FM Transmitter Research Articles

Detailed Analysis of Split-Level Combining

High level combining is a practical way to upgrade existing FM transmitters to IBOC. Very well understood, with readily available 10 dB couplers, it is a very attractive method with which to upgrade even the highest power levels in the field. Unfortunately, if offers only a combining efficiency of 83%, as 90% of the IBOC power is wasted into a dummy load, along with 10% of the generated FM power. Additionally, the power headroom demanded from the FM transmitter is proving to be an unsurpassable requirement for some existing sites ready to upgrade. This paper presents an innovative combining technique that minimizes the FM and IBOC power loss in high level combining. Instead of combining two totally incoherent signals with its known resulting losses, this method first achieves partial coherence of the signals, and only then combines them at an optimum coupling ratio. A system implemented this way offers two main benefits; a higher overall system efficiency, and the elimination of the need for FM headroom. Though the paper focuses on the particular case of FM HD radio upgrade, this technique can also be used whenever low loss is needed when combining dissimilar signals.

MP3 Users Beware

MP3 players are used in daily life more than ever. One of their main features is their ability to broadcast music from the player to a radio by attaching a low-powered FM transmitter. This is now commonly used in operating theatres instead of playing CDs or listening to the radio. However, according to current UK law (Wireless Telegraphy Act, 1949),1 the use of all FM broadcasting equipment in the UK requires a licence. Under European law, The Office of Communications (Ofcom), cannot prevent the sale of radio equipment in the UK that fully complies with the relevant EU directives.2 However, this does not guarantee permission to use it and the use of low-powered FM transmitters without a licence remains illegal. The European Conference of Postal and Telecommunications made a recommendation that devices of this type could be allowed to operate in Europe, provided that they meet necessary requirements.3 Ofcom is currently reviewing its policy on these transmitters. Those of us, however, broadcasting MP3 players using low-powered FM transmitters should be aware of the current laws and that hospitals are liable to prosecution for allowing their use on their premises without a licence.

FM Transmitters in the Operating Theatre

FM Transmitters in the Operating Theatre

Hardly hard-hearted: heart rate responses of incubating Northern Giant Petrels (Macronectes halli) to human disturbance on sub-Antarctic Marion Island

Guidelines for visitors to sub-Antarctic Marion Island recommend 15 and 100 m minimum approach distances for breeding Northern (Macronectes halli) and Southern (Macronectes giganteus) Giant Petrels, respectively. Using artificial eggs containing FM transmitters, we measured the heart rate responses of incubating Northern Giant Petrels to pedestrian approaches. The mean resting heart rate was 80 beats per minute. Heart rates increased upon the detection of a person approximately 40 m away, and continued to increase during the approach to 5 m. Maximum increases over resting heart rate in response to natural disturbances and human approach were 97 and 204%, respectively. Northern Giant Petrels appear at least as sensitive to human disturbance as their congenerics. While low-key disturbance is unlikely to affect this solitary breeder as severely as it would the colonial Southern Giant Petrel, improved protection from disturbance could be achieved by restricting human passage through breeding colonies of Northern Giant Petrels to defined paths.

Micropower Circuits for Bidirectional Wireless Telemetry in Neural Recording Applications

State-of-the art neural recording systems require electronics allowing for transcutaneous, bidirectional data transfer. As these circuits will be implanted near the brain, they must be small and low power. We have developed micropower integrated circuits for recovering clock and data signals over a transcutaneous power link. The data recovery circuit produces a digital data signal from an ac power waveform that has been amplitude modulated. We have also developed an FM transmitter with the lowest power dissipation reported for biosignal telemetry. The FM transmitter consists of a low-noise biopotential amplifier and a voltage controlled oscillator used to transmit amplified neural signals at a frequency near 433 MHz. All circuits were fabricated in a standard 0.5-microm CMOS VLSI process. The resulting chip is powered through a wireless inductive link. The power consumption of the clock and data recovery circuits is measured to be 129 microW; the power consumption of the transmitter is measured to be 465 microW when using an external surface mount inductor. Using a parasitic antenna less than 2 mm long, a received power level was measured to be -59.73 dBm at a distance of one meter.

ANALISA RUGI-RUGI ANTENA PEMANCAR FM ISTAKALISA YOGYAKARTA

Everyone basically knows and perceives about the function of antenna. The antenna is a tool or device which has function to receive and transmit signals from a point to another. According to the research of IstaKalisa’s FM Transmitter Radio antenna of Yogyakarta, the writer will give conclusion of research. Loss which affect the working of transmitting radio stations are loss of cord, loss of space damping, and loss of resistance. They make fading on the transmitting power where the fading is in dB unit. Moreover, the position and location of Istakalisa FM transmitter radio station is in the downtown. It does not support to the transmitting system caused by ground conductivity is less than standard and also numbers of high buildings.

An experimental performance evaluation of a novel radio-transmitter identification system under diverse environmental conditions

In this paper, the effects of environmental conditions on a radio-transmitter identification system are investigated. Transmissions from 10 commercial VHF FM transmitters operating under varying environmental conditions are analyzed using an experimental setup. It is observed that a change in environmental conditions such as battery voltage or ambient temperature causes the feature vectors to spread over the feature space, resulting in classification performance degradation. It is experimentally shown that performance degradation resulting from changing environmental conditions can be compensated for by training the system with data collected in a range of battery-voltage and ambient temperature levels. The signal-to-noise ratio versus probability of correct classification is also determined for systems operating in noisy channels in order to obtain a confidence measure for the classification decision to be made. The transient features are extracted using a technique based on the amplitudes and phase changes of the received signals. This technique is well suited to radio-transmitter turn-on transient signals, and classification with these features, as shown, outperforms current techniques.

A dual-channel FM transmitter for acquisition of flight muscle activities from the freely flying hawkmoth, Agriusconvolvuli

Moths can perform various flight maneuvers by the contraction of some direct and indirect flight muscles. Multi-channel recording from these flight muscles and analysis of their interaction is very important for understanding insect flight motor system. In this study, we developed a dual-channel FM transmitter for acquisition of muscle potentials, with which a male hawkmoth ( Agrius convolvuli) could fly freely and perform pheromone triggered zigzag flight in a wind tunnel. The transmitter weighs only 0.25 g including single battery, has a 5 m receivable range and works for more than 30 min. Doubling channels was achieved by providing two oscillators (the carrier frequencies were 82 and 85 MHz), and interference between them was overcome by buffer amplifiers and independent reference electrodes for each channel. With this transmitter, we could acquire muscle potentials from some direct and indirect muscles during free flight. Combined with simultaneous high-speed video analysis, we observed distinct changes of motor patterns during takeoff. Our radio-telemetric system allows acquisition of actual information from freely flying moths; such information will lead to further progress in the study of insect flight.

Joint estimation of Doppler and time-difference-of-arrival exploiting cyclostationary property

For the problem of estimating the time-difference-of-arrival (TDOA) of radio waves impinging on one or a pair of antennas for the purpose of actively or passively locating the source of a communications or telemetry signal in the presence of interfering signals and noise, W. A. Gardner has developed some effective methods, such as CCCC and SPECCOA etc. However, it is shown that CCCC, SPECCOA and related methods do not apply to moving targets because the Doppler shift changes the cycle frequencies of the signal of interest. Two new methods based on the cyclic cross-ambiguity (CCA) function and the spectrally cyclic cross-ambiguity (SCCA) function are introduced in the paper for the joint TDOA and Doppler estimation, and their consistency in estimating the TDOA and Doppler is also discussed. Practical experiments, utilising FM radio signals emitting from a remote FM transmitter to detect the planes and estimate the values of TDOA and Doppler, have been carried out. Experimental results demonstrate the efficiency of the CCA and SCCA methods in the estimation of TDOA and Doppler.

1102 力学的エネルギーによって駆動するカード端末用薄型発電機の発電特性

We measured the average power of thin linear-driven generators for use in card-type mobile communication terminals, which produce electricity from mechanical movement. A cellular phone sized-Voice Coil Generatorl driven by energy and a spring, stroke length : 50mm, yoke width : 20mm, thickness : 12mm generates 9.6mW with efficiency of 32%. When the VCG1 is oscillated at about 5.8Hz with amplitude of 5mm, the generated electric power is 38mW and by shaking the generator for about 6 hours, a 20-farad super capacitor was charged to 2V. The FM transmitter, whose power consumption is 9.6mW, operated for 37 minutes by the stored power.

A telemetry-based device to determine the force–displacement behaviour of materials in high impact loading situations

Meaningful testing of stab resistant body armour requires the use of realistic body tissue simulants. A device for the determination of the force–displacement behaviour of materials in high impact loading situations has been developed for the testing of such simulants. Force measurement is achieved with the use of electrical foil strain gauges applied to a cylindrical load cell. A piezo-resistive accelerometer (±500 g) is used to calculate the displacement of the device through double integration of its signal, with the impact velocity used as a boundary condition. The signals from the strain gauge circuit and the accelerometer are sampled at 2500 Hz. The data are transmitted to a receiver via telemetry using a 418 MHz FM transmitter and from the receiver to a laptop PC via the serial port. Calibration of the device is described and sample results showing forces up to 2500 N and displacements up to 0.04 m are presented.

Radiotelemetry system for apnea study in lambs

Neonatal apneas are being studied in the laboratory using polysomnographic recordings in lambs. Standard equipment, requiring animal restraint, disrupts sleep and prevents development of spontaneous apneas. The aim of the current work was to develop and validate a wireless recording equipment to study freely moving lambs. Firstly, a radiotelemetry equipment composed of a multichannel FM transmitter and a receiver was developed. Secondly, to test the telemetry equipment, each biopotential—[electroencephalogram (EEG), electrooculogram (EOG), electrocardiogram (ECG), electromyograms (EMGs), nasal airflow]—was recorded simultaneously by standard equipment and by telemetry (5 lambs). The results indicated an excellent concordance between signals obtained by both systems. Finally, the 8-channel telemetry prototype was tested for polysomnographic recordings (16 lambs). Results obtained confirmed the possibility of recording frequent REM sleep periods and spontaneous apneas. In conclusion, this radiotelemetry polysomnographic equipment brings new possibilities for research on neonatal apneas.

Adjustable frequency selectivity of auditory forebrain neurons recorded in a freely moving songbird via radiotelemetry

One of the hearing system's basic properties that determines the detection of signals is its frequency selectivity. In the natural environment, a songbird may achieve an improved detection ability if the neuronal filters of its auditory system could be sharpened to adapt to the spectrum of the background noise. To address this issue, we studied 35 multi-unit clusters in the input layer of the primary auditory forebrain of nine European starlings ( Sturnus vulgaris). Microelectrodes were chronically implanted in this songbird's cortex analogue and the neuronal activity was transmitted from unrestrained birds via a miniature FM transmitter. Frequency tuning curves (FTCs) and inhibitory sidebands were determined by presenting a matrix of frequency-level combinations of pure tones. From each FTC, the characteristic frequency (CF) and several parameters describing the neurons' filter characteristics were derived and compared to the same recording site's filter function while simultaneously stimulating with a continuous CF tone 20 dB above the response threshold. Our results show a significant improvement of frequency selectivity during two-tone stimulation, indicating that spectral filtering in the starling's auditory forebrain depends on the acoustic background in which a signal is presented. Moreover, frequency selectivity was found to be a function of the time over which the stimulus persisted, since FTCs were much sharper and inhibitory sidebands were largely expanded several milliseconds after response onset. Neuronal filter bandwidths during two-tone stimulation in the auditory forebrain are in good agreement with psychoacoustically measured critical bandwidths in the same species. Radiotelemetry proved to be a powerful tool in studying neuronal activity in freely behaving birds.

Bit-error rate of TDMA links under cochannel interference in overlaid cellular networks

This paper presents a series of numerical experiments conducted to investigate the error performance of a simulated digital time-division multiple-access (TDMA) radio link between a portable handset and the base station serving it, subject to interference coming from other portable handsets. The experiments take radio channel impairments such as fading, shadowing, and distance loss into account. Analytical expressions for the bit-error probability in uncoded digital radio transmission bursts under interference from nearby analog FM or digital minimum-shift keying (MSK) transmitters are reviewed. Numerical methods are used to extend analytical estimates of symbol error probability of a link with a single interferer, without channel impairments, to the case where the interference is due to a random distribution of transmitters whose signals are subject to fading, shadowing, and distance power loss. Specifically, three links, each based on one of three different modulation methods, MSK, quadrature phase-shift keying (QPSK) (proposed in the North American Digital Cellular Standard IS-54), and Gaussian MSK (GMSK) [used in the Global Standard for Mobile communications (GSM)] are simulated, and the bit-error rate (BER) results reported. The BER results generated thus indicate the sensitivity of the digital radio link to the user density for a given radio frequency (RF) bandwidth and, where applicable, to fading depth and postmodulation intersymbol interference (ISI) removal method. Possible extensions and applications of the simulation model to the problem of resource sharing between coexisting networks are suggested.

Dual-channel telemetry system for recording vocalization-correlated neuronal activity in freely moving squirrel monkeys

A miniature telemetric system is described which allows simultaneous measurements of neural activity and vocalization in freely moving monkeys within their social group. Single and multi-unit activities were detected with medium impedance electrodes that were fixed to self-made microdrives allowing accurate vertical positioning over a range of 8 mm. Vocalizations were registered by means of a piezo-ceramic device sensing the vocalization-induced skull vibrations. This allowed identification of the vocalizing animal in a larger group and eliminated environmental noise. Neuronal activity and vocalization were transmitted via separate channels of a FM transmitter using different carrier frequencies. The signals were decoded in two conventional FM receivers equipped with an automatic frequency control. The signals were stored for off-line analysis on a HiFi-videotape recorder.

Golden Jubilee Year of Independence: Roadmap of Broadcasting in India

Broadcasting in India during last fifty years, has seen a tremendous growth in terms of its reach and impact. Starting from six medium wave and twelve short wave transmitters in 1947, it has at present a massive network of 192 programme generating centres, 144 medium wave, 52 short wave and 101 FM transmitters for sound broadcasting. On the TV side, it has 41 programme generating centres, 92 high power and 831 low power transmitters. This paper traces the history of this growth and the future of broadcasting in the country.

A low-cost biotelemetry system for long time monitoring of physiological data.

A biotelemetry system based on digital data processing and transmission is implemented. The transmitter digitizes analog physiological signal, converts into serial form, forms a digital data packet by summing data and synchronization information and transmits the packets via an FM transmitter. The receiver side amplifies and pulse-shapes the received data packet, separates the data and synchronization information, converts serial data into 8-bit parallel form and then into analog signal. A special coding method provides high noise immunity and proper synchronization between transmitter and provides high noise immunity and proper synchronization between transmitter and receiver. The system shows a stable and high performance within a distance of 100 m.

HeadHole: Malfunctions and Dysfunctions of an FM Exciter

Quietly, let's unplug everything, blindfolded. Ears plugged, nose clamped, tongue tied, let's strip the hardware off radio. The exciter, heart of the FM transmitter, comes last. Once off, the purring winds down and we find ourselves radiophilic without transmitter. Commonly, the resultant dead air spells anguish and panic. No longer can the signal signify the voice and radiate it with power. For the moment, however, we will dwell and even revel in the air dead. There are remnants and potentials in our voices hereto untapped that will be sufficient to carry this broadcast home. The regular hosts from the Center for Radio Telecommunications Contortions have decided to invite some special guests as cohosts for this program: the Analphabt the Wireless Wired-a posthumous telephone; and the Transpiring Transistor-a translator exercise.

Method and apparatus for inducing audio vibrations

A method and apparatus of inducing vibrations and buzzes within a vehicle, e.g., from panel trim, provides a reliable and repeatable way to identify the sources of such vibrations and buzzes. According to the method, an FM transmitter modulates and transmits predetermined frequency signals to a standard FM receiver located in the interior of the car. The FM receiver receives and demodulates the signal, and then applies it to audio speakers also located within the vehicle. The output signal from the speakers induces sympathetic vibrations in vehicle components, allowing a tester to identify the sources of the vibrations and buzzes so that they may be corrected. The transmitter provides a means for a user to maintain a constant frequency or to vary the frequency within a predetermined range of frequencies. The frequency may be generated by digitally storing one complete sine wave in successive memory locations. The values can then be retrieved and converted to an analog signal. Higher frequencies are obtained by sampling at a constant rate, but skipping some of the values, thereby retrieving the sine wave at a faster rate.

A telemetric device for measuring smoking topography

The Telemetric Topography Device (TTD) introduces new technology to the measurement of cigarette smoking topography that has advantages over existing instruments. It consists of a 90.8-g miniature vacuum transducer coupled to an FM transmitter contained within a 11/4-in.-diameter × 41/4-in. free-standing plastic cylinder. As a subject smokes through a modified commercial cigarette holder, the TTD transmits a tone proportional to the vacuum pressure change in the cylinder. Received tones are converted to voltage data and then digitized by an A/D board in a personal computer. This information can either be displayed and stored on line or recorded on audio tape and digitized during playback. The TTD has no visible electronic parts, thereby minimizing subjects’ awareness of monitoring.