Vol.:(0123456789) 1 3 Iranian Journal of Science and Technology, Transactions of Electrical Engineering https://doi.org/10.1007/s40998-019-00188-5 RESEARCH PAPER Dual‑Message Amplitude Modulation (DMAM) Mosslem Amiri 1  · Mohammad Ali Masnadi‑Shirazi 2  · Mahdi Hatam 3 Received: 17 August 2016 / Accepted: 4 March 2019 © Shiraz University 2019 Abstract In this paper, a new method is proposed for AM modulation of two separate messages (dual message). The proposed method uses only one carrier and does not need any transformer or multiplexer device, while the existing methods need two carriers or a transformer or a multiplexer device for modulating a dual message. The procedure of this modulation is quite simple. First, the carrier signal is divided into positive and negative half cycles. Then, one of the message signals is inserted into positive half cycles by a simple voltage-controlled resistor (e.g., a JFET in the linear region). Another message signal is inserted into negative half cycles using the same process. Finally, the half cycles are added together and the resultant signal would have two different envelopes on negative and positive half cycles. Detection of these two messages is easy too. The demodulator consists of two simple diode detectors. One of them gets the message signal from positive half cycles, and the other gets the negative half cycles signal. Altogether, the most important advantages of this design compared to the existing methods for modulating a dual message are less power consumption and more simplicity of modulating and demodulating procedures and circuits. In addition, this method decreases the cost of the modulator system. Keywords Dual-message amplitude modulation · Message signals · RF carrier · JFET attenuator network · Envelope demodulator · Frequency analysis 1 Introduction Plenty of electronics systems have dual relative signals. Sys- tems like TV- and other AV (audio–video)-based systems, RDS (radio data systems), VOIP, and multimedia network systems and also industrial sensors such as dual-axis mag- netic sensors and liquid-quality sensors use this type of sign- aling. Since all the modulation systems traditionally used to be designed for systems with a single message, transmis- sion of dual relative signals could be an issue for designers. Clearly, dual-message systems can use two separate a single- message modulators such as DSB to modulate two relative messages. Although in some cases SSB and QAM can be used as alternative methods, they do not grant simplicity and efficiency of DSB. In this paper, a new method is proposed for AM modulation of two separate messages (dual mes- sage). This method can provide a proper way for mentioned systems to modulate and transmit dual signals by an efficient procedure and a very simple hardware. It is an important privilege for DMAM that modulates two messages simulta- neously without losing amplitude modulation advantages. We will describe the principles of DMAM (dual-message amplitude modulation) in the first two sections. Then, the major properties of the output signals will be described in the next two sections. In the sixth section, the demodulation circuit of DMAM is described. Applications of the proposed system, as well as comparison with existing methods, will be studied in the next sections. Then, an example of modulation of two real and non-sinusoidal messages will be illustrated in a separate section and also effects of non-ideal components and parasitic reactive elements will be studied. Finally, the pros and cons of the proposed method will be described. * Mosslem Amiri mosslem.amiri@gmail.com Mohammad Ali Masnadi-Shirazi masnadi@shirazu.ac.ir Mahdi Hatam mahdihatam@shirazu.ac.ir 1 Automation and Instrumentation Department, HGS Ltd., Shiraz, Iran 2 Department of Communications and Electronics, School of Electrical and Computer Engineering, Shiraz University, Shiraz, Iran 3 Independent researcher, Independent researcher, Shiraz, Iran