Dual-band bandpass filters using novel stub-loaded resonators (SLRs) are presented in this letter. Characterized by both theoretical analysis and full-wave simulation, the proposed SLR is found to have the advantage that the even-mode resonant frequencies can be flexibly controlled whereas the odd-mode resonant frequencies are fixed. Based on the proposed SLR, a dual-band filter is implemented with three transmission zeros. To further improve the selectivity, a filter with four transmission zeros on either side of both passbands is designed by introducing spur-line. The measured results validate the proposed design.

Dual-Band Bandpass Filters Using Stub-Loaded Resonators

A synthesizing method is presented to design and implement digital dual-band filters in the microwave frequency range. A dual-band filter consists of a bandstop filter and a wide-band bandpass filter in a cascade connection, wherein the transfer functions of both the bandpass filter and bandstop filter are expressed in the Z domain. The bandstop filter is implemented by using a coupled-serial-shunted line structure, while the wide-band bandpass filter is constructed by using a serial-shunted line configuration. In particular, the bandwidth of each passband of the dual-band filter is controllable by adjusting the characteristics of both the bandpass filter and bandstop filter. By neglecting the dispersion effect between microstrip lines of different widths over a wide bandwidth, a dual-band filter is realized in the form of microstrip lines and its frequency responses are measured to validate this method.

Dual-band bandpass filters using equal-length coupled-serial-shunted lines and Z-transform technique

Photonic signal processing has been considered a solution to overcome the inherent electronic speed limitations. Over the past few years, an impressive range of photonic integrated signal processors have been proposed, but they usually offer limited reconfigurability, a feature highly needed for the implementation of large-scale general-purpose photonic signal processors. Here, we report and experimentally demonstrate a fully reconfigurable photonic integrated signal processor based on an InP–InGaAsP material system. The proposed photonic signal processor is capable of performing reconfigurable signal processing functions including temporal integration, temporal differentiation and Hilbert transformation. The reconfigurability is achieved by controlling the injection currents to the active components of the signal processor. Our demonstration suggests great potential for chip-scale fully programmable all-optical signal processing. Scientists experimentally demonstrate a fully configurable photonic integrated signal processor based on an InP–InGaAs material system by controlling the injection currents to the active components.

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A fully reconfigurable photonic integrated signal processor

This paper presents a rigorous design of microstrip bandpass filters with a dual-passband response in parallel-coupled and vertical-stacked configurations. Based on resonance characteristics of a stepped impedance resonator (SIR), the second resonant frequency can be tuned over a wide range by adjusting its structure parameters. Emphasis is placed on filter synthesis for simultaneously matching in-band response and singly loaded Q by using tapped input/output couplings for the two designated passbands. Fractional bandwidth design graphs are used to determine proper geometric parameters of each coupled stage when filter specification is given. Realizable fractional bandwidths of the two passbands for a coupled SIR structure are clearly depicted in fractional bandwidth design graphs. Several experimental filters are fabricated and measured to demonstrate the design.

https://ir.nctu.edu.tw:443/bitstream/11536/13833/1/000228365600027.pdf

Design of microstrip bandpass filters with a dual-passband response

A novel method for designing multiband bandpass filters has been proposed in this paper. Coupling structures with both Chebyshev and quasi-elliptic frequency responses are presented to achieve dual- and triple-band characteristics without a significant increase in circuit size. The design concept is to add some extra coupled resonator sections in a single-circuit filter to increase the degrees of freedom in extracting coupling coefficients of a multiband filter and, therefore, the filter is capable of realizing the specifications of coupling coefficients at all passbands. To verify the presented concept, four experimental examples of filters with a dual-band Chebyshev, triple-band Chebyshev, dual-band quasi-elliptic, and triple-band quasi-elliptic response have been designed and fabricated with microstrip technology. The measured results are in good agreement with the full-wave simulation results

Design of Dual- and Triple-Passband Filters Using Alternately Cascaded Multiband Resonators

In this paper, a novel approach composed of digital signal-processing techniques and optimization algorithms is developed to design and implement filters at microwave frequencies. The design phase begins with the adoption of digital filter prototypes and the implementation phase is facilitated by using both parametric modeling techniques and optimization algorithms. All the zeros of digital filter prototypes are removed first; the remaining part of the prototypes is then transformed to an autoregressive (AR) process by parametric modeling techniques. The values of characteristic impedances of transmission lines synthesizing the filters are adjusted according to the AR process by optimization algorithms. Both low-pass and bandpass filters are designed and then implemented in the form of a microstrip line, and their frequency responses are measured to validate the novel approach.

Design and implementation of filters using transfer functions in the Z domain

Simple and accurate formulations are employed to represent discrete-time infinite impulse response processes of both first- and second-order differentiators in the Z-domain. These formulations, in conjunction with the representations of transmission-line elements in the Z-domain, lead to transmission-line configurations that are eligible for wide-band microwave differentiators. Both the first- and second-order differentiators in microstrip circuits are implemented to verify this method. The experimental results are in good agreement with simulation values.

Implementation of first-order and second-order microwave differentiators

A fully symmetrical six-polarization circular patch antenna is proposed. This antenna is coaxial-fed at center with 12 p-i-n diodes placed across a circular ring slot on the patch. By turning these p-i-n diodes on or off, six linear polarizations at a 30° interval can be produced. Due to the circular symmetry, in theory all these polarizations share the same characteristics. A prototype operating at 2.4 GHz is designed and fabricated. The measured gains of these six polarizations are from 2.64 to 3.52 dBi. Simulated and measured results are in good agreement.

A Symmetrical Reconfigurable Multipolarization Circular Patch Antenna

A novel time-domain reflectometry technique is developed for detecting the physical structures of transmission lines by using arbitrary waveforms. By discretizing both incident and reflected waves, we formulate the reflection coefficient of a nonuniform transmission line as a polynomial ratio in the Z-transform, wherein the numerator and denominator represent the reflected and incident waves, respectively. A reconstruction scheme is derived to obtain the characteristic impedance profile of a transmission line. Some examples are presented to illustrate the validity of this new technique.

Ching-Wen Hsue

Papers

Dual-band bandpass filters using equal-length coupled-serial-shunted lines and Z-transform technique

Design and implementation of filters using transfer functions in the Z domain

Implementation of first-order and second-order microwave differentiators

A Symmetrical Reconfigurable Multipolarization Circular Patch Antenna

Time-domain reflectometry using arbitrary incident waveforms