Frekvenssyntese
Blokdiagram af en almindelig type af faselåst kredsløb baseret frekvenssyntese.
Blokdiagram af en superheterodynmodtager hvor lokaloscillatoren er en frekvenssyntese. Den ekstra linje fra frekvenssyntese til RF filter, er et DC-signal, som anvendes til styring filterets resonansfrekvens.
En frekvenssyntese er et elektronisk kredsløb, som kan generere et enkelt signal med en frekvens ud af mange mulige frekvenser fra en enkelt referencefrekvens.
Frekvenssynteser bliver anvendt i mange moderne apparater (2017) såsom radio radiomodtagere, fjernsyn, mobiltelefoner, radiotelefoner, walkie-talkies, CB-radioer, tv-modtagerbokse, satellitmodtagere og GPS-navigationsenheder.
En frekvenssyntese kan benytte sig af teknikkerne frekvensmultiplikation, frekvensdivision, direct digital synthesis, elektronisk mikser og faselåst kredsløb til at genererer dens frekvenser. Stabiliteten og nøjagtigheden af frekvenssynteserens output er relateret til stabiliteten og nøjagtigheden af dens referencefrekvens input. Derfor anvender frekvenssynteser en stabil og nøjagtig referencefrekvens, såsom en krystalstyret elektronisk oscillator.
Se også
- Superheterodynmodtager
- Dual-modulus prescaler
- Wadley-loop
Kilder/referencer
- Banerjee, Dean (2006), PLL Performance, Simulation and Design Handbook (4th udgave), National Semiconductor, arkiveret fra originalen 21. november 2008, hentet 7. juli 2017. Also PDF version Arkiveret 20. november 2008 hos Wayback Machine.
- Crawford, James A. (1994), Frequency Synthesizer Design Handbook, Artech House, ISBN 0-89006-440-7
- Egan, William F. (2000), Frequency Synthesis by Phase-lock (2nd udgave), John Wiley & Sons, ISBN 0-471-32104-4
- Gardner, Floyd M. (1966), Phaselock Techniques, John Wiley and Sons
- Kroupa, Venceslav F. (1999), Direct Digital Frequency Synthesizers, IEEE Press, ISBN 0-7803-3438-8
- Kroupa, Venceslav F. (1973), Frequency Synthesis: Theory, Design & Applications, Griffin, ISBN 0-470-50855-8, arkiveret fra originalen 16. februar 2017, hentet 7. juli 2017
- Manassewitsch, Vadim (1987), Frequency Synthesizers: Theory and Design (3rd udgave), John Wiley & Sons, ISBN 0-471-01116-9
- Popiel-Gorski, Jerzy (1975), Frequency Synthesis: Techniques and Applications, IEEE Press, ISBN 0-87942-039-1
Yderligere læsning
- Ulrich L. Rohde "Digital PLL Frequency Synthesizers – Theory and Design ", Prentice-Hall, Inc., Englewood Cliffs, NJ, January 1983
- Ulrich L. Rohde " Microwave and Wireless Synthesizers: Theory and Design ", John Wiley & Sons, August 1997, ISBN 0-471-52019-5
Eksterne henvisninger
 | Wikimedia Commons har medier relateret til: |
- Hewlett-Packard 5100A Arkiveret 26. juli 2008 hos Wayback Machine (tunable, 0.01 Hz-resolution Direct Frequency Synthesizer introduced in 1964; to HP, direct synthesis meant PLL not used, while indirect meant a PLL was used)
- Frequency Synthesizer U.S. Patent 3,555,446, Braymer, N. B., (1971, January 12)
Medier brugt på denne side
Receiver with frequency synthesizer.svg
Forfatter/Opretter: Chetvorno, Licens: CC0
Block diagram of a superheterodyne radio receiver using a frequency synthesizer. Older superheterodynes use a LC oscillator as the local oscillator which is tuned to different stations with a variable capacitor. However this type of oscillator's frequency is not very stable, causing the receiver to drift off the frequency of the station, Modern receivers use a master crystal oscillator which uses the vibrations of a quartz crystal to produce a very stable frequency. Since a crystal oscillator's frequency cannot be varied, to tune the receiver to different stations a digital circuit called a frequency synthesizer is used to generate different frequencies from the master oscillator signal. The synthesizer uses a phase locked loop so that the new frequency is locked to the master oscillator frequency. The frequency to be generated is specified by a digital "frequency control word" (FCW), which is generated by digital channel selection logic
Forfatter/Opretter: Chetvorno, Licens: CC0
Block diagram of a superheterodyne radio receiver using a frequency synthesizer. Older superheterodynes use a LC oscillator as the local oscillator which is tuned to different stations with a variable capacitor. However this type of oscillator's frequency is not very stable, causing the receiver to drift off the frequency of the station, Modern receivers use a master crystal oscillator which uses the vibrations of a quartz crystal to produce a very stable frequency. Since a crystal oscillator's frequency cannot be varied, to tune the receiver to different stations a digital circuit called a frequency synthesizer is used to generate different frequencies from the master oscillator signal. The synthesizer uses a phase locked loop so that the new frequency is locked to the master oscillator frequency. The frequency to be generated is specified by a digital "frequency control word" (FCW), which is generated by digital channel selection logic
PLL frequency synthesizer 2.svg
Forfatter/Opretter: Chetvorno, Licens: CC0
Block diagram of an "indirect" or phase-locked loop (PLL) frequency synthesizer, widely used in superheterodyne radio receivers to generate the local oscillator signal applied to the mixer to convert the incoming radio frequency signal to the lower intermediate frequency
Forfatter/Opretter: Chetvorno, Licens: CC0
Block diagram of an "indirect" or phase-locked loop (PLL) frequency synthesizer, widely used in superheterodyne radio receivers to generate the local oscillator signal applied to the mixer to convert the incoming radio frequency signal to the lower intermediate frequency