Passive microwave components are electrical elements without gain or directionality, yet they perform a range of functions such as signal attenuation, filtering, dividing/combining and routing. Designed for every medium from RF boards to System in Packages (SiP) to integrated circuits (MMIC/RFIC), passives are ubiquitous and essential. Driven by complex communication systems, today’s passives must address high performance and unprecedented miniaturization at the lowest possible cost. Given these demands, considerable engineering effort is focused on developing enhanced passive devices.
As a result, Microwave Journal receives numerous papers detailing the use of new materials and circuit topologies. Among the various types of passives, the majority of submitted papers discuss novel technologies applied to filters and power combiners/dividers/couplers. This month, we are publishing a number of papers from our editorial backlog that address these types of passive designs.
From our divider/combiner/coupler files, we offer three board designs. Two of these tackle multi-band operations: one with an enhanced bandwidth Wilkinson power divider, the other with an N-way power divider. Both board designs demonstrate easy, low cost fabrication with minimal bill of materials and reasonable performance at the dual frequencies of 915, 2450 MHz and 1, 2.5 GHz. Our third divider paper is based on an ultra-broadband Wilkinson power divider operating from 15 to 45 GHz. This paper provides an excellent tutorial on basic multi-section divider theory and its implementation. Each of these three papers offers practical design information that should prove beneficial to our readers.
With multi-band radios and crowded frequency bands, filter performance is also important and therefore garners a good deal of engineering effort. While many filter companies keep quiet about their product’s “secret sauce,” the academic world is extremely generous in supplying Microwave Journal with content. Among these, we offer four technical papers this month.
A bandpass filter (BPF) can take many shapes as demonstrated in one paper discussing a compact elliptic-function BPF with slotted hexagonal resonators and open stubs for capacitive loading. Alternatively, an ultra-wideband (UWB) BPF operating from 3.1 to 10.6 GHz with a notched band from 7.5 to 7.6 GHz is achieved with two cascaded inter-digital hairpin resonators and four semicircle defected ground structures (S_DGS). Improved selectivity and miniaturization are both addressed with a compact multi-layer filter design utilizing split-ring resonator (SRR) metamaterials and skew-symmetric feeds. Lastly, we offer a paper that integrates a balun and BPF with a center frequency of 2.45 GHz and a 90 MHz bandwidth utilizing a dual-ring structure to improve the balanced port characteristics.
If you design either type of passive, we hope this issue is particularly useful. If you currently don’t, save this Journal for the day that you might. After all, even though these devices are passive, their impact on system performance is anything but inert.
