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We propose a low-profile dual-linearly-polarized unit cell in X-band, and its capability is demonstrated by a circularly polarized transmitarray. The unit cell comprises three metallic layers etched on two dielectric slabs without air gap. Cross strips are inserted in cross slots on the top and bottom layers, and the T-slot structure is etched on the middle layer. The proposed unit cell has high isolation between the dual polarizations, and its total thickness is only 1 mm. Prototype of a 341-element transmitarray, which transforms the incident linearly polarized wave into the outgoing circularly polarized wave, is also fabricated and tested. The measured results show that the proposed transmitarray realizes 3.5% (9.8-10.15 GHz) axial ratio bandwidth and 4% (9.7-10.1 GHz) 1-dB gain bandwidth. The measured peak gain at 10 GHz is 21.9 dBi, with the aperture efficiency of 36%.

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A k-band broadband monolithic distributed frequency multiplier based on nonlinear transmission line * Huang Jie(黄 杰) a)b) † , Dong Jun-Rong(董军荣) a) , Yang Hao(杨 浩) a) , Zhang Hai-Ying(张海英) a) , Tian Chao(田 超) a) , and Guo Tian-Yi(郭天义) a)

A millimeter wave large-signal model of GaAs planar Schottky varactor diodes based on a physical analysis is presented. The model consists of nonlinear resistances and capacitances of the junction region and external parasitic parameters. By analyzing the characteristics of the diode under reverse and forward bias, an extraction procedure of all of the parameters is addressed. To validate the newly proposed model, the PSVDs were fabricated based on a planar process and were measured using an automatic network analyzer. Measurement shows that the model exactly represents the behavior of GaAs PSVDs under a wide bias condition from -10 to 0.6 V and for frequencies up to 40 GHz.

A broadband frequency doubler using left-handed nonlinear transmission lines (LH NLTLs) based on MMIC technology is reported for the first time. The second harmonic generation on LH NLTLs was analyzed theoretically. A four-section LH NLTL which has a layout of 5.4 0.8 mm 2 was fabricated on GaAs semi-insulating substrate. With 20-dBm input power, the doubler obtained 6.33 dBm peak output power at 26.8 GHz with 24-43 GHz 6 dBm bandwidth. The experimental results were quite consistent with the simulated results. The compactness and the broad band characteristics of the circuit make it well suit for GaAs RF/MMIC application.