This paper proposes a noise reduction technology for a specific frequency band that uses the pulse coding controlled method to automatically set the notch frequency in DC-DC switching converters of communication equipment. For reducing the power levels at the frequency and its harmonics in the switching converter, we often use a frequency-modulated clock. This paper investigates a technology that prevents modulated clock frequency noise from spreading into protected frequency bands; this proposed noise reduction technology does not distribute the switching noise into some specified frequency bands. The notch in the spectrum of the switching pulses is created by the Pulse Width Coding (PWC) method. In communication devices, the noise in the receiving signal band must be as small as possible. The notch frequency is automatically set to the frequency of the received signal by adjusting the clock frequency using the equation Fn = (P+0.5)Fck. Here Fn is the notch frequency, Fck is the clock frequency, and P is a positive integer that determines the noise spectrum location. Therefore, simply be setting the notch frequency to the received signal frequency can suppress the noise present. We confirm with simulations that the proposed technique is effective for noise reduction and notch generation. Also we implement a method of automatic switching between two receiving channels. The conversion voltage ratio in the pulse width coding method switching converter is analyzed and full automatic notch frequency generation is realized. Experiments on a prototype circuit confirm notch frequency generation.

In this paper a chaotic spiking neuron is presented and its response characteristics to various periodic inputs are analyzed. A return map which can analytically describe the dynamics of the neuron is derived. Using the map, it is theoretically shown that a set of neurons can encode various periodic inputs into a set of spike-trains in such a way that a spike density of a summation of the spike-trains can approximate the waveform of the input. Based on the theoretical results, some potential applications of the presented neuron are also discussed. Using a prototype circuit, typical encoding functions of the neuron are confirmed by experimental measurements.

A new device consisting of an optical pulse generation section and pulse coding section monolithically integrated on a single-chip has been developed. The pulse generation section consists of a multiple quantum well (MQW) electroabsorption modulator integrated with an MQW DFB laser. The modulator operates at large-signal modulation and low voltage (from 2 to 3-V DC bias with a 3.2-V peak-to-peak RF signal). The second modulator is operated independently as a pulse encoder. An approximately transform-limited optical pulse train, whose full width at half maximum (FWHM) in the time domain is less than 17-ps and spectral FWHM is 28-GHz, is obtained with a repetition frequency of 10-GHz. Compressive strain is introduced in both InGaAsP quantum wells in order to obtain efficient device characteristics. These include a low threshold current (18-mA) for the laser, and low driving voltage (30-dB for 3-V swing) and high-speed operation (over 12-GHz for a 3-dB bandwidth) for the modulators. Demonstrations show that this new device generates short optical pulses encoded by a pseudo-random signal at a rate of 10 Gbit/s. This is the first time 10 Gbit/s modulation has been achieved with a multi-section electroabsorption modulator/DFB laser integrated light source. This monolithic device is expected to be applied to optical soliton transmitters.