To have a broadband 180 phase differentiation, we added two sections of a RHTL and a LHTL to the lumped-element Wilkinson power divider as shown in Figure 2. The result is shown in Figure 6. For the same frequency range mentioned above, the insertion loss varies from À0.51 to À1.78 dB, whereas the minimum return loss at all ports and the isolation are below À10.2 dB. The output phase difference for the frequency range is just 69.5 only as shown in Figure 6(b), which agrees very well with the theory (Fig. 4).
CONCLUSIONSIn this article, we present a compact and broadband balun made with lumped elements only. Unlike the previous works, we achieved both a small size and a broadband phase differentiation. Also, only this work is compatible with the modern integrated circuit design. The detailed theory suggested, and the measured results agree very well. The insertion loss and return loss can be better, if an optimized design is incorporated in the MMIC design. Also, the size can be further minimized in such a design. Applications exist in many microwave systems where a broadband and balanced signal generation is required.