本研究透過橋式T線圈有效縮小電路尺寸，再藉由多級電路設計有效提升頻寬，進而達成實現微型化寬頻六埠網路接收機的設計目標，可助於將六埠網路接收機技術導入次世代手持式無線通訊裝置。 ;The target of this work is the development of wideband six-port receiver front-end with compact size, which is composed of a Wilkinson power divider, branch line couplers and power detectors. The wide bandwidth is achieved by multi-section designs of the divider and coupler, while the circuit size can be largely reduced by using the bridged-T coils to substitute transmission line sections. In this way, compact circuit size and wide bandwidth can be achieved simultaneously. The bridged-T coil can be designed as a wideband transmission-line equivalent. It can be realized by a balanced inductor and metal-insulator-metal (MIM) capacitors in the integrated passive device (IPD) process with very compact circuit size. The bridged-T coil can be used to replace the required transmission line sections in wideband divider and coupler designs to achieve wideband and compact six-port network using the IPD process, which can then enable the SiP (system in package) design of six-port receiver front-end. Firstly, test kits of bridge-T coils in IPD are implemented to demonstrate the design procedure and performance. They are then applied to wideband Wilkinson power divider designs to achieve compact size with no bandwidth reduction. Two kinds of Wilkinson power divider designs are presented, i.e. two-section and four-section designs. The center frequency of the two-section Wilkinson power divider is designed at f0 = 2.2 GHz with a circuit size of only 0.024λ0×0.020λ0 at f0 and a bandwidth of 120% (return loss > 15dB). The four-section one is designed with f0 = 12 GHz, and the circuit size is only 0.042λ0×0.017λ0 at f0 with a bandwidth of 173% (return loss > 10dB). Then, bridged-T coils are also used in the design of two kinds of wideband branch line coupler with compact size. The two-section branch line coupler is designed with an f0 of 1.95 GHz, and the circuit size is 0.028λ0×0.018λ0 at f0 with a bandwidth of 53.8% (return loss >15dB). The three-section one is designed at 2.2 GHz with bandwidth of 83.6% and a circuit size of 0.045λ0×0.021λ0 at f0. The proposed wideband Wilkinson power divider and branch line couplers are then integrated with power detectors to form two compact six-port receiver front-ends. The first one is designed at 2.6 GHz with an electrical size 0.024λ0×0.020λ0 at f0. The second one is designed at 1.95 GHz with a circuit size of 0.227λ0×0.147λ0 at f0 and a wideband bandwidth of 64.1% (return loss >10dB).
By using bridged-T coils to implement transmission lines, the circuit size of six-port network can be largely reduced, while the bandwidth can be improved by using the multi-section divider and coupler designs. The proposed six-port receiver front-end features very compact size and wide bandwidth, and can be implemented in handheld wireless communication devices for mobile communication applications.
