Super Wide-bandwidth Power Splitter

Introduction

Microwave splitters are generally octave bandwidth or lower. In lab and instrumentation applications, this poses a problem, as one has to buy a series of splitters to cover a bandwidth. Mini-Circuits has designed a 2-way and 4-way splitter covering 10:1 band width, 500-5000 MHz. These splitters have good insertion loss (0.8 dB typ. for 2-way, 1 dB typ. for 4-way, excellent isolation 23 dB typ. and good return loss, 18 dB typ.

Construction

These power splitters use micro strip construction and are manufactured on low loss microwave substrate. These use traditional Wilkinson topology. A number of sections are cascaded to achieve wide band performance. Circuit analysis was done to optimize the performance over the wide frequency range. The circuit is housed in a metal case and SMA connectors are provided as an external connection interface. Figure 1 shows a photograph of the 2-way and Figure 2 that of 4-way splitter.

Performance

Figure 3 shows the insertion loss of the 4-way splitter as a function of frequency. It has a very low insertion loss of 6.3 dB (0.3 dB above 6 dB) at 500 MHz and increases to 1.2 (1.2 dB above 6 dB) dB at 5000 MHz. This loss helps to minimize power dissipation and enables the circuit to handle up to 10W of power. All the four out put ports split power equally, the measured amplitude unbalance is of the order of 0.1 dB. Figure 4 shows the graph of isolation as a function of frequency. Opposite ports (2-3) have higher isolation (30 dB typical) than adjacent ports (1-2, 23 dB typ.). Opposite ports can be used to combine signals when higher isolations are required. The splitters also have excellent phase balance, 1° typically. All ports are matched well into 50Ω. Figure 5 shows the VSWR a function of frequency, it is typically 1.3:1 at the port S and 1.1:1 at the output ports.

Table 1 provides a summary of the electrical specifications of the 2-way splitter ZN2PD2-50 and also that of ZN4PD1-50.

Conclusions

Two very wide band splitters have been developed and are produced in connectorized cases. These will be useful for power combining and splitting applications in lab and for instrumentation use. These are very useful for wide band inter-modulation measurements where multiple tones are combined and fed to a device under test as the splitters cover a wide frequency range. These splitters cover popular application bands such as cellular, WCDMA, fixed satellite, line-of-sight links.