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This paper presents a low-insertion-loss open-loop resonator (OLR)-based microstrip diplexer with high-selective for wireless applications. We used two series capacitive gaps in the microstrip transmission line, loaded with rectangular-shaped half-wavelength OLRs, to create a high-selectivity bandpass filter (BPF). The planned BPFs are linked through a T-junction combiner, precisely tuned to align with both filters and the antenna port in order to produce the proposed diplexer. The system is implemented on a rogers TMM4 substrate with a loss tangent of 0.002, a dielectric constant of 4.7, and a thickness of 1.52 mm. The suggested diplexer has dimensions of (90×70) mm². It achieves a modest frequency space ratio of R=0.1646 in both transmit and receive modes by having two resonance frequencies of ft=2.191 GHz and fr=2.584 GHz, respectively. The simulated structure displays good insertion losses of approximately 1.2 dB and 1.79 dB for the two channels, respectively, at fractional bandwidths of 1.24% at 2.191 GHz and 0.636% at 2.584 GHz. The simulated isolation values for 2.191 GHz and 2.584 GHz are 53.3 dB and 66.5 dB, respectively. [ABSTRACT FROM AUTHOR]

There has been a lot of interest in microstrip diplexers lately due to their potential use in numerous wireless and computer communication technologies, including radio broadcasts, mobile phones, broadband wireless, and satellite-based communication systems. It can do this because it has a communication channel that can combine two distinct filters into one. This article presents a narrow-band microstrip diplexer that uses a stepped impedance resonator, a uniform impedance resonator, tiny square patches, and a meander line resonator. The projected diplexer might be made smaller than its initial dimensions by utilizing the winding construction. To model the microstrip diplexer topology for WiMAX and WIFI/WLAN at 1.66 GHz and 2.52 GHz, the Advanced Wave Research (AWR) solver was employed. It exhibited an insertion loss of 3.2 dB and a return loss of 16 dB for the first channel, while the insertion loss and return loss were 2.88 dB and 21 dB, respectively, for the second channel. When both filters were simulated, the band isolation was 31 dB. The projected microstrip diplexer has been fabricated using an FR4 epoxy laminate with dimensions of 32 × 26 mm2. The simulated S-parameters phase and group delay closely matched the measurements. [ABSTRACT FROM AUTHOR]

This paper presents a high-selectivity, low-insertion-loss open-loop resonator (OLR)-based microstrip diplexer designed for wireless communication systems. We employed a microstrip transmission line with two serial capacitive gaps, incorporating rectangular half-wavelength open-loop resonators, to create a bandpass filter (BPF) with remarkable selectivity. The intended BPFs are interconnected by a T-junction combiner, which is matched to both filters and the antenna port, thereby creating the modelled diplexer. The system is implemented on a Rogers TMM4 substrate featuring a loss tangent of 0.002, a dielectric constant of 4.7, and a thickness of 1.52 mm. The suggested diplexer has dimensions of (90×70) mm². It achieves a modest frequency spacing ratio of R=0.1646 in both transmit and receive modes, with resonance frequencies of ft = 2.191 GHz and fr = 2.584 GHz, respectively. The simulated structure demonstrates favorable insertion losses of approximately 1.2 dB and 1.79 dB for the two channels at fractional bandwidths of 1.24% (2.191 GHz) and 0.636% (2.584 GHz). The simulated isolation values at 2.191 GHz and 2.584 GHz are 53.3 dB and 66.5 dB, respectively. Notably, the simulated and measured results exhibit a high degree of consistency. However, minor variations between the simulated and actual results have been noted, primarily attributable to the inherent fabrication tolerances. [ABSTRACT FROM AUTHOR]

In this work, a microstrip diplexer with 0.004 λg2 (10.1 × 23 mm) overall size is designed, analyzed and fabricated. The proposed diplexer has the smallest size compared to the previously reported microstrip diplexers. The proposed diplexer has a simple and novel structure, wide flat channels and very low S 11 dB . An innovative microstrip structure based on thin coupled lines is used to design of the proposed diplexer. Since in a simple structure the possibility of manufacturing errors reduces, having a simple structure is one of its advantages. Another advantage of this diplexer is two low S 11 dB of 0.17 and 0.14 dB at the lower and upper channels. The operational frequencies of our diplexer are tuned to work at 0.9 GHz and 1.8 GHz for GSM application. It has the privileges of very compact size, simple structure, small S 11 dB , two wide fractional bandwidths (FBWs) of 21 and 24.3% and acceptable S 11 dB and isolation. Due to its two wide FBWs, the presented diplexer is suitable for broadband communication systems. We have fabricated and measured the introduced diplexer to verify the design methodology and simulation results. The obtained results of the diplexer measurement confirm the simulation. [ABSTRACT FROM AUTHOR]

This paper presents the design of a novel lowpass–bandpass diplexer with compact size and good performance using microstrip cells. For this purpose, two microstrip lowpass and bandpass filters are separately designed and mathematically analyzed. The proposed microstrip diplexer has a novel and simple structure. It occupies a compact area of 0.037 λ g2 (722 mm2), and its insertion loss and S 11 at both channels are low. The insertion loss at the lower and upper channels is only 0.047 and 0.16 dB, respectively. Meanwhile, both channels are flat with the maximum group delay of 1.68 ns which is the lowest compared to the previously reported diplexers mentioned in this paper. To design the proposed diplexer, first, a lowpass diplexer with good performance is designed which has low losses and a good figure of merit. It has a flat passband with a sharp roll-off. Then, to achieve the proposed diplexer, a bandpass resonator is added to the lowpass filter without any extra matching circuit, which saves the overall size. The proposed diplexer is designed, simulated, and fabricated, where the simulation and measurement results are close. [ABSTRACT FROM AUTHOR]

Microstrip Diplexers play an important role in modern wireless communication systems. In this paper, a novel compact microstrip diplexer based on spiral cells is presented. The proposed resonator primarily consists of two spiral thin lines connected to a pair of coupled lines. This novel resonator is analyzed mathematically to find its behavior and tune the dimensions of the final layout easily. Using the analyzed resonator, two bandpass filters (BPFs) are designed. Then, a novel high-performance microstrip diplexer is obtained by designing and integrating these two BPFs. The center frequencies of the first and second channels of the proposed diplexer are 1.86 GHz and 4.62 GHz, respectively. The proposed diplexer boasts a remarkably small size of 0.004 λg2 and features flat channels with low insertion losses of only 0.048 dB and 0.065 dB for the first and second channels, respectively. The maximum group delays of S21 and S31 are 0.31 ns, 0.86 ns, respectively, which are good values for a modern communication system. Meanwhile, inside its passbands for some frequency ranges, its group delays are negative. Thus, using this diplexer can decrease the signal dispersion. The 1st and 2nd passbands are wide with 47.3% and 47.1% fractional bandwidths (FBW), respectively. Therefore, this diplexer can be easily and successfully used in designing high-performance RF communication systems.

There has been a lot of interest in microstrip diplexers lately due to their potential use in numerous wireless and computer communication technologies, including radio broadcasts, mobile phones, broadband wireless, and satellite-based communication systems. It can do this because it has a communication channel that can combine two distinct filters into one. This article presents a narrow-band microstrip diplexer that uses a stepped impedance resonator, a uniform impedance resonator, tiny square patches, and a meander line resonator. The projected diplexer might be made smaller than its initial dimensions by utilizing the winding construction. To model the microstrip diplexer topology for WiMAX and WIFI/WLAN at 1.66 GHz and 2.52 GHz, the Advanced Wave Research (AWR) solver was employed. It exhibited an insertion loss of 3.2 dB and a return loss of 16 dB for the first channel, while the insertion loss and return loss were 2.88 dB and 21 dB, respectively, for the second channel. When both filters were simulated, the band isolation was 31 dB. The projected microstrip diplexer has been fabricated using an FR4 epoxy laminate with dimensions of 32 × 26 mm2. The simulated S-parameters phase and group delay closely matched the measurements.

In this paper, the design and hardware implementation of a squared open-loop resonator (SOLR)-based microstrip diplexer with high isolation, low insertion loss, and high selectivity are introduced. We employed four SOLRs, with each pair of coupled SOLRs used to build a high selectivity bandpass filter (BPF). To assemble the proposed diplexer, the designed BPFs are linked together via a T-junction combiner that is matched to the two filters and the antenna port. For transmit and receive modes, the proposed diplexer has two resonance frequencies of ft = 1.81 GHz and fr = 2.03 GHz, respectively achieving a small frequency space ratio of R = 0.114. The simulated structure exhibits good insertion losses of about 1.98 dB and 1.9 dB for the two channels, respectively, with fractional bandwidths of 2.25% at 1.81 GHz and 3% at 2.03 GHz. For 1.81 GHz and 2.03 GHz, the simulated isolation values are 58 dB and 46 dB, respectively. While the fabricated structure exhibits better insertion losses of about 1.25 dB and 1.22 dB at the measured transmit and receive frequencies of 1.801 GHz and 2.001 GHz, respectively, with smaller fractional bandwidths of 2.23% at 1.801 GHz and 2.98% at 2.001 GHz. For 1.801 GHz and 2.001 GHz, the measured isolation values are 48.99 dB and 57.02 dB, respectively.

Two new compact balanced-to-balanced diplexers composed of two multiband balanced bandpass filters in a multilayer configuration are proposed in this letter to perform dual- and tri-band responses. The balanced bandpass filters are based on the use of magnetically coupled open-loop resonators. The magnetic coupling results in a strong inherent common-mode rejection, greater than 40 dB within all the dual-band diplexer passbands and greater than 30 dB for the tri-band diplexer passbands. All passbands in both diplexers are close to each other and well separated thanks to the presence of several transmission zeroes between them. Operating frequencies have been selected to be within the L band, used for many applications such as mobile services or satellite navigation. Specifically, the dual-band diplexer passbands are located at 1.08/1.58 GHz and 1.3/1.8 GHz with fractional bandwidths of 7/5.2 % and 7.4/5.5 %, while the tri-band diplexer passbands are located at 1.7/2.2/2.79 GHz and 1.97/2.37/2.95 GHz with fractional bandwidths of 4.1/4.6/3.5 % and 5.6/4.6/3.7 %. Measurements of two different prototypes are provided to validate the obtained simulation results, illustrating in this manner the usefulness of the proposed design methodology.

In this paper, the design and hardware implementation of a squared open-loop resonator (SOLR)-based microstrip diplexer with high isolation, low insertion loss, and high selectivity are introduced. We employed four SOLRs, with each pair of coupled SOLRs used to build a high selectivity bandpass filter (BPF). To assemble the proposed diplexer, the designed BPFs are linked together via a T-junction combiner that is matched to the two filters and the antenna port. For transmit and receive modes, the proposed diplexer has two resonance frequencies of ft = 1.81 GHz and fr = 2.03 GHz, respectively achieving a small frequency space ratio of R = 0.114. The simulated structure exhibits good insertion losses of about 1.98 dB and 1.9 dB for the two channels, respectively, with fractional bandwidths of 2.25% at 1.81 GHz and 3% at 2.03 GHz. For 1.81 GHz and 2.03 GHz, the simulated isolation values are 58 dB and 46 dB, respectively. While the fabricated structure exhibits better insertion losses of about 1.25 dB and 1.22 dB at the measured transmit and receive frequencies of 1.801 GHz and 2.001 GHz, respectively, with smaller fractional bandwidths of 2.23% at 1.801 GHz and 2.98% at 2.001 GHz. For 1.801 GHz and 2.001 GHz, the measured isolation values are 48.99 dB and 57.02 dB, respectively. [ABSTRACT FROM AUTHOR]

A class of multi-band planar diplexer with sub-sets of frequency-contiguous transmission bands is reported. Such a radio frequency (RF) device is suitable for lightweight high-frequency receivers aimed at multi-band/multi-purpose mobile satellite communications systems. It consists of two channelizing filters, each of them being made up of the in-series cascade connection of replicas of a constituent multi-passband/multi-embedded-stopband filtering stage. This building filtering stage defines a multi-passband transfer function for each channel, in which each main transmission band is split into various sub-passbands by the multi-stopband part. In this manner, each split passband gives rise to several sub-passbands that are imbricated with their counterpart ones of the other channel. The theoretical RF operational principles of the proposed multi-band diplexer approach with sub-sets of imbricated passbands are detailed by means of a coupling–routing–diagram formalism. Besides, the generation of additional transmission zeros in each channelizing filter for higher-selectivity realizations by exploiting cross-coupling techniques into it is also detailed. Furthermore, for experimental demonstration purposes, a microstrip proof-of-concept prototype of second-order octo-band diplexer in the frequency range of 1.5–2.5 GHz that consists of two quad-band channelizing filters with pairs of imbricated passbands is developed and characterized. [ABSTRACT FROM AUTHOR]

In this work, a novel structure of a microstrip diplexer consisting of coupled patch cells is presented. It works at 2.5 GHz and 4.7 GHz for wireless applications. The proposed structure is well miniaturized with a compact area of 0.015 λg2, fabricated on 0.787 mm substrate height. It has two wide fractional bandwidths (FBWs) of 28% and 17.9% at the lower and upper channels, respectively. Another feature of the proposed design is the low group delays, which are better than 0.4 ns for both channels. Moreover, the designed diplexer can suppress the harmonics up to 10 GHz. Meanwhile, the insertion losses at both channels are low. The design method is based on proposing an approximated equivalent LC circuit of a novel basic resonator. The information about the resonator behavior is extracted from the even and odd modes analysis of the proposed equivalent LC circuit. Finally, our introduced diplexer is fabricated and measured to verify the simulation results, where the simulated and measured results are in good agreement.

A novel design method of microstrip diplexer without extra matching circuit is proposed in this paper. Because of the synthesizable circuit parameters and controllable transmission zeros (TZs) in composite resonator (CR) cell, diplexer A based on CR cell is proposed. By allocating TZs at center frequency of the opposite channel, as well as the using of impedance transformations of J inverters, high isolation and good passband selectivity are realized in diplexer A without extra matching circuit. In order to improve the stopband performance, diplexer B based on coupled CR cells is proposed. Furthermore, diplexer B using the proposed design method is implemented by directly combining two bandpass filters (BPFs), which simplifies significantly the design process of diplexers. Diplexer A operated at 1/1.2 GHz and diplexer B operated at 1/1.5 GHz are designed and fabricated. The measured isolation characteristics in diplexer A and diplexer B are all higher than 40 dB. Good agreements between simulated and measured results are achieved, which successfully verifies the proposed design method of diplexers.

This study presents a planar dual‐channel bandpass microstrip diplexer based on a novel structure. It has the very compact size of 0.0081 λg2 (95.7 mm2) fabricated on 0.787 mm dielectric substrate height. Due to the use of close microstrip sections, several coupling capacitors are created. These capacitors can increase the degree of freedom for controlling the diplexer performance while it is optimized easily. Accordingly, the designed diplexer has a high performance in terms of wide fractional bandwidths, attenuated harmonics, flat channels, high return losses and low insertion losses. The wide fractional bandwidths (FBWs%) of 34.3% at the first channel and 38.6% at the second channel make the proposed diplexer appropriate for the broadband applications. The resonance frequencies are located at f1 = 1.6 GHz for the L‐band and f2 = 3 GHz for WiMAX applications. The maximum harmonic level is less than −20 dB for the frequencies up to 6.5 GHz (4f1). The maximum group delays are <1.26 ns at the first passband and 0.56 ns at the second passband. The proposed diplexer is fabricated and measured for verification. The comparison shows that both measured and simulated results are in a reasonable agreement. [ABSTRACT FROM AUTHOR]

A class of coupled-multiline quasi-elliptic-type balanced diplexer device with closely spaced channels and its balanced coupling-routing-diagram formalism to simultaneously model its differential- and common-mode operation are reported. It employs third-order combline-type bandpass filters (BPFs) in its filtering channels, whose resonating lines are connected at one of their extremes to the symmetry plane of the balanced-circuit structure (i.e., virtual grounds for the differential mode), along with a multiextracted-pole/coupled-multiline dual-band BPF junction and single-band BPF output cells. In differential-mode operation, the dual-band BPF junction adds one in-band pole to each diplexer channel and three transmission zeros (TZs) to both channels, whereas the single-band BPF output cells incorporate one in-band pole and two TZs in their corresponding channels. In this manner, increased-selectivity differential-mode BPF transfer functions for the diplexer channels when compared to those of its third-order combline-type BPFs are obtained. Grounded resistors are connected at the symmetry plane of the balanced diplexer for all the resonating lines of the combline-type BPFs, which become detuned with regard to the poles associated with the dual-band BPF junction and the single-band BPF output cells under common-mode excitation. This allows for high common-mode suppression levels in wide spectral ranges to be realized for both channels while maintaining the same TZs as in differential-mode operation. For practical-validation purposes, a 1.6-GHz/1.8-GHz microstrip prototype is manufactured and tested. [ABSTRACT FROM AUTHOR]

In this paper, a planar wideband balanced-to-balanced microstrip diplexer with excellent reflectionless characteristics is presented. In order to solve the problem of interference caused by reflected energy in wireless communication systems for conventional balanced diplexers, a novel design concept of a balanced absorptive diplexer with reflectionless characteristics is realized by loading reflectionless stubs with different operating frequencies at differential transmission ports and differential reception ports. To confirm the validation of modeling design, a microstrip prototype of a balanced absorptive diplexer is manufactured and measured with lower and upper channels centered at 1.2 and 1.8 GHz, with a 3-dB bandwidth of 36.7 % and 33.3 %, respectively. [ABSTRACT FROM AUTHOR]

A class of balanced dual-band planar diplexer with frequency-contiguous channels for the differential mode and high common-mode rejection is presented. It exploits double-stub-loaded filtering cells with resistors connected at the symmetry plane of the overall diplexer. In this manner, a sharp-rejection dual-band operation for each diplexer channel with transmission zeroes (TZs) at both sides of the differential-mode dual passbands is obtained. In addition, broadened common-mode suppression and low common-mode in-band input power reflection can be realized. The theoretical foundations and design guidelines for the devised dual-band differential-mode diplexer are provided. Moreover, for practical-validation purposes, a microstrip prototype with imbricated 1.51-GHz/2.41-GHz and 1.92-GHz/2.85-GHz lower and upper dual-band channels is manufactured and tested. [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, a high-isolation microstrip diplexer with enhanced stopband characteristics is presented for GSM and Wireless Local Area Network (WLAN) application. The proposed diplexer consists of two compact bandpass filters (BPFs) using short-circuit centered stepped impedance resonators (SCSIRs), operated at 1.8 and 2.45 GHz, respectively. Due to the intrinsic characteristics of the SCSIRs, multiple transmission zeros can be generated for high selectivity and wide upper-stopband. By locating the transmission zero of one channel at the passband of the other channel, and utilizing good impedance matching between two BPFs, high output isolation can be achieved. A microstrip diplexer prototype is designed and fabricated. The upper-stopband of two channels in experiment is extended up to 10.2 GHz with an insertion loss larger than 28 dB. Meanwhile, the measured isolation greater than 48 dB in GSM passband and more than 52 dB in WLAN passband is achieved between two channels. A satisfactory agreement between the simulated and measured results validates the proposed configuration. The size without the 50-Ω feed lines is only [ABSTRACT FROM AUTHOR]

A microstrip eight-channel diplexer with a compact size and a wide stopband is presented. There are sixteen stepped-impedance resonators controlling the passband characteristics. Every two resonators are used for one passband resulting in a high design freedom. There are four passbands filtered out at each of the two output ports. The circuit size is only 0.1 \lambda{g}^{{{2}}} at the lowest channel frequency. The isolation is more than 29 dB, and the 20 dB upper stopband extends up to 8.22\,\times the lowest operation frequency. [ABSTRACT FROM PUBLISHER]

In this letter, a compact balanced-to-balanced microstrip diplexer with high isolation and common-mode (CM) suppression is proposed for wireless local area networks (WLAN) and worldwide interoperability for microwave access (WiMAX) applications simultaneously. The proposed diplexer is designed via the combination of two balanced bandpass filters (BPF) without extra junction matching network. Both BPFs are composed of uniform impedance resonators (UIR) and short- ended microstrip parallel-coupling feedlines. Finally, the proposed diplexer is fabricated and measured. The measured differential-mode (DM) isolation in the two passbands is more than 33 dB. While for the CM signal, the insertion loss is below 30 dB in the two operation bands. The simulated and measured results exhibit a satisfactory agreement to validate the proposed configuration. The diplexer size is only 0.26\lambdag\times 0.38\lambdag, where \lambdag is the guided wavelength at 2.45 GHz. [ABSTRACT FROM PUBLISHER]

Microstrip diplexer using Koch fractal shape is proposed for the first time. By constructing the microstrip coupled-lines in Koch fractal shapes, the second harmonic of the fractal microstrip diplexer can be significantly suppressed and, higher the iteration order of the fractals, the more apparent this effect becomes. In this paper, a fractal-shaped microstrip diplexer for 3G wireless communication system is designed, fabricated, and measured; the measurement results verified the proposed method. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2973–2975, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22897 [ABSTRACT FROM AUTHOR]

A high performance hairpin line diplexer for the direct sequence ultra-wideband communication is designed and implemented. This microstrip diplexer is mainly composed of two hairpin line wideband bandpass filters and a tapped open stub. The design concept is proposed in detail and has been verified by the experimental results of the fabricated diplexer, including the two isolated wideband bandwidths of 3.1-5.0 GHz and 6.02-10 GHz, low insertion loss and high isolation. Experimental results also show a good agreement with the simulated results. [ABSTRACT FROM PUBLISHER]

A novel electrically compact and high isolation microstrip diplexer is engineered for Radio Occultation (RO) System for future planetary systems. The radio occultation technique is being utilized extensively in examining properties of a planetary atmosphere. A detection of shift in microwave signal is primary method to measure the occultation. The On-board RO transmitter utilizes the frequency synthesizers at two distinct frequency bands. The proposed microstrip diplexer has self-symmetrical structure that permits reduction in the tradeoff between miniaturization and port isolation. The balanced geometry of two intrinsic filters permits several transmission zeros creating sharp edge, wider stopband and significant port isolation. The further tuning of the diplexer is possible without junction matching however; the insertion loss and isolation may vary based on the frequency shift. The electrical size of the proposed diplexer is 0.52λ × 0.625λ at lower frequency. The optimized structure provides fraction bandwidth of around 4.6% at 6.7 GHz and 4.34% at 8.4 GHz frequencies. The isolation is better than 27 dB for both frequencies. The validation of simulated results is carried out through measurements on fabricated prototype. [ABSTRACT FROM AUTHOR]

A highly miniaturized microstrip diplexer composed of pseudointerdigital quasi-elliptical bandpass filters is proposed. Compactness of diplexer is achieved through the combination of the bandpass filters, which does not require matching network. The proposed microstrip diplexer, having a size of 30.7 × 5.6 mm at a center frequency of 2.7 GHz at channel 1 and 3.8 GHz at channel 2 is designed, fabricated, and tested. Experimental results of the fabricated microstrip diplexer are in very good agreement with the simulated results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2701–2702, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23733 [ABSTRACT FROM AUTHOR]