Uncategorized

Chapter 3: Oscillators, Phase-locked Loops, and Frequency Synthesizers – Review Notes

Chapter 3: Oscillators, Phase-locked Loops, and Frequency Synthesizers

This is the summary notes of the important terms and concepts in Chapter 3 of the book "Electronic Communications System" by Wayne Tomasi. The notes are properly synchronized and concise for much better understanding of the book.Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.


CHAPTER 3

OSCILLATORS,
PHASE-LOCKED LOOPS, ANDFREQUENCY SYNTHESIZERS


Items

Definitions

Terms

1

This word means to fluctuate between two states or conditions.

Oscillate

2

A device that produces oscillations or generates repetitive
waveform. Converts a dc input voltage to an ac output voltage.

Oscillator

3

A self-sustaining oscillator where the changes in the waveform
are continuous and repetitive; they occur at a periodic rate.

Free-running Oscillator

4

Are oscillators that are not self-sustaining requiring an
external input signal or trigger to produce a change in the output waveform?

Triggered or One-shot
Oscillators

5

An amplifier with a feedback loop or path for energy to
propagate from the output back to the input.

Feedback

6

According to this criterion, for a feedback circuit to sustain
oscillations, the net voltage gain around the feedback loop must be unity or
greater, and the net phase shift around the loop must be a positive integer
multiple of 360º.

Barkhausen Criterion

7

Is a positive feedback where the positive means that its phase
aids the oscillation process and does not necessarily indicate a positive or
negative polarity?

Regenerative Feedback

8

Is a negative feedback and supplies a feedback signal that
inhibits oscillations from occurring.

Degenerative Feedback

9

Is an untuned RC phase shift oscillator that uses both
positive and negative feedback? The oscillator that Hewlett and Packard used
in their original signal generator design.

Wien-bridge Oscillator

10

Added to the circuit to compensate for imbalances in the
bridge and variations in component values due to heat.

Automatic Gain Control
( AGC )

11

Are oscillator circuits that utilize LC tank circuits for the
frequency determining components?

LC Oscillators

12

An LC oscillator that uses a tapped coil.

Hartley Oscillator

13

The operation of this oscillator is very similar to that of
Hartley except that a capacitive divider is used instead of a tapped coil.

Colpitts Oscillator

14

An oscillator circuit identical to the Colpitts except with
the addition of a small capacitor Cs placed in series with L1.

Clapp Oscillator

15

The ability of an oscillator to remain at a fixed frequency.

Frequency Stability

16

Frequency stability affected predominantly by fluctuations in
dc operating voltages.

Short-term Stability

17

Frequency stability which is a function of component aging and
changes in the ambient temperature and humidity.

Long-term Stability

18

Feedback oscillator circuits where a crystal is used for the
frequency determining component.

Crystal Oscillator

19

The study of the form, structure, properties, and
classifications of crystals. It deals with lattices, bonding, and behavior of
slices of crystal material that have been cut at various angles with respect
to the crystal’s axes.

Crystallography

20

The _______ occurs when oscillating mechanical stresses
applied across a crystal lattice structure generate electrical oscillations
and vice versa.

Piezoelectric Effect

21

In this mode the oscillator is tuned at the third, fifth,
seventh, or even the ninth harmonic of the crystal’s fundamental frequency.

Overtone

22

The direction of frequency change is the same as the
temperature change.

Positive Temperature Coefficient

23

The change in frequency is in the direction opposite to the
temperature change.

Negative Temperature
Coefficient

24

Is almost a perfect zero-coefficient crystal from freezing to
boiling but is useful only at frequencies below a few hundred kilohertz.

GT-cut Crystal

25

A crystal oscillator circuit that has very good frequency
stability and reasonably simple circuitry.

Discrete Pierce Oscillator

26

A crystal oscillator circuit that has low cost and simple
digital interfacing capabilities.

IC-based Pierce Oscillator

27

A crystal oscillator circuit that has best frequency
stability.

RLC Half-bridge

28

Consists of a crystal-controlled oscillator and a
voltage-variable component such as a varactor diode.

Crystal Oscillator Module

29

A specially constructed diode whose internal capacitance is
enhanced when reversed biased, and by varying the reverse-bias voltage, the
capacitance of the diode can be adjusted.

Varactor Diode or Varicap

30

An oscillator circuit that generates well-defined, stable
waveforms that can be externally modulated or swept over a given frequency
range.

Waveform Generator

31

A monolithic function generator integrated circuit
manufactured by EXAR Corporation capable of producing high quality sine,
square, triangle, rap, and pulse waveforms with both a high degree of
stability and accuracy.

XR-2206

32

A free-running oscillator with a stable frequency of
oscillation that depends on an external timing capacitance, timing
resistance, and control voltage.

Voltage Controlled
Oscillator

33

A monolithic voltage controlled oscillator (VCO) integrated
circuit featuring excellent frequency stability and a wide tuning range. The
circuit provides simultaneous triangle- and square wave outputs over a
frequency range of from 0.01 Hz to 1 MHz.

XR-2207

34

A monolithic variable-frequency oscillator circuit featuring
excellent temperature stability and a wide linear sweep range.

XR-2209

35

A closed-loop feedback control system in which either the
frequency or the phase of the feedback signal is the parameter of interest
rather than the magnitude of the signal’s voltage or current.

Phase Locked Loop
( PLL )

36

The VCO’s output frequency when the PLL is not locked.

Preset/Natural Free Running
Frequency

37

The voltage produced by the phase comparator that is
proportional to the difference in frequency between the two signals.

Error Voltage

38

The PLL state when there is no external input frequency or the
feedback loop is open.

Free-Running State

39

The state when the PLL is in the process of acquiring
frequency lock.

Capture State

40

The state when the VCO output frequency is locked onto (equal
to) the frequency of the external input signal.

Lock State

41

The time required to achieve lock.

Acquisition Time

42

The band of frequencies centered around the VCO natural
frequency where the PLL can initially establish or acquire frequency lock
with an external input signal from an unlocked condition. Also known as
acquisition range.

Capture Range

43

The capture range expressed as a peak value.

Pull-in Range

44

The band of frequencies centered around the VCO natural
frequency over which a PLL can maintain frequency lock with an external input
signal. Also known as tracking range.

Lock Range

45

The lock range expressed as a peak value.

Hold-in Range

46

An oscillator with a stable frequency of oscillation that
depends on an external bias voltage.

Voltage-Controlled Oscillator

47

Sometimes called a phase detector which is a nonlinear device
with two input signals: an external input frequency and the VCO output
signal.

Phase Comparator

48

The difference in phase between an external input frequency
and the VCO output signal.

Phase Error

49

The product of the individual gains or transfer functions
around the loop for the PLL.

Loop Gain

50

An ultra stable monolithic phase-locked-loop system designed
by EXAR Corporation for a wide variety of applications in both analog and
digital communications systems. Can operate over a relatively wide frequency
range from 0.5 Hz to 35 MHz.

XR-215

51

PLL that are used to track digital pulses rather than analog
signals, such as in clock recovery circuits.

Digital PLL

52

This word means to form an entity by combining parts or
elements.

Synthesize

53

Are used to generate many output frequencies through the
addition, subtraction, multiplication, and division, of a smaller number of
fixed frequency sources.

Frequency Synthesizer

54

A method of frequency synthesis where multiple output
frequencies are generated by mixing the outputs from two or more
crystal-controlled frequency sources or by dividing or multiplying the output
frequency from a single-crystal oscillator.

Direct Frequency
Synthesis

55

A method of frequency synthesis where a feedback-controlled
divider/multiplier such as PLL is used to generate multiple output
frequencies.

Indirect Frequency Synthesis

56

The minimum frequency separation between output frequencies
for a synthesizer.

Resolution

57

An advanced dual-modulus low-power, ECL prescaler manufactured
by Signetics Company. The maximum input signal frequency is 1.2 GHz for
cellular and other land mobile applications.

NE/SA701

58

A bipolar, single-chip frequency synthesizer manufactured in
SUBILO-N technology (components laterally separated by oxide). It performs
all the tuning functions of a PLL radio-tuning system. Also manufactured by Signetics.

TSA6057/T

Complete List of Reviewers in Electronic Communications System per Chapter

Important List of Communications Engineering Materials

Leave a Reply

Your email address will not be published. Required fields are marked *