# A Novel Wideband Splitter for a Four-Element Antenna Array
## 2 Related Work
The achieved flatness of the frequency response was up to \(\pm 12\) dB. Another three-port array-antenna feeding network operating at 2.5 GHz with a fractional bandwidth of 20% was proposed by [PERSON] et al. [13]. The proposed design is based on a novel concept of a two-way signal-interference power divider configuration with added filtering functionality. Based on the presented experimental results, the minimum insertion loss was about 0.7 dB and the reflection coefficient was less than \(-3\) dB. According to the provided results, the flatness of the frequency response was up to \(\pm 22\) dB. A high power-handling wideband power divider was proposed by [PERSON] et al. in [14]. The power-handling capability was achieved by using grounded 50 \(\Omega\) loads. In the experimental evaluation of the designed power divider, the reflection coefficient was less than \(-15\) dB and insertion losses of about 0.5 dB were achieved over a 52% fractional bandwidth in the frequency range from 7 up to 12 GHz. A fully self-packaged in-phase power divider with a wideband bandpass response was presented by [PERSON] et al. in [15]. In this case, the three-port power divider was designed based on a four-port coupled-line common-mode network by keeping one of the ports shorted. The prototype was manufactured using multilayer liquid crystal polymer circuit technology. The operating frequency of the proposed power splitter was 2 GHz with a fractional bandwidth of 80%. Based on the experimental results, the achieved insertion loss was about 0.75 dB and the reflection loss was 15 dB. A Gysel type unbalanced-to-balanced (UTB) power divider (PD) with arbitrary power division was proposed by [PERSON] et al. in [16]. The UTB PD was proposed as a five-port device with arbitrary power division. The developed UTB PD was designed for a 2 GHz frequency and a power division ratio of 1:2. Based on the experimental measurementsperformed at the prototype of the proposed power divider, a fractional bandwidth of 21% and an insertion loss of about 0.56 dB were achieved. A novel design of a ring-cavity multiple-way power divider with UWB performance was presented by [PERSON] and [PERSON] in [17]. In the proposed design, a UWB coaxial taper feeding port was used to provide uniform excitation for the ring-cavity parallel power divider with large numbers of power-dividing ports. A prototype of a 32-way UWB ring-cavity power was manufactured. During experimental measurements, good amplitude and phase balance, very low loss, and very flat group delay were achieved. A dual-band Wilkinson power divider with a high power split ratio was proposed by [PERSON] et al. [18]. The authors replaced high transmission lines with dual-band T-shaped sections. A dual-band power divider with a power split ratio of 7:5:1 was fabricated and tested. The authors concluded that their design achieved a high split ratio, and good insertion loss, isolation, and return loss. A planar 14-way radial power combiner with a two-octave bandwidth was proposed by [PERSON] and [PERSON] in [19]. The authors claimed that the main advantage of the proposed solution is the ease and economy of manufacturing thanks to the use of standard PCB material. According to the presented results of experimental measurements, the output port was matched better than \(-10\) dB and the amplitude balances were better than \(\pm 0.75\) dB. The fabricated combiner had an average intersession loss of 2 dB; moreover, the authors claimed this could be further reduced with a low-loss dielectric substrate. [PERSON] et al. proposed a four-way out-of-phase slotline power divider in [20]. Based on the achieved results, acceptable input impedance matching, low insertion loss, and good amplitude balance were achieved. On top of that, the proposed design of a power divider demonstrated reasonable isolation among the output ports.