Design of Miniaturized Rat-Race Couplers With Arbitrary Power Division Ratios

Abstract

Abstract-A miniaturized rat-race coupler with arbitrary power division ratio is proposed in this paper. The design formulas of the rat-race coupler with arbitrary power division ratio are derived using even-odd decomposition analysis. The proposed structure demonstrates miniaturized size and perfect isolation due to adding phase inverter to the branch. For demonstration, a 20 dB rat-race coupler operating at 1 GHz with 81.34% size reduction is designed and fabricated. There is good agreement between measured and simulated results.

A New Miniaturized Microstrip Branch-Line Coupler With Wide Suppression Band

“…Relative Area Harmonic Suppression Conventional 100% No. [5] 63.0% N/A [6] 58.0% 5th [7] 24.0% 3rd [8] 28.0% 2nd [9] 29.3% 4th [10] 26.8% 2nd [11] 25.0% 4th [12] 90.4% 2nd [13] 60.0% N/A [14] 74.0% N/A [16] 56.8% 2nd This Work 19.1% 7th…”

“…These properties will degrade the performance of the coupler. Therefore, much work has been reported in recent years to achieve both compact design and harmonic suppression for branch-line couplers [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”

“…Even so, it only has 2nd harmonic suppression performance [8]. Size reduction methods were also reported in [9][10][11][12][13][14][15][16][17]. These couplers achieve compact size, but the harmonic suppressions still need improvement.…”