Optically Controlled 24GHz Oscillator

In the detection of modulated light in fiberoptic links, PIN photodiodes play an important role. These devices are essentially junction devices. Under proper biasing conditions, the junction capacitance of these devices can be changed by light illumination. This paper reports the results of tuning and frequency modulation experiments with a 24.5GHz HEMT oscillator configured with a PIN photodiode as the tuning element. In addiion to microwave applications of the PIN photodiode, the optical perfomance of the PIN photodiode was also investigated. Experimental results supported the detection of a frequency reference at 8.230GHz and a pulsed modulated IF at 4.399 GHz. By this procedure, we were able to simultaneously synchronize the HEMT oscillator, amplify the IF, and mix the IF with HEMT oscillation frequency.