This article proposes a synthesis method based on phase modulation to design broadband oversized smooth-walled horns for high-power millimeter-wave applications. The bandwidth of oversized smooth-walled horn is confined by the mismatch of the relative phase between TE11 mode and TM11 mode. By analyzing the mode conversion along horn, it is found that the phase of the generated TM11 mode can be influenced by the TE11 mode. Therefore, the synthesis method uses a slow waveguide taper, in which the generated TM11 mode is in a small fraction and its phase is efficiently influenced by TE11 mode, to modulate the relative phase of TE11 mode and TM11 mode. Using the proposed method, an oversized smooth-walled horn is designed, of which the phase mismatch is ±10° in the range of 32–38 GHz. The simulation results show that the proposed horn has a highly symmetric far-field pattern with a peak gain greater than 28 dBi in the range of 32–38 GHz and the sidelobe level has −19 dB decline compared with the peak gain. A prototype is fabricated and the near-field pattern measurement is carried out. The high correspondence of the simulated near-field patterns with the measured ones proves that the proposed method is an appropriate option to design broadband feed horns for high-power millimeter wave.

中文翻译：

---

大功率毫米波宽带超大平滑壁喇叭的合成

本文提出了一种基于相位调制的合成方法，为大功率毫米波应用设计宽带超大光滑壁喇叭。超大光滑壁喇叭的带宽受限于 TE11 模式和 TM11 模式之间相对相位的不匹配。通过分析沿喇叭的模式转换，发现产生的TM11模式的相位会受到TE11模式的影响。因此，该合成方法使用慢波导锥形，其中生成的 TM11 模式占一小部分，其相位受 TE11 模式有效影响，以调制 TE11 模式和 TM11 模式的相对相位。使用所提出的方法，设计了一个超大的光滑壁喇叭，其相位失配在 32-38 GHz 范围内为 ±10°。仿真结果表明，所提出的喇叭具有高度对称的远场模式，在 32-38 GHz 范围内峰值增益大于 28 dBi，与峰值增益相比，旁瓣电平下降 -19 dB。制造原型并进行近场模式测量。模拟近场图与实测图的高度对应证明所提出的方法是设计用于大功率毫米波的宽带馈源喇叭的合适选择。