Analog Signal Transmission Research Articles

Optical Analog Signal Transmission in Ambulatory ECG System

Analog optical transmission is incorporated to improve the noise immunity of the lead of ambulatory ECG system. Immunity for the magnetic artifacts is improved by50dB by replacing the electrical leads with an optical fiber. The effect of nonlinearity of electrooptical portion was successfully suppressed as low as0.4%by the digital equalization.

The Japanese scene [digital HDTV

Japan is the only country, so far, to be actually broadcasting high-definition television services. MUSE (multiple sub-Nyquist sampling encoding) is the basis for systems applying bandwidth compression to the transmission of both analog and digital signals. It encodes a signal of 1125 lines and 60 fields per second, a high-definition television (HDTV) signal into an 8-Hz bandwidth. Experimental MUSE broadcasts started in 1990 and have continued ever since. Meanwhile, work has been in progress in areas other than MUSE. Enhanced-definition television, a terrestrial system, is entering its second generation. Integrated digital broadcasting looks to spin many services into a single digital thread for transmission over a single channel. Digital sound broadcasting and hierarchical television transmission will also come in for consideration. The MUSE system depends on digital technology for signal processing, but the HDTV signal that is broadcast is analog, the outcome of frequency modulation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Small planar packaging system for high-throughputATM switching systems

A small planar packaging (SPP) system is described that can be combined with card-on-board (COB) packaging in ATM switching systems with throughputs of over 40 Gbit/s. Using a newly developed quasicoaxial zero-insertion-force connector, point-to-point 311 Mbit/s of 8 bit parallel signal transmission is achieved in an arbitrary location on the SPP system&apos;s shelf. Also 5400 I/O connections in the region of the planar packaging system are made, and thus the SPP system eliminates the I/O pin count limitation. Furthermore, the heat flux of the SPP system is five times higher than that of conventional COB packaging because of its air flow control structure.

Dead time of dual detector tools : J. A. Czubek, Nuclear Geophysics, 8(4), 1994, pp 317–326

A theory of the dead time for the dual detector nuclear tool with the analogue signal transmission is given in the paper. At least two different times exist in such tools: the dead time of detectors (for final computation they are assumed identical to each other) and the dead time of the signal transmission set-up. A method of two radioactive sources is proposed to measure these two different dead times. When the times used for measuring every countrate needed in the dead time determination algorithm are taken into account, the statistical accuracy of the dead time determinations can be obtained. These estimations are performed by the computer simulation method. Two codes have been designed: DEADT2D (DEAD Time for 2 Detectors) and DEADT2DS (DEAD Time for 2 Detectors with Statistics)

Image sensing and processing by a bacteriorhodopsin-based artificial photoreceptor

Sensing and processing of optical information have been conducted with a unique bioelectronic image sensor that immobilizes bacteriorhodopsin (bR) as a photosensitive retinal protein. A thin film of bR-containing purple membranes was coated on a two-dimensional pixel array of electrodes and was made into a junction with an electrolyte gel layer having a counterelectrode to form an artificial photoreceptor. Photocurrent signals from each pixel showed a differential responsivity to light intensity, intrinsic to this liquid-junction photocell. Images detected and processed by the bR-based artificial photoreceptor were simultaneously displayed on a light-emitting-diode monitor panel through parallel signal-transmission circuitry. The experiment revealed that the photoreceptor is, as a retina model, capable of selectively detecting motion of images in real time and of performing vectorial extraction of their edge components, similar to the visual processing function of biological photoreceptors.

A low temperature coefficient optomodulator for analog signal transmission

Recent studies have proven that Mach-Zehnder type optomodulators have a good potential for analog signal transmission. If it does not have too large a temperature coefficient, it could be an excellent device for future experiments. The authors have studied its temperature coefficient and developed a unit that has a low enough temperature coefficient so that it could be used for some physics experiments. A light wavelength of 1.55 mu m is chosen for the unit.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analogue optical fibre communications

* Chapter 1: Subcarrier multiplexing in optical communication network * Chapter 2: Coherent techniques in analogue signal transmission * Chapter 3: Analogue intensity modulation for optical-fibre video transmission * Chapter 4: Pulse time modulation techniques for optical fibre communications * Chapter 5: Soliton pulse position modulation * Chapter 6: Optical fibre digital pulse position modulation * Chapter 7: Performance assessment of subcarrier-multiplexed optical systems * Chapter 8: Optoelectronics for millimetre-wave radio over fibre systems * Chapter 9: Optical generation and delivery of modulated mm-waves for mobile communications * Chapter 10: Optical receiver design for optical-fibre SCM systems * Chapter 11: Optical fibre amplifiers and WDM

The burgeoning interest in compressed video

A t a time when all organizations are searching for new ways to work, think and learn more efficiently and effectively, interactive technologies of all kinds are being employed. One of these technologies is live, two-way, audio and video communication. Twoway interactive video isn't new, but how it is done has taken a new turn. As opposed to transmission of analog signals, video is now being compressed and converted to digital information which requires far less space on a cartier whether it be satellite, microwave or terrestrial lines. This compressed video (CV) can be transmitted at a variety of rates. Businesses have used compressed video since the early 1980's to cut travel time and costs for the purposes of training and videoconferencing. Educational institutions have also begun to explore the potential of CV in the past few years.

Quasi-feed-forward linearization of electro-optic modulators for analog signal transmission

A quasi-feed-forward (QFF) linearization scheme for use with electro-optic modulators is presented. This scheme provides an increase in the intermodulation-free dynamic range of the modulator as well as substantial cancellation of laser relative intensity noise (RIN) of the cw source. The results of this investigation indicate that such a scheme is adequate for the transmission of 100 or more Canadian television channels transmitted in a vestigial sideband AM format using a cw source with a RIN of only - 130 dB/Hz. A tolerance analysis has been performed to predict the effects of a nonideal practical implementation.

The effect of laser chirping on optical subcarrier multiplexed system with high-bit-rate baseband signal

The mixed transmission of digital and analog signals via single-mode fiber has potential in future fiber-optic systems. We have studied the effect of chirping of the baseband digital signal on the analog subcarrier channels using computer simulation. If the location of the subcarriers or the bias of the laser is selected properly, the SNR penalty due to chirping and cross talk will be less than 0.5 dB.

Polarization-independent transmission on a single mode fiber using coherence modulation of light

A polarization-independent transmission link on a single mode fiber at 1300-nm wavelength is demonstrated using coherence multiplexing. The use of a source with a very short coherence length (about 200 mu m) allows an easy implementation of the suitable optical delays (some millimeters) using LiNbO/sub 3/ modulators matched to fiber interferometers. Experiments were conducted with transmission of analog signals and baseband TV signals on a 2500-m-long single mode fiber. The polarization-independence of the method is obtained at the cost of relatively high losses. The high losses are introduced by the interferometers that are required at both ends of the link (theoretical losses of -3 dB/interferometer). They are physically inherent in the coding and detection process, which requires optical delays greater than the coherence length, and hence cannot be decreased. >

Guided-wave devices and circuits

Two decades have passed since the first, tentative experiments the first, tentaive experiments in guidedwave electro-optics were performed. During that time, development has been spurred on particularly by the successful penetration of fibre optics into many diverse fields and by the need for associated devices of ever increasing sophistication. Single-mode fibre is well established as the choice for the trunk backbone of modern telecommunications networks and is set for further applications in local networks. Fibre optics is now responsible for high performance sensor systems and is beginning to impact on analogue signal transmission, notably at RF, in fields such as radar systems and satellite communication antennae. These applications have driven research and development in both discrete electro-optic devices and in integrated electro-optic circuits.

Simultaneous transmission of 2 Gbit/s digital data and ten FM-TV analogue signals over 16.5 km SM fibre

The simultaneous transmission of a 2 Gbit/s digital signal and ten channels of FM-TV signals (3.7–4.2 GHz) over a 16.5 km single-mode fibre is reported. The system uses a 1300 nm directly modulated multimode laser diode without optical isolators, a ternary pin diode, and a simple commercial 50Ω wideband amplifier as a front-end preamp. The combined transmission of digital and analogue signals via single-mode fibre is of potential value in transition scenarios to future BISDN systems.

Pedestal drift and cable pickup problems in multiplexed analog signal transmission

Sample-and-hold circuits followed by analog multiplexing are often used to reduce the number of cables required between large multielement high-energy detectors and their associated analog-to-digital converters. All sample-and-hold circuits have charge-injection pedestals that can vary with time, temperature, and power supply voltages. These variations are often correlated among many channels so that total energy sums may be degraded, even though individual pedestal drifts remain negligible. A double-sampling system is described that substantially decreases charge-injection pedestals and their variations. The effects of low-frequency pickup in long signal cables, which also tend to be correlated, are very much reduced as well. >

Effect of varying gray-scale resolution for detectability of bone lesions in intraoral radiographs digitized for teletransmission.

Visual communication equipments were developed early by radiologists for the transmission of analog signals, whereas today's transmission systems are based on digitization of the radiograph. For teletransmission of dental radiographs, it is essential to assess the diagnostic accuracy of various spatial and gray-scale resolutions. Each of 83 dry mandibles was divided into four regions. By random assignment it was decided for each region whether or not a hole should be drilled. Intraoral radiographs (3 x 4 cm) were performed of each region and interpreted. The radiographs were thereafter recorded by a video camera connected to an IBM-PC. The personal computer held a hardware digitization card defined at a 512 x 512 spatial resolution with the possibility of selecting varying gray-scale resolutions. All radiographs were assessed in resolutions with 256 (8 bit), 128 (7 bit), 64 (6 bit), and 32 (5 bit) shades of gray. In no case was the original radiograph more accurate than the 512 x 512 x 8 resolution. In two of the regions evaluated, the images providing 32 shades of gray were less accurate (percentage of true positives and negatives) than the other resolutions (P less than 0.05) while in one region resolutions of 8 bit depth (256 shades of gray) provided a significantly greater accuracy than did the original radiograph and the other image resolutions (P less than 0.05). This was due to fewer false negative scores and was not followed by an increase in false positive scores. It can be concluded that a 512 x 512 spatial resolution is satisfactory for the detection of bone lesions in digitized intraoral radiographs and that 64 shades of gray provide an equally good diagnostic accuracy as do the original radiograph. This might be relevant when transmission times are of importance.

High-speed, polyimide-based semi-insulating planar buried heterostructures

We describe planar buried heterostructure lasers which have low capacitance (lpF), large bandwidth (19GHz), high power (&gt;20mW/facet) and high temperature operation (100°C). These lasers are very suitable for long-distance, highspeed digital and analogue signal transmission.

Zero redundancy channel coding in vector quantisation

Gray-coding of signal amplitudes can protect PCM transmission of analogue signals from the effects of channel bit errors. We generalise this to VQ, and provide a ‘vector switching’ algorithm that reduces the expected signal distortion by suitably assigning code words to the codevectors in a given code-book.

Pulse width modulation for analog fiber-optic communications

The pulse width modulation (PWM) technique has been revisited and analyzed to evaluate its merits for application to analog signal transmission in fiber-optic links. Fourier analysis of the PWM signal reveals that it can be used as a vehicle to launch an analog signal onto optical fiber when a symmetrical natural sampling process is used. The SNR of the modulated signal depends on the timing jitter of the carrier pulses and a wide-band (45 MHz) SNR of 45 dB has been obtained with a commercially available multimode laser transmitter. A linear dynamic range of over 50 dB has been experimentally demonstrated. The full fiber bandwidth can be utilized by using a very high pulse carrier frequency, while a more popular pulse frequency modulation technique provides about a 10-MHz analog signal bandwidth when 1 km of multimode fiber is used in conjunction with a short wavelength (0.87 μm) LED transmitter. Analog transmission capability was experimentally demonstrated by constructing a simple video link using common laboratory equipment. The performance of the video link supports the PWM modulation theory developed here and elsewhere. The experimental results indicated that PWM is potentially very attractive for low-cost broad-band local area network (LAN) application, including future highly interactive offices, hospitals, and automated factory floors.

Optimal Discrete-Time Delta Modulation System

Delta modulation communication systems are a popular and effective approach for transmitting analog signals over a binary channel. The performance of a discrete-time linear and leaky delta modulator is compared to the performance of the optimal delta modulator for a firstorder Gauss-Markov source.

Improving the Performances of Silicon Detector Electronics in High Energy Experiments by Optoelectronic Transmission of Analog Signals between Beam Line and Counting Room

The optoelectronic link described here transmits short analog signals from the beam line of the accelerator where the detectors and the front-end circuits are located to a remote counting room. Features of the electronic link that turn out to be important in high energy applications of silicon detectors are the distorsionless transmission of short signals, which results in improved counting rate capabilities and insensitivity to environment noise. This paper describes the design criteria employed to realize an optoelectro nic link with good linearity, high stability and very low intrinsic noise. The application of the link as a part of an analog processor for low noise data acquisition from solid state active targets is discussed.