2021-07-08

## What is block diagram of QPSK and its working?

The QPSK Modulator uses a bit-splitter, two multipliers with local oscillator, a 2-bit serial to parallel converter, and a summer circuit. Following is the block diagram for the same. At the modulator’s input, the message signal’s even bits (i.e., 2nd bit, 4th bit, 6th bit, etc.)

### What is the symbol duration of QPSK?

In QPSK, the phase-shift θ(t) assumes one of the four constant values for every two input bits (i.e., the entire duration of a symbol), depending on the two consecutive bits being transmitted.

#### What’s the difference between BPSK and QPSK modulation?

For BPSK modulation the symbol duration for each bit is same as bit duration, but for QPSK the symbol duration is twice the bit duration: . Therefore, if the QPSK symbols were transmitted at same rate as BPSK, it is clear that QPSK sends twice as much data as BPSK does.

How is quadrature phase shift keying ( QPSK ) different from BPSK?

The Quadrature Phase Shift Keying (QPSK) is a variation of BPSK, and it is also a Double Side Band Suppressed Carrier (DSBSC) modulation scheme, which sends two bits of digital information at a time, called as bigits. Instead of the conversion of digital bits into a series of digital stream, it converts them into bit pairs.

How is demodulation done with QPSK in MATLAB?

The simulation involves, generating random message bits, modulating them using QPSK modulation, addition of AWGN channel noise corresponding to the given signal-to-noise ratio and demodulating the noisy signal using a coherent QPSK receiver. The waveforms at the various stages of the modulator are shown in the Figure 4.

## How is the QPSK signal defined within a symbol?

The QPSK signal within a symbol duration is defined as Therefore, the four possible initial signal phases are and radians. Equation (1) can be re-written as The above expression indicates the use of two orthonormal basis functions: together with the inphase and quadrature signaling points: .