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This work presents the design and analysis of a novel dual-wideband bandpass filter (BPF) using the transversal filtering section (TFS), coupled lines (CLs), and stepped impedance stubs (SISs). Initially, a dual-band BPF employing TFS and CLs is designed. To enhance the bandwidth and selectivity, SIS units and quarter wavelength transmission lines are attached at the input and output ports. This novel filter’s frequency response has six transmission zeros in the stopband and four transmission poles in each passband. A prototype with center frequencies of 1.17 and 2.4 GHz is realized on a biodegradable substrate and tested. The tested and simulated results are in high congruence, validating the proposed design circuit and theory.

In this brief, for the first time, dual-band bandstop filters (DBBSF) for millimeter-wave operation at 30/80 GHz bands are presented in 0.18 $\mu \text{m}$ CMOS process. The filter design is based on TFMS shunt open-ended stepped-impedance resonators, which exhibit dual stopband response with impedance controlled center frequencies and bandwidths. Lossless transmission line model is used for theoretical analysis, where the conditions for acquiring two stopbands and to achieve good stopband isolation are investigated using single and double resonators. Furthermore, an improved design for good passband at mid-band has been proposed, resulting in a DBBSF that could also replace a wideband bandpass filter with sharp-rejection on both sides. Two prototype filters with optimally compact geometries are fabricated and characterized to demonstrate dual-band bandstop characteristics at 30/80 GHz. The measured results are in good agreement with full-wave electromagnetic simulations.

In this brief, a modified coupled-line (CL) hairpin unit topology with short-circuited ends is proposed to design a compact millimeter-wave ultra-wideband (UWB) bandpass filter (BPF). Thin film microstrip configuration is used for the implementation of CL hairpin unit. The passband return loss bandwidth is enhanced by three attenuation poles achieved by appropriately selecting a single set of CL impedances. Explicit design equations along with graphs are provided by using even-and-odd mode analysis. A prototype filter is fabricated using 0.35- ${\mu }\text{m}$ BiCMOS technology. The fabricated UWB BPF achieves an extended passband from 25 GHz to 95 GHz around 60 GHz with more than 115% fractional bandwidth along with a wide return loss bandwidth. The filter size is very small with the overall width comparable to the width of a 50 ${\Omega }$ line. The measured results are in good agreement with those of predicted ones up to 110 GHz.

This paper presents the design and implementation of a millimeter-wave on-chip dual-band bandpass filter (DBBPF) using 0.35 µm standard BiCMOS process. A compact transmission line topology based on stub-loaded coupled line unit is proposed to implement the DBBPF. Sharp-rejection passbands are realized with five transmission zeros (TZ) that are controlled by the impedances of the proposed configuration. Only three impedances are involved in the entire design and the topology is compact and free from the usage via holes and multiple metallization levels. A prototype 35/70 GHz DBBPF is demonstrated and the measured results are found to be in good agreement with the simulation results. Five TZs are seen in both simulation and measurements resulting in sharp roll-off characteristics.

This paper presents development of a compact and a robust high performance diplexer implemented using co-axial guide at S-band. It is designed to operate at a power level of around 200 W in the frequency band from 2.02 GHz to 2.3 GHz with an insertion loss better than 1.0 dB. To achieve the stringent isolation requirements between adjacent uplink & downlink frequency bands, higher order filters with a rejection of 100 dB are designed. The diplexer is used in Transportable antenna Terminal for tracking & commanding of satellites & launch vehicles. The measured results conform to the required specifications. In-addition, innovative fabrication aspects are also presented which is extremely critical to successfully achieve such high performance diplexers.

In this paper, uniplanar design of harmonic/higher order mode suppression microstrip antenna is proposed in contrast to the usual defected ground plane structure/photonic bandgap techniques. The main advantages of present design include ease of integration without the requirement of air gap beneath the antenna and less sensitive to the alignment and mounting issues. The suppression of the higher order harmonics is achieved by using a compact multi-stub unit resonator, which occupies only 37% size of patch dimensions. This resonator consists of a printed metallization in the same layer. Comparing with conventional inset-fed square microstrip patch antenna, the radiated power of the proposed antenna at the first two higher order mode frequencies is reduced by 14 dB and 10 dB, respectively, while exhibiting the good performance at the fundamental operating frequency.

A novel application of signal-interference technique to branch-line coupler design is proposed for miniaturization and wideband harmonic passband suppression. The coupler's second, third and fourth harmonic passband responses are attenuated due to a pole at each of these harmonics. Design equations and graphs are provided using lossless transmission line model. A prototype coupler, having a compact (λ g /6)2 area, that is 44.4% of the (λ g /4)2 conventional coupler area, is fabricated in microstrip form for validation purposes. The input matching, isolation, amplitude and phase balance bandwidths of the proposed coupler are comparable to those of the conventional coupler.

In this paper, simple shunt open-stub units are used to design a compact balun with suppressed harmonic response. The stopband response of shunt stubs has been utilized to suppress the harmonic passbands. Design guidelines are presented with equations and graphs based on transmission line model. To validate theoretical predictions, an experimental prototype microstrip balun, with suppressed harmonic passbands up to six times the operating frequency, and occupying only 25% of the conventional balun circuit area is presented.

A novel application of a dual-transmission line is proposed to design a lowpass filter (LPF). The proposed structure uses only transmission line elements to produce an equiripple LPF response with sharp roll-off. Design equations are derived using a lossless transmission line model. Controlling the electrical lengths, three transmission-zeros are realized in the stopband to obtain a sharp roll-off rate and wide stopband bandwidth. A single unit microstrip LPF with a 3-dB cut-off frequency at 1.0 GHz having a roll-off of 135 dB/GHz along with a stopband bandwidth of 69.5% is designed for validation.

In this article, we demonstrate that the compact bandstop filter (BSF) configuration consisting of an edge-coupled microstrip line connected in parallel to a transmission line section can produce multiple transmission zeros in the stopband. A lossless transmission model is used to derive the condition for two, three, or four transmission zeros. A prototype BSF at 2 GHz achieving a wide 20 dB stopband bandwidth of 92.8% with sharp rejection along with a better than 30 dB return loss in the passband is fabricated for validation purposes. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2265–2268, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26258

This article presents the design of harmonic suppressed compact microstrip balun, using shunt open-stubs. Two approaches using Π-shaped and T-shaped open-stub configurations are investigated. Because of the stopband effect of the open-stubs, the harmonic passband responses are suppressed effectively. A compact-size balun is realized because both kinds of structures have slow wave characteristics. To validate theoretical predictions, two prototype baluns operating at f0 = 1 GHz, showing size reduction up to 75% and no spurious passband up to 4f0 compared with the conventional design are fabricated in microstrip form. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011. © 2011 Wiley Periodicals, Inc.

In this letter, explicit transmission zero conditions, for the ultra-wide bandstop filter (BSF) with five transmission zeros, are derived using even-odd mode, analysis. The BSF topology is obtained by folding the two connecting transmission lines in a conventional optimum BSF to compose a stub-loaded coupled-line section and using λ g/2 end open-stubs. A necessary and sufficient condition is explored for the crucial coupled-line section to produce three transmission zeros. Further, it is shown that the same five zeros BSF stopband bandwidth and rejection level performance is obtained with compact three zeros BSF (without λ g/2 open-stubs) with improved passband flatness and return loss.

A simple design of a sharp-rejection microstrip bandpass (BPF) filter is presented. By creating multiple transmission zeros in the lower and upper stopbands, sharp rejection characteristics are obtained. The basic filter unit consists of a single parallel coupled-line section and an open-ended stub. A lossless transmission line model approach is used to derive the design equations for frequency responses and transmission zero positions. The bandwidths are controllable by the zero locations that in turn are controlled by varying the impedances of the configuration. To validate theoretical predictions, two prototype BPFs operating at lower band 2.4 GHz of WLAN are fabricated in microstrip form.

In this article, the design of a broadband branch-line coupler (BLC) with reduced size and suppressed harmonic passband response is presented. The proposed approach can be used to replace the low impedance λ/4 lines of the conventional BLC by an equivalent structure almost λ/12 in length. The main advantage of the proposed BLC is that, it has approximately the same bandwidth as that of a conventional BLC. A prototype broadband coupler having fractional bandwidth >50% at 1.1 GHz and of size less than one third of a conventional three-section wideband BLC topology is realized. In addition, at least 20 dB suppression of up to fourth harmonics is achieved. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011. © 2011 Wiley Periodicals, Inc.

In this article, a single coupled-line configuration is presented for the design of compact, sharp-rejection, wide-stopband low-pass filters. The proposed filter topology consists of parallel coupled-lines shorted at the middle. The filtering action results from the generation of three transmission zeros brought about by cross coupling. Design equations and guidelines to adjust both bandwidth and the rejection depth are provided. Theoretical predictions are validated in microstrip line by fabricating a two-unit prototype filter having better than 25 dB stopband, which is at least five times the filter cut-off frequency. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1402–1405, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25166

In this article, a novel transmission line (TL) shunt stepped impedance open stub configuration has been presented to design a dual-band bandstop filter with impedance controlled center frequencies and bandwidths. Design guidelines are derived using lossless TL model. The high-impedance lines required for TL sections facilitate convenient meandering that makes the geometry compact. To validate theoretical predictions, a prototype filter operating at two bands 1.5 and 3.4 GHz has been fabricated. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2274–2277, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24635

This paper describes the design of a folded rectangular waveguide cavity band pass filter, incorporating virtual negative coupling (VNC) by means of circular iris, at X-band. Thus, the filter is robust from mechanical aspects, and hence apt for space application. The filter realized at 8310 MHz with 1.2 percent fractional bandwidth, has a sharp roll-off due to VNC. As a result, rejection better than 40 dBc is achieved at just 100 MHz offset from band centre. Compared to traditional all pole filter, introduction of VNC has resulted in around 20% size reduction.

Millimeter-wave ultra-wideband (UWB) bandpass filter implemented in a standard 0.18-μm CMOS process is presented in this paper. Thin film microstrip structure (TFMS) is constructed appropriately on the low-resistivity silicon substrate without any post processing steps. Using the transmission line topology composed of quarter-wavelength short-circuited shunt stubs and port extensions, a wide return loss bandwidth is achieved so as to make up a class of UWB TFMS bandpass filter at 60 GHz. A compact geometry with sinuous shaped lines is designed and fabricated. The predicted and measured results are in good agreement up to 110 GHz.

A compact parallel-coupled transmission line section, connected at their both ends, is presented to obtain multiple transmission zeros. As much as five transmission zeros can be obtained. The zeros can be arranged to design a sharp rejection wideband bandstop filter (BSF). A lossless transmission line model is used to analyze the structure and hence to obtain closed form expressions for the -parameters and design graphs to facilitate the filter synthesis procedure. Theoretical predictions are validated by fabricating a BSF in microstrip line technology. The single filter unit provides 29 dB stopband over a fractional bandwidth of 60% at the mid-band frequency of 1.47 GHz.

A novel application of shunt open-stubs at the feed points of a center fed coupled-line hairpin resonator is presented for the design of compact lowpass filter (LPF) with very wide stopband. The transmission zeros of the basic unit are minimally affected by its association with the stubs. The stopband bandwidth and filter roll-off rates achieved here are larger than those achieved earlier. A prototype microstrip LPF having a very wide stopband up to nine times the filter cutoff frequency is fabricated.

A novel transmission line topology, using coupled-line and stepped impedance open-stub, is proposed for the design of compact bandpass filter. The topology produces high selective asymmetric bandpass response by realizing a transmission zero either lower side or higher side of the centre frequency. The overall size of the filter unit is compact, which is less than λ g /4 × λ g /4. Further due to the dual-mode like behavior, the filter exhibits low insertion loss. Design equations are derived explicitly based on lossless transmission line model analysis. Two filter prototypes operating at S-band having narrow bandwidths ( 30 dB at f 0 ±200 MHz are fabricated and demonstrated.

This study presents the implementation of a millimeter-wave compact bandstop filter (BSF) using the standard 0.18 μm CMOS process. The topology is based on transversal signal interference technique, obtained by connecting two transmission lines with proper characteristic impedances and electrical lengths in parallel. Sharp-rejection characteristics are obtained without using any extra resonators. Moreover, BSF having single-characteristic impedance is analyzed for design simplicity. A compact thin film microstrip structure with meandered signal line is properly constructed without any post processing steps. The overall filter occupies a compact circuit area of less than 0.25 λ g × 0.25 λ g and exhibits a 20 dB stopband fractional bandwidth of 21% and high-rejection of about −38 dB at centre frequency of 60 GHz. A good agreement between the predicted and measured results is observed up to 110 GHz.

Two via-free lumped-element compact quadrature hybrid couplers are presented, which enables low loss and ease of fabrication. The present approach uses lumped LC elements in ring form without short-circuit connections and the number of elements used is less than that required for the conventional designs. Furthermore, the present approach exhibits wider coupler bandwidth than that of the conventional coupler. Design equations are derived explicitly and graphs are provided. A prototype coupler, using three inductors and four capacitors, is fabricated at 375 MHz for validation along with the conventional coupler. The designs are suitable for low frequency and ultra-miniature high frequency couplers applications.

This letter presents the design of a compact bandstop filter (BSF) operating at two frequencies. The proposed BSF consists of open-ended stepped impedance resonators (OSIR) and an end-shorted parallel-coupled microstrip line (E-PCML). The OSIRs are used to achieve the impedance-controlled stopband positions. The wide BSF bandwidths are achieved through enhanced coupling of the E-PCML. Explicit design guidelines are derived using a lossless transmission line model. To validate theoretical predictions, a prototype dual-band BSF operating at 900 MHz and 2,100 MHz with fractional bandwidths of 72% and 36%, respectively, is implemented in microstrip.

In this letter, a modified optimum bandstop filter (BSF) design is presented. Broad stopband and sharp rejection characteristics are achieved by realizing three transmission zeros near the passband edges. Stopband rejection depth and bandwidth can be controlled by the impedances of the configuration. A lossless transmission line model analysis is used to derive design equations. Further, a compact geometry is chosen by replacing the low impedance section with its equivalent dual-high impedance lines, which facilitates convenient folding. To validate the theoretical prediction, a single unit sharp-rejecting prototype BSF having a 20 dB rejection bandwidth of 126% at 1.5 GHz has been fabricated.

We present the design of a compact microstrip lowpass filter with a wide stopband which is up to ten times the cutoff frequency. The filter is based on a coupled-line configuration and shunt open stubs. The open stubs create additional transmission zeros, which are used to extend the stopband of the filter without any additional components or cascaded units. A prototype lowpass filter with a 3 dB cutoff frequency of 0.428 GHz and a 15 dB stopband extended up to 4.77 GHz is fabricated to validate the theoretical predictions.

A design of a miniaturized rat-race coupler with higher-order harmonic suppression is presented in this article. The slow wave effect and stopband produced by a shunt open-stub is utilized to miniaturize the occupying area and suppress higher order harmonics, respectively. Design guidelines are obtained using a transmission line model. A prototype coupler has been fabricated in microstrip line to validate the theoretical predictions. The fabricated coupler occupies 18.4% area of that of a conventional coupler. At the same time, the second to tenth harmonics are suppressed by at least 15 dB. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2812–2814, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23840

In this article, a compact microstrip coupled-line configuration has been presented to design a wideband bandstop filter with three transmission zeros. These transmission zeros are utilized to obtain sharp rejection characteristics. A loss-less transmission line model is used to obtain the filter design parameters. To validate the theoretical prediction, a single section sharp-rejecting, compact, bandstop filter having a 20-dB rejection bandwidth of ∼100% at 1.5 GHz has been fabricated. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2955–2957, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23819

In this article, a new configuration has been proposed for miniaturization of a branch-line 90° hybrid coupler. The present coupler is obtained by replacing the low impedance series arms of a conventional coupler by their equivalent parallel high impedance lines. This arrangement facilitates meandering, used to realize a compact geometry. The main advantage of the proposed coupler is that it has approximately the same bandwidth as that of a conventional one. A prototype coupler area is 45.3% of that of a conventional branch-line coupler. The design is validated by full-wave electromagnetic simulation and measurement. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1135–1137, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23320

A novel design of micostrip bandstop filter (BSF) based on branch-line coupler structure is presented. The present BSF is obtained by modifying the branch-line coupler with open-circuits at the coupled and isolated ports. The usefulness of the present topology is demonstrated by comparing the filter performances with a standard two transmission line (TTL) signal interference BSF of same total electrical length. The proposed structure does not increase the physical dimension of the BSF, but improves the performance significantly. For given impedance ratio, the transmission zero separation bandwidth of the proposed BSF is always larger than the TTL-BSF. Measured prototype at 1.0 GHz validates the design approach.