為了克服單模近似法在分析矩形柵慢波系統高頻特性時的局限性，采用了一種新的方法，即在表示槽區內的場時，保留其高次項，表為一無限本征駐波之和的形式，利用場匹配法得到其色散特性，進而求得耦合阻抗。然后針對矩形柵慢波系統進行了數值計算，并分析了金屬柵的幾何尺寸對系統高頻特性的影響，以作為器件設計的參考。設計出3cm、8mm波段的矩形柵高頻結構模型，進行實驗測量，得到的實驗值與理論值符合良好。

In order to overcome the limit of Single-Mode Approximation (SMA), this paper adopts a new method that when expressing the fields inside the grooves, the higher orders are retained as an infinite sum of standing eigen-waves. The dispersion relation is obtained by field-matching method, while the coupling impedance is subsequently obtained from the relevant equations. A lot of numerical computations and analysis are done for rectangular grating slow-wave system. And the effects of the geometrical characteristics of the grating are analyzed. Finally, rectangular waveguide gratings at 3 cm band and 8 mm band are designed and measured, experimental values match theoretical values very well.