Multichannel Video Signals Research Articles

新型机载多路音视频记录系统的设计与实现

Aiming at the requirements of high resolution, mass of data and high real-time performance for airborne multi-channel audio / video recording systems, a real-time multi-channel audio / video recording system was proposed based on embedded platform. Davinci video processors from Texas Instruments Incorporated( TI) were adopted to control the efficient real-time digitizing,coding and storage for fourchannel XGA( 1024 × 768@ 60 frames / s) videos, one channel PAL( 720 × 576@ 25 frames / s) video, and two-channel audios. Cyclone devices were exploited to transmit the compressed multimedia data. The testing results show that the system can implement recording and storage of multi-channel audio and video signal with high image resolution and good real-time performance. The system can find wide applications in the field of airborne recorders.

A Multiplexer with Split Devices for High Channel Isolation

A multiplexer with split devices for high channel isolation was proposed in this paper. The multiplexer is the most essential circuitry for multi-channel video signal acquisition systems. In the multi-channel applications, high isolation performance is required basically for the efficient signal processing. The noise propagation between channels is unexpected. The split devices technique is employed in the design work. Redundant transistors are inserted between the split cells to realize the noise grounded. This multiplexer is simulated and verified in the commercial CMOS process, and the isolation of more than 70dB was achieved. It has been embedded in a multi-channel analog signal processing system.

The Key Issues to the Switch of the Multi-Channel Video Signal

This paper proposes a multi-channel video signal switch system. The authors introduce a key technology which uses AD8108/AD8109 as switching devices, micro-controller LPC2214ARM as the control unit to form a multi-channel video switch. Firstly, this paper analyzes the working principle of AD8108/AD8109 and LPC2214. Then the authors give the hardware structure of the multi-channel video switch system, and the software design of the system. Finally, this paper puts forward the key issues to the switch of the multi-channel video signal after experiments. Facts have shown that these factors must be taken into account in the design of successful video signal switch systems.

Evolution of IR detection and possible outcomes for astrophysics

Infrared focal plane technology has evolved rapidly in the past two decades. The detector format has grown from single pixel detectors to 4K × 4K pixel arrays, and a mosaic of 4 × 4 2K × 2K pixel arrays and six mosaics of 2 × 2 2K × 2K pixel arrays are already in operation at ground based telescopes. The quantum efficiency of these arrays is close to 100%, the readout noise a few electrons rms and the dark current a few electrons per hour. However, the latent image problem has not been solved yet. A persistence model and a mitigation strategy will be discussed briefly. Specialized ASIC readout chips which digitize the multichannel video signals of large arrays directly on the focal plane are becoming available for large format arrays and they will eventually replace conventional controllers. In the mid infrared a high flux version of the MIRI detector is being developed for ground based applications. Fast low noise infrared sensors are needed for wavefront sensors of adaptive optics (AO) systems. To meet both the speed and the noise requirements two different technical approaches are being followed. One solution is the use of high gain CTIA amplifiers in the detector unit cell, the other solution is to exploit the noiseless gain mechanism of HgCdTe electron avalanche photodiode (eAPD) arrays.

Texture multichannel measurements for cancer precursors’ identification using support vector machines

Colorectal cancer is one of the leading types of cancer in the developed countries. Epidemiological studies have shown that the risk of developing colorectal cancer can be significantly reduced through early detection and removal of cancer precursor lesions. We propose a novel framework for the automated identification of colon cancer precursors based on the processing of color video frames acquired during endoscopy. The spectral information of the three color channels forming the endoscopic frames is used for the description of the colonic mucosa. The suitability of different color models for this application is investigated. The textural properties of the colonic mucosal surface are measured using second order statistical descriptors on the wavelet transform of the multichannel video signals. A new reduced set of measures based on the inter-channel covariance of the features has proven to provide high discrimination of image regions corresponding to normal and abnormal tissue. The proposed framework was tested using a Support Vector Machine classifier on different video frame sets presenting adenomatous polyps and the average sensitivity and specificity was estimated to reach 94% and 95.7%, respectively.

Multichannel Video and IP Signal Multiplexing System Using CWDM Technology

This paper describes how coarse wavelength-division multiplexing can realize a multiplexed multichannel video and Internet protocol (IP) system. In the proposed configuration, each signal is optically amplified separately to extend the service area. The IP signals are boosted by cost-effective erbium-doped fiber amplifiers, which have a simple configuration optimized for single-channel use. Two multiplexer/demultiplexer configurations are described. The proposed configurations yield a contents distribution network that offers bidirectional IP service in addition to the multichannel video service, which is transmitted as an analog signal. This paper presents an experiment that confirms the feasibility of this proposed system.

Millimeter-wave remote self-heterodyne system for extremely stable and low-cost broad-band signal transmission

We have developed a millimeter-wave remote self-heterodyne transmission system that enables extremely stable and low-cost broad-band transmission in the millimeter-wave band. The system was applied to a 60-GHz-band transmission system for the first time. The transmitter of the developed system transmits RF modulated signals and a local oscillation signal simultaneously, and the receiver detects these signals by using a square-law-type detection technique, thus creating a very stable and low phase-noise millimeter-wave transmission link without the use of an expensive and more advanced frequency-stabilization technology. Since the receiver no longer requires a millimeter-wave oscillator for frequency conversion, the devices used in this system can be miniaturized and the cost of the system can be reduced. This paper discusses the performance of the developed system in terms of its phase-noise degradation and carrier-to-noise power ratio (CNR). We also discuss the optimal transmitter design to obtain the maximum CNR. Using our miniaturized monolithic millimeter-wave integrated-circuit-based 60-GHz-band experimental system, we demonstrate that our millimeter-wave transmission link is completely free of phase-noise and frequency-offset degradation due to the use of a millimeterwave local oscillator. We show that equal transmission-power distribution between the RF signal and local carrier gives the maximum CNR under the transmission-power-limited conditions. Also, we demonstrate that QPSK-modulated satellite broadcast multichannel video signals with a 300-MHz bandwidth, in total, can be successfully transferred over a distance of 8 m.

A low power dissipation 0.4∼7 GHz transimpedance amplifier IC for SCM optical communication system

A low power dissipation and broadband transimpedance amplifier IC has been developed for sub-carrier multiplexing (SCM) optical communication systems such as a multi-channel video signal transmission system. A 0.25 μm pseudomorphic double-heterojunction modulation-doped FET (MODFET) is adopted for the IC to achieve the required bandwidth and noise performance. Specifically, transimpedance gain of 52 dBΩ with equivalent input noise current of 12 pA/√Hz has been obtained between 0.4–7 GHz. In order to minimize the group delay (GD) deviation, a peaking control technique is investigated. We also adopted the flip-chip bonding method to reduce the parasitic elements. As a result, group delay deviation of less than 30 ps has been obtained. A novel SrTiO 3 (STO) capacitor process technology is incorporated to realize low power dissipation. By using integrated STO capacitors for DC blocking, single power-supply voltage of 5 V and power dissipation of 300 mW are realized. This power dissipation is less than one half of that required by conventional transimpedance amplifiers.

CNR limitations of Er-doped optical fiber amplifiers in AM-VSB video lightwave trunking systems

The CNR limitations of two different types of 980-nm pumped in-line Er-doped optical fiber amplifiers with the same small-signal noise figure to transport multichannel AM-VSB video signals is studied. Experimental results and frequency-domain simulations suggest that the noise figure of a high-power in-line erbium-doped fiber amplifiers (EDFA) should be 5 dB or less when operating deep in saturation (optical input power +3 dBm). Using two such in-line amplifiers produced an AM CNR greater than 50 dB with negligible CSO and CTB distortion degradation for a lightwave trunking link transporting 71 AM-VSB video channels with a total optical link budget of 39 dB. These results can clarify the EDFA selection criteria for AM video lightwave links.

Digitizing multichannel video signals for lightwave transmission

This paper presents a new approach to the design of lightwave multichannel CATV transmission systems using broadband digital coding to convert an all-analog multiplexed video signal to a string of pulses suitable for digital transmission. Four broadband coding methods have been discussed and compared, which are: uniform and optimal companding PCM, as well as uniform and adaptive DM. The principle advantages of this approach include the benefits obtainable from digital transmission and also direct compatibility with current CATV networks. CNR limits have been investigated for all of these methods.

Low-noise Pr 3+ -doped fluoride fibre amplifier

The authors have constructed a Pr3+-doped fluoride amplifier (PDFA) module pumped by an Nd-YLF laser. The maximum signal gain and noise figure were 20 dB and 5 dB, respectively. An output power of 19.2 dBm was achieved at an input signal power of 11.0 dBm. It was confirmed that this PDFA module has low-noise characteristics from experimental results on its use in a subcarrier multiplexed multichannel AM-VSB video signal transmission.

Vector measurement of nonlinear transfer function

A technique for the precise frequency-domain characterization of weakly nonlinear RF/microwave networks is described. The method, which is capable of measuring the so-called nonlinear (Volterra) transfer function, proves to be invaluable in designing high-performance predistorters to linearize nonlinear RF/microwave devices. The nonlinearity under test (NLUT) is subjected to stimuli from several sinusoidal signals, and a beat frequency is observed. The stimulus signals also feed a reference nonlinearity which too generates a beat at the same frequency. The phases of these two signals are compared in a pair of coherent, tuned receivers, as in a Vector Network Analyzer. A calibration technique allows us to de-embed the effect of the linear networks preceding and following the NLUT and the reference nonlinearity. The implementation is described in the context of a broadband (50-1000 MHz) nonlinear predistorter for linearizing a Mach-Zender type optical modulator, used for transmitting multichannel video (CATV) signals over optical fibers. As the technique is simple to set up and easily automated, it can be used in both engineering and production environments.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance of Pr -doped fluoride fibre amplifier for multichannel AM-VSB transmission

The system performance of a Pr-doped fluoride fibre amplifier was examined for multichannel AM-VSB video signal transmission for the first time. For a CNR of 51 dB, a loss budget of 15.1 dB was obtained with the amplifier, and for a CNR of 46 dB, the loss budget was expanded to 20.1 dB.

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. >

Applications of traveling-wave laser amplifiers in subcarrier multiplexed lightwave systems

Describes applications of traveling-wave laser amplifiers (TWLAs) in subcarrier-multiplexed distribution systems for both frequency-modulated (FM) and amplitude-modulated vestigial-sideband (AM-VSB) video signal distribution. The characteristics of a 1300-nm facet-angled and antireflection-coated TWLA are described. Analytical carrier-to-noise ratio (CNR) characterizations of subcarrier-multiplexed systems employing TWLAs are given. Experimental results of using TWLAs in multichannel FM and AM-VSB video signal systems are described. The potential optical-reflection problems associated with the residual reflectivities of optical fiber connectors and splices while using TWLAs are briefly described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optimizing Optical Transmitters and Receivers for Transmitting Multichannel Video Signals Using Laser Diodes

Analog transmission using laser diodes is quite attractive for transmitting multiplexed video signals, owing to the wide modulation bandwidth of laser diodes. Optimizations for transmitting color-TV signals (7 channel frequency division multiplexed) in the VHF band using buried heterostructure laser diodes are investigated. The major transmission objectives are a carrier to noise ratio of larger than 48 dB and intermodulation products of less than -55 dB. Design curves for minimizing distortion at the transmitter are demonstrated. A modulation index of 70 percent is shown to be capable of attaining the objective. Both the avalanche photodiode (APD) and the pinphotodiode (PD) are considered for use in the receiving amplifier. Minimum receiving power of -11 dBm obtained with the PD receiver is in good agreement with theoretical values. Deterioration of signal to noise ratio due to fiber guided transmissions is also reviewed in comparison with aerial transmissions.

Analysis of Single Sideband Modulation in Microwave Systems for Television (Video) Transmission

This paper analyzes the problem of intermodulation distortion of single sideband amplitude modulation (SSB-AM) for the transmission of multi-channel video signals using microwave radio systems. Microwave television transmission using SSB-AM is attractive due to its potential to reduce costs and to improve spectrum utilization. However, the usage of SSB-AM for multi-channel microwave video transmission has been restricted mainly because of the unacceptable level of third order distortion components generated in a microwave system.