Broad band impedance matching device with reduced line width

#This invention relates to an impedance matching device.

#More particularly, the present invention relates to stripline used to form electronic impedance transformers on low temperature co-fired ceramics.

#Impedance transformers, also known as impedance matching circuits, are used to connect circuits or devices of differing impedances in order to obtain maximum performance. For example, a power amplifier with an output impedance of 4 Ω would need an impedance transformer in order to get maximum power transferred to a 50 Ω antenna. With the proliferation of multi-mode, multi-band wireless systems and the advent of the software definable radio, broadband impedance transformers will play a crucial role in these systems. Without some form of broadband output matching network, multi-band radios would require a multiplicity of narrow, single band radio frequency (hereinafter referred to as RF) power amplifiers. However, single band RF power amplifiers are typically large in size and expensive to fabricate. Further, they tend to have large, unwanted inductive parasitics.

#The foregoing and further and more specific objects and advantages of the instant invention will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment thereof taken in conjunction with the following drawings:

#FIG. 1 is an isometric view of a broad band impedance matching device in accordance with the present invention;

#FIG. 2 is an exploded view of a broad band impedance matching device in accordance with the present invention; and

#Turn now to FIG. 1, which illustrates an isometric view of a simplified broad band impedance matching device 5 with a bandwidth in accordance with the present invention. Impedance matching device 5 includes a plurality of stripline sections electrically connected in series through conductive vias. Device 5 also includes an input impedance, Zin, and an output impedance, Zout. Zin is the impedance measured at an input 20 and Zout is the impedance seen when measured at an output 86, as will be discussed separately. In this example, impedance matching device 5 includes a stripline section 12, a stripline section 30, and a stripline section 50, which are illustrated as individual units for convenience of description.

#As illustrated in FIG. 1, section 12 has input impedance Zin12 and an output impedance Zout12, section 30 has an input impedance Zin30 and an output impedance Zout30, and section 50 has an input impedance Zin50 and output impedance Zout. In general, a stripline section is sandwiched therebetween ground planes and includes N stripline regions wherein N is a whole number greater than or equal to one. The spacing between ground planes in the same section and the stripline taper can be adjusted to obtain the desired Zin and Zout. A stripline region includes a stripline with a characteristic impedance sandwiched therebetween dielectric layers, wherein each dielectric layer has a thickness and wherein each adjacent stripline in the same section is connected in parallel. By connecting each adjacent stripline in parallel, the line width ratio is reduced, as will be discussed separately. Further, each adjacent stripline region in the same section is separated by a ground plane.

#For example, in this simplified embodiment, stripline section 12 includes a ground plane 14 whereon a dielectric layer 16 with a thickness 26 is positioned. A tapered stripline 18 with an input width 27, an output width 39, and a characteristic impedance is positioned thereon dielectric layer 16. A dielectric layer 22 with a thickness 28 is positioned thereon tapered stripline 18 and dielectric layer 16, and a ground plane 24 is positioned thereon dielectric layer 22, wherein N is equal to one. In this embodiment, thickness 26 is chosen to be equal to thickness 28, as will be discussed separately. Further, input 20 is electrically connected to tapered stripline 18.