Study on a power combiner using an oversized-waveguide resonator at short millimeter wavelengths.

本研究计划利用空间功率合成技术，研制一种工作在短毫米波频率的高功率固态振荡器。为此，超大(过模)波导谐振器将含有固态器件的TE_(10)模波导阵列集成到谐振器中，用于对谐波模器件进行有效的功率合成。在过模波导谐振器中，固态器件，在我们的例子中是耿氏二极管，以同相基频振荡，然后产生二次谐波。来自多个二极管的谐波被相干地和空间地组合在同一个谐振器中，因此即使在90 GHz以上的高频下也可以获得更高的功率。理论和实验结果如下：1.首次实现了15个Gunn二极管在89 GHz~99 GHz范围内的相干功率合成。2.采用5×3波导型Gunn二极管阵列，在94 GHz频段实现了约67%的功率合成和0.25W(连续波)的输出。这些结果表明，用于谐振器空间功率合成的过模波导谐振器对于产生强短毫米波是非常有用的。3.为了设计过模波导谐振器，从理论上建立了过模波导谐振器的等效电路，并进行了实验验证。4.证实了片状背短路的有效性。5.研究发现，功率合成效率主要取决于二极管射频特性的均匀性。

This research project has been planed to develop a high power solid-state oscillator operating at short-millimeter wave frequencies utilizing a spatial power combining technique. For this purpose, an oversized (overmoded) -waveguide harmonic oscillator which incorporates an array of TE_<10> mode waveguides containing solid state devices into the resonator, have been used for an efficient power combining of harmonic-mode devices. In the overmoded-waveguide resonator, solid state devices, in our case Gunn diodes, oscillate at the fundamental frequency in phase and then generate the second harmonic waves. The harmonic waves from a number of the diodes are combined coherently and spatially in the same resonator, so that higher power can be attained even at high frequencies above 90 GHz. The theoretical and experimental results are as follows,1.Coherent power combining of fifteen Gunn diodes has been demonstrated for the first time at the harmonic frequencies between 89GHz and 99 GHz.2.A power combining efficiency of about 67% and an output power of 0.25 W (continuous wave) at 94 GHz band has been achieved with a 5x3 waveguide Gunn diode array. These results indicate that the overmoded waveguide resonator for spatial power combining of harmonic-mode devices is very useful for producing intense short-millimeter waves.3.In order to design the resonator, the equivalent circuit for the overmoded waveguide harmonic oscillator has been developed theoretically and verified experimentally.4.Effectiveness of a lamellar back short which can tune the resonator at both the fundamental and the second harmonic frequencies has been confirmed.5.It has been found that the power combining efficiency has been determined mainly by uniformity of rf-characteristics of the diodes.