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.
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CHAPTER 3 |
OSCILLATORS, PHASE-LOCKED LOOPS, ANDFREQUENCY SYNTHESIZERS |
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Items |
Definitions |
Terms |
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1 |
This word means to fluctuate between two states or conditions. |
Oscillate |
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2 |
A device that produces oscillations or generates repetitive waveform. Converts a dc input voltage to an ac output voltage. |
Oscillator |
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3 |
A self-sustaining oscillator where the changes in the waveform are continuous and repetitive; they occur at a periodic rate. |
Free-running Oscillator |
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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 |
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5 |
An amplifier with a feedback loop or path for energy to propagate from the output back to the input. |
Feedback |
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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 |
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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 |
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8 |
Is a negative feedback and supplies a feedback signal that inhibits oscillations from occurring. |
Degenerative Feedback |
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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 |
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10 |
Added to the circuit to compensate for imbalances in the bridge and variations in component values due to heat. |
Automatic Gain Control ( AGC ) |
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11 |
Are oscillator circuits that utilize LC tank circuits for the frequency determining components? |
LC Oscillators |
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12 |
An LC oscillator that uses a tapped coil. |
Hartley Oscillator |
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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 |
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14 |
An oscillator circuit identical to the Colpitts except with the addition of a small capacitor Cs placed in series with L1. |
Clapp Oscillator |
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15 |
The ability of an oscillator to remain at a fixed frequency. |
Frequency Stability |
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16 |
Frequency stability affected predominantly by fluctuations in dc operating voltages. |
Short-term Stability |
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17 |
Frequency stability which is a function of component aging and changes in the ambient temperature and humidity. |
Long-term Stability |
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18 |
Feedback oscillator circuits where a crystal is used for the frequency determining component. |
Crystal Oscillator |
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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 |
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20 |
The _______ occurs when oscillating mechanical stresses applied across a crystal lattice structure generate electrical oscillations and vice versa. |
Piezoelectric Effect |
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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 |
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22 |
The direction of frequency change is the same as the temperature change. |
Positive Temperature Coefficient |
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23 |
The change in frequency is in the direction opposite to the temperature change. |
Negative Temperature Coefficient |
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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 |
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25 |
A crystal oscillator circuit that has very good frequency stability and reasonably simple circuitry. |
Discrete Pierce Oscillator |
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26 |
A crystal oscillator circuit that has low cost and simple digital interfacing capabilities. |
IC-based Pierce Oscillator |
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27 |
A crystal oscillator circuit that has best frequency stability. |
RLC Half-bridge |
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28 |
Consists of a crystal-controlled oscillator and a voltage-variable component such as a varactor diode. |
Crystal Oscillator Module |
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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 |
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30 |
An oscillator circuit that generates well-defined, stable waveforms that can be externally modulated or swept over a given frequency range. |
Waveform Generator |
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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 |
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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 |
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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 |
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34 |
A monolithic variable-frequency oscillator circuit featuring excellent temperature stability and a wide linear sweep range. |
XR-2209 |
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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 ) |
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36 |
The VCO’s output frequency when the PLL is not locked. |
Preset/Natural Free Running Frequency |
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37 |
The voltage produced by the phase comparator that is proportional to the difference in frequency between the two signals. |
Error Voltage |
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38 |
The PLL state when there is no external input frequency or the feedback loop is open. |
Free-Running State |
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39 |
The state when the PLL is in the process of acquiring frequency lock. |
Capture State |
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40 |
The state when the VCO output frequency is locked onto (equal to) the frequency of the external input signal. |
Lock State |
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41 |
The time required to achieve lock. |
Acquisition Time |
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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 |
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43 |
The capture range expressed as a peak value. |
Pull-in Range |
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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 |
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45 |
The lock range expressed as a peak value. |
Hold-in Range |
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46 |
An oscillator with a stable frequency of oscillation that depends on an external bias voltage. |
Voltage-Controlled Oscillator |
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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 |
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48 |
The difference in phase between an external input frequency and the VCO output signal. |
Phase Error |
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49 |
The product of the individual gains or transfer functions around the loop for the PLL. |
Loop Gain |
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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 |
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51 |
PLL that are used to track digital pulses rather than analog signals, such as in clock recovery circuits. |
Digital PLL |
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52 |
This word means to form an entity by combining parts or elements. |
Synthesize |
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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 |
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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 |
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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 |
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56 |
The minimum frequency separation between output frequencies for a synthesizer. |
Resolution |
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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 |
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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 |
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