance, technical quality and usefulness. A device designed for UTM Electrical Engineering students as a trainer in FM telecommunications system learning medium practiced in the UTM Department of Electrical Engineering

Construction of a Mobile Frequency Modulation Transmitter

A Frequency Modulation (FM) transmitter is an electronic device that produces radio waves with the aid of an antenna. The transmitter generates radio frequency alternating current, that is applied to the antenna. When the antenna is excited by the alternating current, the antenna begins to radiate radio waves by varying the frequency of the radio signal. The transmitter is a Very High Frequency (VHF) Colpitts oscillator capable of transmitting sound to standard FM receiver fitted with a capacitor microphone which picks weak sound signals. This design was achieved using: transistors, resistors, inductors and capacitors. A transmission frequency of ± 5% 100 MHz was used and transmitted up to a distance of 5 metres. The testing of the transmitter was carried out by powering it using a 9 V DC battery and tuning a suitable FM receiver to the transmission frequency of the constructed transmitter. A transmission distance of 5 metres was achieved therefore making it possible to use the transmitter as a portable cordless microphone used for public address (P.A.) systems. The achieved fixed frequency of transmission 56.4 MHz, away from all other radio stations transmission frequencies. This gives the best range and with the least of interferences. With increased power, the range can easily be extended.

POTENTIAL EXPOSURE LEVELS FROM BROADCAST TRANSMITTERS IN GHANA.

The protection of man and his environment from undue exposure from radio frequency electromagnetic field requires identification of the location where exposures are likely to be higher than safe levels established by international safety standards. A wideband measurement with a spectrum analyzer and a log-periodic antenna in conjunction with the three-point spatial average method was used. The results ranged from 16.21 to 2907.00mVm-1 and complied with a maximum of 1.08% of the ICNIRP reference level. Private frequency modulation (FM) sources were identified as the major source of exposure to the public with a mean value of 337.70±133.70mVm-1 against 122.30±36.47mVm-1 for the public FM transmitters. Even though the result was lower than a workplace assessment, it was, however, higher than similar works conducted in Africa and Palestine. Finally, four sensitive locations were identified for further research work.

Frequency Modulation System and Bone Conduction Hearing Aid: Electroacoustic Verification.

Introduction A protocol has not yet been developed to perform electroacoustic measurements and behavioral tests to fit the frequency modulation (FM) system in bone conduction hearing aid (BCHA) users. Electroacoustic verification, with “FM transparency” achieved, ensures user audibility of FM transmitter and hearing aid signals. Objective To propose and validate a protocol for electroacoustic verification of the FM system coupled to the BCHA. Method Twenty-four sets of FM system and BCHA were submitted to electroacoustic verification, using a receiver and a plastic adapter to connect the BCHA to a 2cc coupler in the hearing instrument analyzer. The measurements were performed in the acoustic box, at 65 dB sound pressure level (SPL), with International Speech Test Signal (ISTS), first to the BCHA microphone and then to the FM system microphone, to determine the transparency, in which equivalent inputs for both microphones result in equivalent outputs. The FM gain or volume has been adjusted to try to gain transparency for the outputs of the two input devices. Results Transparency was achieved for all sets evaluated, but in some combinations, adjustments to the FM receiver gain over the manufacturer's default setting were required. Conclusion The proposed protocol proved to be effective for the electroacoustic verification of the FM system coupled to the BCHA.

Implementasi Sistem Komunikasi FM Pada Prototype Pendeteksi Dini Gempa

An earthquake is a vibration that occurs due to plates at the base of the earth rubbing against each other. An earthquake can have several impacts, namely material loss and loss of life and trauma for some people who feel it. This happens because people are not fast enough in getting information. Therefore we need an earthquake detection device that is relatively inexpensive. In this study designed a prototype for earthquake early detection using Frequency Modulation (FM) communication. The components of this system are Arduino Uno which functions as a microcontroller, SW-420 vibration sensor to detect vibrations, buzzer as the output of the SW-420 sensor in the form of sound and FM transmitter V2.0 which functions as a medium for transmitting radio frequency signals and sending sound from the buzzer . The level of vibration that indicates that an earthquake occurred namely 3-5 with a conversion of 5-10 SR. The system would have the ability to provide information in the form of sound received by a radio or FM receiver. The distance that can be emitted by the FM transmitter module V2.0 is 17.87 meter

<italic>In Vitro</italic> Evaluation of an Injectable EEG/ECG Sensor for Wireless Monitoring of Hibernation in Endangered Animal Species

Hibernation is a unique metabolic adaptation employed by several animal species for survival where its study would further enhance our understanding of metabolic disorders, such as diabetes and obesity. As a primate animal with close genetic ties to humans, the recent discovery of hibernation in dwarf lemurs of Madagascar has attracted the attention of researchers. Traditional recording systems require the physical tethering of the animals to the recording apparatus or the use of implantable devices. Scalp and needle electrodes interfere with the natural hibernation process and limit the continuity of the experiments, while invasive procedures are banned on endangered species. By integrating a full-wave rectifier, low-noise signal conditioning circuit, frequency modulation transmitter, and antenna in a single application specific integrated circuit (ASIC), we have developed an ultra-miniaturized wireless system that measures $34 \times 4 \times 2.6$ mm3 in volume. It only requires three off-chip components (a coil wound around a ferrite rod and two external capacitors) to be powered wirelessly through a 1-MHz inductive link, such that it can be packaged inside a glass or polymer capsule and injected subcutaneously underneath the scalp or chest without requiring a surgery, thereby addressing the shortcomings of the traditional monitoring systems. Our recording device provides an input/output correlation coefficient greater than 80% for input amplitudes ranging from 60 to 260 $\mu V_{\mathrm{ pp}}$ , with a wireless data transmission range of ~2.5 cm while operating near the 902–928 MHz ISM frequency band. This system would enable future studies of electroencephalography and electrocardiography in hibernating dwarf lemurs. The ASIC was fabricated using the ON Semiconductor 0.5- $\mu \text{m}$ CMOS process with an active area of 2.5 $\times $ 1 mm2 and has a power consumption of 7.75 mW from a 3.1 V supply. In this paper, we demonstrate the in vitro functionality of the system using simulated physiological signals directly applied to the ASIC or through standard stainless steel electrodes immersed in saline solution.

Design and development of low-range frequency modulated signal (F.M.) transmitter

Frequency Modulated (FM) signal transmitter is a small device that can transmit Frequency Modulated signal over short range. [1] This document consists of most simple and economical technique for building a FM transmitter using basic electronic components like resistor, capacitor, inductor etc. The FM transmitter receives human voice signals though microphone. It further amplifies it, modulate it over carrier and finally transmit it. Assuming favorable conditions, output of transmitter can be received by anyone who tunes it in frequency of our transmitter. Here, I have described Circuit diagram, its working, components required, uses of various components in our circuit, its practical applicability. The design is simulated using NI Multisim and is further implemented on bread-board. This design is capable of transmitting signal for distance of radius 20m, tuned at 97.1 MHz One could clearly hear sound produced at microphone of transmitter.BIBECHANA 15 (2018) 30-36

A Wireless Electronic Esophageal Stethoscope for Continuous Monitoring of Cardiovascular and Respiratory Systems during Anaesthesia.

The basic requirements for monitoring anesthetized patients during surgery are assessing cardiac and respiratory function. Esophageal stethoscopes have been developed for this purpose, but these devices may not provide clear heart and lung sound due to existence of various noises in operating rooms. In addition, the stethoscope is not applicable for continues monitoring, and it is unsuitable for observing inaccessible patients in some conditions such as during CT scan. A wireless electronic esophageal stethoscope is designed for continues auscultation of heart and lung sounds in anesthetized patients. The system consists of a transmitter and a receiver. The former acquires, amplifies and transmits the acquired sound signals to the latter via a frequency modulation transmitter. The receiver demodulates, amplifies, and delivers the received signal to a headphone to be heard by anesthesiologist. The usability and effectiveness of the designed system was qualitatively evaluated by 5 anesthesiologists in Namazi Hospital and Shahid Chamran Hospital, Shiraz, Iran on 30 patients in several operating rooms in different conditions; e.g., when electro surgery instruments are working. Fortunately, the experts on average ranked good quality for the heard heart and lung sounds and very good on the user friendly being of the instrument. Evaluation results demonstrate that the developed system is capable of capturing and transmitting heart and lung sounds successfully. Therefore, it can be used to continuously monitor anesthetized patients' cardiac and respiratory function. Since via the instrument wireless auscultation is possible, it could be suitable for observing inaccessible patients in several conditions such as during CT scan.

Cancer incidence vs. FM radio transmitter density

ABSTRACTBackground: In 2002, a strong association was highlighted between local melanoma incidence and the number of locally covering main Frequency Modulation (FM) transmitters in Sweden. This study investigated whether an association also exists between melanoma incidence and the average density of main FM transmitters in different European countries. Methods: Twenty-three different European countries were asked to disclose the number of main transmitters used for the FM broadcasting band (87·5–108 MHz) in the respective country. Incidences of melanoma, breast cancer and all cancers together per country were correlated with their respective average density of transmitters per 10,000 km2. Findings: Both melanoma and breast cancer, as well as all cancers together, appear to be significantly associated with the density of main FM broadcasting transmitters in the European countries examined. Interpretation: The findings present strong support to the earlier presented hypothesis that body-resonant broadcasting radiation emitted by horizontally polarized main FM transmitters has an immune-disturbing effect. Funding: This study was financed by internal funds within Hallberg Independent Research only.

Interference Mitigation for Multistatic Active Sonar

Two methods for detecting and classifying mutual interference between sources in multistatic active sonar systems are developed and compared for frequency-modulated transmissions. Both methods compare the output of matched-filtered time-series data using two different waveform replicas: the intended transmit replica and a hypothesized interferer replica. The first method compares the absolute magnitudes of the two outputs, whereas the second method compares the local shape of the magnitude of the outputs to idealized replica correlations using an ${L}_{5}$ -norm. Simulated examples indicate that the two methods are both effective, but with different tradeoffs. The magnitude-based method often performs better when the interference is relatively strong, and the shape-based method often performs better when the interference is weaker, and thereby harder to detect. It is also shown that excising the detected interfering direct blast at the beamformer output level effectively reduces clutter on displays and removes false contacts due to the interferer. The approach also shows potential for improving multistatic detection across platforms.

Better Speech Recognition with Digital RF System in Study of Cochlear Implants

Better Speech Recognition with Digital RF System in Study of Cochlear Implants

Analytic signal demodulation of phase-modulated frequency-chirped signals

Both interferometers and frequency-modulated (FM) radios create sinusoidal signals with phase information that must be recovered. Often these two applications use narrow band signals but some applications create signals with a large bandwidth. For example, accelerated mirrors in an interferometer naturally create a chirped frequency that linearly increases with time. Chirped carriers are also used for spread-spectrum, FM transmission to reduce interference or avoid detection. In both applications, it is important to recover the underlying phase modulations that are superimposed on the chirped carrier. A common way to treat a chirped waveform is to fit zero crossings of the signal. For lower signal-to-noise applications, however, it is helpful to have a technique that utilizes data over the entire waveform (not just at zero crossings). We present a technique called analytic signal demodulation (ASD), which employs a complex heterodyne of the analytic signal to fully demodulate the chirped waveform. ASD has a much higher sensitivity for recovering phase information than is possible using a chirp demodulation on the raw data. This paper introduces a phase residual function, R(θ), that forms an analytic signal and provides a complex demodulation from the received signal in one step. The function defines a phase residual at each point on the chirped waveform, not just at the zero crossings. ASD allows sensitive detection of phase-modulated signals with a very small modulation index (much less than 0.01) that would otherwise be swamped by noise if the raw signal were complex demodulated. The mathematics used to analyze a phase-modulated chirped signal is quite general and can easily be extended for frequency profiles more complicated than a simple chirp.

Effects of Noise Reduction on AM and FM Perception

The goal of noise reduction (NR) algorithms in digital hearing aid devices is to reduce background noise whilst preserving as much of the original signal as possible. These algorithms may increase the signal-to-noise ratio (SNR) in an ideal case, but they generally fail to improve speech intelligibility. However, due to the complex nature of speech, it is difficult to disentangle the numerous low- and high-level effects of NR that may underlie the lack of speech perception benefits. The goal of this study was to better understand why NR algorithms do not improve speech intelligibility by investigating the effects of NR on the ability to discriminate two basic acoustic features, namely amplitude modulation (AM) and frequency modulation (FM) cues, known to be crucial for speech identification in quiet and in noise. Here, discrimination of complex, non-linguistic AM and FM patterns was measured for normal hearing listeners using a same/different task. The stimuli were generated by modulating 1-kHz pure tones by either a two-component AM or FM modulator with patterns changed by manipulating component phases. Modulation rates were centered on 3 Hz. Discrimination of AM and FM patterns was measured in quiet and in the presence of a white noise that had been passed through a gammatone filter centered on 1 kHz. The noise was presented at SNRs ranging from -6 to +12 dB. Stimuli were left as such or processed via an NR algorithm based on the spectral subtraction method. NR was found to yield small but systematic improvements in discrimination for the AM conditions at favorable SNRs but had little effect, if any, on FM discrimination. A computational model of early auditory processing was developed to quantify the fidelity of AM and FM transmission. The model captured the improvement in discrimination performance for AM stimuli at high SNRs with NR. However, the model also predicted a relatively small detrimental effect of NR for FM stimuli in contrast with the average psychophysical data. Overall, these results suggest that the lack of benefits of NR on speech intelligibility is partly caused by the limited effect of NR on the transmission of narrowband speech modulation cues.

Low-Invasive Implantable Devices of Low-Power Consumption Using High-Efficiency Antennas for Cloud Health Care

This paper presents low-invasive and low-power implantable biomedical devices based on a novel high-efficiency antenna for cloud health care. The proposed simple architecture was applied to fulfill a low-power consumption implantable system, including a readout circuit, an oscillator, a power management circuit, and an implantable antenna. This paper proposes a novel compact antenna for teeth implanting to attach on a low-invasive biomedical device to monitor human health conditions. A low-power consumption oscillator was connected directly to the antenna without any additional power amplifier. A hybrid of Archimedean spirals and Hilbert-based curve 3-D folded antenna was designed and fabricated on ceramic denture (ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) in Medical Radio (MedRadio) band. A compact, high gain, and large bandwidth antenna was achieved. In addition, such simple architecture also performs a high precise measurement, demonstrated by the temperature sensing of basal body temperature (BBT), indicating the conditions of female endocrine abnormalities. High sensitivity was enhanced by a negative resistance sample amplifier, and the biological BBT signals were transmitted by a frequency-modulation transmitter. The wireless measurement results indicate a small error of ±0.058°C at a distance of 60 cm indoors, and satisfy the BBT resolution requirement of 0.1 °C.

Simultaneous Occupational Exposure to FM and UHF Transmitters

Occupational exposure caused by large broadcasting transmitters exceeds current reference levels. As it is common for different radio and TV transmitters to share the location, we analysed combined exposure on a 40-m high mast. The frequency modulation (FM) transmitter, located between the 10th and 30th metre, had the power of 25 kW, whereas an ultra-high frequency (UHF) transmitter of 5 kW occupied the top 8 m of the mast. Measured and calculated values of the electric field strength exceeded the reference levels up to 10 times; however, the results for the specific absorption rate (SAR) values show that the reference levels are very conservative for FM exposure, i.e., basic restrictions are not exceeded even when the reference levels are exceeded 10 times. However, for UHF exposure the reference levels are not conservative; they give a good prediction of real exposure.

Occupational Exposure Assessment on an FM Mast: Electric Field and SAR Values

Electric field strengths normally exceed the reference levels for occupational exposure in close vicinity to large frequency modulation (FM) transmitters. Thus, a detailed investigation on compliance with basic restrictions is needed before any administrative protection measures are applied. We prepared a detailed numerical model of a 20-kW FM transmitter on a 32-m mast. An electrically isolated anatomical human model was placed in 3 different positions inside the mast in the region where the values of the electric field were highest. The electric field strengths in this region were up to 700 V/m. The highest calculated whole-body specific absorption rate (SAR) was 0.48 W/kg, whereas the maximum 10-g average SAR in the head and trunk was 1.66 W/kg. The results show that the reference levels in the FM frequency range are very conservative for near field exposure. SAR values are not exceeded even for fields 10 times stronger than the reference levels.