SIW planar balun with enlarged bandwidth

Abstract

An X‐band substrate integrated waveguide (SIW) balun, based on a Y‐type divider with enlarged bandwidth, is presented in this study. In most SIW Y‐type dividers, the undesired TE30 mode either leads to the deterioration of the in‐band reflection or constrains the bandwidth by a transmission zero. The cause of the transmission zero is analysed and the modes coupling, rather than the step impedance matching, is utilised to reduce its impact. In the traditional Y‐type divider, the frequency band is split by this transmission zero, while in the proposed wideband configuration, the co‐existences of the TE10 and TE30 modes are employed to combine the two non‐contiguous bands. A broadband balun is designed and fabricated, with the improved Y‐type wideband divider serving for the power‐dividing part. The dividing ports are connected to the reversely placed transitions, achieving inherent out‐of‐phase performance and good amplitude property. The measurement of the balun suggests a 43.94% bandwidth from 8.23 to 12.89 GHz, with 15 dB return loss. The measured amplitude and phase imbalance between two output ports are below 0.7 dB and ±3°, respectively. The performance of the fabricated balun is in agreement with the simulation, and it is promising for wideband applications.

Cyclic olefin copolymer‐based copper clad laminate and the application for low loss broadband baluns

“…In contrast to conventional waveguide, the SIW structure has broadband monomode characteristics, as the reason is that the SIW is a quasi‐rectangular waveguide formed by periodic via‐hole or slot arrays connected between two metal layers, which supports only the TEm0 mode 25,26 . The operating frequency band of SIW is commonly occupied between the cut‐off frequencies of the TE10 and TE20 modes, which also depends on the in‐band reflection 27 . Moreover, compared to other solutions such as microstrip and CPW, the SIW exhibits better loss characteristic for application at millimeter‐wave or higher frequencies.…”

“…As can be seen in Table 4, the “designed balun” based on the “COC‐HMSIW” with resistors achieves a wider band and good isolation. The baluns in Fu et al 27 based inherent electric field distribution of the TE 10 and TE 30 mode provide wideband and great amplitude imbalance, but this type of baluns lacks of isolation characteristic. The balun in Huang et al 26 incorporates absorbing material to obtain isolation, the baluns in Pasian et al 30 require multiple layers and increase structure complexity.…”

A BTB UWB power divider with arbitrary power‐dividing ratio based on three‐slotline structure

“…Recently, most of the reported works are single ended‐to‐single ended (SETSE) 4‐7 . In Reference 4, a wideband power divider (PD) with arbitrary power division ratio (PDR) was presented with a tunability of PDR from 0.5:1 to 2:1 across wideband range of 60% and a controllable band from 35% to 63.2%.…”

“…In Reference 5, a new equivalent circuit model of an electrical size‐reduced coupled line radio frequency Marchand balun was proposed. In References 6,7, two design of substrate‐integrated waveguide (SIW) PDs were presented. Several balanced‐to‐single ended (BTSE) PDs are also reported lately.…”