Most communication satellites contain well over a hundred filters
in their payload. Current technology in typical satellite multiplexers
use dual-mode cavity or dielectric resonator filters that are
large (~25 to 125 in.3) and heavy
(up to 600 g). As the complexity of future advanced electronic
systems for satellite communications increases, even more filters
will be needed, requiring filter miniaturization without performance
degradation. Such improvements in filter technology will enhance
satellite performance. To reduce the size, weight, and cost of
the multiplexers without compromising performance, the NASA Lewis
Research Center is collaborating with industry to develop a new
class of dual-mode multilayer filters consisting of
YBa2Cu3O7-d
high-temperature superconducting (HTS) thin films on LaAlO3
substrates.
A major limiting factor in the continuing improvement of satellite
communication systems is the unavailability of high-performance
(i.e., high-Q) miniaturized filters that are compatible with monolithic
microwave integrated circuits (MMIC) components. The poor Q factor
of current miniature, planar components is due primarily to conductive
loss, which can be significantly reduced by using HTS thin films
(For example, at 77 K the surface resistance of
YBa2Cu3O7-d
thin films at 10 GHz is more than 2 orders of magnitude lower
than that of copper at the same temperature and frequency). Therefore,
it will be advantageous to replace dual-mode cavity and dielectric
resonator filters with HTS thin-film-coated printed circuits that
are dramatically smaller, lighter, and potentially less costly.
In this work, a new class of miniaturized filters based on a multilayered
stack of dual-mode stripline or microstrip resonators coupled
through irises, is being developed. These filters, which are extremely
small in size and mass, can be fabricated of thin-film superconductors
such as YBa2Cu3O7-d. All current
filter types that have dual-mode cavities or dielectric resonators
can be replaced with those having this novel filter structure.
For example, in the C-band this configuration will occupy
only 1 percent of the volume of its dielectric resonator counterpart.
Also, the multilayer configuration is smaller and lighter than
the previously introduced dual-mode microstrip filters (ref. 1).
The YBa2Cu3O7-d/LaAlO3
multilayer filters being pursued in this work can be based on
a variety of dual-mode, planar resonator structures similar to
those used in dual-mode microstrip filters. These include square
patches, circular disks, and rings (ref. 2). Coupling between
the dual orthogonal modes supported by these resonators is achieved
by introducing a perturbation to the symmetry of the previously
single-mode resonator at a location that is offset 45° from the
axes of coupling to and from the resonator. Proof-of-concept of
these miniaturized multilayer filters has already been demonstrated
in our laboratory (ref. 3), and work is underway to optimize their
performance through more detailed analysis, fabrication, and testing.
Previous articleLast updated April 30, 1997
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