Showing papers on "Carrier-to-noise ratio published in 1991"

Optimized performance of erbium-doped fiber amplifiers in subcarrier multiplexed lightwave AM-VSB CATV systems

Abstract: The authors study the effects of noise when erbium-doped fiber amplifiers are used as signal boosters for signal distribution in amplitude modulation, vestigial-sideband (AM-VSB) subcarrier multiplexed lightwave cable television (CATV) systems. A procedure for finding the amplifier length required to achieve a desired carrier-to-noise ratio at the receiver, while maximizing the allowed post-amplifier splitting ratios and transmission losses has been developed. A simple and easy-to-use approach that circumvents the computationally intensive optimization procedure and allows the design of systems whose performance is very close to optimal is discussed. >

The impact of laser phase noise on the coherent subcarrier multiplexing system

Abstract: In coherent optical subcarrier multiplexing (CSCM) systems, the laser phase noise may cause signal spectrum broadening and hence, causes significant deterioration in the system performance. The impact of phase noise on the CSCM system is analyzed in terms of carrier-to-noise ratio, intermodulation distortion, and adjacent channel crosstalk. The optimal modulation index and carrier to noise ratio are also presented. Some numerical results are outlined. >

PWM signal demodulation method and apparatus

Abstract: A PWM signal demodulation method measuring the leading edge period of a modulated signal and a time between adjoining leading and trailing edges of the signal and finding the modulation factor in terms of the ratio of the period to the time. Reliable demodulation is ensured even if the carrier frequency of the modulated signal varies significantly. This novel method eliminates one disadvantage of the prior art demodulation method encountered when a varying carrier frequency exceeds the linearity domain of an integrator in its integrating characteristic, causing unreliable demodulation.

Uniform CNR design rules for coherent subcarrier multiplexed system with multioctave frequency allocation

Abstract: For a CSCM system with multioctave configuration, the CNR difference among channels is significant and needs to be taken into consideration. Here the authors take 'equal optimal CNR of the first and central channels' as a criterion, then derive a design rule to reduce CNR difference significantly. The example shows that it can be lessened from 7 to 1.5 dB with lower received signal power to achieve the same CNR requirement.

AFC circuit with fast acquisition for a TDMA cellular mobile communication system

Abstract: A novel AFC (automatic frequency control) circuit for a TDMA (time-division multiple-access) digital cellular mobile communication system with pi /4-shifted QPSK (quadrature phase-shift keying) modulation is described The AFC circuit satisfies the two contradictory requirements of fast acquisition and stable operation even under low CNR (carrier-to-noise ratio) channel conditions, simultaneously The performance of a 40-kb/s TDMA transmission system was measured to confirm the availability of the AFC circuit An E/sub b//N/sub 0/ penalty of the differential demodulator is compressed to less than 01 dB by the AFC circuit when carrier frequency deviation is within +or-1 kHz The results obtained show that the differential detection can be applied to a receiver of the TDMA digital cellular mobile communication system when the proposed AFC circuit is implemented >

Required protection ratios for co-frequency PAL FM TV transmissions

Abstract: This paper contains the results of a measurement campaign to determine the protection ratio requirements for PAL FM TV satellite transmissions in a form suitable for direct application in satellite planning exercises. The following cases were considered in the study: (a) the mutual interference between two co-frequency PAL TV signals frequency modulated using a deviation sensitivity of either 16 MHz/V or 25 MHz/V (b) the interference effects created by two independent co-frequency PAL TV carriers interfering with the same victim PAL TV carrier, with all signals frequency modulated using a deviation sensitivity of 25 MHz/V. Protection ratios were assessed with a wide variety of different conditions assumed for the wanted and interfering signals, such as the target picture quality and the operating carrier to noise ratio. The analysis of the results indicates that the required protection ratio is dependent upon some of the study parameters such as the picture content of the wanted signal. Protection ratio guidelines are derived on the basis of this analysis for co-frequency interference into PAL FM TV signals. The results also confirm that, for planning purposes, multiple interfering signals can be treated by addition on a power basis.

A Study On The Digitization Of Audio Signals For S-VHS VCR

Abstract: The recording and reproducing characteristics of the PCM (pulse code modulation) audio signal, reduction of interference to the video signal by the PCM audio signal, and performance against tracking error have been studied on a digital audio system for S-VHS VCR (video cassette recorder). A block error rate of 5*10/sup -4/ is attained without degradation of both video and FM audio signals. Amorphous heads have been used for both video and audio heads and the PCM signal carrier-to-noise ratio of 19 dB in the EP mode has been obtained without degradation of the video signal. It is confirmed that the uncorrectable error rate is under 1 symbol/second even in the case of a tracking error of -20 mu m to 9 mu m in the EP mode. >