Jongheun Lee

In this article, we present a novel generic reflectionless filter topology that can produce an arbitrary predefined transmission response while having the perfect impedance matching at both ports. A detailed procedure for synthesizing reflectionless filters using our topology is also given in this article. One of the unique features of our reflectionless filter topology is that the even- and odd-mode half circuits are not correlated with each other, which makes the filter synthesis straightforwa

This article is to present a complete method to design transmission-line reflectionless filters. Our approach can be used to accord a transmission-line filter to feature an infinite frequency range of reflectionless response. It can be applied to reflectionless filter prototypes consisting of filtering and matching sections that comply the Cauer topology. Hence, it does not limit by the filter order and/or the filter response type. Design equations supporting our approach are provided, and their

In this letter, we present a systematic design method for a reflectionless bandstop filter using distributed-element resonators. One unique feature of the presented filter structure is that it is capable of producing a broadband impedance matching at both ports with a flat passband. For verifying the design approach, a second-order Butterworth reflectionless bandstop filter centered at 2 GHz with fractional bandwidth of 8% has been designed, fabricated, and measured. The measurement shows that t

In this article, we present a rigorous design method for a symmetric reflectionless bandstop filter with coupled lines. Analytic design equations and the detailed procedure for formulating narrowband reflectionless bandstop filter structures are given in this article. The presented design theory allows us to design a symmetric reflectionless bandstop filter with a predefined transmission response and an excellent impedance matching performance over a wide frequency range. Using the circuit formu

In this article, we present a new generic reflectionless filter topology that can be used in designing not only a filter having zero reflection at one port but also a filter having zero reflection at both ports. Detailed mathematical analysis of the presented reflectionless filter topology is provided. The three unique features, which will be described throughout this article, allow us to straightforwardly synthesize a reflectionless filter with ease. Hence, the synthesis procedure does not nece

This article discusses a rigorous and straightforward method to synthesize and design a transmission-line-based reflectionless bandstop filter with high performance in terms of reflectionless range. Our design strategy targets to allow a reflectionless bandstop filter to feature three distinguished advantages that are incomparable to others. First, the presented filter structure is capable of producing an exceptional broadband impedance matching performance. Second, it can be designed to have an

This article presents a systematic approach for formulating transmission-line canonical cross-coupled filters. It will be shown that a filter schematic can be formulated from a coupling diagram having an arbitrary sign combination of the coupling coefficients by properly utilizing the two types (N- and P-types) of standard building blocks. Several practical filter schematics and their design formulas will be presented. Design instructions—how to use the design formulas in actual filter designs—w

An accurate method to implement a bandpass-domain coupled-line Foster section is presented. Two types of practical coupled-line structures are presented and closed-form equations for their design parameters are given in terms of lowpass prototype parameters, reference impedance, and fractional bandwidth so that one can readily use them in various filter designs. The design process of a bandpass filter using Foster sections is described via an example.

This article presents a novel and rigorous technique to design transmission-line quadruplet filters. Unlike the prevailing approaches relying on electromagnetic (EM) simulations for coupling tests, the proposed design technique completely counts on rigorous circuit transformations. As all design parameters (lengths and line impedances) can be rigorously calculated from the design equations provided in this work, a quadruplet filter can be designed without conducting EM simulations to find the di

In this paper, we present a new method for designing absorptive bandpass filters using coupled lines. The new design method and filter structure allow an absorptive bandpass filter to have good impedance matching performance over a wider frequency range in comparison with distributed-element absorptive filters reported in the literature. Closed form design equations are provided so that a filter can be designed in a way to produce a target frequency response. For verifying the presented design a

A new filter topology for a second-order absorptive bandstop filter with Butterworth response is presented in this paper. Closed-form design equations for having a Butterworth transmission response and no reflection at all frequencies are also provided. Hence, an absorptive bandstop filter can be designed such that its transmission response is identical to the one of a conventional reflective filter. For verifying the presented filter topology and design formulas, an absorptive bandstop filter w

This article presents a rigorous synthesis method of a transmission-line filter whose second passband can be placed at any multiple of the center frequency, in theory. Two coupled-line schematics for harmonic-controlled bandpass filters are derived from fundamental <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> filter prototypes. Their design parameters are provided in closed-form expressions so filter dimensions can be acquired rigorousl

Characterization of devices operating under large signal conditions at nonlinear regions requires specific measurement setups since the output power value, operation efficiency, power gain, and linearity are functions of the source impedance, input signal level, biasing values, and load impedance. Hence, measuring a device’s parameters while varying the source or load impedance (called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">source-pull</

A practical reflectionless bandstop filter topology is presented in this paper. One unique feature of the presented distributed-element reflectionless filter circuit compared to others is that it only requires to design and tune N+1 pairs of coupled lines for an Nth-order filter. Closed-form design equations for a second-order filter have been provided, and they can be expanded for higher-order filters. For verifying the presented filter topology and the design method, a reflectionless bandstop

This paper presents a symmetric reflectionless filter topology that is capable of producing the canonical Butterworth responses with zero reflections at both ports. Straightforward design methods of a coupled-line bandpass filter using the newly synthesized filter topology are also given. Hence, a filter can be designed analytically without relying on a time-consuming numerical method. The measured frequency responses are in a good agreement with the synthesis.