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An admittance‐inverter‐based two‐section topology is proposed for filtering power dividers in this article aiming at high and wideband output isolation. Different from the classic two‐section Wilkinson power dividers, the bulky quarter‐wave transmission lines are removed and replaced by using two pairs of admittance inverters, which are realized by the input external quality factor (Qe‐in) and coupling coefficient (k12), respectively. Since the electric size of these coupling effects (Qe‐in and k12) are negligible, a significant size reduction is easily realized. In addition, two isolation elements are added between the input resonators and the output ones, respectively. Two‐prefect absorption points are accordingly realized in |S23|, indicating wider and higher output isolation compared with the reported designs using one isolation element. For demonstration, one two‐section filtering power divider is designed and fabricated. The circuit size is only 0.009λg2, while the output isolation exceeds 41.5 dB over the passband. [ABSTRACT FROM AUTHOR]

Aiming at high and wideband output isolation, a new topology of filtering power divider based on complex isolation impedance and surface wave mitigation techniques is proposed. Different from previously published filtering power dividers using pure resistor, an analytical design method by using complex impedance is proposed in this article. To formula the complex impedance, the LC equivalent circuit model is introduced, and the closed-form derivation is given accordingly. Based on the calculated impedance, high isolation can be theoretically realized in circuit level. However, the output isolation is limited below 20 dB in practical EM simulations. To solve this issue, the filtering power divider is further investigated in field level. To reduce the crosstalk between adjacent filtering channels, the surface wave mitigation techniques are investigated. Accordingly, a 16-dB enhancement of output isolation is realized, without sacrificing other filtering specifications. For experimental verification, a filtering power divider is designed, fabricated, and measured. A significant size reduction and 36-dB output isolation with over 500% isolation bandwidth can be observed, verifying the validity of the proposed design method. [ABSTRACT FROM AUTHOR]

A bandpass push–pull high power amplifier (PA) based on substrate integrated waveguide (SIW) filtering balun power divider is proposed in this article. The filtering characteristic of the PA is realized by the complementary split rings resonators (CSRRs) defected in the balun based on the SIW. Inherent to the middle metal plane of the SIW balun, the 180° phase difference power division can be achieved. Due to the natural differential characteristic of the balun, the proposed design can produce second-harmonic suppression. Greater output power is obtained owing to the filtering balun power combiner. For the fabricated bandpass push–pull PA, it exhibits high-selectivity bandpass response and good PA performance with the peak power-added efficiency (PAE) of 48.7% at 38.5-dBm output power. [ABSTRACT FROM AUTHOR]