Balanced-to-Unbalanced Quadrature Couplers With Wide-Band Common-Mode Suppression

Slow‐wave substrate integrated suspended parallel strip line and its application to rat‐race coupler

“…In recent years, double-sided parallel-strip line (DSPSL) 1 has become a widely used transmission line in radiofrequency (RF) and microwave devices. DSPSL was first analyzed by Wheeler in the 1960s, 2,3 and then various circuits including transitions, 4,5 couplers, [6][7][8][9] filters, 10,11 and balun 12 have been investigated. DSPSL consists of two metal traces on opposite sides of a dielectric substrate, and the voltage polarities of the upper and lower metal traces are opposite, allowing balanced or differential signals to be transmitted.…”

“…DSPSL consists of two metal traces on opposite sides of a dielectric substrate, and the voltage polarities of the upper and lower metal traces are opposite, allowing balanced or differential signals to be transmitted. In many DSPSLbased balanced or differential circuits, [6][7][8][9][10][11] the DSPSL is still used as a single-ended transmission line where the balanced function is mainly achieved by the topology. DSPSL can be directly used in balanced or differential circuits by using a transition to differential pairs at the ports.…”

“…DSPSL can be directly used in balanced or differential circuits by using a transition to differential pairs at the ports. 13,14 The reported DSPSL-based single-ended or balanced circuits [1][2][3][4][5][6][7][8][9][10][11][12][13][14] are mainly based on uniform DSPSLs, and the circuit sizes are generally large. In Shen et al, 6 a wideband 180°hybrid with an overall circuit area of 0.92 λg × 0.76 λg is presented, and the core circuit used uniform DSPSL.…”

“…In Wu et al, 8 a compact DSPSL rat-race coupler with dual-band arbitrary power divisions is proposed, and the component circumferences are reduced by 65%-70% as compared to the conventional 540°counterpart. In general, the reported DSPSLbased couplers [6][7][8] still occupy a relatively large area, and the physical size of the circuit will be much larger, especially at lower frequencies such as below 2 GHz. Besides, the traditional DSPSL designs generally need to be suspended for testing or actual application due to the double-sided strips and also face packaging problems.…”

“…The reported DSPSL‐based single‐ended or balanced circuits 1–14 are mainly based on uniform DSPSLs, and the circuit sizes are generally large. In Shen et al, 6 a wideband 180° hybrid with an overall circuit area of 0.92 λg × 0.76 λg is presented, and the core circuit used uniform DSPSL.…”