Issac Koga

Issac Koga (古賀 逸策) was an inventor and scientist.

Early life and education
He was the eldest of seven children born in Tashiro Village (now Tosu), Saga Prefecture. In July 1920, at the age of 20, he started to study at the Department of Electrical Engineering at Tokyo Imperial University (later renamed University of Tokyo). After graduation in August 1925, he moved to the new Tokyo City Electrical Institute, which was established to develop and promote radio broadcasting technology under the directorship of Kotaro Kujirai, a pioneer of the research and teaching of radio science.

Initially an engineer, he became an assistant professor in 1929. Under the guidance of Professor Kujirai, he studied crystal oscillators. This formed the basis of his PhD thesis, completed in April 1930, entitled "Characteristics of the Crystal Oscillator." This work included making the first quartz tuning forks in 1927. In 1929, he became an associate professor at the Tokyo Institute of Technology and a professor in 1939. In 1944, he worked as a concurrent professor at the University of Tokyo, later became a professor emeritus there, and reached emeritus status at Tokyo Institute of Technology in 1961.

Research works
His research and education were in the areas of electronics and communications. Dr. Koga is known as an inventor of temperature insensitive quartz cut (R1-cut) of quartz plate quartz crystal: in April 1933, Issac Koga at Tokyo Institute of Technology reported R1-cut quartz crystal plates having a zero temperature-coefficient of frequency. He applied the R1-cut plate to wireless communications and quartz clocks; his achievement provided drastically stable frequency of oscillator used in communications and clocks for time standard. Today, this type of temperature-insensitive quartz crystal oscillator has proven indispensable to all radio communication systems and much of information electronics. (Theory of Vibration Analysis) [1] I. Koga, "Longitudinal Vibration of Short Circular Cylinders" (in Japanese), Journal of the Institute of Electrical Engineers of Japan, Vol. 50, No. 508, pp. 1209-1224, November 1930. [2] I. Koga, "Thickness Vibration of Piezoelectric Oscillating Crystal", Physics, Vol. 3, No. 2, pp. 70-80, August 1932. [3] I. Koga, (the same item as Ref. [2], in English), Report of Radio Researches and Works in Japan, Vol. II, No. 2, pp. 157-173, September 1932. (Zero-Temperature Temperature-Coefficient Oscillation Plates) [4] I. Koga, "R-cut Quartz Oscillating Plates and Harmonic Oscillation (in Japanese)", Proc. of 2nd Conference on Engineering, Electrical Engineering Section, No. 102, p. 170, April 1932. [5] Japan Patent No. 95637, "Piezoelectric Vibration Plates", Koga (inventor), Takeuchi (patentee), April 30, 1932 (granted). [6] I. Koga and K. Ichinose, "Quartz Oscillating Plates with Small Temperature Coefficients for Short-Wave" (in Japanese), Proc. of 8th Joint Conference on Electrical Engineering, No. 135, pp. 205-206, April 2, 1933. [7] I. Koga and N. Takagi, "Piezoelectric Oscillating Quartz Plates with Temperature Coefficients less than 10-7 /°C" (in Japanese), Journal of the Institute of Electrical Engineers of Japan, Vol. 53, No. 543, p. 940, October 10, 1933. [8] I. Koga and N. Takagi, "Temperature Coefficients of Elastic Constants of Quartz" (in Japanese), Journal of the Institute of Electrical Engineers of Japan, Vol. 53, No. 545, p. 1141, December 1933. [9] I. Koga, "Thermal Characteristics of Piezoelectric Oscillation of Quartz Plates", Report of Radio Researches and Works in Japan, Vol. 4, No. 2, pp. 61-76, February 1934. (Quartz Clock) [10] I. Koga, "Quartz Electric Clock" (in Japanese), OHM, Vol. 25, No. 5, pp. 425-426, May 1938. (Subsequent Studies on Quartz Crystal) [11] I. Koga and H. Fukuyo, "Vibration of Thin Piezoelectric Quartz Plates (Especially on R1 -Cut Rectangular Plates" (in Japanese), Journal of the Institute of Electrical Communication Engineers of Japan, Vol. 36, No. 2, pp. 59-67, February 1953. [12] I. Koga, M. Aruga and Y. Yoshinaka, "Theory of Plane Elastic Waves in a Piezoelectric Crystalline Medium and Determination of Elastic and Piezoelectric Constants of Quartz", Physical Review, Vol. 109, No. 5, pp. 1467-1473, March 1958.

Awards and recognitions
He was awarded the Japan Academy Prize in 1948 (the citation reads for "Theoretical and Experimental Investigation upon the Fundamental Characteristics of Piezoelectric Oscillating Crystal and Quartz Crystal Oscillator Circuit and Their Applications to Wireless Communication and Crystal Clock"), the Order of Cultural Merit award in 1963 and became a member of the Japanese Academy in 1971. He served as president of the International Union of Radio Science (URSI) between 1963 and 1968.

Koga died on September 2, 1982. In his honor, the International Union of Radio Science, URSI, named a young scientist award after him (the Issac Koga Gold Medal ) first awarded in 1984 and subsequently awarded every 3 years.