Sideband Ratio Research Articles

Performance of DCS-RZ single-sideband signal in 40 Gbit/s long-haul transmission systems

Optical sideband suppression (SS) by means of optical filtering is proposed for duobinary-carrier-suppressed return-to-zero (DCS-RZ) coding format. The performance of DCS-RZ with SS format generated using three different SS filters is investigated through numerical simulation. The power of the nonsuppressed sideband to the power of the suppressed sideband ratio (SSPR) is used to categorise the level of sideband suppression. A minimum level of SSPR of 20 dB is required to generate single-sideband (SSB) signals. It is shown that, for all three SS filters, an SSPR higher than 20 dB can be accomplished by choosing properly the SS filter bandwidth and detuning. Hence, the SS filter can generate single-sideband (SSB) signals. Transmission performance over different distances is assessed numerically. Results reveal that a double-sideband (DSB) modulation format shows better performance (Q-factor improvement of ∼3 dB, for optimum input power levels), even after 8 transmission spans of standard single-mode fibre, than the SSB formats. However, the optically generated SSB signals increase the DSB signal tolerance to dispersion compensation ratio variation more than three times, showing remarkable robustness to optical filter parameter variation, revealing that the DCS-RZ-SSB format is a good candidate for long-haul transmission systems.

Millimeter-Wave Radiometer for the Measurement of Stratospheric ClO Using a Superconductive (SIS) Receiver Installed in the Southern Hemisphere

A new sensitive radiometer for atmospheric minor constituents has been developed by Nagoya University and the National Institute for Environmental Studies (NIES). The instrument equipped low-noise superconducting (SIS) mixer with a system noise temperature of ≈200K (SSB) at 204GHz. The SIS mixer is operated in a single side band mode with a side band ratio grater than 10dB by adjusting the two tunable backshorts of the mixer. Since any additional SSB filters are not necessary, we can simplify the quasi-optical system and reduce the standing waves which makes difficult to achieve a flat spectral baseline. We installed the observation system at Las Campanas Observatory, Chile in December 1999, and started the test observation from 2000 October. We have detected significant ClO emission at 204.3 GHz with an actual observation time of only 4 hours. This is the first detection of the ClO at 40km altitude from the mid-latitude region of the southern hemisphere. The Nagoya-NIES system has enabled continuous monitoring of ClO in the stratosphere with a time resolution of 4 or 5 hours.

Design and characterization of a 250-350-GHz fixed-tuned superconductor-insulator-superconductor receiver

A fixed-tuned superconductor-insulator-superconductor (SIS) receiver has been designed to operate in the 250-350-GHz frequency band. This receiver has a double-side-band noise temperature of between 35 and 45 K, or about 3h/spl nu//k/sub B/, over its entire operating band. Extensive characterization of the receiver has been carried out using techniques developed for submillimeter waves. The input noise, side-band ratio, 1 dB compression point, optimum LO drive level, and vector near-field beam profile have all been measured experimentally. The measurement techniques and results are presented and discussed.

Principal components analysis of cells in cat visual cortex

Cortical cells differ along many dimensions, and statistical techniques are needed to study the relationships among them. We have used principal components analysis to study variation within a population of cells in the visual cortex of the cat. This procedure transforms the data which may then be projected onto a small number of independent axes. The axes are hierarchically ordered in terms of the sample variance they account for so that subsequent components account for decreasing proportions of the total sample variance. Four principal components (PCs) were identified by the analysis. The contributing variables on these components were respectively: (1) cutoff velocity, peak response, receptive field area and spontaneous activity; (2) tuning width, orientation selectivity, occular dominance ratio and obliquity; (3) directionality ratio, monocularity and vvariability; and (4) width to length ratio, variability and sideband ratio. We hypothesize that each of these components identifies a physiologically important feature of cortical organization. PC 1 and PC 4 describe those relationships among variables that have been used previously by other workers to classify cells in the visual cortex of the cat. Specifically, PC 1 is highly correlated with those variables associated with type of afferent input and PC 4 is highly correlated with those variables that differentiate simple cells from complex cells. PC 2 and PC 3, however, are highly correlated with variables that have not been used in classiying cells. Our results demonstrate that: (1) each of two major classification schemes (simple/complex and classification by afferent input) describe important differences among neurons in the cat's visual cortex and both must be incorporated into a comprehensive system for classifying cells in the cat's visual cortex; and (2) these two schemes when combined do not account for all the major differences among neurons in cat visual cortex, and at least two additional components are required: one related to orientation selectivity and dominance by the ipsilateral eye, and another related to directional selectivity and the degree of binocular interaction.

Frequency Modulation of Speech

Frequency modulation of speech is an effect produced by periodically modulating the speech frequencies during transmission. This effect is detectable by the wavering or buzzing quality that it imparts to the speech as received. The detection limits of frequency modulation of speech were determined using the Békésy tracking technique. Modulation rates from 10 to 200 cps were used on speech produced by both male and female talkers. Detection limits, expressed as a function of signal to sideband ratio, were found to vary as a function of sex of the talker, modulation rate, and received-speech level. Detectability is greater with female than with male talkers, and peaks at a higher modulation rate for the female talkers than for the male talkers.

Compatible Single Sideband

A compatible single-sideband (CSSB) wave is a new type of modulated wave which is compatible with existing AM receivers. Spectrum analysis and measurement indicate that if the CSSB system is applied to a conventional AM broadcast transmitter, a desired-to-undesired sideband ratio of slightly better than 30 db will be achieved under normal modulation conditions. Also described is a beat frequency problem which introduces a special type of undesired sideband component. This component falls extremely close to the carrier and should not be present during the vast majority of program conditions. Thus, the technique meets the requirement of theoretically distortion-free envelope characteristics with a good desired-to-undesired sideband ratio. Measurements are described which show the advantages of the system. It appears that the main advantage of the technique is to reduce co- and adjacent-channel interference effects. CSSB also provides a higher fidelity signal when received by conventional inexpensive broadcast receivers. The on-the-air tests indicated good listener acceptance of the new system. The system also appears to have applications in communications service where cost and size bar the use of conventional sideband techniques. The technique does not suffer from Doppler shift difficulties.