Half-wavelength Stepped-impedance Resonator Research Articles

Optimization and Design of Balanced BPF Based on Mixed Electric and Magnetic Couplings

A balanced bandpass filter (BPF) with an improved frequency selectivity for differential-mode (DM) excitation and high rejection for common-mode (CM) excitation is proposed in this paper. Two half-wavelength stepped impedance resonators (SIRs) are employed based on mixed electric and magnetic couplings to realize a DM passband centered at 2.48 GHz. The center frequency and bandwidth can be easily controlled by optimizing the dimensions of SIRs and the coupling between them, respectively. Meanwhile, two transmission zeros (TZs) are generated based on the mixed electric and magnetic couplings and are independently controlled by tuning the coupling strength. Moreover, a wide DM stopband can be realized by optimizing the SIRs. The proposed balanced BPF is fed by balanced U-type microstrip–slotline transition structures, which can achieve high wideband CM rejection without influencing the DM responses, and the design complexity can be clearly reduced. Finally, a balanced BPF is fabricated, and a good agreement between the simulation and the measurement is observed, which verifies the design method.

A dual‐band reconfigurable filtering antenna using PIN diodes for WiMAX and WLAN applications

The realization of a compact dual band reconfigurable filtering antenna is described for WiMAX and WLAN application through this communication. First and foremost, a dual band filter is offered employing four open ended half wavelength Stepped Impedance Resonators (SIRs) to resonate at 3.2 GHz and 5.35 GHz. PIN diodes have been connected to the edges of the innermost resonators to switch the operation from dual passband to two different single passbands and to all stop configuration. Multipath coupling helps to create transmission zeroes on either side of passband enriching the selectivity. In order to implement the filtering antenna, a compact monopole antenna is presented using two triangular radiating patches radiating at 3.2 GHz and 5.35 GHz. Finally, the filter and the antenna structures are combined to accomplish the proposed dual band reconfigurable filtering antenna. The results with reference to return loss and radiation pattern are provided and good performances are obtained. The suggested filtering antenna has the reflection coefficient lower than −16 dB for all the desired operating bands. As well, it offers gain of about 3.21 dBi and 5.08 dBi at the two radiating bands. The developed prototype is fabricated and measured to examine the anticipated and simulated results where a close agreement is established between them.

Miniaturised highly selective bandpass filter with very wide stopband using meander coupled lines

A compact wideband bandpass filter with a very wide stopband for terrestrial radio (TETRA) band applications is proposed. The proposed filter employs two types of resonators: one is tri-section half wavelength stepped impedance resonator (SIR) and the other is stub-loaded shorted ring resonator. The proposed filter has adopted SIRs and meandering technique in achieving miniaturised size. Spur-lines and tapped feeding techniques are infused in the filter to suppress harmonics so as to achieve wide stopband. Cross-coupling is introduced in the filter for acquiring good selectivity. This highly selective filter has a miniaturised size of 0.09 × 0.12λg (28 × 36.8 mm2) with a wide stopband up to 8.75f0 (f0 is the centre frequency of filter) with 25 dB harmonics suppression level.

Tri‐section stepped‐impedance resonator filter with controllable mixed electric and magnetic cross‐coupling

A novel tri-section stepped-impedance resonator (SIR) filter with controllable mixed electric and magnetic cross coupling is proposed. Two quarter-wavelength shorted-end SIRs and one half-wavelength SIR are used to realise tri-section topology. The electric and magnetic couplings in mixed cross coupling can be controlled by the inter-digital capacitor structure and the gap between shorted lines, respectively. Then, additional transmission zeros can be obtained for better frequency selectivity and high rejected level in stopband. One filter sample is designed and fabricated with single-layer PCB. Good agreements are achieved between the measured and simulated S -parameters.

Wide‐stopband Wilkinson power divider with bandpass response

A wide-stopband Wilkinson power divider with bandpass response and good isolation is presented. A 3-terminal, 2-pole bandpass filter and two 3-pole lowpass filters are used to replace the two quarter-wavelength transformer in a conventional Wilkinson power. The divider consists of two shorted-circuited half-wavelength stepped-impedance resonators and two 3-pole microstrip stepped-impedance lowpass filters. Thus, the divider achieves not only a bandpass response but also a very wide stopband. For the upper stopband performance, the rejection level is >10 dB up to 22.2 times the centre frequency.

A planar compact dual-band bandpass filter using stepped impedance resonator and interdigital capacitor

In this paper a dual-band bandpass filter with sharp rejection is proposed. The filter is realized by using two half-wavelength stepped impedance resonators to operate at the passbands 2.5 and 3.5 GHz. To increase the band width further to about 45 MHz at the lower passband and 115 MHz at the higher passband, interdigital capacitors are introduced between resonator and input and output combining network. Measured insertion loss is about 1.45 and 1.7 dB at first and second passbands, respectively. A finite transmission zero in between two passbands at 2.84 GHz is realized to improve the selectivity of the filter. The design procedure to get highly selective response of the proposed filter is explicitly explained. An equivalent circuit model of proposed filter is developed that matches well with measured results.

Analytical Design of Microstrip Short-Circuit Terminated Stepped-Impedance Resonator Dual-Band Filters

This paper proposes an analytical method to design a dual-band Alter using the short-circuit terminated half-wavelength stepped-impedance resonator (SIR). The SIR has an advantage to easily control the first and second resonances by adjusting its structural parameters. In the proposed method, the structural parameters of the SIR are obtained analytically according to the two passband center frequencies and bandwidths of the filter. As a result, the achievable specifications of the dual-band filter can be rapidly determined. The coupling between adjacent SIRs is realized by a short-circuited stub, which is characterized as a K-inverter network. The dual-frequency transformer incorporated with the tapped-line input/output structure is used for the external coupling. Applying the analytical equations in the design process, a dual-band filter can be easily and quickly realized. More importantly, compared to the published dual-band filters, the proposed method is easier to design, especially for a relatively high-order dual-band filter. Two fourth-order and one sixth-order dual-band filters are designed and fabricated to demonstrate the proposed method.

Compact UWB antenna with sharp band-notched characteristics for lower WLAN band

A compact ultra-wideband (UWB) antenna with sharp band-notched characteristics is presented. The sharp band-notched characteristic is realised by inserting a half wavelength C-shaped slot in the patch and adding two half wavelength stepped impedance resonators around the feed-line. Simulated and experimental results show that the designed antenna, with compact size of 30×36mm2, has an impedance bandwidth of 3.1–10.6 GHz for return loss less than −10, except the lower WLAN band of 5.15–5.35 GHz (return loss >−5 dB). The ratio of −5 dB notched bandwidth to −10 dB notched bandwidth is 0.79. Moreover, the antenna has good omnidirectional radiation patterns in the H-plane.

COMPACT MICROSTRIP BANDPASS FILTER WITH MULTISPURIOUS SUPPRESSION

A compact microstrip bandpass fllter (BPF) with multispurious suppression is presented. The fllter consists of two coupled half-wavelength stepped impedance resonators (SIRs) and tapped input/output (I/O) lines. With tuning the impedance ratio (K) and length ratio (fi) of SIRs, a very wide stopband can be easily achieved. The fllter is designed at 2.4GHz (f0) with a wide stopband to 20GHz (8.16f0) and an average rejection level better than 25dB. This study provides a simple and efiective method to achieve a fllter with very wide stopband and compact circuit size simultaneously. Good agreement between the full-wave electromagnetic (EM) simulation and measurement is compared.

Method of determining feed positions in coupled half-wavelength stepped impedance resonator bandpass filter

In this study, the input impedance of coupled half wavelength stepped impedance resonator bandpass filter with directly tapped feed structure is deduced, and the method of determining the feed positions in the filter is proposed by using the concept of impedance matching. Two microstrip bandpass filter examples are described for demonstrating the procedure. The simulated and measured results indicate that the proposed method is an effective way for designing similar filters.

Dual-Band Microstrip Stepped-Impedance Bandpass Filter with Defected Ground Structure

A compact dual-band stepped impedance bandpass filter with a defected ground structure (DGS) is proposed. The half-wavelength stepped impedance resonator is adopted to result in two tunable passbands. A DGS is constructed under the two coupling stepped impedance resonators to achieve good passband performance. Compact size and high selectivity is realized with the tap input/output coupling structure. For demonstration, one RF filter operating at 2.45 and 5.2 GHz is designed. Simulated and measured results are provided.

Novel Design of Microstrip Bandpass Filters with a Controllable Dual-Passband Response: Description and Implementation

SUMMARY Novel microstrip dual-band bandpass filters with controllable fractional bandwidths and good in-between isolation are presented and implemented. A half-wavelength stepped-impedance resonator is firstly characterized, aiming at producing the two resonant frequencies at 2.4 and 5.2 GHz. Two types of coupled microstrip lines in the parallel and anti-parallel formats are then investigated in terms of unified equivalent J-inverter network. Extensive results are derived to quantitatively show their distinctive frequency-distributed coupling performances under different coupling lengths. The coupling degrees of these two coupled lines at the two resonances are properly adjusted to achieve the dual-passband response with varied or tunable bandwidths. In addition, the parallel coupled line is modeled to bring out a transmission zero between the two resonances so as to achieve the good in-between isolation. The three two-stage bandpass filters are initially designed to exhibit their dual-band response with changeable dual-band bandwidths. A three-stage dual-band filter is in final optimally designed and its predicted performance is confirmed in experi

The Quasi-elliptic Bandpass Filter Using Quarter-wavelength Stepped Impedance Resonators

A bandpass fllter is designed using two end-connected quarter-wavelength stepped impedance resonators. The quarter-wavelength stepped impedance resonators are implemented by a half-wavelength stepped impedance resonator with its middle shorting to ground. Hence, the modes that the ‚=4 stepped impedance resonator supports are the (1+2n)=4 which also occur on the branches of a combline. An enhanced U-shape coupling feed is adopted in the fllter design to reduce the insertion losses as well as suppressing the harmonics. The proposed fllter has a quasi-elliptic frequency response. An equivalent circuit model is developed and the experiments are conducted for circuit design veriflcation.

Compact dual-band microstrip bandpass filter without external feeds

A compact dual-band microstrip bandpass filter is proposed and designed to operate at 2.4 and 5.2GHz without needing any external impedance-matching block. The modified half-wavelength stepped-impedance resonator with sinuous configuration is constructed to simultaneously excite the dual resonances at these two specified frequencies with miniaturized overall size. The parallel-coupled microstrip line is properly characterized to minimize the return losses within both dual passbands. The optimized results exhibit the good dual-band filtering performances with return losses higher than 20dB as well being confirmed by experimentation with a fabricated filter circuit.