A coupling-matrix approach for the theoretical
design of a type of input-reflectionless RF/microwave bandpass
filters (BPFs) and bandstop filters (BSFs) is presented.
They are based on diplexer architectures with arbitrary-order
bandpass and bandstop filtering channels that feature complementary
transfer functions. The transmission behavior of
these reflectionless filters is defined by the channel that is not
loaded at its output, whereas the input-signal energy that is
not transmitted by this branch is completely dissipated by the
loading resistor of the other channel. Analytical formulas for the
coupling coefficients for the first-to-fourth-order filter designs
are provided and validated through several synthesis examples.
This theoretical design methodology, along with an optimization
step, is also exploited to design input-quasi-reflectionless quasielliptic-
type BPFs with a transmission-zero-(TZ)-generation cell
in their bandpass filtering channel. In addition, the application
of the proposed input-reflectionless BPF and BSF networks
to input-quasi-reflectionless multiplexer design is approached.
It is shown that a single resistively terminated multi-band BSF
branch can absorb the input-signal energy not transmitted by
the multiplexer channels in their common stopband regions to
achieve quasi-reflectionless characteristics at its input. Moreover,
experimental microstrip prototypes consisting of 2-GHz
third-order BPF and BSF circuits, a 2-GHz sharp-rejection thirdorder
BPF with two close-to-passband TZs, and a second-order
diplexer device with channels centered at 1.75 and 2.1 GHz are
developed and measured.
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Input- Reflectionless Acoustic-Wave-Lumped- Element Resonator-Based Bandpass Filters
This paper reports on an RF design methodology for acoustic-wave-resonator-(AWR)-based bandpass filters (BPFs) with input-reflectionless behavior in both their passband and stopband regions. The proposed concept is based on acoustic-wave-lumped-element resonators (AWLRs) that are incorporated in series-cascaded reflectionless stages (RLSs). Each RLS comprises a first-order bandpass section-shaped by three impedance inverters and one AWLR-and a first-order resistively-terminated bandstop section-shaped by two impedance inverters and one AWLR-that are designed to exhibit complementary transfer functions. In this manner, an input-reflectionless behavior can be obtained both at the passband and stopband regions of the filter. In addition, the use of AWLRs in the RLSs facilitates the realization of high-quality-factor quasi-elliptic-type transfer functions with fractional bandwidths (FBWs) that are wider than the electromechanical coupling coefficient (kt 2 ) of its constituent AWRs. For proof-of-concept validation purposes, one- and two-state prototypes were manufactured, and measured at 418 MHz using commercially-available surface-acoustic-wave resonators.
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- Award ID(s):
- 1731956
- NSF-PAR ID:
- 10106100
- Date Published:
- Journal Name:
- 2018 IEEE/MTT-S International Microwave Symposium - IMS
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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