8 QAM Constellation Diagram Quiz & Flashcards

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the key feature of Offset-QPSK (OQPSK) modulation compared to standard QPSK?

Higher data rate

I and Q channel bit waveforms are not phase-shifted

I and Q channel bit waveforms are phase-shifted by half a bit time (correct)

Lower spectral efficiency

What is the number of possible conditions in a QPSK modulation scheme?

4 (correct)

In a QPSK modulator, how many possible output phases can be generated for each dibit code?

4 (correct)

How many bits are encoded to form tribits in an 8-PSK modulation scheme?

3 Signup and view all the answers

What is the number of different output phases produced in an 8-PSK modulation scheme?

8 Signup and view all the answers

In Quadrature-Amplitude Modulation (QAM), what combination does each symbol carry information about?

Both Phase and Amplitude Signup and view all the answers

What is the minimum double-sided Nyquist bandwidth (fN) for an 8-PSK modulator with an input data rate of 10 Mbps?

30 MHz Signup and view all the answers

In a 16-PSK modulation, how many different output phases are possible?

16 Signup and view all the answers

In Quadrature-Amplitude Modulation (QAM), where is the digital information contained?

In both the amplitude and the phase Signup and view all the answers

What is the relationship between bandwidth and baud for 16-PSK modulation?

$f_b = 4B$, $B = 4f_b$ Signup and view all the answers

Which type of modulation combines amplitude and phase shifts to optimize signaling elements' positions on constellation diagrams?

OQPSK Signup and view all the answers

For an 8-PSK modulator with a carrier frequency of 70 MHz, what would be the baud if the input data rate is 20 Mbps?

$\frac{1}{4}$ MHz Signup and view all the answers

What is the bandwidth efficiency defined as?

Ratio of the transmission bit rate to the minimum bandwidth required for a particular modulation scheme Signup and view all the answers

In Quadrature-Amplitude Modulation (QAM), what does the 'Q' stand for?

Quadrant Signup and view all the answers

What is the minimum double-sided Nyquist frequency, and baud for a 16-QAM modulator with an input data rate of 10 Mbps and a carrier frequency of 70 MHz?

fN = 35 MHz, Baud = 5 Msps Signup and view all the answers

What is the purpose of using Quadrature Phase-Shift Keying (QPSK) modulation in communication systems?

To double the transmission rate without increasing the bandwidth Signup and view all the answers

How many distinct phases are typically used in 8-PSK modulation?

8 Signup and view all the answers

What does the 'O' in Offset Quadrature Phase-Shift Keying (OQPSK) refer to?

Original Signup and view all the answers

Study Notes

Phase-Shift Keying (PSK)

BPSK (Binary PSK): N = 2, M = 2
QPSK (Quaternary PSK): N = 2, M = 4
QPSK combines binary input data into groups of two bits (dibits) and generates one of four possible output phases (45°, 135°, 45°, and 135°)

QPSK

QPSK transmitter: generates four possible output phases based on dibits
QPSK truth table: shows the relationship between dibits and output phases
QPSK phasor diagram: represents the output phases
QPSK constellation diagram: represents the possible states of the signal
QPSK bandwidth and baud: 𝑓𝑏 𝐵= 2 𝑓𝑏 𝑏𝑎𝑢𝑑 = 2

QPSK Sample Problem

For a QPSK modulator with an input data rate (fb) of 10 Mbps and a carrier frequency of 70 MHz, determine the minimum double-sided Nyquist bandwidth (fN) and the baud

Offset-QPSK (OQPSK)

Modified form of QPSK where the bit waveforms on the I and Q channels are offset or shifted in phase from each other by one-half of a bit time
OQPSK transmitter: generates four possible output phases based on dibits
OQPSK constellation diagram: represents the possible states of the signal

8-PSK

8-PSK: three bits are encoded, forming tribits and producing eight different output phases
8-PSK transmitter: generates eight possible output phases based on tribits
8-PSK truth table: shows the relationship between tribits and output phases
8-PSK phasor diagram: represents the output phases
8-PSK constellation diagram: represents the possible states of the signal
8-PSK bandwidth and baud: 𝑓𝑏 𝐵= 3 𝑓𝑏 𝑏𝑎𝑢𝑑 = 3

8-PSK Sample Problem

For an 8-PSK modulator with an input data rate (fb) of 10 Mbps and a carrier frequency of 70 MHz, determine the minimum double-sided Nyquist bandwidth (fN) and the baud

16-PSK

16-PSK: an M-ary encoding technique where M=16; four bits (called quadbits) are combined, producing 16 different output phases
16-PSK bandwidth and baud: 𝑓𝑏 𝐵= 4 𝑓𝑏 𝑏𝑎𝑢𝑑 = 4
16-PSK truth table: shows the relationship between quadbits and output phases
16-PSK constellation diagram: represents the possible states of the signal

Quadrature-Amplitude Modulation (QAM)

Form of digital modulation similar to PSK except the digital information is contained in both the amplitude and the phase of the transmitted carrier
Amplitude and phase-shift keying are combined to optimize the distance between elements on the constellation diagram

8-QAM

8-QAM transmitter: generates eight possible output phases based on input data
8-QAM output wave: represents the modulated signal
8-QAM truth table: shows the relationship between input data and output phases
8-QAM phasor diagram: represents the output phases
8-QAM constellation diagram: represents the possible states of the signal
8-QAM bandwidth and baud: 𝑓𝑏 𝐵= 3 𝑓𝑏 𝑏𝑎𝑢𝑑 = 3

16-QAM

16-QAM transmitter: generates 16 possible output phases based on input data
16-QAM truth table: shows the relationship between input data and output phases
16-QAM phasor diagram: represents the output phases
16-QAM constellation diagram: represents the possible states of the signal
16-QAM bandwidth and baud: 𝑓𝑏 𝐵= 4 𝑓𝑏 𝑏𝑎𝑢𝑑 = 4

Bandwidth Efficiency

Bandwidth efficiency: ratio of the transmission bit rate to the minimum bandwidth required for a particular modulation scheme
Bandwidth efficiency formula: 𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝑟𝑎𝑡𝑒 (𝑏𝑝𝑠) 𝐵𝜂 = 𝑚𝑖𝑛𝑖𝑚𝑢𝑚 𝑏𝑎𝑛𝑑𝑤𝑖𝑑𝑡ℎ (𝐻𝑧)

Bandwidth Efficiency Sample Problem

For an 8-PSK system, operating with an information bit rate of 24 kbps, determine (a) baud, (b) minimum bandwidth, and (c) bandwidth efficiency

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on Quadrature-Amplitude Modulation (QAM) with questions about 8-QAM and 16-QAM transmitters, truth tables, phasor diagrams, constellation diagrams, bandwidth, and baud rates.

Quadrature-Amplitude Modulation (QAM) Transmitter and Diagrams Quiz

Choose a study mode