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# Pdf Square Law Amplitude Modulation And Demodulation

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The present invention relates to a demodulation device for a four phase modulated wave, more particularly to a Costas loop carrier recovery circuit which is suitably formed on a semiconductor integrated circuit and is excellent in a linearity. Since a digital phase modulation method for a carrier wave called a PSK Phase Shift Keying method is generally superior in its predetermined band characteristic and error ratio characteristic to other methods such as amplitude modulation, frequency modulation and bias modulation, the digital phase modulation method has been widely used for microwave digital communication using a microwave pulse code modulation, satellite broadcast communication and data transmission modems.

## Lab 1: Amplitude Modulator and Demodulator

In order to understand the theory along with the experiments behind this course, the review sections were prepared. Please see the instructor for any further information.

Analog Communication is an information transmitting mechanism, i. The significant invention made by Marconi in was a radio. Later, the foundation of Trans-Atlantic Communication Systems had been taken place. Although digital communications systems are much more efficient, cost-saving, more reliable, some communication systems are still analog. Taub, , p. In case of carrier, which could be used sine or cosine wave.

Practically, there is no difference except degree phase shift. Any signal is summed by a constant value means that this signal is raised by the same constant value with respect to the vertical axis in time domain. In order for the low-pass to detect the information envelope, the frequency of the carrier must be as high as possible. However, as you can imagine the noise from the nature i. As it is clearly seen that the AM model is exactly based upon the mathematical foundation provided in the theoretical section.

The message signal is multiplied by the modulation index, then it is added a DC carrier, finally is multiplied with a sinusoidal carrier signal in order to transmit the AM modulated signal. Apply the similar procedure. You will have the demodulation structure as shown in the following figure:.

Here, we will implement the DSB-AM baseband modulator and demodulator using a music file as a source. In this case, since the source is a multimedia file rather than a pure sine wave, we need the DSP process, which is the resampling and filtering. You will not be kept responsible for DSP processes. However, you can find them very useful when comprehending sampling rate, rate conversion, Finite Impulse Response FIR , decimation and interpolation etc.

You can also check the following resource:. Now, we will go one further step to transmit a music file, and then receive it via USRP hardware. In this case the transmission is real time, therefore unlike the simulations, you will observe the noise through the air. You will find them very useful while answering prelab questions and comprehending lab tasks.

The passband received signal after the demodulation is converted to baseband. This process is simply:. Connect the AWGN channel. Set the variance from mask as 0.

What do you observe in each case? Comment your result. Taub, D. Principles of Communication Systems 3rd ed. McGraw Hill. Boulmalf, Y. Toggle navigation ECE Labs. Figure 1: Basics of Analog Communications. Figure 2: Analog Modulation Techniques. Figure 3: AM Waveforms. Figure 5: Amplitude Modulation Model in Simulink. Figure 8:Signals in time scope. Figure 9: Results in Spectrum Analyzers. Figure Resampling. Figure Baseband Demodulation.

Figure Baseband Modulation and Transmission. Figure Resampling and Filtering. Figure Receiver. Figure Demodulation Blocks subsystem. Figure Model for the Task

## Amplitude Modulation

This article is available in PDF format for easy printing. An envelope detector of the series type is shown in Fig. Hello This video will explain the concept and working of envelop detector. A simple and e cient detector can improve the communication quality and reduce the cost. Their waveshapes for 2 a sinusoidal baseband signal are exemplified in Fig.

AM signal after square-law demodulation in time domain and frequency Carrier is modulated during amplitude modulation and frequency modula- tion.

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In order to understand the theory along with the experiments behind this course, the review sections were prepared. Please see the instructor for any further information. Analog Communication is an information transmitting mechanism, i. The significant invention made by Marconi in was a radio.

The circuit that generates the AM waves is called as amplitude modulator and in this post we will discuss two such modulator circuits namely :. Both of these circuits use a non-linear elements such as a diode for their implementation. Both these modulators are low power modulator circuits. Generation of AM Waves using the square law modulator could be understood in a better way by observing the square law modulator circuit shown in fig.

#### Square Law Modulator

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