Fig.6.RT5880LZ substrate based fabricated prototype of the proposed 4×4 BM.
The simulated and measured S-parameters responses of the 4 × 4 Butler matrix result for different ports are as shown in Fig. 7, respectively. The P1 of the BM excited return loss was better than 17dB. This could be seen in the simulation and measured results of the return loss and insertion loss, which were S11 = -20.5 dB, S15 = -5.91 dB, S16 = -5.5 dB, S17 = -6.3 dB, S18 = -5.7 dB, and S11 = -18 dB, S15 = 6.41 dB, S16 = -5.6 dB, S17 = -5.8 dB, S18 = -6.0 dB, illustrate in Fig. 7(a - b). Hence, the average insertion loss for simulated and measured (S15,S16,S17,S18) were -5.9, 6.0 ± 2 dB, respectively. The P2 of the BM excited return loss was better than 14 dB. The simulation and measured results of the return loss and insertion loss were S22 = -25 dB, S25 = -6.35 dB, S26 = -6.4 dB, S27 = -5.43 dB, S28 = -5.85 dB, and S22 = -34 dB, S25 = -6.72 dB, S26 = -6.65 dB, S27 = -5.81 dB, S28 = -6.76 dB, as illustrated in Fig 7(c - d), The average insertion loss for simulated and measured (S25,S26,S27,S28) were -6.0, 6.5 ± 2, and dB, respectively. The P3 of the BM excited return loss was better than 10 dB. The simulated and measured results of the return loss and insertion loss were S33= -24 dB, S35 = -5.3 dB, S36 = -6.2 dB, S37 = -6.25 dB, S38 = 6.4 dB, and S33= -15 dB, S35 = -5.8 dB, S36 = 6.7 dB, S37 = 6.56 dB, S38 = -7 dB, as shown in Fig. 7 (e-f), The average insertion loss for simulated and measured (S35,S36,S37,S38) were -6.0 ±2 dB, respectively. The P4 of the BM excited return loss was better than 15 dB. The simulated and measured results of the return loss and insertion loss were S44= -20 dB, S45 = -5.4 dB, S46 = -5.18 dB, S47 = -5.0 dB, S48 = -6.19 dB, and S44= -24 dB, S45 = -5.95 dB, S46 = -6.37 dB, S47 = -7.1 dB, S48 = -6.65 dB, as shown in Fig. 7(g-h). The average insertion loss for simulated and measured (S45,S46,S47,S48) were -6.1 ± 2dB, respectively. All the results for P1, P2, P3, and P4 were at centre frequency of 3.5 GHz. The overall results, when P1, P2, P3, and P4 were excited, the simulated and measured proposed design 4 × 4 BM had good agreement between them, although there some variation observed in the results due to the extra loss phase shifts induced by the cable and connector.