Switching time
Encyclopedia
For a frequency synthesizer
, the switching time or more colloquially the switching speed is the amount of time from when the command for the next frequency is requested until the time that the synthesizer's output becomes usable and meets the specified requirements. Such requirements will vary depending on the design of the synthesizer. In the 1970s switching speeds ranged from 1 milli-sec to 10 micro-seconds. A more general statement has been given by James A. Crawford: 50 reference cycles as a general rule of thumb. By this rule, a reference frequency of 50 kHz has a settling time of 1 milli-seconds. Two other authors state (Hamid Rategh and Thomas H. Lee
) that the switching time (i.e., settling time) is a function of the percentage change in the feedback division ratio. So according to them, the delta N over N itself determines the switching time, where N is the frequency synthesizer
's feedback divisor.
Frequency synthesizer
A frequency synthesizer is an electronic system for generating any of a range of frequencies from a single fixed timebase or oscillator. They are found in many modern devices, including radio receivers, mobile telephones, radiotelephones, walkie-talkies, CB radios, satellite receivers, GPS systems,...
, the switching time or more colloquially the switching speed is the amount of time from when the command for the next frequency is requested until the time that the synthesizer's output becomes usable and meets the specified requirements. Such requirements will vary depending on the design of the synthesizer. In the 1970s switching speeds ranged from 1 milli-sec to 10 micro-seconds. A more general statement has been given by James A. Crawford: 50 reference cycles as a general rule of thumb. By this rule, a reference frequency of 50 kHz has a settling time of 1 milli-seconds. Two other authors state (Hamid Rategh and Thomas H. Lee
Thomas H. Lee (engineering professor)
Thomas H. Lee is an electrical engineering professor at Stanford University. In 1994 he founded the Stanford Microwave Integrated Circuits Laboratory. He has written and co-authored several books and papers....
) that the switching time (i.e., settling time) is a function of the percentage change in the feedback division ratio. So according to them, the delta N over N itself determines the switching time, where N is the frequency synthesizer
Frequency synthesizer
A frequency synthesizer is an electronic system for generating any of a range of frequencies from a single fixed timebase or oscillator. They are found in many modern devices, including radio receivers, mobile telephones, radiotelephones, walkie-talkies, CB radios, satellite receivers, GPS systems,...
's feedback divisor.
Further reading
- * Crawford, James A. 1994. Frequency Synthesizer Design Handbook, Artech House, ISBN 0-89006-440-7
- * Rategh, Hamid and R. Lee, Thomas H. (Stanford UniversityStanford UniversityThe Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...
) 2001. Multi-GHz Frequency Synthesis & Division:Frequency Synthesizer Design for 5 GHz Wireless LAN Systems, Kluwer, ISBN 0-7923-7533-5