Pembangkit Sinyal ELT pada Frekuensi 121,5 MHz

An ELT is a beacon indicating the location of distress or crash of aircraft on land or sea. The ELT is placed in an airplane, which is a transmitter with low transmit power and an antenna. The ELT transmitter has been widely used for flights at the frequency of 121.5 MHz (civilian) and 243 MHz (military). The purpose of this study is to produce ELT signal generators at the 121.5 MHz frequency, with low-cost devices that meet specifications for civil aviation. In this research has been produced a design of an ELT signal generator at the frequency of 121.5 MHz, consist of a crystal oscillator, a sawtooth generator, a VCO, and an amplitude modulator. Based on the measurement and test results, the sawtooth generator generated a sawtooth signal at the frequency of 1.8 to 3.6 Hz, the VCO generated a sinusoidal signal at the frequency of 316 to 366 Hz, the RF generator generated a sinusoidal at the frequency of 121.505 MHz. The ELT signal generator was able to generate AM signals at the minimum amplitude deviation of 100 mVpp to maximum one of 156 mVpp, the modulation index (m) of 21.875%, and the frequency of 121.505 MHz. The results of this study are ELT signal generators at the frequencies of 121.5 MHz that are in accordance with specifications for civil aviation.

Design of a Sawtooth Generator Applied for Class-D Audio Power Amplifier

A systematic introduction to principles and advantages of the class-D audio amplifier based on pulse width modulation (PWM) are presented in this paper. The traditional sawtooth generator needs voltage-regulator tube to server as a core component. Against to such a disadvantage a simple way based on the charging and discharging capacitance is proposed to achieve sawtooth generator. The circuit design is based on SIMC 0.18um process. Spectre simulation results show that the sawtooth generator's performance is good. And it suits for the design of class-D audio power amplifier chip.

Current-Controlled Sawtooth Generator

A simple current-controlled sawtooth generator is presented. Both the amplitude and the frequency of the generated sawtooth can be current-controlled. The circuit uses off-the-shelf components. Experimental results are included.