一种新型宽频率比的双频环形耦合器

A Novel Dual-band Rat-race Coupler with Wide-Range Frequency Ratio

针对传统双频环形耦合器频率比范围窄的问题，通过在传统T型双频四分之一波长阻抗变换器并联短路枝节。增加了设计自由度，减小了物理实现阻抗范围的限制，从而实现了宽频率比范围（1．5～4．9）。为了验证该方法的可行性，运用该结构设计了一款的新型双频环形耦合器，在低频和高频处的带宽分别达到90MHz和120MHz。并将并联短路枝节折叠进耦合器内部空间，实现了更加紧凑的结构，尺寸约为（0．147λ L×0．294λ L）。

As the conventional rat-race coupler is of narrow operation frequency ratio. Through the traditional T dual-band 1/4 wavelength impedance converter shunt short-circuit stub. Increased the design degrees of freedom, reduced the physi- cal implementataion impedance range limit, So as to realize the wide frequency range （ 1.5 to 4. 9 ）. Moreover, a new dual -band rat-race coupler is designed with this structure to verify the proposed design method, attaining 90MHz and 120MHz respectively at low frequency and high frequency bandwidth, and the short-circuit in parallel side fold into the internal space of the coupler. Meanwhile, which come into being a more compact structure with new size （ About 0.147λ L×0.294λ L）.