Now a day wireless technologies face the challenges of multipath signal fading, attenuation and phase delay which led to the interference between users and there is the possibility of limited spectrum. Linear and Non Linear receiver is used to combat
Orthogonal Frequency Division Multiplexing OFDM is an exceptional case of Frequency Division Multiplexing. The dilemma of OFDM is its sensitivity to frequency offset between the transmitted and received carrier frequencies. This frequency offset esta
Technological University of the Philippines College of Engineering Electronics Engineering Department
Digital Communications, Lec
Goupwork Quadrature Multiplexing
Submitted By: Landicho, Larish Mariam T. Lobo, Abigail D. Orubia, Carla Joy L. BSECE – 4A 4A
Submitted To: Engr. Maria Victoria Padilla
March 8, 2018
OBJECTIVE 1: To determine what quadrature multiplexing is and how it works. A Quadrature Carrier Multiplexing (QCM) or Quadrature Amplitude Modulation (QAM) is a form of modulation which is widely used for modulating data signals onto a carrier used for radio communications. It is widely used because it offers advantages over other forms of data modulation such as PSK, although many forms of data modulation operate alongside each other. It is a method enables two DSBSC modulated waves, resulting from two different message signals to occupy the same transmission band width and two message signals can be separated at the receiver. Questions: 1. Explain briefly how quadrature multiplexing works. . It conveys two analog message signals, or two digital bit streams, by changing (modulating) the amplitudes of two carrier waves, using the amplitude-shift keying (ASK) digital modulation scheme or amplitude modulation (AM) analog modulation scheme. The two carrier waves of the same frequency, usually sinusoids, are out of phase with each other by 90° and are thus called quadrature carriers or quadrature components — hence the name of the scheme. The modulated waves are summed, and the final waveform is a combination of both phase-shift keying (PSK) and amplitude-shift keying (ASK), or, in the analog case, of phase modulation (PM) and amplitude modulation. In the digital QAM case, a finite number of at least two phases and at least two amplitudes are used. PSK modulators are often designed using the QAM principle, but are not considered as QAM since the amplitude of the modulated carrier signal is constant. QAM is used extensively as a modulation scheme for digital telecommunication systems, such as in 802.11 Wi-Fi standards. Arbitrarily high spectral efficiencies can be achieved with QAM by setting a suitable constellation size, limited only by the noise level and linearity of the communications channel. 2. How many signals can be multiplexed? Multiplexing is a way of sending multiple signals or streams of information over a communications link at the same time in the form of a single, complex signal.
3. Draw a simplified block diagram of a quadrature multiplexer and demultiplexer. MULTIPLEXER
DEMULTIPLEXER
4. What does “quadrature” mean? In dictionary, it is the process of constructing a square with an area equal to that of a circle, or of another figure bounded by a curve.
