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The design of mixed-technology quasi-reflectionless planar bandpass filters (BPFs), bandstop filters (BSFs), and multi-band filters is reported. The proposed quasi-reflectionless filter architectures comprise a main filtering section that determines the power transmission response (bandpass, bandstop, or multi-band type) of the overall circuit network and auxiliary sections that absorb the reflected radio-frequency (RF) signal energy. By loading the input and output ports of the main filtering section with auxiliary filtering sections that exhibit a complementary transfer function with regard to the main one, a symmetric quasi-reflectionless behavior can be obtained at both accesses of the overall filter. The operating principles of the proposed filter concept are shown through synthesized first-order BPF and BSF designs. Selectivity-increase techniques are also described. They are based on: (i) cascading in-series multiple first-order stages and (ii) increasing the order of the filtering sections. Moreover, the RF design of quasi-reflectionless multi-band BPFs and BSFs is discussed. A hybrid integration scheme in which microstrip-type and lumped-elements are effectively combined within the filter volume is investigated for size miniaturization purposes. For experimental validation purposes, two quasi-reflectionless BPF prototypes (one- and two-stage architectures) centered at 2 GHz and a second-order BSF prototype centered at 1 GHz were designed, manufactured, and measured.
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Input-Reflectionless Out-of-Phase 3-dB Bandpass Filtering Couplers
A class of out-of-phase 3-dB bandpass-filtering couplers with input-reflectionless capabilities is presented. To obtain the bandpass-filter (BPF) functionality, identical BPF sections are respectively co-integrated in the coupler signal paths from the input to the direct and coupled ports. Furthermore, a resistivelyterminated bandstop-filter (BSF) section with complementary transfer function with regard to the one of the BPF section is loaded at the coupler input access. In this manner, the RF inputsignal energy that is not transmitted to the direct and coupled terminals is dissipated by the loading resistor of the BSF section. Hence, the input-reflectionless behavior is realized. Optimizationbased first-to-third-order design examples are shown. Moreover, for practical-validation purposes of this RF tri-functional device, a 2-GHz second-order microstrip prototype is built and tested.
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- Award ID(s):
- 1731956
- PAR ID:
- 10106144
- Date Published:
- Journal Name:
- 2019 IEEE Radio and Wireless Symposium (RWS)
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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