Search Results (11)

In this paper, a miniaturized broadband bandstop filter with a simple structure is proposed, synthesized, and developed. The proposed broadband bandstop filter is designed using asymmetrically loaded parallel-coupled microstrip lines, resulting in five transmission zeros within the stopband. Closed-form formulas of the entire set of generated transmission zeros are derived to guide a practical design procedure. To demonstrate the effectiveness of the proposed concept and synthesis method, a miniaturized broadband bandstop filter centered at 3 GHz with a 20 dB rejection bandwidth of about 100% is designed, fabricated, and measured. The core circuit size of the developed broadband bandstop filter is only 0.5 λ_g × 0.1 λ_g (31.2 mm × 6.5 mm). Full article

In this paper, we examine an ultra-compact on-chip balanced filter based on novel hybrid resonators (NHRs) comprising short transmission line sections (STLSs) and series LC blocks using low-temperature co-fired ceramic (LTCC) technology. Based on a rigorous theoretical analysis, the proposed NHR demonstrates the potential for intrinsic ultra-wideband differential-mode (DM) and common-mode (CM) suppression without any additional suppressing structures. Furthermore, the resonance of NHRs was determined by four degrees of freedom, providing flexibility for miniaturization. Theoretical extensions of the Nth-order topology can be easily achieved by the simple coupling schemes that occur exclusively between STLSs. For verification, a balanced filter covering the 5G band n78 with an area of 0.065λ_g × 0.072λ_g was designed using the proposed optimization-based design procedure. An ultra-low insertion loss of 0.8 dB was obtained. The quasi-full CM stopband with a 20 dB rejection level ranged from 0 to 12.9 GHz. And the ultra-wide upper DM stopband with a 20 dB rejection level ranged from 4.4 to 11.5 GHz. Good agreement between the theoretical, simulated, and measured results indicate the validity of the proposed design principle. Full article

A novel compact broadband negative group delay (NGD) circuit with flatness and bandwidth enhancement is presented. The presented negative group delay circuit (NGDC) consists of a high-impedance transmission line connected by two resistors, which are linked together with two coupled lines and a low-impedance transmission line. The flatness of the NGD is enhanced by tuning the characteristic impedance of the transmission lines. In order to verify the method, a compact broadband NGDC with a size of 29.4 mm × 58.1 mm (0.14 λ_g × 0.29 λ_g) is designed, fabricated, and measured at the center frequency of 1.0 GHz. The measured results show that an NGD time of −0.49 ns at the center frequency is obtained with return loss and insertion loss of 35.0 dB and 18 dB, respectively. And, the flat-NGD bandwidth reaches 509 MHz (50.9%) over 0.766 to 1.275 GHz with 19% group-delay fluctuation. Full article

Absorptive bandpass filters (ABPFs) are highly attractive in modern microwave communication systems due to their ability to internally absorb the harmful stopband RF-power reflections. This paper reports an approach to designing quasi-elliptic ABPFs with ultra-wide reflectionless range, enhanced selectivity, and compact size. The method is realized based on a fourth-order quasi-elliptic absorptive lowpass filter (ALPF) prototype with a simplified structure. This ALPF prototype exhibits both good impedance-matching over the whole normalized frequency domain and an adjustable transmission zero close to the passband. By applying an equivalent impedance transformer model, a coupled-line-based ABPF scheme is devised from the ALPF prototype, which eliminates conventional dispersive transmission line inverters, resulting in an ultra-wide reflectionless range and a compact size. Closed-form equations are derived to support the filter synthesis. A 2.45 GHz microstrip ABPF with 30% fractional bandwidth is designed for verification. The measured minimum in-band insertion loss is 0.83 dB and the reflectionless range of return loss better than 10 dB is from DC to 12.88 GHz. Both the upper and lower stopband suppression exceed 20 dB, with the upper stopband extending up to 6.80 GHz. The upper and lower out-of-band roll-off rates are 93.9 and 121.4 dB/GHz, respectively. The overall circuit size is 0.12 λ_g². Full article

A novel quasi-twisted miniaturized wideband branch line coupler (BLC) is proposed. The design is based on bisecting the conventional microstrip line BLC transversely and folding bisected sections on double-layered substrates with a common ground plane in between. The input and output terminals, each with a length of λ_g/4, and the pair of quarter-wavelength horizontal parallel arms are converted into a Z-shaped meandered microstrip line in the designed structure. Conversely, the pair of quarter-wavelength vertical arms are halved into two lines and transformed into a periodically loaded slow-wave structure. The bisected parts of the BLC are placed on the opposite side of the doubled-layer substrate and connected through four vias passing through the common ground plane. This technique enabled a compact BLC size of 6.4 × 18 mm², which corresponds to a surface area miniaturization by ~50% as compared to the classical BLC size of 10 × 23 mm² at 6 GHz. Moreover, the attained relative bandwidth is 73.9% (4.6–10 GHz) for S11, S33, S21, and the phase difference between outputs (∠S21 − ∠S41). However, if a coupling parameter (S41) of up to −7.5 dB is considered, then the relative bandwidth reduces to 53.9% (4.6–10 GHz) for port 1 as the input. Similarly, for port 3 as the input, the obtained bandwidth is 75.8% (4.5–10 GHz) for S33, S11, S43, and the phase difference between outputs (∠S43 − ∠S23). Likewise, this bandwidth reduces to 56% (4.5–8 GHz) when a coupling parameter (S23) of up to −7.5 dB is considered. In contrast, the relative bandwidth for the ordinary BLC is 41% at the same resonant frequency. The circuit is constructed on a double-layered low-cost FR4 substrate with a relative permittivity of 4.3 and a loss tangent of 0.025. An isolation of −13 dB was realized in both S₁₃ and S₃₁ demonstrating an excellent performance. The transmission coefficients between input/output ports S₂₁, S₄₁, S₂₃, and S₄₃ are between −3.1 dB to −3.5 dB at a frequency of 6 GHz. Finally, the proposed BLC provides phase differences between output ports of 90.5° and 94.8° at a frequency of 6 GHz when the input ports 1 and 3 are excited, respectively. The presented design offers the potential of being utilized as a unit cell for building a Butler matrix (BM) for sub-6 GHz 5G beamforming networks. Full article

By leveraging the advantages of the uniform transmission line, this manuscript presents a broadband high-selectivity filter range starting from 2.5 GHz to 16.8 GHz, utilizing a simple uniform transmission line structure loaded with three-quarter-wavelength stubs. The proposed UWB filter is studied using the ABCD network parameter method. After that, a shorted T-shaped stub-loaded resonator is coupled with the transmission line of the UWB filter to obtain dual-notch features at 4.4 GHz (for long distance wireless ISPs (WISPs), 4G/5G operator for LTE backhaul) and 7.5 GHz (for X-band downlink communication). The overall footprint is specified as 22.5 mm × 12 mm or 1.12 λ_g × 0.6 λ_g, where λ_g represents the wavelength at the central frequency. The operating principle of such a filter is explained, and its controllable broadband response, as well as controllable stopband frequencies, are optimized to show some of the attractive features of the new scheme, such as a super wideband response of about a 148.18% fractional bandwidth; an out-of-band performance up to 25 GHz; five single-resonator transmission poles filtering behaviour at different frequencies, with highly reduced radiation losses greater than 10 dB; a simple topology; a flat group delay; a low insertion loss of 0.4 dB; and high selectivity. Additionally, the filter is fabricated and evaluated, and the results show a good match for experimental validation purposes. Full article

This paper introduces a novel algorithm for designing a low-pass filter (LPF) and a microstrip Wilkinson power divider (WPD) using a neural network surrogate model. The proposed algorithm is applicable to various microwave devices, enhancing their performance and frequency response. Desirable output parameters can be achieved for the designed LPF and WPD by using the proposed algorithm. The proposed artificial neural network (ANN) surrogate model is employed to calculate the dimensions of the LPF and WPD, resulting in their efficient design. The LPF and WPD designs incorporate open stubs, stepped impedances, triangular-shaped resonators, and meandered lines to achieve optimal performance. The compact LPF occupies a size of only 0.15 λg × 0.081 λg, and exhibits a sharp response within the transmission band, with a sharpness parameter of approximately 185 dB/GHz. The designed WPD, operating at 1.5 GHz, exhibits outstanding harmonics suppression from 2 GHz to 20 GHz, with attenuation levels exceeding 20 dB. The WPD successfully suppresses 12 unwanted harmonics (2nd to 13th). The obtained results demonstrate that the proposed design algorithm effectively accomplishes the LPF and WPD designs, exhibiting desirable parameters such as operating frequency and high-frequency harmonics suppression. The WPD demonstrates a low insertion loss of 0.1 dB (S₂₁ = 0.1 dB), input and output return losses exceeding 30 dB (S₁₁ = −35 dB, S₂₂ = −30 dB), and an output ports isolation of more than 32 dB (S₂₃ = −32 dB), making it suitable for integration into modern communication systems. Full article

Multi-bit phase shifters are typically implemented by cascading multiple phase-shifting units, therefore incurring large dimensions and higher insertion losses. This paper presents highly compact single-unit two-bit reflection-type phase shifters (SUTBRTPSs), with large phase shifts range and lower insertion loss by using only one 3-dB hybrid coupler, unlike traditional multi-bit reflection-type phase shifters. To achieve this, two identical dual-voltage controlled reactance blocks (DVCRBs) are loaded to the 3-dB hybrid directional coupler at through and coupled ports, and 04 states of phase shifts are obtained between the input and isolated ports. Each DVCRB consists of 03 open-circuited transmission lines and switching p-i-n diodes and provides half of the required susceptance to achieve the desired phase shifts. Design theory is presented in detail, and for validation and demonstration, two typical SUTBRTPSs (0°/45°/90°/135° and 0°/22.5°/180°/202.5°) are designed, fabricated and measured. Being implemented in a single-unit structure, the proposed method yields highly compact dimensions of 0.44 λg × 0.46 λg and 0.54 λg × 0.46 λg, respectively. The simulation and measurements results are in good agreement and indicate maximum insertion losses of 1.7 and 2.1 dB with a return loss better than 20 dB and phase error of less than 1.5°. Full article

The key elements used for receiving and processing signals in communication systems are the bandpass filters. Initially, a common operating mechanism was applied for the design of broadband filters, i.e., by cascading low-pass filters or high-pass filters using multiple line resonators with length quarter-half- or full-wavelength with central frequency, but using these approaches, the design topology becomes expensive and complex. The above mechanisms can be possibly overcome using a planar microstrip transmission line structure due to its simple design fabrication procedure and low cost. So, pointing out the above problems in bandpass filters such as low-cost, low insertion loss, and good out-of-band performance, this article presents a broadband filter with multifrequency suppression capability at 4.9 GHz, 8.3 GHz, and 11.5 GHz using a T-shaped shorted stub-loaded resonator with a central square ring coupled to the basic broadband filter. Initially, the C-shaped resonator is utilized for the formation of a stopband at 8.3 GHz for a satellite communication system, and then a shorted square ring resonator is added to the existing C-shaped structure for the realization of two more stopbands at 4.9 GHz and 11.5 GHz for 5G (WLAN 802.11j) communication, respectively. The overall circuit area covered with the proposed filter is 0.52 λg × 0.32 λg (λg is the wavelength of the feed lines at frequency 4.9 GHz). All the loaded stubs are folded in order to save the circuit area, which is an important requirement of next-generation wireless communication systems. The proposed filter has been analyzed using a well-known transmission line theory, even–odd-mode, and simulated with the 3D software HFSS. After the parametric analysis, some attractive features were obtained, i.e., compact structure, simple planar topology, low insertion losses of 0.4 dB over the entire band, good return loss greater than 10 dB, and independently controlled mutli stopbands, which make the proposed design unique and can be used in various wireless communication system applications. Finally, a Rogers RO-4350 substrate is selected for the fabrication of the prototype using an LPKF S63 ProtoLaser machine and then measured using a ZNB20 vector network analyzer for matching the simulated and measured results. After testing the prototype, a good agreement was found between the results. Full article

The consumption of multimedia content is ubiquitous in modern society. This is made possible by wireless local area networks (W–LAN) or wire service systems. Bandpass filters (BPF) have become very popular as they solve certain data transmission limitations allowing users to obtain reliable access to their multimedia content. The BPFs with quarter–wavelength short stubs can achieve performance; however, these BPFs are bulky. In this article, we propose a compact BPF with a T–shaped stepped impedance resonator (SIR) transmission line and a folded SIR structure. The proposed BPF uses a T–shaped SIR connected to a J–inverter structure (transmission line); this T–shaped SIR structure is used to replace the λ_g/4 transmission line seen in conventional stub BPFs. In addition, a folded SIR is added to the short stubs seen in conventional stub BPFs. This approach allows us to significantly reduce the size of the BPF. The advantage of a BPF is its very small size, low insertion loss, and wide bandwidth. The overall size of the new BPF is 2.44 mm × 1.49 mm (0.068λ_g × 0.059λ_g). The proposed BPF can be mass produced using semiconductors due to its planar structure. This design has the potential to be widely used in various areas including military, medical, and industrial systems. Full article

In this paper, two implementations of reconfigurable bandwidth bandpass filters (BPFs) are demonstrated both operating at a fixed center frequency of 2.4 GHz. The proposed reconfigurable bandwidth filters are based on a square ring resonator loaded with λ_g/4 open-ended stubs that are permanently connected to the ring and converted to either 3λ_g/4 open-ended stubs or λ_g/2 short-ended stubs by means of positive-intrinsic-negative(PIN) diodes to implement two reconfigurable bandwidth states for each case. Due to the symmetrical nature of the design, even- and odd-mode analysis is used to derive the closed-form to describe the reconfigurable filters’ behavior. The switching between narrowband and wideband is achieved using PIN diodes. In the first implementation (λ_g/4 open-ended stubs to 3λ_g/4 open-ended stubs), a reconfigurable bandwidth bandpass filter is proposed where additional out-of-band transmission zeros are generated by integrating a λ_g/2 open-ended stub at the input port. In the second implementation (λ_g/4 open-ended stubs to λ_g/2 short-ended stubs), further improvement in the upper stopband is achieved by utilizing a pair of parallel coupled lines (PCLs) as feeding lines and a pair of λ_g/4 high impedance short-ended stubs implemented at the input and output ports. To verify the validity of the simulated results, the prototypes of the proposed reconfigurable filters were fabricated. For the first case, measured insertion loss is less than 1.8 dB with a switchable 3-dB fractional bandwidth (FBW) range from 28% to 54%. The measured results for the second case exhibit a low insertion loss of less than 1 dB and a 3-dB fractional bandwidth that can be switched from 34% to 75%, while the center frequency is kept constant at 2.4 GHz in both cases. Full article