Push-push design extends bipolar frequency range

In connection with reliability, performance, and economic considerations, the bipolar transistor has been found useful in the design of linear voltage-controlled oscillators with low FM noise and good stability. However, in single-transistor applications, the bipolar transistor cannot be operated above mid C-band. The employment of a push-push configuration makes it possible to extract power at twice the fundamental frequency. Thus, bipolar transistors can be used in voltage-controlled oscillators in the X-band. Attention is given to the schematic of a push-push oscillator, a 200-MHz push-push oscillator using 2N5108 transistors, the output power spectrum, and aspects of transistor selection.