Abstract:

The document discusses Quadrature Amplitude Modulation (QAM) in the context of digital radio
communication. It provides an overview of QAM, its advantages, and its application in achieving
high data rates. The document also includes detailed explanations and diagrams for 8-QAM and
16-QAM modulation techniques. Additionally, it covers the bandwidth considerations for both
modulation techniques and describes the receivers for each.

Chapter 1: Introduction to QAM

- QAM is a digital modulation technique where the digital information is contained in both the
amplitude and phase of the transmitted carrier.
- QAM combines Amplitude Shift Keying (ASK) and Phase Shift Keying (PSK) to optimize the
signaling elements' positions on the constellation diagrams.

Chapter 2: 8-QAM Modulation

- 8-QAM is an M-ary encoding technique with 8 possible amplitude-phase combinations.
- The output signal from an 8-QAM modulator is not a constant-amplitude signal.
- The 8-QAM transmitter block diagram and truth table for 2-to-4 level converters are provided.
- An example is given to determine the output amplitude and phase for a specific input in the 8-
QAM modulator.

Chapter 3: 8-QAM Bandwidth Consideration

- The bit rate in the I and Q channels for 8-QAM is one-third of the input binary rate.
- The highest fundamental modulating frequency and fastest output rate of change in 8-QAM are
the same as in 8-PSK.
- The minimum Nyquist bandwidth formula is used to calculate the bandwidth for 8-QAM
modulation.
Chapter 4: 8-QAM Receiver
- 8-QAM receivers are mostly identical to 8-PSK receivers with differences in the PAM levels at
the output of the product modulator and the binary signals at the output of the analog-to-digital
converters.
- The binary output signals from the I channel analog-to-digital converter are the I and C bits, and
the binary output signals from the Q channel analog-to-digital converter are the Q and C bits.

Chapter 5: 16-QAM Modulation

- 16-QAM is an M-ary system with 16 possible amplitude-phase combinations.
- Both the phase and amplitude of the transmit carrier are varied in 16-QAM.
- The 16-QAM transmitter block diagram and truth tables for 2-to-4 level converters are provided.
- An example is given to determine the output amplitude and phase for a specific input in the 16-
QAM modulator.

Chapter 6: 16-QAM Bandwidth Consideration

- The bit rate in the I, I', Q, or Q' channel for 16-QAM is equal to one-fourth of the binary input
data rate.
- The 2-to-4 level converters see a change in their inputs and outputs at a rate equal to one-fourth
of the input data rate in 16-QAM.
- The minimum Nyquist bandwidth formula is used to calculate the bandwidth for 16-QAM
modulation.

Chapter 7: Example Calculation

- An example is provided to calculate the minimum double-sided Nyquist frequency and the baud
rate for a 16-QAM modulator with specific input data rate and carrier frequency.

Summary:

On page 3, it is mentioned that Quadrature Amplitude Modulation (QAM) is a digital modulation

technique where the digital information is encoded in both the amplitude and phase of the
transmitted carrier. It combines Amplitude Shift Keying (ASK) and Phase Shift Keying (PSK) in
a way that optimizes the positions of signaling elements on the constellation diagrams, reducing
the likelihood of misinterpretation between elements. This page also provides the address of the
Technological University of the Philippines.

On page 4, it is stated that the most reliable method to achieve high data rates in a narrowband
channel is by increasing the number of bits per symbol. By using Quadrature Amplitude
Modulation (QAM), a finite number of allowable amplitude-phase combinations can be utilized to
encode the digital information. Additionally, the formula for the average power of a QAM signal
is provided

On page 6, the document explains that 8-QAM (8-Quadrature Amplitude Modulation) is an M-

ary encoding technique where the number of possible amplitude-phase combinations is 8. Unlike
8-PSK (8-Phase Shift Keying), the output signal from an 8-QAM modulator is not a constant-
amplitude signal.

On page 7, the document presents the block diagram of an 8-QAM transmitter and the truth table
for 2-to-4 level converters. The block diagram illustrates the components involved in the 8-QAM
transmission process, showcasing the different stages and their interconnections. The truth table
for 2-to-4 level converters outlines the input and output combinations for this specific conversion
process

On page 8, an example calculation is provided for an 8-QAM transmitter. The input is given as Q
= 0, I = 0, and C = 0 (000). The page instructs to determine the output amplitude and phase for this
input based on the 8-QAM transmitter's block diagram.
On page 10, the document discusses the bandwidth consideration for 8-QAM modulation. It states
that the bit rate in the I and Q channels for 8-QAM is one-third of the input binary rate, which is
also the case for 8-PSK modulation. The highest fundamental modulating frequency and fastest
output rate of change in 8-QAM are the same as in 8-PSK. The document then provides the formula
for calculating the minimum Nyquist bandwidth for 8-QAM modulation, which is given as 2 times
the inverse of the bit rate.

On page 11, the document discusses the 8-QAM receiver. It states that 8-QAM receivers are
mostly identical to 8-PSK receivers, with two key differences. First, the PAM (Pulse Amplitude
Modulation) levels at the output of the product modulator are different for 8-QAM compared to 8-
PSK. Second, the binary signals at the output of the analog-to-digital converters differ between the
two modulation techniques. In the case of 8-QAM, the binary output signals from the I channel
analog-to-digital converter are the I and C bits, while the binary output signals from the Q channel
analog-to-digital converter are the Q and C bits.

On page 13, the document describes 16-QAM (16-Quadrature Amplitude Modulation). It states
that like 16-PSK, 16-QAM is an M-ary system with 16 possible amplitude-phase combinations.
The input data is processed in groups of four, resulting in 16 possible combinations. Similar to 8-
QAM, both the phase and amplitude of the transmit carrier are varied in 16-QAM.

On page 14, the document presents the block diagram of a 16-QAM transmitter. This diagram
illustrates the components involved in the transmission process for 16-QAM modulation.
However, no specific details or explanations about the block diagram are provided on this page.

On page 15, the document provides the truth tables for the I- and Q-channel 2-to-4 level converters
in a 16-QAM transmitter. The truth tables outline the input and output combinations for these
specific converters in both the I and Q channels. However, no further details regarding the 16-
QAM transmitter or its components are provided on this page.

On page 16, an example calculation is provided for a 16-QAM modulator. The input is given as I
= 0, I' = 0, Q = 0, and Q' = 0 (0000). The page instructs to determine the output amplitude and
phase for this input based on the 16-QAM modulator's block diagram.

On page 18, the document focuses on the bandwidth consideration for 16-QAM modulation. It
states that in 16-QAM, the input data is divided into four channels, resulting in the bit rate in the
I, I', Q, or Q' channel being one-fourth of the binary input data rate. The page also highlights that
the I, I', Q, and Q' bits are outputted simultaneously and in parallel, causing the 2-to-4 level
converters to experience input and output changes at a rate equal to one-fourth of the input data
rate. Additionally, it states that in a 16-QAM modulator, a change in the output signal (either in
phase, amplitude, or both) occurs for every four input data bits.
On page 19, the document explores the bandwidth consideration for 16-QAM modulation. It
presents the calculation for the minimum Nyquist bandwidth, which is equal to half the bit rate
divided by 8.

On page 20, Example 3 is presented, which involves a 16-QAM modulator with an input data rate
of 10 Mbps and a carrier frequency of 70 MHz. The example aims to determine the minimum
double-sided Nyquist frequency and the baud rate. The calculation involves dividing the input data
rate by 4 to obtain the minimum double-sided Nyquist frequency. The baud rate is then calculated
by dividing the minimum double-sided Nyquist frequency by the number of phase and amplitude
levels in 16-QAM.