• # QPSK (Quadrature Phase Shift Keying)

QPSK (Quadrature Phase Shift Keying) is a phase modulation algorithm.

Phase modulation is a frequency modulation version where the carrier wave’s phase is modulated to encode bits of digital information in each phase change.

The “PSK” in QPSK refers to the use of Phased Shift Keying. Phased Shift Keying is a form of phase modulation that is accomplished by using a discrete number of states. QPSK refers to PSK with 4 states. With half that number of states, there is a BPSK (Binary Phased Shift Keying). With twice the number of states as QPSK, there is a 8PSK.

The “Quad” in QPSK refers to four phases in which a carrier is sent in QPSK: 45, 135, 225, and 315 degrees.

## QPSK Encoding

Because QPSK has 4 possible states, QPSK can encode two bits per symbol.

Phase Data
45 degrees Binary 00
135 degrees Binary 01
225 degrees Binary 11
315 degrees Binary 10

QPSK is more tolerant of link degradation than 8PSK, but does not provide as much data capacity.

1. #### Asmita Roy

12 June, 2017 at 7:23 am

What are the different parameters that change according to the change of modulation techniques?

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2. #### vinoth

27 February, 2012 at 9:26 am

Hi the \$5 deg equilent binasry is 2b1001 like that how i calculate cau help me plz

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3. #### Jonna

16 November, 2011 at 8:02 am

@Shaitan

Get matured soon. You are still a kid, learn to be a human from good people.

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4. #### Shaitan

26 May, 2011 at 1:59 pm

Where is signal representation you mother fuckers!!

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5. #### Asad

17 February, 2011 at 12:05 pm

Hi…. Nice article.

I have question stated below;

What is QPSK 0.5 Single, QPSK 0.5 Dual, QPSK 0.75 Single & QPSK 0.75 Dual?

I will be anxiosly waiting for reply. (asadtempestian@yahoo.com)

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• #### Shaitan

26 May, 2011 at 2:00 pm

Google pe daal mil jayega einstien ki olaad!!

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• #### aasad

25 November, 2015 at 8:58 pm

phudi kai why you even here?

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