Transmission Line Transformers (TLT):

• Optimal Characteristic Impedance: For a standard 1:4, Z₀ = sqrt(Z_in × Z_out). For 1:9 Guanella (3 lines), Z₀ = Z_in × N_lines.
• Guanella (Current): Focuses on providing high common-mode choking impedance. Excellent bandwidth and balance.
• Ruthroff (Voltage): Uses bootstrap voltage addition. Tends to have less high-frequency bandwidth than Guanella due to phase delay.
• Current at port: I = sqrt(P / Z)  |  Voltage: V = sqrt(P × Z)