A class of frequency-reconfigurable input-reflectionless/absorptive RF/microwave filters is presented. They consist of tunable complementary-duplexer architectures that are composed of a main and an ...auxiliary channel with opposite filtering transfer functions. By loading the auxiliary channel with a reference-impedance resistor and by taking the output node of the main channel as the output terminal of the overall circuit, a filtering network of the same type of the main channel with theoretically perfect input-reflectionless behavior at all frequencies can be realized. This technique can be applied to design spectrally agile completely input-reflectionless filters with any kind of transfer function, such as low-pass, high-pass, and single/multiband bandpass/bandstop filters. The theoretical analysis of the first-order absorptive bandpass/bandstop filtering sections based on a coupling-matrix formulation is detailed. Furthermore, the synthesis of high-selectivity reflectionless filters either by cascading multiple first-order cells or using high-order channels in a single complementary duplexer is also described. For practical-demonstration purposes, frequency-tunable lumped-element and microstrip prototypes are manufactured and characterized. They correspond to first- and second-order bandpass/bandstop filters. In addition, their in-series cascade connection is used to implement a bandpass filter with spectrally controllable passband and out-of-band notches.
Various families of flat-in-band-group-delay RF planar bandpass filters (BPFs) with multiple out-of-band transmission zeros (TZs) in their filtering transfer function are presented. As the first ...approach, a type of BPFs with theoretically-constant group-delay profile and perfect two-port-reflectionless behavior is proposed. The theoretical sufficient conditions to obtain a frequency-constant group delay in a generalized form of transfer function for these BPFs are derived. They are then particularized in transmission-line-based transversal-circuit realizations with flat-in-band-group-delay and quasi-reflectionless characteristics. Afterwards, a class of reflective-type BPFs based on directional power couplers that are arranged in transversal-mode topologies are addressed toward its practical demonstration for the first time. These BPFs, which exhibit flat in-band group delay, are compared with their classic Bessel-type BPF counterparts without TZs. Moreover, discrete-time models of such BPFs are derived, analyzed, and discussed. For experimental-validation purposes, proof-of-concept microstrip prototypes centered at 2.5-GHz of the engineered quasi-absorptive<inline-formula> <tex-math notation="LaTeX">\bm{/}</tex-math> </inline-formula>reflective-type flat-in-band-group-delay BPFs are designed, manufactured, and characterized.
Microwave planar balanced single-/dual-band bandpass filters (BPFs) with symmetrical quasi-reflectionless differential-mode behavior are presented in this letter. They are made up of a direct ...single-/dual-band BPF branch with virtually short-ended stubs in differential-mode operation, whose input and output accesses are loaded with stub-loaded-type single-/dual-band bandstop filter (BSF) branches that are terminated with a resistor. These BSF branches exhibit a quasi-complementary transfer function with regard to the one of the BPF branch and absorb the differential-mode input-signal energy not transmitted by the filter to achieve quasi-reflectionless capabilities. The theoretical foundations of the proposed balanced quasi-absorptive single-/dual-band BPFs and synthesis examples are given. Furthermore, for experimental-demonstration purposes, microstrip prototypes of 3-GHz second-order single-band and 2.85/3.15-GHz first-order dual-band BPFs are manufactured and characterized.
Lossy Signal-Interference Filters and Applications Gomez-Garcia, Roberto; Yang, Li; Munoz-Ferreras, Jose-Maria ...
IEEE transactions on microwave theory and techniques,
02/2020, Letnik:
68, Številka:
2
Journal Article
Recenzirano
Lossy signal-interference transversal filtering sections (TFSs) composed of two in-parallel transmission-line segments with input-output matching lines-reflective-type part-and open-ended stubs with ...input resistors-lossy part-are presented. First, in their bandstop and dual-band bandpass versions, this class of lossy TFS is applied to the design of filtering networks with input-/two-port-quasi-reflectionless (QR) stopbands, such as wide-band bandstop filters (BSFs) and dual-band bandpass filters (BPFs). Furthermore, multistage circuit architectures made up of equal and dissimilar lossy TFSs for higher rejection and broader stopband realization, respectively, and higher selectivity dual-band BPF synthesis are described. Subsequently, in its bandpass counterpart, the conceived approach of lossy TFS is exploited to develop single-/multistage sharp-rejection bandpass filters (BPFs) with a flattened transmission band. The operational foundations of the engineered types of lossy TFSs for the suggested applications and theoretical design examples are provided. In addition, for experimental-validation purposes, four microstrip filter prototypes are manufactured and characterized, as follows: 2-GHz two-stage symmetrical QR BSFs with similar and frequency-contiguous bandstop TFSs for higher rejection and broader stopband shaping, respectively, a 1.4/2.6-GHz input-QR dual-band bandpass TFS, and a 2-GHz five-stage lossy BPF with enhanced passband amplitude flatness and spectrally enlarged attenuated bands.
An approach to design quasi-elliptic-type planar filters with single-and dual-band bandpass transfer functions and input-absorptive capabilities is presented. Two-branch channelized passive circuit ...configurations are exploited for this purpose, in which the low-order reflective-type filtering profile of their branches is converted into the desired sharp-rejection input-reflectionless filtering action in the overall circuit. This is achieved by means of fully-destructive and frequency-selective transversal signal-interference effects at the total input and output accesses of the channelized filter, respectively. The theoretical operational principles of the proposed concept of single<inline-formula> <tex-math notation="LaTeX">/</tex-math> </inline-formula>dual-passband input-reflectionless two-branch channelized filter are detailed, along with design considerations for their RF transmission-line-based implementation. Besides, its generalization to <inline-formula> <tex-math notation="LaTeX">\bm{N}</tex-math> </inline-formula>-channel architectures is also analyzed. Furthermore, as the fundamental elements of the devised channelized filtering philosophy to increase selectivity, alternative solutions to realize their output phase-delay sections for a more-flexible control of the transmission zeros in the overall transfer function are discussed. For experimental-demonstration purposes, two microstrip proof-of-concept prototypes are developed and measured. They consist of 3-GHz single-band and 2.58<inline-formula> <tex-math notation="LaTeX">/</tex-math> </inline-formula>3.43-GHz dual-band designs with input-quasi-reflectionless spectral ratio above 2.5:1 and 3:1, respectively.
The theoretical design and practical development of RF analog filtering devices with co-integrated lowpass, single<inline-formula> <tex-math notation="LaTeX">\bm{/}</tex-math> ...</inline-formula>multi-band bandpass, and highpass transfer functions is reported. For this purpose, two different classes of generalized frequency transformation that convert the equivalent normalized lowpass filter prototype into the desired RF filter with several co-designed filtering actions are proposed. They realize a frequency mapping of the reactance of a normalized unitary capacitor into that of a one-port single<inline-formula> <tex-math notation="LaTeX">/</tex-math> </inline-formula>multi-resonance cell with added lowpass and highpass filtering capabilities. For these devised frequency transformations, the theoretical foundations and various illustrative filter examples designed at the ideal-circuit-model level are presented. In addition, higher-selectivity filter architectures based on the generation of additional out-of-band transmission zeros (TZs) by means of cross-coupling techniques are shown. Afterwards, the extension of this design methodology to RF multi-functional filtering components, such as input-reflectionless<inline-formula> <tex-math notation="LaTeX">\bm{/}</tex-math> </inline-formula>absorptive filters based on complementary-diplexer circuit networks and two-way filtering power-distribution circuits, is also demonstrated. Furthermore, two design examples of distributed-element and inverterless lumped-element RF filters are provided. Besides, for the distributed-element circuit, a proof-of-concept microstrip prototype is manufactured and measured as experimental validation.
A type of compact single/multi-band coupled-multiline filtering section and its application to the design of RF filtering devices are presented. This one-port filtering cell is made up of N + 1 ...intercoupled quarter-wavelength transmission-line segments for the generation of a transfer function with a total of N + 1 transmission zeros (TZs) distributed at both sides of all its N first-order passbands when arranged in the transmission mode. Design formulas for the produced poles and TZs of its corresponding normalized coupling-routing diagram and illustrative theoretical responses are provided. Furthermore, for experimental demonstration purposes, microstrip prototypes of the following RF filtering components that exploit the conceived filtering section are manufactured and measured: 1) a quasielliptic-type diplexer with a dual-band bandpass filter (BPF) junction; 2) two input-reflectionless triple-band BPF and bandstop filter (BSF) circuits; and 3) an out-of-phase equal-power-division bandpass filtering coupler with input-quasi-reflectionless behavior.
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 quasi-elliptic-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 third-order 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.
The direct synthesis of a family of digital-filter-based RF analog circuits with transmission zeros (TZs) and constant-group-delay behavior is reported. The adopted RF circuit consists of a ...transversal filtering network composed of transmission-line segments that are connected through a multi-way power divider and combiner at its input and output terminals, respectively. The synthesis procedure starts by obtaining the coefficients of a finite-impulse-response (FIR) digital filter of interest and finalizes with the determination of the electrical parameters of the RF circuit. In particular, designs corresponding to Dolph-Chebyshev windows are addressed in this brief. For experimental-demonstration purposes, two 5-GHz proof-of-concept microstrip prototypes of a symmetrical-quasi-reflectionless bandpass filter (BPF) with Dolph-Chebyshev-type response and the in-series cascade connection of two replicas of it are designed, manufactured, and tested.
Symmetrical Quasi-Absorptive RF Bandpass Filters Gomez-Garcia, Roberto; Munoz-Ferreras, Jose-Maria; Psychogiou, Dimitra
IEEE transactions on microwave theory and techniques,
04/2019, Letnik:
67, Številka:
4
Journal Article
Recenzirano
Odprti dostop
A type of symmetrical RF bandpass filters (BPFs) with quasi-absorptive functionality are presented. They are composed of a bandpass section that is loaded at its input/output ports with nearly ...complementary resistively terminated bandstop sections. In this manner, the input-signal energy that is not transmitted by the bandpass section is dissipated by the loading resistors of the bandstop sections to attain the quasi-reflectionless behavior. The theoretical analysis of the first-order symmetrical quasi-absorptive BPF stage is detailed. In addition, synthesis examples of higher attenuation and sharper rejection designs based on in-series-cascade arrangements, higher order realizations, and cross-coupling techniques are illustrated. A coupling-matrix-level loss analysis of the devised symmetrical quasi-reflectionless BPF configuration for uniform and nonuniform quality-factor (<inline-formula> <tex-math notation="LaTeX">{Q} </tex-math></inline-formula>) distribution is also carried out. Furthermore, for experimental validation, 2.5-GHz microstrip BPF demonstrators consisting of an in-band linear-phase two-stage in-series-cascade circuit and a second-order prototype are manufactured and characterized.
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