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2025-06-25 10:31 本頁面
【正文】 mplest open circuit structure is the quarterwavelength shortcircuit stub, but its bandwidth is quite limited. To improve the bandwidth, some modified structures have been proposed, such as to use the twin short stubs or radial stubs [4][5], but their sizes are still large. Recently, a twinspiral slotline shortstub structure was proposed to reduce the size of CPWtoslotline transition [6]. Based on the same idea, novel ?180 hybridring couplers with singlespiral and twinspiral type phase inverters are proposed and carefully examined. These hybridring couplers may achieve the goal of small size and good bandwidth, thus, may find applications in MIC and MMIC. SPIRALTYPE UNIPLANAR PHASE INVERTERS Reverse phase along a CPW line can be achieved by using either one of the uniplanar (CPW) phase inverters as shown in Fig. 1. In these phase inverters, the signal strip of left CPW is connected to the ground planes of right CPW and the signal strip of right CPW is connected to the ground planes of left CPW by two bond wires. Here, an open circuit at the CPW crossover region is realized by using either the singlespiral or twinspiral type slotline short stub, which is the modified version of the conventional 4/g? shortstub structure. The singlespiral type phase inverter (Fig. 1(a)) has the advantages of small size and low radiation loss but its bandwidth is relatively limited. To improve the bandwidth and also to keep the size small, the twin 4/g? shortstub structure is modified [6] to form the twinspiral type uniplanar phase inverter as shown 4 in Fig. 1(b). Since the twinspiral section is symmetric and is fed by a slotline, the two half parts of the twinspiral section are excited with a 180o phase difference. To pensate the effect of slotline bend, the length of spirallike stub should be slightly longer. In this study, both singlespiral and twinspiral type CPW phase inverters are fabricated on the FR4 substrate (ε r =, tanδ =, thickness h =). They are measured by the HP8510B work analyzer together with the TRL (throughreflectline) calibration technique. Theoretically they are also simulated by the IE3D software, which is based upon an integralequation and methodofmoment algorithm. Fig. 2 shows the measur
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