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oscillator must produce a stable frequency with low harmonics. Stability must take into account temperature, voltage, and mechanical drift as factors. The oscillator must produce enough output power to effectively drive subsequent stages of circuitry, such as mixers or frequency multipliers. It must have low
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frequencies used from the satellite down to the receiving antenna are converted to lower frequencies by a local oscillator and mixer mounted at the antenna. This allows the received signals to be sent over a length of cable that would otherwise have unacceptable signal loss at the original reception
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Application of local oscillators in a receiver design requires care to ensure no spurious signals are radiated. Such signals can cause interference in the operation of other receivers. The performance of a signal processing system depends on the characteristics of the local oscillator. The local
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is one common type of local oscillator that provides good stability and performance at relatively low cost, but its frequency is fixed, so changing frequencies requires changing the crystal. Tuning to different frequencies requires a
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where the timing of the signal is critical. In a channelized receiver system, the precision of tuning of the frequency synthesizer must be compatible with the channel spacing of the desired signals.
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which leads to a compromise between stability and tunability. With the advent of high-speed digital microelectronics, modern systems can use
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to obtain a stable tunable local oscillator, but care must still be taken to maintain adequate noise characteristics in the result.
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frequency. In this application, the local oscillator is of a fixed frequency and the down-converted signal frequency is variable.
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soldiers had equipment which could detect the local oscillator emissions. This led to soldiers creating what is now known as a
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Detection of local oscillator radiation may disclose the presence of the receiver, such as in detection of automotive
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to change the frequency of a signal. This frequency conversion process, also called
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circuit. They are also used in many other communications circuits such as
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soldiers were not allowed to have superheterodyne receivers because the
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The ARRL Handbook for Radio
Amateurs Sixty-Eighth Edition
358:Bowick, Christopher; Blyler, John; Ajluni, Cheryl:
46:. Unsourced material may be challenged and removed.
304:, oscillator and a Gilbert cell multiplier mixer.
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254:unlicensed television broadcast receivers
106:Learn how and when to remove this message
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44:adding citations to reliable sources
150:Local oscillators are used in the
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320:L. D. Wolfgang, C.L. Hutchinson,
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360:RF Circuit Design (2nd Edition)
171:frequency division multiplexing
31:needs additional citations for
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349:, sections 12.3.5 and 12.3.6.
234:variable-frequency oscillator
297:Optical heterodyne detection
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282:Direct conversion receiver
256:in some countries. During
197:(antijamming) systems. In
173:systems used in telephone
154:, the most common type of
195:electronic countermeasure
210:Performance requirements
152:superheterodyne receiver
244:Unintended LO emissions
386:Electronic oscillators
238:frequency synthesizers
128:electronic oscillator
292:Heterodyne detection
199:satellite television
40:improve this article
252:, or detection of
287:Homodyne detection
229:crystal oscillator
55:"Local oscillator"
391:Radio electronics
368:978-0-7506-8518-4
362:. Elsevier 2008
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96:November 2012
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370:pp. 190–191.
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38:Please help
33:verification
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324:, ARRL1990
223:Types of LO
217:phase noise
126:(LO) is an
120:electronics
380:Categories
347:111997836X
309:References
175:trunklines
66:newspapers
203:microwave
185:systems,
183:telemetry
181:systems,
140:converter
396:Feedback
276:See also
80:scholar
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262:Allied
160:modems
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87:JSTOR
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