Abstract: PROBLEM TO BE SOLVED: To prevent a signal transmission efficiency from being deteriorated by making a modulation signal the most likelihood estimation in a receiver side without transmitting any control signal in a transmitter side in an adaptive modulation system that is applicable to a mobile communication system or the like and where only a modulation index is changed based on a channel power gain especially. SOLUTION: A modulation index estimate section 110 calculates a square error of a minimum distance among respective distances between respective signal points to be received in a modulation index for every modulation index and signal points of a received signal. A reception power measurement device 109 measures a reception power level of the received signal. The modulation index estimation section 110 calculates a value obtained by calculating a weight calculated from a switching power level to switch the modulation figure and the reception power level for the square error calculated for the every modulation index as a likelihood value for the every modulation index. Then, the modulation index estimate section 110 estimates a modulation index corresponding to the most likelihood value among the likelihood values for the every modulation index as the modulation index of the received signal.

Abstract: Using data from the Voyager 1 plasma wave instrument, a series of direction-finding measurements is presented for the intense 1992-93 heliospheric 2- to 3-kHz radio emission event, and several weaker events extending into 1994. Direction-finding measurements can only be obtained during roll maneuvers, which are performed about once every three months. Two parameters can be determined from the roll-induced intensity modulation, the azimuthal direction of arrival (measured around the roll axis), and the modulation index (the peak-to-peak amplitude divided by the peak amplitude). Measurements were made at two frequencies, 1.78 and 3.11 kHz. No roll modulation was observed at 1.78 kHz, which is consistent with an isotropic source at this frequency. In most cases an easily measurable roll modulation was detectable at 3.11 kHz. Although the azimuth angles have considerable scatter, the directions of arrival at 3.11 kHz can be organized into three groups, each of which appears to be associated with a separate upward drifting feature in the radio emission spectrum. The first group, which is associated with the main 1992-93 event, is consistent with a source located near the nose of the heliosphere. The remaining two groups, which occur after the main 1992-93 event, have azimuth angles well away from the nose of the heliosphere. The modulation indexes vary over a large range, from 0.06 to 0.61, with no obvious trend. Although the variations in the directions of arrival and modulation indicies appear to reflect changes in the position and angular size of the source, it is also possible that they could be caused by refraction or scattering due to density structures in the solar wind.

Abstract: An open loop fiber optic gyroscope having improved linearity and scale factor accuracy in the rate signal output and improved modulation index control is disclosed. A digital phase tracker is utilized to derive the Sagnac phase shift from signals proportional to cosine and sine values of the Sagnac phase shift. The rate output is independent of the amplitude of the optical power in the gyroscope and is linear for very large input rates. A modulation servo utilizes the second and fourth harmonic signals from the output of the fiber optic gyroscope to control modulation.

Abstract: The paper reports on a standard microcontroller implementation of a pulsewidth modulator and near-deadbeat current regulator for high switching frequency. The application is in high-performance positioning systems. The control strategy relies on a simplified machine model without incurring performance degradations. Changes between different modulation strategies are programmed depending on the modulation index. The values of switching time durations are obtained exclusively by decision making, thus minimizing computational load. Features like overmodulation, dynamic overmodulation, anti-windup, and reduction of switching frequency at thermal overload are included.

Abstract: In this paper, we analyze the dynamic behavior of directly modulated semiconductor lasers as the modulation index is varied, with an emphasis on the influence of noise at two different biasing levels. We studied the route to chaos followed by the deterministic system when the modulation frequency is two times the resonance frequency. We found that the behavior is more complex than that of a Feigenbaum sequence. In addition, a period tripling stable solution, which appears due to a fold bifurcation, coexists with the Feigenbaum sequence for certain values of the modulation index. Their coexistence gives rise to hysteresis loops and chaotic bifurcations, namely boundary crisis. Due to the coexistence of solutions in the deterministic system, the role of noise can be expected to be of great importance. When noise fluctuations are introduced in the model, the behavior evolves from the single periodic response through period doubling, period quadrupling, and period tripling in accordance with recent experimental studies. We have also found agreement in the behavior at different conditions of the analysis by varying the biasing point and the modulation frequency. Our results show that in the route to chaos, the period-doubling sequence is effectively truncated due to random noise. The reason for the truncation is found in the nearby coexisting period-three solution.

Abstract: The use of per survivor processing (PSP) is considered in the detection of a continuous phase frequency shift keying (CPFSK) signal. It is shown that PSP can enable the use of a trellis structure for the demodulation that is different from the trellis structure used to generate the CPFSK signal. This allows one to select a receive trellis structure with fewer phases, resulting in a reduced state sequence estimation algorithm. Results are presented using a receive trellis of 3 states to receive binary CPFSK signals with a modulation index, h, of 7/10. The complexity of the receiver is reduced by a factor of 3.3 with minimal performance degradation. An application of this PSP technique is also discussed which enables one to perform maximum likelihood sequence estimation (MLSE) of a digital FM signal, where the modulation index is only approximately known. Results presented for the binary case show this technique to provide a significant detection efficiency advantage over conventional techniques such as limiter-discriminator detection or non-coherent detection.

Abstract: This paper presents a control strategy to apply in the control of current type PWM rectifiers. These converters use LC filters on the AC side, and as a consequence, undesired oscillations take place. These oscillations are not dependent on the PWM technique used but depend on the LC filter size. A simple, cost effective and efficient damping system is presented and discussed in this paper. This damping system uses the voltages across the AC inductors as feedback variables. The DC current is controlled with an outer linear PI controller with anti-reset windup and a nonlinear function that determines the AC current references by the product of the PI output and the actual DC current. This allows a transfer function linearization between the modulation index, that is the output of the PI controller, and the DC current. The system is analysed with a simplified model and analytical expressions are presented to synthesise the feedback loops. The PWM space vector modulation technique adapted to current inverters is used to verify the performance of the proposed feedback loops. The results presented show excellent behaviour in steady state and in transient regime.

Abstract: An amplitude and phase demodulator circuit for signals with very low modulation index, including: amplifier circuitry adapted to amplify a modulated signal coming from a transmitter, the modulated signal being composed by a carrier and by a modulating component, circuitry adapted to cancel said carrier from said modulated signal; the circuitry adapted to cancel the carrier receiving in input the output signal of the amplifier circuitry and a sync signal coming from the transmitter, the output signal of the amplifier circuitry being delivered to receiver circuitry.

Abstract: An autodyne phenomenon in the O-type Weak-Resonant Backward Wave Oscillator of Ka-band working in chaotic oscillatory regime is under investigation. The main attention is paid to the studying of the action of decorrelated reflected signals on the modulation of the power spectral density of the chaotic oscillations. Physical mechanisms are revealed and phenomenological model is suggested to explain the strong PSD modulation observed under the affect of the small refelected signal. The PSD modulation index has been introduced and its anomalous increase with the enlargement of the distance to the load is revealed experimentally, as well as the physical explanation for that effect is presented. All physical results obtained are valid for the autodyne effect in any chaotic oscillator. The results obtained can be used for the design of different autodyne based devices for the remote sensing, microwave telemetry and control systems.

Abstract: In this paper, we analyze the power dissipation mechanisms and derive the overall power efficiency of a Class D output stage realized using the finger and waffle layouts. We propose two design methodologies to determine the aspect ratios of the transistors in the output stage for optimum power efficiency: (i) optimization to a single modulation index point, and (ii) optimization to a range of modulation indices. For the design of an output stage with optimum power efficiency (and small IC area), we recommend the waffle layout realization optimized to a range of modulation indices. The theoretical analysis and derivations are verified on the basis of computer simulations and measurements on fabricated prototype ICs.

Abstract: Using the amplitude-modulation pulse (AMP) representation of continuousphase modulation (CPM) introduced more than a decade ago by Laurent, the power spectral density (PSD) of minimum-shift-keying (MSK)-type modulations (modulation index equal to one-half) is computed in the presence of data imbalance The advantage of this technique is that closed-form expressions can be obtained that clearly elucidate the partitioning of the spectrum into components due to the efiective AMP pulse shapes and those due to the AMP sequence correlations As such, these expressions give insight into the nature of the PSD distortion produced by the imbalance, ie, a tilt in the main lobe and a relative unbalance between the upper and lower side-lobe levels caused by the correlation between the in-phase (I) and quadrature-phase (Q) components of the complex AMP data sequences and the correlation between the sequences themselves It is demonstrated that data imbalance does not change the rate at which the side lobes roll ofi It also is shown that, for all practical purposes, the PSD can be computed based on a two-pulse stream AMP approximation

Abstract: The invention relates to a data transmission method and transmitter comprising an encoder (204), a first multiplier (212) for multiplying a signal to be transmitted by a modulation index, and a frequency modulator (220). The signal to be transmitted may have different data rates. To advantageously enable the transmission of different data rates, the transmitter comprises means (212, 216) for multiplying the signal to be transmitted by the modulation index which depends on the data rate of the signal to be transmitted.

Abstract: In order to evaluate the cortical model proposed in Todd [these proceedings] it was applied to the phenomenon of modulation detection. It was assumed that a discrimination task involves the correlation of the spatio‐temporal power spectra of two image sequences, such as may occur in a typical 2A‐2IFC procedure. The correlation was computed by k(1−r), where r is the product moment correlation, for four different modulation frequencies, 4, 16, 64, and 256 Hz at four modulation depths for both AM and FM of a 1000‐Hz carrier of 1000‐ms duration against the image power spectrum of an unmodulated 1000‐Hz 1000‐ms tone. The obtained measures were then linearly regressed (with no intercept) as a function of the square of the modulation index. In all cases k(1−r) gave a good fit (R2>0.95) for both AM and FM. For each of the modulation frequencies the slope of the regression could be used to estimate the model thresholds. The model shows the correct behavior for AM and FM detection. This mechanism, it is suggested, ...

Abstract: A phase locked loop based architecture is proposed for generation and frequency stabilization of direct Gaussian minimum shift keying (GMSK) at microwave and millimeterwave frequencies. A continuous phase frequency shift keyed (CPFSK) signal with a modulation index of 0.5 is produced at the desired output frequency using a full 360 degree linear continuous phase modulator that is controlled by the integrated baseband information signal. This modulated signal is used as the reference signal for a phase locked high power voltage controlled oscillator. The phase locked loop facilitates reference signal frequency tracking and provides Gaussian spectral shaping to the modulated output signal. Phase locked loop imperfections and their effect on the modulated output signal are considered and simulation results are presented.

Abstract: The ability to detect periodic irregularity in the temporal envelope of a modulated stimulus was measured with a 2IFC procedure. Irregular amplitude modulation (AM) was generated with a periodic phase modulation (PM) of the sinusoidal modulator of wideband noise. The modulation index of the PM was adaptively varied in terms of delta envelope rate to determine the threshold to just detect the PM of the sinusoidal amplitude modulation (SAM). Base SAM rate ranged from 4 to 256 Hz. For each SAM rate, the PM rate ranged from 2 to half the SAM rate. The PM waveshape was either sinusoidal or had linear ramps with slope varied across conditions. At low SAM rates, PM waveshape had little effect with thresholds across conditions rising with PM rate. At higher SAM rates, an effect of waveshape was obtained; thresholds were highest at lower PM rates with a steeply sloping linear‐ramped PM. For the other PM waveshapes at the higher SAM rates, thresholds were roughly constant across change in PM rate. Results suggest two rate regions in processing AM with the regions separated at roughly the corner frequency of the temporal modulation transfer function. [Work supported by NIH and AFOSR.]

Abstract: High-frequency self-pulsing effects in combined index and gain coupled two-section DFB lasers in a single cavity laser are investigated by numerical simulations. The gain coupling increases the modulation index and frequency of the intensity oscillations. The results show that the signals of oscillation frequencies up to 200 GHz may be possible to generate using such devices.

Abstract: In this paper we study the influence of random noise on route to chaos followed by directly modulated laser diode as we found that is more complex than just a Feigenbaum sequence. We have already shown that when the laser is modulated at twice its resonance frequency and the modulation index is increased, a period tripling stable solution coexists with the Feigenbaum sequence for certain values of the modulation index, giving rise to hysteresis loops and chaotic bifurcations. This coexistence gives the noise a relevant role in determining the dynamic behavior. We have studied the route to chaos of the laser diode when the random noise fluctuations are introduced in the model. For this study, we have used three different numerical methods. We have employed a single step fourth order Runge- Kutta algorithm, which has been commonly used in previous studies, and its results have been compared to those provided by two stochastic integration methods: Euler- Maruyama and a stochastic Heun method. In all three cases, the behavior evolves from the single periodic response through period doubling, period quadrupling and period tripling in accordance with recent experimental studies, showing that in the route to chaos, the period doubling sequence is effectively truncated due to random noise. The reason for the truncation is found in the nearby coexisting period three solution. Nevertheless, the Runge-Kutta algorithm smoothes off the random noise fluctuations, probably due to its large correlation time.

Abstract: A new modified command voltage of the third harmonics injected PWM inverter is proposed in overmodulation mode. By analyzing the relationship between the modulation index and the peak of the fundamental component of the modified reference voltage, we can settle the problem in over modulation mode without iteration Then we can increase the maximum fundamental component of the third harmonics injected PWM inverter comparative to six-step inverter continuously in over modulation mode.

Abstract: In practical analog/digital hybrid optical transmission, carriers are modulated by video signals or digital data, and the amplitude of a multiplexed signal composed of these modulation signals is more compressed than that of the carriers. This causes a decrease in the frequency of clipping of the multiplexed signal at the laser threshold. Consequently, the BER of the M-QAM signal in a practical hybrid transmission is lower than that of the experimental results for same optical modulation index (OMI). However, it is difficult to prepare many practical modulation signals for experiments in a laboratory. Therefore, there is demand for a BER analysis method for a multiplexed signal that includes modulation signals needs to evaluate the BER and determine optimum OMI in a practical hybrid transmission. In this paper, we describe such a BER analysis method that can effectively estimate the BER in a practical hybrid transmission by using representative profiles of the modulation signals. In practical systems, a black pictures gives the largest averaged amplitude for the AM-VSB signal, and the most severe conditions for clipping occurrences. However, in such systems, the BER was greatly improved over the BER of a multiplexed signal of carriers. Furthermore, BER degradations due to clipping can be neglected for the AM-VSB signals in setting a practical OMI range.

Abstract: High-frequency self-pulsing effects in combined index and gain coupled two-section DFB lasers in a single cavity laser are investigated by numerical simulations. The gain coupling increase the modulation index and frequency of the intensity oscillations. Simulation results show that the signals of oscillation frequencies up to 200 GHz may be possible to generate using such devices. Preliminary experimental results agree well with simulation.

Abstract: The Bragg network photo-etching technique directs ultra-violet (UV) light onto an optical guide (4) to form an apodisic (continuous variation of the modulation index). Bragg network response. The continuously variable formation is achieved using a variable position masking element (10) with a rotating printing mask (50) producing a variable modulation curved response.

Abstract: In a parametric array, highly directional low‐frequency sound is generated by the self‐demodulation of an intense, amplitude‐modulated high‐frequency sound beam as a result of nonlinear propagation effects. The term ‘‘audio spotlight’’ was introduced by Yoneyama et al. [J. Acoust. Soc. Am. 73, 1532 (1983)] for a parametric array in air used to generate directional audio frequency sound with an ultrasonic primary beam. Berktay’s far‐field solution [Berktay, J. Sound Vib. 2, 435 (1965)] predicts a demodulated secondary waveform along the axis of the beam that is proportional to the second time derivative of the square of the modulation envelope. The secondary wave is therefore generated with high levels of harmonic distortion, even at moderate modulation indexes [Blackstock, J. Acoust. Soc. Am. 102, 3106(A) (1997)]. Integrating the modulation signal twice and taking the square root removes this distortion; however, the resulting reduction in distortion due to taking the square root is severely limited by the bandwidth of the primary beam transducer. Here, the characteristics of the transducer are taken into account in developing an appropriate predistortion scheme to achieve high quality reproduction. Relationships between distortion, modulation index, secondary bandwidth, and secondary sound‐pressure level are also discussed, and results of simulations are presented. [Work supported in part by ARL:UT IR&D.]

Abstract: We report the modulation characteristics of a waveguide-type optical frequency comb generator (WG-OFCG) with the advantages of compactness, high modulation index and low driving power. The characteristics of the optical frequency comb (OFC) generated when the modulation index exceeds 2/spl pi/ are discussed. The power of the modulation sidebands was measured by the optical heterodyne method with an external-cavity laser as a local oscillator. The dependence of the modulation index of the WG-OFCG on the modulation frequency up to 40 GHz was measured. The generation span of the OFC at the modulation frequency detuned from an integer multiple of the free spectral range (FSR) is discussed.