Injection Locking

What is "injection locking" phenomenon? In 17th century Dutch scientist, Christian Huygens invented pendulum clock. When he hung two pendulum clocks close to each other on the wall, he noticed that the pendulums moved in unison [1]. It was the first observation of a phenomenon which called injection locking. Injection locking occurs when two oscillatory systems have proper coupling and close frequencies. In such a situation one of the oscillators tends to lock to another one. After lock, frequency of the oscillator under injection will be the same as that of injection source. As another example, biological clock of human being is injection locked to the frequency of earth's cycle.

There are many research papers about injection locking in different fields but for the first time Adler formulated this phenomenon mathematically [2]. Injection locking also has applications in communication circuits and lasers. From integrated circuit point of view, injection locking can be used for phase noise and jitter reduction in oscillatory systems. Frequency division is another application for this phenomenon in electronics.

References:

[1] A. E. Siegman, Lasers, Mill Valley, CA: University Science Books, 1986

[2] R. Adler, "A study of locking phenomena in oscillators," Proc. IEEE, Vol. 61, pp. 1380-1385, Oct. 1973

Summer

Summer is going to be finished soon, at least in Sweden. Always Swedish people are joking about seasons in their country. They say that there are only two seasons in Sweden: long white winter and short green winter! But I think Sweden is one of the most beautiful countries in the summer. I have taken above pictures in our city and in a city close to ours called "Norrkoping".

This summer was very nice and warm in Sweden. During July it was hardly rainy and people always were enjoying sunny weather. Actually one of the drawbacks! of this kind of weather is that working becomes very hard in an office with window to the outside. Always you like to go out and enjoy fresh air. I think in such a summer performance of people is in its minimum. :)

Explanation

On July 29, 2005 I wrote something about the story of getting visa and its influence on my life. I got many emails from different people which show me that mentioned post has somehow different theme than my weblog's, and on the other hand there are different perceptions which might cause some misunderstandings. I prefer to delete this post. Hopefully I will write more about my trip later on.