Frequency stabilization of quasi-optical power combining oscillator arrays.

摘要

The spatial or quasi-optical power combining technique provides an efficient way to combine power from many individual solid-state devices to obtain high power at millimeter wave frequencies by eliminating the losses associated with power combining circuitry. The grid oscillator, a promising planar spatial power combining structure, has drawn much attention in the past decade due to its capability of combining power from on the order of hundred of active devices and the potential for integrating the circuits monolithically. The frequency stabilization of power combining grid oscillator arrays, however, has not been addressed. In this dissertation, we investigate the possibility of frequency stabilization by way of phase locking techniques as well as the technique of fast phase modulation of grid oscillators via phase locked loops. The new modulation technique reported in this dissertation overcomes the limit on modulation frequency imposed by the bandwidth of the phase locked loop.;Finite grid oscillator arrays and voltage controlled grid oscillator arrays are examined and discussed. The modeling accuracy of finite grid oscillator arrays and the effects of edge loading stubs were examined through the measurement of three finite grid oscillator arrays with different number of unit cells. The measured results were compared with the predicted results obtained from the theory. By integrating varactor diodes into the grid array, the frequency tuning range reached 600MHz and 300MHz for the two arrays we fabricated.;The frequency stabilization of grid oscillator arrays by means of loop phase locking technique and injection locking techniques are discussed in detail. Measured results have shown that both techniques can provide significant phase noise improvement and frequency stability improvement. Finally, a new phase modulation method through a phase locked loop that overcomes the limitations on the modulation speed imposed by the loop bandwidth is described. The experiment was performed with the 4.7GHz phase locked grid oscillator array and the modulation frequency reached 1MHz which is ten times higher than the loop bandwidth (100kHz).