Multichannel FM Research Articles

Multi-channel FM transmission of vibrotactile signals on 2-D communication textile

Multi-channel FM transmission of vibrotactile signals on 2-D communication textile

Efficient Implementation of Multichannel FM and T-DMB Repeater in FPGA with Automatic Gain Controller

In this study, we implemented a high-performance multichannel repeater, both for FM and T-Digital Multimedia Broadcasting (DMB) signals using a Field Programmable Gate Array (FPGA). In a system for providing services using wireless communication, a radio-shaded area is inevitably generated due to various obstacles. Thus, an electronic device that receives weak or low-level signals and retransmits them at a higher level is crucial. In addition, parallel implementation of digital filters and gain controllers is necessary for a multichannel repeater. When power level is too low or too high, the repeater is required to compensate the power level and ensure a stable signal. However, analog- and software-based repeaters are expensive and they are difficult to install. They also cannot effectively process multichannel in parallel. The proposed system exploits various digital signal-processing algorithms, which include modulation, demodulation, Cascaded Integrator Comb (CIC) filters, Finite Impulse Response (FIR) filters, Interpolated Second Ordered Polynomials (ISOP) filters, and Automatic Gain Controllers (AGCs). The newly proposed AGC is more efficient than others in terms of computation amount and throughput. The designed digital circuit was implemented by using Verilog HDL, and tested using a Xilinx Kintex 7 device. As a result, the proposed repeater can simultaneously handle 40 FM channels and 6 DMB channels in parallel. Output power level is also always maintained by the AGC.

Compressive sensing based high-resolution passive bistatic radar

Passive bistatic radar (PBR) systems using different communication signals can only offer low-resolution target detection due to their inherent low bandwidth. In this paper, compressive sensing (CS) is applied to multichannel FM and GSM PBR to achieve improved range-Doppler resolutions and avoid some limitations of classical multiband PBR processing. In CS context, block-structured time-domain dictionary which is formed from multichannel signals suffers from coherence when fine range resolution is employed. To overcome such a pitfall, this work first transforms the dictionary to spectral domain where only the most important spectral components are retained. Principle component analysis followed by a whitening method are then applied to this spectrally transformed data in order to reduce the dimensionality of problem, thereby reducing the dictionary size and most importantly fulfilling the required condition of dictionary incoherence for better CS-based recovery. Two different block-structured dictionary formations are tested. The performance of the recovery of spatially close targets, in both FM and GSM PBR setups, are reported.

FPGA-based simultaneous multichannel fm broadcast receiver for audio indexing applications in consumer electronics scenarios

The paper describes a Software Defined Radio architecture that simultaneously demodulates all radio stations in the Frequency Modulated (FM) band, and is intended as a preprocessor for content and metadata indexing applications. The system, which contains an overlap-add type channelizing filterbank and a massively parallel frequency demodulation block, is implemented in a single Field- Programmable Gate Array, thus offering the possibility of replacing more traditional media indexing installations containing tens of individual receivers. It is believed to be the first single chip full-band channelization system intended for consumer broadcast media indexing applications. Chip resource utilization details and experimental results from the developed system are also 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.

Optical fiber two way FM video signal transmission for video conferencing applications

This paper describes an optical fiber transmission system to transmit two-way multi-channel FM video signals for video conferencing applications. A two-way optical fiber signal transmission system is built using a pair of optical distributors and a single optical fiber of 1 km for bidirectional communications. A pair of LEDs were used as light sources at 1.3 /spl mu/m and the bandwidth of the optical fiber transmission system was 300 MHz. >

Optical fiber transmission of multi-channel FM audio and video signals

An optical-fiber transmission system with a bandwidth of greater than 100 MHz for transmitting multichannel FM audio and video signals is described. This system for distributing FM audio and video signals on up to five channels to the respective receiver was constructed using a high-speed LED (light-emitting diode) and a wideband amplifier. The differential gain and differential phase were less than 2% and 3 degrees , respectively, and the SNR was 56 dB. The proposed system will be used for high-quality, high reliability distribution of multiple TV channels instead of the coaxial cable distribution systems. >

Intermodulation distortion in 48 TV channel FM-FDM optical transmission

The effect of dispersive fibers on multichannel FM video transmission characteristics is experimentally investigated. A directly modulated 1.5 mu m distributed feedback laser diode (DFB-LD) and a LiNbO/sub 3/ external modulator with a continuous-wave (CW) 1.55 mu m DFB-LD are used as optical signal sources. When the 1.3 mu m single-mode fiber (SMF) is used, directly modulated DFB-LDs suffer from second-and third-order intermodulation distortion (IMD). The external modulator realizes good transmission characteristics irrespective of the fiber's dispersion value. This means that external modulators can realize multichannel FM television signal transmission systems that use the standard 1.3 mu m SMF already installed in fiber optic subscriber loops.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Subcarrier multiplexing for lightwave networks and video distribution systems

Applications for subcarrier multiplexing include a variety of analog and digital lightwave transmission systems. An overview of the requirements and capabilities of these systems is presented by describing specific examples of the most popular system types. These examples include multiuser interactive local area networks and multichannel digital, FM, and AM-VSB (vestigal sideband) video distribution systems. Limitations imposed on each by the linearity of directly or externally modulated sources, receiver noise, and relative-intensity noise are discussed. >

CNR requirements for subcarrier-multiplexed multichannel video FM transmission in optical fibre

We clarify the CNR improvement factors applicable to FM video signals provided via satellite links employing energy dispersal waveforms, noting that a CNR of 17.5 dB is required to achieve a weighted SNR of 56 dB for a 525-line C-band NTSC signal with an energy dispersal deviation of 2.5 MHz, accommodated in a 36 MHz satellite transponder channel.

Investigating the efficiency of the compensation method for improving the electromagnetic compatibility of multichannel FM radiocommunication systems

An analysis has been performed of the efficiency of interference compensation systems (ICS) in communication channels with allowance for the errors of engineering implementation, and fadings of the useful and interfering signals on the propagation routes of radio waves. Expressions have been derived for determining the efficiency of a method based on the utilization of ICS for improving the electromagnetic compatibility of multichannel FM radiocommunication systems, and for determining the requirements governing the allowable errors of engineering implementation.

Subcarrier multiplexed lightwave systems for broad-band distribution

Microwave subcarrier multiplexing (SCM) is an important approach to the design of lightwave systems for broadband distribution. Recent progress in the design and performance of both analog and digital multichannel SCM systems is reviewed. The application of broadband SCM systems to both passive and optically amplified distribution networks is discussed. The discussion covers the general features of SCM systems; the electrooptic components that have been used in the system experiments described here, including laser intensity noise and noise due to intermodulation products; the carrier-to-noise ratio requirements; some multichannel FM systems experiments; and a 20-channel digital systems experiment; and a hybrid system carrying 60 FM SCM channels plus a 100-Mb/s baseband digital channel. Several approaches to broadband subscriber distribution networks are analyzed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A survey of interference problems and applications to geostationary satellite networks

The fundamental limitation in the utilization of the geostationary orbit is the mutual interference generated by satellite networks. A review of the theory of operation of communication systems in an interference environment is provided, with particular attention to those systems of importance in space communications, namely multi-channel FM telephony, frequency-modulated television, and coherent PSK digital signals. Examples are then given to show the limiting effects of interference on orbit utilization.

Digital analysis of laryngeal control in speech production

Physiological measurements are made directly on human talkers to determine several dynamic laryngeal functions. The functions are control variables in a speech synthesizer which utilizes acoustic models of the vocal cords and vocal tract. The functions are measured simultaneously and recorded on multichannel FM tape. They are the time variation of vocal-cord (glottal) opening (Ag); the electromyographic (EMG) potentials of three laryngeal muscles−−posterior crico-arytenoid (PCA), interarytenoid (IA), and crico-thyroid (CT); the subglottal air pressure (Ps); the speech output sound pressure waveform (P); and timing pulses from a digital clock. Preliminary data for ten utterances by a man are digitized by a multiplexed A/D converter on a DDP−516 computer, and the results are stored in disk file for analysis. Bandwidth of the multitrack FM playback is 2800 Hz. Each function is sampled at 6250 sec−1 and quantized to 16 bits. Digital filtering is applied to remove dc offsets and enhance information features. The acoustic functions (Ag, Ps, and P) are submitted to programmed pitch analysis. The results show how voice periodicity can be manifested differently at the glottal and sound-output levels. A typical instance is vocal-cord vibration throughout the occluded phase of a voiced stop consonant. The EMG functions are analyzed by computing short-time energy. The results are correlated with voicing onset/offset and with voice pitch. PCA energy is shown to be correlated with voicing offset, and anticipatory to it by about 20–30 msec. IA energy is shown to be correlated with voicing onset, and anticipatory to it by about 40–50 msec. CT energy is found to be nearly directly correlated with the frequency contour for voice pitch. Direct utilization of these physiological parameters for speech synthesis is suggested. Subject Classification: [43]70.20, [43]70.60.

The measurement of wind pressures on two-storey houses at Aylesbury

An account is given of the measurement of wind pressures on a two-storey housing estate on the outskirts of Aylesbury, 65 km north-west of London. The estate immediately adjoins an open country fetch extending uninterruptedly for about 15 km to the southwest. The site and installation are described, including the variable geometry building erected on open ground adjoining the estate. Wind pressures were recorded at a total of 44 positions on seven houses in the estate, and at 72 positions on the experimental building, transducers being mounted on both walls and roofs. Load cells were also installed in the experimental building to record separately total overall loads and total roof loads. Measurements of velocity were made using cup anemometers mounted at 3 m, 5 m, and 10 m, on a fixed mast, suitably sited in the vicinity of the experimental building. In addition, anemometers mounted on a 20 m portable mast were used to investigate the upstream velocity profiles, and also the flow patterns within the urban area. The experimental building housed all the recording equipment which comprised multichannel FM magnetic tape recorders. Records were taken in analogue form and were subsequently digitised in order to calculate mean, rms and extreme values, probability distributions, autocorrelations, power spectra and cross-correlations. Measurements have been made for a variety of wind speeds and directions, and also for several roof pitches on the experimental building between 5° and 45°. Preliminary results are presented and discussed.

Preliminary EMG Investigation of Certain Intrinsic and Extrinsic Laryngeal Muscles in Patients with Spasmodic Dysphonia

EMG studies were conducted on eight patients with nontremor related spasmodic dysphonia. Bipolar hook-wire electrodes were inserted into the cricothyroid, sternothyroid, and throhyoid muscles of each patient. The electromyographic activity from each muscle was recorded along with the voice of each patient on a multichannel FM data recorder for subsequent writeout and analysis. Data were obtained during quiet respiration, as well as during each patient's utterance of a standard sequence of isolated vowels, CV syllables, words, and contextual speech. Data analyses revealed that the characteristic intermittent voice stoppage episodes exhibited by patients with spasmodic dysphonia occur in association with sharp, burst-like increases in EMG activity in the cricothyroid and in some instances the sternothyroid and thyrohyoid muscles. Patients with spasmodic dysphonia tend to show prolonged contraction of the muscles under study prior to and following phonation. The postphonatory time data provide evidence suggestive of a problem in muscle relaxation. Implications of these preliminary observations will be discussed and directions for further investigation suggested.

A New Microwave Amplifier for Multichannel FM Signals Using a Synchronized Oscillator

Because of the excellent results of the noise-loading test on an IMPATT oscillator that is phase-locked to an external FM driving signal, a new microwave amplifier for multichannel FM signals using a synchronized oscillator is proposed. An IMPATT oscillator, injection-synchronized with an FM signal, is regarded as an amplifier and its noise characteristics for multichannel signals are evaluated with the noise-loading method as recommended by the International Radio Consultative Committee. The results show that when this oscillator satisfies the noise characteristics for 960 telephone message channels, it assures a gain of approximately 15 dB at 11 GHz, and in this sense, this oscillator can be regarded as an amplifier for multimessage channels. The degradation of SNR of this amplifier is less than 2 dB. This excellent result is obtained because of the following. In the video band, the modulation suppression of an FM driving signal in the injection-synchronized oscillator, such as the IMPATT, is very small, while the oscillator noise, which dominates the entire output characteristic, is considerably reduced by the synchronizing action of the oscillator. This amplification continues up to the high-frequency range in which this principle of operation applies.

Digital storage of radioisotope indicator concentration data on FM analog magnetic tape

A practical and functional design is presented for the storage of radioisotope indicator concentration data in digital form on FM analog magnetic tape. The converter is designed to utilize the 12-bit parallel binary output of a Baird Atomic Digital Ratemeter (Model 425) which is converted into a 4 line 1–2–4–8 binary-coded-decimal (BCD) pattern suitable for recording on any multichannel FM instrumentation tape recording. The output levels are set at ± 1 volt compatible with Laboratory Instrument Computer (LINC) external line logic levels. The LINC is used to process the digital ratemeter data on-line and off-line in experiments dealing with tube models and anesthetized animals in which the mean transit time ( MTT), appearance time ( T Λ ), flow ( Q ̇ ) and volume ( V) are computed. The stability and reproducibility of the experimental digital data stored in this form far exceeds that of equivalent analog data. This design should further extend the accuracy of blood-flow and cardiac-output determinations using radioisotope indicator-dilution techniques.

Noise loading performance of a phase-locked IMPATT oscillator for multichannel FM signals

Results of a noise loading test for an IMPATT oscillator which is phase-locked to an external FM driving signal [1] are discussed. Amplification (the ratio of power output of the oscillator to power input of the driving signal) of about 15 dB could be obtained for 960 telephone message channels.

Multiple-access communications satellites

The causes of degradation in the speech channels of multi-channel telephony FM signals, when several such signals are amplified in a common amplifier (e.g., in a multiple-access communications satellite), are briefly considered. It is shown how previous results on interference between FM systems can be readily applied to this problem.