Active Multiplier Realization Using Harmonic Loading at Ku-Band

Signal generation is one of the most critical problems in the microwave and millimeter-wave communication market. The demands of greater stability and low phase noise further increase complexity in the circuit design. Signal generation in the millimeter-wave bands can be realized either directly by an oscillator or by multiplication from a lower frequency. An effective solution is to multiply the output of a low noise oscillator. FET frequency multipliers appear attractive compared to diode multipliers because of their potential to have better conversion loss and output power, along with their compatibility with MMIC processes [1]. Moreover, HEMT is the preferable choice in the family of the transistors due to its higher cut-off frequency, better noise characteristics and mature technology both as a discrete device and in MMIC configuration. Mostly, active multipliers have been configured as frequency doublers, although many system configurations operating in the millimeter-wave ranges may require frequency triplers. Still, developing frequency triplers with low drive, low loss and simplicity in design is still a challenge at the higher end of microwave frequencies. The high RF input power might effect the lifetime of the transistor due to rectified current in the gate-channel junction. Also very little has been discussed concerning the agreement between simulated and practical results, particularly for bias operation. This article discusses the approach in designing a frequency tripler using a HEMT device at Ku band, in MIC configuration, keeping simplicity and repeatability as prime considerations by incorporating a harmonic loaded band pass filter at the output.