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Conventional broadband couplers use multi‐sectioning techniques and consist of multiple coupled lines. In this study, in contrast to traditional methods, one pair of coupled lines is used to design multi‐octave broadband couplers. In the proposed microstrip couplers, the coupled lines are weakly coupled and are of one‐eighth wavelength at the highest operating frequency. The weakly coupled lines exhibit a linear coupling response with a slope of 6 dB/octave. To compensate the coupling response, one‐pole low‐pass networks with a slope of −6 dB/octave are cascaded with the microstrip coupled lines. To validate the design concept, two broadband microstrip couplers for the frequency range of 30–500 MHz and 1–3 GHz have been designed and fabricated. The couplers exhibit a coupling of 52 and 39 dB, respectively. The broadband couplers provide a ripple of 0.5 dB in the coupling response. The proposed weakly coupled couplers are adequate for high‐power measurements. The weak coupling permits lumped‐element surface mount devices to be used as the compensating network. The multi‐octave couplers are realised in small areas.

In this work, a planar broadband high-power combiner in the ultra-highfrequency band (UHF) is presented. The proposed broadband combiner is a modified version of the conventional Wilkinson power combiner. The isolation resistor of 100 Ω in the conventional Wilkinson combiner is replaced by two 50 Ω terminating resistors. Two overlay couplers transform the terminating resistors to a floating resistor between the input branches. Terminating resistors are preferred to a floating resistor because of higher power handling and lower parasitics. Even-and odd-mode method is employed for the analysis. The design goal is 20 dB isolation and ports return loss in an octave bandwidth. To verify the design concept, a high-power combiner in the frequency range of 470 to 860 MHz used for digital video broadcasting-terrestrial (DVB-T) applications is designed and constructed. Full-wave simulations are compared with measurements. The fabricated power combiner handles 400 W output power. Analytical formulations presented in this work are not restricted to UHF band and can be used to design an octave bandwidth combiner in other frequency bands.

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