A Miniaturized wide Stopband Low-pass Filter using T and Modified L Shapes Resonators

A new structure of microstrip-based low-pass filter with wide stopband and sharp roll-off is introduced, in this paper. In the proposed topology, resonators with T and modified L Shapes have been used. To improve the suppression factor and relative stopband bandwidth, the second resonator has been added to the first resonator. The designed filter has been fabricated on a 20 mm thickness RO4003 substrate, which has a loss tangent of 0.0021 and a relative dielectric constant equal to 3.38. All parameters including roll of rate, stopband, bandwidth, return loss, insertion loss, and figure of merit have significant coefficients. Simulation has been ran using advanced design system software. The 3dB cutoff frequency is appropriate. The value of the insertion loss parameter is <0.1 dB and the S11 parameter is −22 dB at this point. The stopband is extended from 2.42 up to 24 GHz, which shows an ultra-stopband. The results of the simulation and experiment are almost similar, which indicates a proper performance of the designed structure

Compact Dual-band Parallel Coupled T-shaped SIR Filter for WLAN Applications

In this article, a new compact dual-band bandpass filter was introduced. The filter utilized two operating bands centered at 2.45 GHz and 5 GHz widely used for wireless local area network applications. The filter consists of T-shaped sections of step impedance resonator. The structure is an even symmetrical around electrical or magnetic wall, so the operation mechanism of the filter can be analyzed by an even- and odd-mode transmission line theory. The resonator structure is parallel coupled to a pair of 50 Ω input/output ports. Proper feeding and coupling structures can realize at least two transmission zeros around each of the operating band. To enhance the spurs rejection in the out of the band response of the filter, additive transmission zero at 10 GHz was created by adding stub of quarter guided wavelength at a selected distant from the output port edge. The filter is designed and optimized using the full wave Electromagnetic simulator. The center frequency of the designed bands can be easily refined by the filter dimensions. The overall dimension of the filter is (where  is the guided wavelength at the frequency of 2.45 GHz) corresponding to 14.3 mm x 22 mm

Design and Analysis of a Wide Stopband Microstrip Dual-band Bandpass Filter

A novel configuration of a dual-band bandpass filter (BPF) working as a harmonic attenuator is introduced and fabricated. The proposed filter operates at 3 GHz, for UHF and SHF applications, and 6.3 GHz, for wireless applications. The presented layout has a symmetric structure, which consists of coupled resonators. The designing of the proposed resonator is performed by introducing a new LC equivalent model of coupled lines. To verify the LC model of the coupled lines, the lumped elements are calculated. The introduced filter has a wide stopband up to 85 GHz with 28th harmonic suppression, for the first channel, and 13th harmonic suppression, for the second channel. The harmonics are attenuated using a novel structure. Also, the proposed BPF has a compact size of 0.056 λg2. Having several transmission zeros (TZs) that improve the performance of the presented BPF is another feature. The proposed dual-band BPF is fabricated and measured to verify the design method, where the measurement results confirm the simulations

Review on UWB Bandpass Filters

Rapid development of a number of wireless communication systems imposed an urgent requirement for a technology which contains multi-wireless communication standard. Since the ultra-wideband (UWB) technologies are of advantage in broad bandwidth and high-speed transmission, much attention has been paid to exploiting the UWB bandpass filters. In this chapter, the development process of the UWB bandpass filters and the regulation of the UWB bandpass filter are initially introduced. Subsequently, the application scenarios of UWB filters in UWB communication systems and unique merits of UWB filters were explored. In addition, the primary performance specifications of the UWB filters, including insertion loss, return loss, the level of out-of-band attenuation, and roll-off rate, are also presented. After a brief discussion of microwave network theory, several methods for implementing UWB filters are summarized. Furthermore, the design of the UWB filter with notch band is presented in Section 5. The last section, the Conclusion section, is given at the end of this chapter

Miniaturised and reconfigurable planar filters for ultra-wideband applications

An increasing demand for electromagnetic spectrum has resulted from the emergence of feature-rich and faster throughputs wireless applications. This necessitates the developments of dynamic reconfigurable or multifunctional systems to better exploit the existing spectrum. Future wireless devices will be expected to communicate over several bands with various other devices in order to fine tune the services they provide to the user. Each band may require a separate RF transceiver and such modern wireless multi-band multi-mode communication systems call for high performance, highly integrated compact modules. Since the Federal Communications Commission (FCC) released the unlicensed frequency band 3.1-10.6 GHz for ultra-wideband (UWB) commercial communications, the development race for commercialising UWB technology has seen a dramatic increase around the world. The aim of this research is to develop reconfigurable planar microwave filters for ultrawideband applications. The project investigates some key design issues of reconfigurable filters, which are being observed constantly in the latest development and realisation of microwave filters. Both analytical and numerical methods are performed to construct a realistic and functional design. Two different types of frequency reconfigurability are investigated in this thesis: discrete (e.g. PIN diode, Optical switch) and continuous (e.g. varactor diode). Using the equivalent circuits and considering the direct coupled filter structure in most cases, several topologies with attractive features are developed for future communication systems. The proposed works may be broadly categorised into three sections as follows. The first section explores a square ring shape close loop resonator along with an opencircuited stub in the symmetry plane. To realise a reconfigurable frequency states within the same spectrum, an innovative approach is developed for this case. An optical or photoconductive switch, comprised of a silicon die activated using near infrared light is investigated as a substitute of PIN diode and performances are evaluated to compare the feasibilities. In addition, a in-band interference rejection technique via externally coupled Tshape resonator is shown. However, it is observed that both structures achieve significant size reductions by utilising the inner part of the resonators. To improve the filter selectivity, a convenient design approach generating a pair of transmission zeros between both passband edges and a single zero in the stop band for harmonic suppression is discussed in the second section. Moreover, the development of notched rejection bands are studied and several novel methods to create a single and multiple notched bands employing the square ring shape structure are proposed. On inspection, it is found that the notch structure can be implemented without deteriorating the filter performances. The discussions are supplemented with detailed design examples which are accompanied by theoretical, simulated and experimental results in order to illustrate the filter development process and showcase practical filter performance. The third section reveals a novel highly compact planar dual-mode resonator with sharp rejections characteristics for UWB applications. A bandwidth reconfiguring technique is demonstrated by splitting its even-mode resonance. Filter structure with the dual-mode resonator is shown to have a relatively wide tuning range, significantly low insertion loss and a constant selectivity along with frequency variations in comparison to similar published works. Finally, the earlier dual-mode structure are modified to realise a dual wideband behaviour. A detail analysis with comprehensive design procedures is outlined and a solution for controlling the frequency bandwidths independently according to the application interest is provided. In line with the previous section, experimental verification is presented to support and supplement the discussions

UWB Technology

Ultra Wide Band (UWB) technology has attracted increasing interest and there is a growing demand for UWB for several applications and scenarios. The unlicensed use of the UWB spectrum has been regulated by the Federal Communications Commission (FCC) since the early 2000s. The main concern in designing UWB circuits is to consider the assigned bandwidth and the low power permitted for transmission. This makes UWB circuit design a challenging mission in today's community. Various circuit designs and system implementations are published in this book to give the reader a glimpse of the state-of-the-art examples in this field. The book starts at the circuit level design of major UWB elements such as filters, antennas, and amplifiers; and ends with the complete system implementation using such modules

A review article of multi-band, multi-mode microstrip filters for RF, WLAN, WiMAX, and wireless communication by using stepped impedance resonator (SIR)

Filters are the basic part in wired, and wireless telecommunications and radar system circuits and they play an important role in determining the cost and performance of a system. The increasing demand for high performance in the fields of RF, WLAN, WiMAX and other wireless communications led to the great revolution in the advancement of the development of a compact microstrip resonator filter design. All these have made a vital contribution to both the required performance specifications for filters and other commercial requirements in terms of low cost, large storage capacity and high-speed performance. This review paper presents several design examples for multi-band, multi - mode microstrip filter resonators to satisfy RF, WLAN, WiMAX, UWB and other wireless communication frequency bands. To analyse the resonant frequencies odd - mode and even -modes can be used for the symmetrical structure. In general, the multi-mode resonators can be designed by using different methods like cross-coupling resonators Structure, and the allocation of the fundamental resonant frequencies of the resonator as stated by the Chebyshev's insertion loss function

A Compact Lowpass Filter with Ultra Wide Stopband using Stepped Impedance Resonator

In this paper, a compact asymmetric-shaped microstrip lowpass filter (LPF) using a stepped impedance resonator is presented. An ultra wide stopband with high attenuation in the stopband region, within very small circuit area is achieved for the proposed filter using novel asymmetric structures for resonator and suppressor. The transmission zeros of the resonators can be adjusted as a function of high impedance and low impedance microstrip lines, and due to the asymmetric structure, the proposed suppressing cell can be located within the resonator structure without occupying a large area. For verification, a 2.92 GHz LPF is designed and fabricated. The experimental results, in comparison with the other LPFs, show that the proposed LPF has significant advantages in the stopband characteristics with acceptable sharp roll off. The measured passband insertion loss is below 0.1 dB, and the rejection band over -20 dB is obtained from 3.42 GHz to 36.2 GHz. The size of filter corresponds to compact electrical size of 0.156 λg × 0.128 λg, where λg is the guided wavelength at 2.92 GHz. Also, the maximum variation of the group delay in 80 percent of the passband region is only about 0.2 ns

Band-pass Filter with Harmonics Suppression Capability

This paper presents a Band-pass Filter (BPF) with a very wide suppressions band. The filter design is based on a modified U-shaped slot. Two pair of U-shaped slots is used to ensure that the filter can suppress the unwanted frequencies up to 4th harmonics. In order to achieve sharp skirt, two transmission zeroes are created near the passband area. Additional transmission zeroes are introduced to deepen the stopband area. Therefore, the passband range starts from 1.3 to 3.3 GHz and the stopband range from 3.3 GHz up to 9 GHz are achieved. The filter performances are verified through simulated and measured results