Ceramic antenna module and methods of manufacture thereof
Circuit modules and methods of construction thereof that contain composite meta-material dielectric bodies that have high effective values of real permittivity but which minimize reflective losses, through the use of host dielectric (organic or ceramic), materials having relative permittivities substantially less than ceramic dielectric inclusions embedded therein. The composite meta-material bodies permit reductions in physical lengths of electrically conducting elements such as antenna element(s) without adversely impacting radiation efficiency. The meta-material structure may additionally provide frequency band filtering functions that would normally be provided by other components typically found in an RF front-end.
1. An antenna module, comprising:
a composite dielectric body including at least one ceramic dielectric inclusion composed of at least one material selected from the group consisting of materials having a relative dielectric permittivity ≧10 and materials having a relative dielectric permeability ≠1, the at least one ceramic dielectric inclusion embedded in a dielectric host material selected from the group consisting of amorphous silica, titania, tantalates, pure alumina, admixtures thereof, and an organic media such that the composite dielectric body has an effective permittivity ≧4;
a metallization layer adjacent the composite dielectric body and including a ground plane and at least one contact pad;
at least one electrically conductive element disposed parallel to the metallization
layer and electrically connected with the at least one contact pad, each conductive element disposed relative to the composite dielectric body such that the conductive element is resonant over a band of frequencies and has a length that is ≦50% of the length that would be required to maintain the same resonance without the composite dielectric body; and
an interconnect structure including:
an oxide ceramic body located on a side of the metallization layer opposite the at least one electrically conductive element;
at least a first conductive contact embedded at a first surface of the oxide ceramic body;
at least a second conductive contact at a second surface of the oxide ceramic body; and
at least one transmission line embedded within the oxide ceramic body at a uniform distance above the ground plane and providing an electrical pathway between the first conductive contact and the second conductive contact through the oxide ceramic body;
wherein the first conductive contact or the second conductive contact is electrically connected to the at least one contact pad.
2. The module of claim 1 , wherein:
the dielectric inclusions each have a maximum nominal grain size of less than 50 nanometers; and
the effective permittivity of the composite dielectric body changes as a function of temperature ≦5×10 −2 ° C. −1 .
3. The module of claim 1 , wherein:
the dielectric inclusions each have a maximum nominal grain size of less than 35 nanometers; and
the effective permittivity of the composite dielectric body changes as a function of temperature ≦9×10 −3 ° C. −1 .
4. The module of claim 1 , wherein the interconnect structure further includes a layer of high permittivity ceramic (∈ R ≧10) disposed between the metallization layer and the at least one transmission line, the ceramic layer having a corresponding one or more vias to accommodate the electrical pathway through the oxide ceramic body.
5. The module of claim 4 , wherein the at least one transmission line has an intrinsic impedance that is tuned to substantially match the output impedance of a semiconductor die electrically connected to the first conductive contact or the second conductive contact.
6. The module of claim 4 , wherein the high permittivity ceramic layer is composed of at least one material selected from the group consisting of titania, tantalate, and niobate oxide ceramic.
7. The module of claim 1 , wherein the interconnect structure further comprises:
a capacitive pad embedded within the oxide ceramic body; and
a branch extending from the transmission line and terminating on the capacitive pad.
8. The module of claim 7 , wherein the transmission line is composed of discrete wire.
9. The module of claim 1 , wherein the oxide ceramic body includes a spun coat layer of oxide ceramic material having a surface roughness ≦0.1 μm RMS upon which the at least one transmission line is disposed.