| 摘要: | 本研究以差動橋式T線圈與相位轉換器為基本組件，將鼠競耦合器的傳輸線用差動橋式T線圈取代，使其可具有寬頻、雙頻、微小化與不等功率輸出的特性。並以積體被動元件製程與0.18 μm CMOS製程實現微型化寬頻鼠競耦合器、雙頻鼠競耦合器與雙頻不等功率分配鼠競耦合器，以展現所達到的電路效能。
首先，使用差動橋式T線圈與相位反轉器實現2.5GHz微型化寬頻鼠競耦合器，因為使用了上述兩個組件，所以使電路面積大幅縮小，實際電路面積為1.13 × 1.19 mm2，電氣尺寸在中心頻率2.5GHz下為0.0190 0.02750，也因為使用了相位反轉器來增加頻寬，反射損耗大於15dB的比例頻寬為69.2%。
其次，沿用微型化寬頻鼠競耦合器的架構，以雙頻差動橋式T線圈取代原本的差動橋式T線圈，達成雙頻操作的效果，並分別使用積體被動元件製程與0.18 μm CMOS製程實現。以積體被動元件製程實現的2.45/5.5GHz雙頻鼠競耦合器，實際電路面積為2.73 × 4.17 mm2，電氣尺寸於2.45GHz為0.0223λ0 × 0.0341λ0，於5.5GHz為0.0501λ0 × 0.0765λ0，反射損耗大於10dB之比例頻寬，在2.45GHz與5.5GHz分別為81.2%與27.3%。而以0.18μm CMOS製程所實現的10/24GHz雙頻鼠競耦合器，實際電路面積為0.871 × 1.18 mm2，電氣尺寸於10GHz為0.029λ0 × 0.0393λ0，於24GHz為0.0697λ0 × 0.0944λ0，反射損耗大於10dB的比例頻寬，在10GHz與24GHz分別為99.8%與30.38%。
最後，藉由改變雙頻差動橋式T線圈的等效阻抗，實現於2.45GHz有3dB功率分配比，於5.5GHz有0dB功率分配比之鼠競耦合器，電路面積為3.1 4.4 mm2，電氣尺寸於2.45GHz為0.0697λ0 × 0.0944λ0，於5.5GHz為0.0697λ0 × 0.0944λ0，以輸出振幅誤差在±0.5dB來計算頻寬，在2.45GHz與5.5GHz兩頻段分別為42%與7.5%。本研究也探討了使用雙頻差動橋式T線圈實現雙頻不等功率分配鼠競耦合器之設計限制，包括兩中心頻率下的功率分配比與頻率比，做為判定可實現規格範圍的依據。
;In this paper, differential bridge-T coils and phase inverter are employed as basic building blocks to realize rat-race couplers with features, like wide bandwidth, dual-band operation, miniaturization and unequal power division ratios. To demonstrate the performance achieved, several design examples are implemented in the integrated passive device (IPD) and 0.18-μm CMOS technology, including wideband rat-race coupler, dual-band rat-race coupler, and dual-band rat-race coupler with unequal power division ratios.
First, by using differential bridge-T coils and phase inverter, a 2.5 GHz miniaturized wideband rat-race coupler is implemented in IPD. The circuit size is only 1.13 × 1.19 mm2 and the corresponding electrical size is 0.0190 0.02750 at 2.5 GHz. The 15-dB return loss bandwidth is 69.2%. It outperforms the conventional rat-race coupler in terms of circuit size and operation bandwidth.
Secondly, by using the same structure of the proposed miniaturized wideband rat-race coupler while replacing the original differential bridge-T coils by dual-band differential bridge-T coils, miniaturized dual-band rat-race couplers are achieved. A 2.45/5.5 GHz dual-band rat-race coupler is realized in IPD, and the circuit size is only 2.73 × 4.17 mm2. The corresponding electrical size is 0.0223λ0 × 0.0341λ0 at 2.45GHz, and it is 0.0501λ0 × 0.0765λ0 at 5.5 GHz. Its 10-dB return loss bandwidth is 81.2% at 2.45 GHz while it is 27.3% at 5.5 GHz. In addition, a 10/24 GHz dual-band rat-race coupler is impemented in 0.18-μm CMOS technology, the circuit size is only 0.871 × 1.18 mm2. The corresponding electrical size is 0.029λ0 × 0.0393λ0 at 10 GHz and it is 0.0697λ0 × 0.0944λ0 at 24 GHz. The 10-dB return loss bandwidth is 99.8% at 10 GHz while it is 30.38% at 24 GHz.
Finally, by varying the equivalent characteristic impedances of the dual-band differential bridge-T coil at the two bands, miniaturized dual-band rat-race coupler that is capable of achieving different power division ratios over the two bands can also be achieved. As an example, a proposed dual-band rat-race coupler having 3dB power division ratio at 2.45 GHz and 0dB power division ratio at 5.5 GHz is realized in IPD. The circuit size is only 3.1 4.4 mm2. The corresponding electrical size is 0.0697λ0 × 0.0944λ0 at 2.45 GHz and it is 0.0697λ0 × 0.0944λ0 at 5.5 GHz. The bandwidth of ±0.5dB amplitude error is 42% at 2.45 GHz and it is 7.5% at 5.5 GHz. Also, the design limitations, of using dual-band differential bridge-T coils for dual-band rat-race coupler designs, including the power division ratio and frequency ratio of the two center frequencies, are thoroughly investigated. |
