Abstract: A waveform synthesizer is controlled in response to a stored program control utilizing tabular data stored in memory as the basis for generating timing signals to drive the power switching devices of the synthesizer. A plurality of tables of differing modulation indices define rated current output and a below rated current output. The table defines rated level output timing signals as both pulse width and frequency modulated to reduce harmonics. Various overload conditions result in selection of different modulation indices or a total current shutdown. A high peak current overload results in a halt in a progressive upward selection of modulation indices during start-up. A high average current overload results in a reduction in modulation indices until the overload has cleared. A low converter voltage signal caused by current limiting in the converter is detected and also used to reduce the modulation index so that less DC current is drawn from the converter and operation is maintained near the maximum average output power capability of the converter.

Abstract: Existing frequency domain models for the active mode locking of diode lasers are appropriate for antireflection- (AR-) coated devices This paper presents the first frequency domain model for non-AR-coated devices The use of uncoated devices permits the independent measurement of all of the important laser parameters required for the model, so that no adjustable parameters are needed An additional novel feature of this model is that the effect of gain saturation on the exact shape of the gain waveform is allowed for in a completely self-consistent fashion Experimental studies were carried out on uncoated undegraded commerical laser diodes Threshold reductions of 25-30 percent were achieved for external cavity operation The mode-locking studies reported in this paper were carried out above the external threshold current, with a sinusoidal modulation near 1 GHz at a modulation index of 4 percent The results of these studies showed good agreement with the predictions of the model presented here, in contrast with the predictions of the existing models Specifically, the modulation frequency corresponding to the shortest most intense mode-locked pulses was found to occur at a fraction of 1 percent below the frequency matched to the external cavity roundtrip time As well, the predicted effects of gain saturation were observed in the detailed structure of the mode-locked pulses, and in their detuning characteristics

Abstract: A nonuniform microstrip directional coupler with sinusoidally modulated coupling function is presented. The ripple and the amplitude response are controlled by the index of modulation m and the periodicity P of the function. For demonstration, a 20 dB ± 6% coupler is constructed on two different substrates and the experiment shows much flatter coupling response than the uniform or exponential line directional couplers.

Abstract: PURPOSE:To detect out-of-lock suitably, by providing two frequency dividers having the same frequency-division each for an output of a reference oscillator and a VCO of a PLL circuit including a phase modulator and giving the output to an EX-OR circuit. CONSTITUTION:Outputs of a reference oscillator 2 and a VCO5 of a PLL circuit 1 provided with a phase modulator 6 after a phase comparato 3, are provided with frequency dividers 21 and 22 having the same frequency-division M. The outputs of the frequency dividers 21 and 22 are inputted to an EX-OR circuit 7 and the output of the circuit 7 is inputted to a level discriminator 9 via an integration circuit 8. The slope of the output of the circuit 8 is mitigated in comparison with the absence of the frequency dividers and the fluctuation width of the output of the circuit 8 is decreased to 1/M with the M frequency-division. Thus, the threshold value of the circuit 9 discriminating out-of-lock can be set to the outside of range of fluctuation due to modulation. The suitable setting of frequency-division M prevents mis-detection of normal modulation as out-of-lock even with a large modulation index.

Abstract: It was observed that an increase in the amount of modulation beyond a certain limit resulted in a rapid decrease of the amplitude of the demodulated signals in a frequency modulated (FM) acoustic system. In order to explain this phenomenon, the demodulated signals have been analyzed taking the frequency characteristics of the system into account. The numerical calculations agreed with the experimental ones qualitatively and the analysis gave a criterion for the upper limit of the modulation index.

Abstract: Rectangular-wave modulated pulse lengths are expressed as a function of the modulation index. The theoretical expressions are experimentally verified. An experimental measurement of signal-to-noise ratio for rectangular-wave modulation confirms the theoretical analysis. Jelonek's signal-to-noise ratio formula for pulse-length modulation is also found applicable to rectangular-wave modulation. It is concluded that rectangular-wave modulation is closed-loop pulse-length modulation.

Abstract: The phenomenon of ultraharmonic synchronization of a class-C oscillator in response to a pure FM signal has been discussed in this paper. The variation of locking range of the oscillator with input modulation index and the influence of the time constant of the automatic biasing circuit on the locking time of the oscillator have been studied. The necessary mathematical tool has been developed and the differences between the locking characteristics of class-C and class-A oscillators have been pointed out. Experiments have also been performed in support of the theory developed.

Abstract: Rectangular-wave modulated pulse lengths are expressed as a function of modulation index. The theoretical expressions are experimentally verified. A pulse-length modulation (PLM) system is obtained...