Published on Nov 30, 2023
Modulation is the process of converting information that can be sent successfully through a medium. The various modulation schemes have contributed towards success of wireless standards, providing efficient transmission with minimal bandwidth and power requirements.
Sampling and Quantization digitize the analog information, and differ from Digital Modulation, where the digital symbols are transmitted across the analog channel.
The Quadrature Form of Modulator using In-phase (I) and Quadrature-phase (Q) channel method acts as the predominant method used in digital modulation. Basically the information bits are given to band-pass signal processing which splits the given bits into two streams as I and Q.
This is a conventional way of doing modulation in which channel I and Q are not transmitted but only the real signal is transmitted. The channel I and Q are independent to each other and is used to create the symbol. Hence QAM is said to be a two dimensional signal.
Quadrature Amplitude Modulation (QAM) is one of the most popular digital modulations. The term "Quadrature" implies, the carrier can have one of the four possible phases, at a given time slot. The phase shift of 90º in each time period, gives four possible states in the complete cycle of 360º. In this type of digital modulation, each phase shift represents 2-bits of information, called ' Symbol '.
Hence it has four symbols in total and each stands for two bits. The means of conveying information through phase variations i.e. the cosine carrier is varied in phase and amplitude is called Quadrature Amplitude Modulation (QAM). Although, this process may seem to be insignificant at initial stage, but this modulation scheme enables the carrier to transmit the 2-bits of information instead of 1-bit. This doubling makes the bandwidth of the carrier, more effective
• Reduced Power dissipation
• Higher throughput rate.
• Higher processing speed
• Fast Computation .
• LFSR can rapidly transmit a sequence that indicates high-precision relative time offsets
• Pattern Generators
• Built-In Self-Test(BIST)
• Encryption.
• LFSR can be used for generating pseudo-random numbers, pseudo-noise sequences, fast digital counters, and whitening sequences.
Pseudo-Random Bit Sequences
VHDL
Simulation: modelsim5.8c
Synthesis: Xilinx 9.1
