#DIGITAL TECHNIQUES PDF SERIES#
Instead of the conversion of digital bits into a series of digital stream, it converts them into bit-pairs. QPSK is a variation of BPSK, and it is also a DSB-SC (Double Sideband Suppressed Carrier) modulation scheme, which send two bits of digital information at a time, called as bigits. The following figure represents the QPSK waveform for two bits input, which shows the modulated result for different instances of binary inputs. If this kind of techniques are further extended, PSK can be done by eight or sixteen values also, depending upon the requirement. This is the phase shift keying technique, in which the sine wave carrier takes four phase reversals such as 0°, 90°, 180°, and 270°. Binary Phase Shift Keying (BPSK): Quadrature Phase Shift Keying (QPSK): In this technique, the sine wave carrier takes two phase reversals such as 0° and 180°.īPSK is basically a DSB-SC (Double Sideband Suppressed Carrier) modulation scheme, for message being the digital information.įollowing is the image of BPSK Modulated output wave along with its input. This is also called as 2-phase PSK (or) Phase Reversal Keying. They are − Binary Phase Shift Keying (BPSK): PSK is of two types, depending upon the phases the signal gets shifted.
#DIGITAL TECHNIQUES PDF BLUETOOTH#
PSK technique is widely used for wireless LANs, bio-metric, contactless operations, along with RFID and Bluetooth communications. Phase Shift Keying (PSK) is the digital modulation technique in which the phase of the carrier signal is changed by varying the sine and cosine inputs at a particular time. The other one is DPSK which changes the phase according to the previous value. These are mainly of two types, namely BPSK and QPSK, according to the number of phase shifts. The phase of the output signal gets shifted depending upon the input. The binary 1s and 0s are called Mark and Space frequencies.
The output of a FSK modulated wave is high in frequency for a binary HIGH input and is low in frequency for a binary LOW input. FSK is a scheme of frequency modulation.įollowing is the diagram for FSK modulated waveform along with its input. The frequency of the output signal will be either high or low, depending upon the input data applied.įrequency Shift Keying (FSK) is the digital modulation technique in which the frequency of the carrier signal varies according to the discrete digital changes. The binary signal when ASK is modulated, gives a zero value for LOW input and gives the carrier output for HIGH input. Amplitude Shift Keying:Īny modulated signal has a high frequency carrier. The amplitude of the resultant output depends upon the input data whether it should be a zero level or a variation of positive and negative, depending upon the carrier frequency.Īmplitude Shift Keying (ASK) is a type of Amplitude Modulation which represents the binary data in the form of variations in the amplitude of a signal.įollowing is the diagram for ASK modulated waveform along with its input. In this chapter, we will be discussing the most prominent digital modulation techniques. There are many types of digital modulation techniques and we can even use a combination of these techniques as well. Hence, digital modulation techniques have a greater demand, for their capacity to convey larger amounts of data than analog ones. Digital Modulation provides more information capacity, high data security, quicker system availability with great quality communication.