طراحی و ساخت یک مبدل مد COBRA اصلاح‌شده با ساختار لنز پیوسته

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشگاه صنعتی خواجه نصیرالدین طوسی

چکیده

بسیاری از منابع توان بالای مایکرویو در خروجی موجبر دایروی خود مود TM01 تولید می‌کنند که بدلیل پرتو دونات شکل، برای تابش مناسب نیستند. برای حل این مشکل از مبدل مد COBRAاستفاده می‌شود که مود TM01 را به مود TE11 تبدیل می‌کند. شکل مرسوم این مبدل بسته به نوع قطبش مورد نیاز از 1 تا 4 پله‌ گسسته در ساختار لنز خود استفاده می‌کند. حداقل تعداد این پله‌ها برای ایجاد قطبش دایروی، 3 است. در این مقاله یک ساختار لنز پیوسته که در حالت حدی معادل بینهایت پله است و با استفاده از فن‌آوری CNC تحقق می‌یابد، بعنوان مبدل COBRA اصلاح شده پیشنهاد شده است. از یک عدسی محدب نیز برای افزایش گین به میزان 1dB استفاده شده است. سطح گلبرگ فرعی در این ساختار در مقایسه با ساختار های متداول COBRA با قطبش دایروی که شامل 3 یا چهار پله هستند، بهبود قابل ملاحظه‌ای یافته است. همچنین پهنای امپدانسی این آنتن بیش از 5.5GHz و پهنای باند نسبت محوری بیش از 4GHz می‌باشد. نتایج شبیه‌سازی و ساخت شباهت زیادی با هم دارند.

کلیدواژه‌ها


عنوان مقاله [English]

Design and fabrication of a modified COBRA mode converter with continuous lens structure

چکیده [English]

Most of high power microwave generators have a TM01 mode in their circular waveguide output which makes them improper due to its doughnut shaped pattern. To overcome this problem, Coaxially Beam Rotating Antenna (COBRA) is used which transforms TM01 mode to TE11. The conventional structure of COBRA, depending on the required polarization type, consists of 1-4 discrete steps. Minimum number of steps to create circular polarization is 3. In this paper, a modified COBRA including a continuous tapering which mimics an infinite number of steps, has been proposed. This structure is implemented using CNC technology. A convex lens is used to increase the gain up to 1dB. Compared to conventional circular polarized COBRA with 3 or 4 steps, this structure has improved side lobe level, significantly. In addition, impedance and axial ratio bandwidths of this antenna are more than 5.5 and 4GHz, respectively. The experimental test results are in good agreement with the computer simulations.

کلیدواژه‌ها [English]

  • Mode Transformer
  • Circular Waveguide
  • Dielectric Lens
  • Circular Polarization
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