Search Results (23)

In this study, a simulation-based investigation of the variations of the bit error rate (BER) and the maximum quality factor are presented for short- (S-), conventional- (C-), and long- (L-) band wavelengths in a photonic ultra-wideband (UWB) circuit using a semiconductor optical amplifier (SOA) with different bias currents and a bandpass filter (BPF). Gaussian quadruplet UWB pulses are generated at the S-, C-, and L-band wavelengths, which are commonly used in fiber transmission lines. An analysis of the temporal and spectral features of the generated pulses is carried out. The highest maximum quality factor and the lowest minimum BER are obtained in the C-band at an SOA bias current of 150 mA. This study simultaneously investigates both UWB pulse generation and transmission performance. The proposed circuit has a simple design and high applicability, as it employs a SOA, a Gaussian optical filter, a low-pass filter (LPF) and a single BPF. Full article

In this paper, a novel multi-mode resonator-based ultra-wideband bandpass filter topology is proposed, analyzed, and experimentally validated. The filter comprises a short shunt-stepped impedance resonator and shunt-open stubs. Thus, it can be easily implemented using microstrip technology, offering a simple and cost-effective alternative to multilayer and high-temperature superconductor thin-film-based bandpass filters. S-parameter expressions for the proposed filter are derived using even- and odd-mode methods. To validate theoretical results, a filter prototype operating at the center frequency ($f_o$) of 6.85 GHz is designed, fabricated, and experimentally tested. The measured 3 dB fractional bandwidth (FBW) of the filter exceeds 176%, and the selectivity factor (SF) reaches 0.87. Additionally, the filter outperforms most existing designs in the literature in terms of insertion loss (IL) and return loss (RL). Finally, a figure of merit (FoM) is proposed to measure the trade-off among key performance parameters (i.e., FBW, IL, RL, SF, $f_o$, and group delay flatness), and confirms that the proposed bandpass filter exhibits the best FoM compared to the state of the art. Full article

The purpose of this paper is to present cascaded frequency selective surfaces (FSSs) with matryoshka geometry to increase the effective bandwidth. We carry out an analysis of the influence of the spacing between the surfaces on the FSSs frequency response. The application involves a two-layer cascaded FSS, one as a band-stop filter with a matryoshka geometry and the other as a band-pass filter with inverted or negative matryoshka geometry. With this framework, it is possible to extend an ultra-wideband (UWB) of a bandwidth up to 2 GHz in the 1.8 GHz to 3.8 GHz range with just two layers and an air gap of 12 mm, in addition to a bandwidth of 2 GHz to 3.2 GHz with a smaller 4 mm gap between layers. Full article

A meta-surface-based arbitrary bandwidth filter realization method for terahertz (THz) future communications is presented. The approach involves integrating a meta-surface-based bandstop filter into an ultra-wideband (UWB) bandpass filter and adjusting the operating frequency range of the meta-surface bandstop filter to realize the design of arbitrary bandwidth filters. It effectively addresses the complexity of designing traditional arbitrary bandwidth filters and the challenges in achieving impedance matching. To underscore its practicality, the paper employs silicon substrate integrated gap waveguide (SSIGW) and this method to craft a THz filter. To begin, design equations for electromagnetic band gap (EBG) structures were developed in accordance with the requirements of through-silicon via (TSV) and applied to the design of the SSIGW. Subsequently, this article employs equivalent transmission line models and equivalent circuits to conduct theoretical analyses for both the UWB passband and the meta-surface stopband portions. The proposed THz filter boasts a center frequency of 0.151 THz, a relative bandwidth of 6.9%, insertion loss below 0.68 dB, and stopbands exceeding 20 GHz in both upper and lower ranges. The in-band group delay is 0.119 ± 0.048 ns. Compared to reported THz filters, the SSIGW filter boasts advantages such as low loss and minimal delay, making it even more suitable for future wireless communication. Full article

This paper presents a novel synthesis of a quasi-Chebyshev Nth order stub-loaded coupled-line ultra-wideband bandpass filter. A unit element of a proposed filter topology consists of two short-circuited stubs loaded at the edges of coupled lines. A distributed equivalent circuit model of a proposed topology is extracted and used to acquire a generalized filtering function. The extracted filtering function is of rational form. The denominator of the filtering function causes a mismatch with Chebyshev type-I polynomials. For conventional narrowband filters, the denominator term can be neglected because of the close vicinity of band-edge frequencies; however, for the ultra-wideband filter response, the factor in the denominator cannot be neglected and hence requires a new mathematical procedure to compensate for the effect of the frequency-dependent term in the denominator. The electrical parameters are calculated using the proposed synthesis and used to design an ideal filter topology on ADS. To validate the proposed design procedure, fabrication is performed on a high-frequency substrate. The proposed filter is miniaturized in size and has good out-of-band performance. The simulated and measured results provide good agreement. Full article

In this paper, a novel design of ultra-wideband (UWB) filtering antenna integrated with the multimode resonator (MMR) bandpass filter is proposed, aiming to enhance band-edge selectivity. At the beginning, a MMR bandpass filter is modified and studied. Based on the classic MMR filter, the proposed filter folds the microstrip transmission line to reduce its size while retaining the original filtering performance. Moreover, an open stub and short stub are added to the proposed filter to obtain a transmission of zero. Then, the folded filter with stubs and a UWB bow-tie antenna are integrated together to form a filtering antenna. The open stub and short stub in the MMR structure enhance the antenna’s upper and lower band-edge selectivity, respectively. Series of parameters are studied to analyze their influences on the frequency selection range and band-edge characteristics. Compared with the original UWB dipole antenna, such an integrated approach brings many benefits. Firstly, the UWB filter not only broadens the bandwidth of the device, but also improves band-edge selectivity, which can eliminate the unwanted passband near the operating frequencies. Secondly, the integrated system reduces the size and cost of the devices, which is very important in the miniaturization of wireless systems. In this research, the reflection coefficient ($S_{11}$) of integrated filtering antenna is lower than −10 dB between 2.92 and 11.51 GHz, and it has a fractional bandwidth of 119%. The measured shape factor is 1.027 (very close to 1), which proves that this design has a better band-edge selectivity. Simultaneously, good radiation characteristics are also attained, with a maximum realized gain of 6 dBi. Theoretical simulation results are similar to the experimental results. The measurement results of the manufactured device effectively validate that its performances have reached the simulation design requirements. Full article

A compact parallel-coupled-line microstrip bandpass filter with a very wideband passband and a narrow notched band is demonstrated in this paper. The presented bandpass filter was constructed from one section of three parallel-coupled-lines which has a length of a quarter wavelength at a midband frequency of 6.9 GHz. For the purpose of increasing the filter selectivity, the middle line is extended by a length of a quarter-wavelength and connected at one end to the ground plane. Therefore, a transmission zero was generated at each side of the passband which effectively improved the filter performance. In addition, a narrow notched band at a precise frequency inside the proposed passband was exhibited by placing a stepped-impedance resonator near the parallel-coupled-line for blocking the unwanted radio signal. The proposed filter was designed, simulated, fabricated, and measured. The fabricated filter has a very compact circuit size and its measured response shows an excellent agreement with the simulated results. Full article

A compact ultra-wideband bandpass filter based on a multilayer printed circuit board (MPCB) structure is proposed in this paper. RO4450F prepreg is used to bond three RO4350B dielectric substrates with different thicknesses in the MPCB structure. The upper surfaces of the three dielectric substrates are respectively provided with copper-coated structures with different patterns. The blind holes and the defected ground structure (DGS) are added to the MPCB of an ultra-wideband bandpass filter. Two groups of loaded quarter-wavelength terminal-open stubs introduce two transmission zeros, which improves the roll-off rates and stopband characteristics, while simple DGS composed of rectangular slots introduces two resonance points in the passband to improve the return loss. Simulation and measurement are consistent. The insertion loss at the center frequency of 12.795 GHz is 0.58 dB and the fractional bandwidth of 3 dB is 40.33% from 10.215 GHz to 15.375 GHz. This bandpass filter can be widely used in wireless and satellite communication. Full article

Targeting the range defined by the FCC (Federal Communication Commission) in 2002 for ultra-passband bandpass filters, i.e., 3.1 to 10.6 GHz, this article presents a simple compact multipoles ultra-wideband bandpass filter (range starting from 2.9 GHz and end at 11.5 GHz with central frequency 7.2 GHz) using parallel coupled microstrip line and multimode resonator with controllable double narrow notched bands at 3.5 GHz and 7.5 GHz by embedded a spur line structure and rectangular stub resonator coupled to the middle section of the multimode resonator to eliminate the interference with the existing radio signals falls in the range of 3.1 to 10.6 GHz, respectively. After optimization of the proposed filter, some attractive features were obtained, i.e., a compact size 21 mm × 5.2 mm, simple topology, good reflection coefficient lower than −18 dB, good passband transmission coefficient –1.1 dB over the entire fractional bandwidth of about 119.4%, and four transmission poles at 3.4 GHz, 4.6 GHz, 6.5 GHz, and 10 GHz, respectively, can be seen which improves the performance of the filter. Finally, the fabricated filter was tested, and the results obtained demonstrated an excellent agreement. Full article

In this paper, ultra-wideband bandpass filters using tapered transmission line resonators are presented. The proposed filters are based on short-circuited tapered transmission line stubs. The use of tapered transmission resonators resulted in a noticeable length reduction, a wider controlled operational bandwidth, and better stopband characteristics for filter applications. Three filters are designed with different tapered ratios using exponential tapered transmission line resonators. The other three filters are also designed using equivalent linear tapered transmission line resonators. The designed filters are simulated and fabricated on a Roger RT5880 substrate with a 2.2 relative permittivity and 0.78 mm thickness. Approximately, the same performance is obtained using either exponential or linear tapered resonators. A good agreement between the simulated and measured results is reported. The realized 112.22% fractional bandwidth filter has a return loss (S₁₁) better than 17 dB and an insertion loss (S₁₂) better than 1 dB over the entire UWB spectrum. Notable improvements in stopband characteristics are also achieved. Full article

This article presents a simple method to design an ultra-wideband (UWB) bandpass filter (BPF) with a notched band. The structure of the filter is simple and is composed of a single half-wavelength resonator loaded with three sets of short-circuit step impedance stubs. An equivalent circuit model is presented to analyze the resonance characteristics. Compared with the traditional quarter-wavelength uniform impedance stub, the novelty of the short-circuit step impedance stub introduces two design parameters: the impedance ratio (K) and the electrical length ratio (α). Therefore, by adjusting these design parameters, the frequencies of the first two notched bands can be tuned widely, so a wide frequency band with a notched band can easily be achieved. With a K of 0.36 and an α of 0.6, the designed filter achieved an ultra-wideband bandpass response with a notched band. The UWB response had a passband range of 2.5 GHz–10.5 GHz and a notched band around 5.1 GHz with an attenuation of about 45 dB. The insertion loss in the entire passband was less than 1.26 dB, and the return loss was larger than 10 dB on average. The maximum group delay variation in the two passbands was less than 0.3 nS. The measurement results showed good agreement with the simulation results. Full article

An ultra-wideband bandpass filter (UWB-BPF) using inductively compensated parallel-coupled lines (ICPCL) is presented in this article. It consists of three circuits: a high-pass filter (HPF), a lowpass filter (LPF), and a transmission line. The HPF and the LPF are independently synthesized from the ICPCL. The proposed filter can suppress unwanted frequencies in the upper stopband and increase the skirt slope of the frequency response in the transition bands. The fabricated UWB-BPF with compact size provides good passband performances, with insertion loss of better than −0.49 dB and return loss of better than −12 dB in the frequency range of 2.92–10.95 GHz (the bandwidth of 8.03 GHz). The 107% bandwidth is achieved. In addition, the proposed filter can suppress the spurious frequencies at 2f₀, which is greater than 30 dB. The measured results accord well with the simulation results. The novelty of the paper is the introduction of the ICPCL for the construction of the compact UWB-BPF. Full article

Microwave sensors have recently been introduced as high-temporal resolution sensors, which could be used in the contactless monitoring of artery pulsation and breathing. However, accurate and efficient signal processing methods are still required. In this paper, the matrix pencil method (MPM), as an efficient method with good frequency resolution, is applied to back-reflected microwave signals to extract vital signs. It is shown that decomposing of the signal to its damping exponentials fulfilled by MPM gives the opportunity to separate signals, e.g., breathing and heartbeat, with high precision. A publicly online dataset (GUARDIAN), obtained by a continuous wave microwave sensor, is applied to evaluate the performance of MPM. Two methods of bandpass filtering (BPF) and variational mode decomposition (VMD) are also implemented. In addition to the GUARDIAN dataset, these methods are also applied to signals acquired by an ultra-wideband (UWB) sensor. It is concluded that when the vital sign is sufficiently strong and pure, all methods, e.g., MPM, VMD, and BPF, are appropriate for vital sign monitoring. However, in noisy cases, MPM has better performance. Therefore, for non-contact microwave vital sign monitoring, which is usually subject to noisy situations, MPM is a powerful method. Full article

Portable wireless communication systems are increasingly in demand in small sizes for human convenience. In wireless communication systems, the performance, size, and unit cost are very important. A band−pass filter is important to sharp cut–off frequency characteristics, size, and frequency selectivity in wireless communication systems. The band−pass filter has three types of techniques in the transmission−zero method, stub−loaded resonator, and stepped impedance resonator for the sharp cut−off frequency characteristic, adjustable bandwidth, and excellent frequency response characteristics. To obtain these characteristics, the impedance ratio and length of a stub are mainly adjusted. It also utilizes a multi–mode technique to increase bandwidth. However, it is analyzed that the problem of reducing the size of the device still remains. To solve these problems, the paper is applied to a stub−loaded resonator and a stepped impedance resonator to control the impedance ratio and the length of the stub to obtain the results of the transmission−zero method, bandwidth control, and size reduction through the folded structure. Dual−band bandwidth was secured by integrating a T−shaped band−stop filter. The designed band–pass filter has center frequencies of 243 GHz and 7.49 GHz, and the insertion loss of a proposed band−pass filter is 0.102 dB and 0.103 dB. Additionally, the return loss of a proposed band−pass filter is 19.13 dB and 19.96 dB, respectively. The bandwidth of a filter is 120% and 105%, respectively. The size of the filter is 0.0708 λg × 0.0533 λg. The designed filter has a good skirt phenomenon, small size, low insertion loss, and dual−band characteristics. Full article

This paper presents a novel design of a modified ultrawideband (UWB) antenna array integrated with a multimode resonator bandpass filter. First, a single UWB antenna is modified and studied, using a P-shape radiated patch instead of a full elliptical patch, for wide impedance bandwidth and high realized gain. Then, a two-element UWB antenna array is developed based on this modified UWB antenna with an inter-element spacing of 0.35 λ_L, in which λ_L is the free space wavelength at the lower UWB band edge of 3.1 GHz, compared to 0.27 λ_L of a reference UWB antenna array designed using a traditional elliptical patch shape. The partial ground plane is designed with a trapezoidal angle to enhance matching throughout the UWB frequency range. The mutual coupling reduction of a modified UWB antenna array enhances the reflection coefficient, bandwidth, and realized gain, maintaining the same size of 1.08 λ₀ × 1.08 λ₀ × 0.035 λ₀ at 6.5 GHz center frequency as that of the reference UWB antenna array. The UWB antenna array performance is investigated at different inter-element spacing distances between the radiated elements. To add filtering capability to the UWB antenna array and eliminate interference from the out-of-band frequencies, a multimode resonator (MMR) bandpass filter (BPF) is incorporated in the feedline while maintaining a compact size. The measurement results showed a close agreement with simulated results. The proposed UWB filtering antenna array design achieved a wide fractional bandwidth of more than 109.87%, a high realized gain of more than 7.4 dBi, and a compact size of 1.08 λ₀ × 1.08 λ₀ × 0.035 λ₀ at 6.5 GHz center frequency. These advantages make the proposed antenna suitable for UWB applications such as indoor tracking, radar systems and positioning applications. Full article