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A Cyclic Shift Chirp Modulation Scheme for Analog Message with Simplified PPM Demodulation
(2026-01-01)
Kaew-In, Chanapat
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Wardkein, Paramote
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Chatchaiphat, Nisukan
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Chodkaveekityada, Peeramed
In this work, a cyclic shift chirp modulation scheme with an analog message signal is presented. The demodulation process is carried out by converting the cyclic shift chirp into pulse position modulation (PPM), followed by three demodulation approaches: (i) direct LPF filtering of the PPM pulses, (ii) inversion of the PPM pulses prior to LPF filtering, and (iii) integration driven by the PPM pulses. The recovered signal in these cases corresponds to the differentiated form of the original message signal. However, when the message signal is preintegrated before PPM modulation, the subsequent demodulation via integration directly yields the original message signal, eliminating the need for an additional integration stage at the receiver. This results in a simplified and less complex receiver compared to conventional PPM schemes without input pre-integration. Analytical and experimental results are in close agreement, validating the effectiveness of the proposed method.
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Pwm and Differential Pwm Generation Circuits Based on Conventional Schmitt Trigger Cooperating with Integrator: Analysis and Implementation
(2025-01-01)
Saechia, Sukkharak
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Kaew-In, Chanapat
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Chatchaiphat, Nisukan
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Wardkein, Paramote
This paper presents systematic approaches to generate the Pulse Width Modulation (PWM) signal by leveraging a simple configuration based on an operational amplifier (op-amp) comprising the Schmitt Trigger circuit and the integrator circuit. Two PWM modulation techniques are proposed according to the input position of the information signal. First, utilizing inverting terminal of the Schmitt Trigger circuit as an input terminal can function as the PWM modulator. The resulting PWM output exhibits its duty cycle proportional to the derivative of the input signal. Second, when input signal is applied to the non-inverting terminal of the integrator circuit, the generated PWM signal whose duty cycle is proportional to both input and its integral. To ensure that the generated PWM signal conveys the message correctly, PWM demodulator is used to validate and confirm the results. Therefore, both proposed configurations effectively function as PWM modulators for both information signal and its integral. Finally, the results of in-depth mathematical analysis are validated and align well with all experimental results.
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Discrete Time Two-Frequency Shift Keying
(2024-01-01)
Wardkein, Paramote
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Kaew-In, Chanapat
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Wanprasert, Thanaree
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Philuek, Pandaree
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Moonthongnoi, Nateekan
In this article, two-frequency shift keying is used to modify the time for generating the Time-Frequency Shift Keying (TFSK). Which both frequencies occupy different times and vary with a message. For this mechanism, it causes M-ary time-frequency pattern coding, where one pattern can code n bits if we have different 2n patterns, which overall code like a Pulse Width Modulation (PWM) combined with binary FSK. To confirm the proposed idea or technique, four-time-frequency coding is simulated with MATLAB, and an experiment is implemented with a commercial FSK IC. Both simulations and experimental results show that they are identical to predictions. Moreover, its bandwidth is predicted, and clock recovery is also implemented.

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