Power Combining Tunnel Diode Oscillators using Metamaterial Transmission Line at Infinite Wavelength Frequency

This paper presents power combining methods for tunnel diode oscillators using the infinite wavelength phenomenon observed in composite right/left-handed (CRLH) metamaterial lines. At this frequency, the electrical length of the transmission line is zero degrees corresponding to an infinitely long wavelength. The first combining scheme uses a series combiner composed of zero degree lines. Each oscillator output port is connected directly to the line and combined in-phase. This circuit is able to equally combine the power in phase regardless of the position and the number of ports along the CRLH transmission line (TL). It is also possible to mode lock the different oscillating modes together through nonlinear interactions among the mode fields (York and Compton, 1991). In the second approach a section of zero degree transmission line was used to implement a stationary wave resonator where the wave amplitude and phase are constant along the line. In this case the oscillators are loosely coupled to the resonator. The resonant characteristics are used to reduce the combine oscillator phase noise. A maximum power combining efficiency of 131% is obtained with the zero^th order resonator with 2 tunnel diodes oscillators at 2 GHz