Stepped-impedance Ring Resonator Research Articles

General rotationally symmetric coupled feeding structure and its application to single- and dual-band balanced filters

This paper proposes a new general rotationally symmetric coupled feeding structure and its applications to the design of single- and dual-band balanced filters for high common-mode (CM) suppression. The balanced feeder consists of two coupling lines coupled with a ring resonator, which can be either a uniform impedance ring resonator or a stepped impedance ring resonator. Under differential-mode (DM) excitation, the voltage distributions of the coupling-line and resonator are both rotationally even-symmetric and the total coupling coefficient adds up, which indicates that the proposed feeding structure can achieve DM transmission characteristic. Under CM excitation, their voltage distributions are rotationally even- and odd-symmetric, respectively, so the total coupling coefficient cancels out to zero and CM suppression property is achieved. For demonstration, four single- and dual-band balanced filters with wide range of CM and harmonic suppression are designed, fabricated, and measured, and the simulation and measured results match well.

A Miniaturized UWB Bandpass Filter Employing Multi-Stub-Loaded Short-Circuited Stepped Impedance Ring Resonator

This article presents a novel microstrip line topology implementation of an ultra-wideband (UWB) bandpass filter. The proposed topology is a short-circuited stepped-impedance ring resonator with an open-circuit stub and a short-circuit stub loaded at the central vertical position of the low impedance of this resonator, respectively. Within the UWB spectrum, five modes are allocated under weak coupling, and to increase filter selectivity, two transmission zeros are added. It is possible to extend the upper stopband and provide sufficient external coupling by utilizing interdigital-coupled lines. To demonstrate the design theory, a prototype is designed and manufactured on a 0.8 mm thick substrate of the affordable F4B-2, and its performance is verified. Measurements show a 3-dB bandwidth span from 2.8 to 9.5 GHz, insertion loss of 0.36 dB, and return loss better than 13 dB.

Balanced Tri-Band Bandpass Filter Design Using Octo-Section Stepped-Impedance Ring Resonator With Open Stubs

A balanced tri-band bandpass filter (BPF) is proposed based on octo-section stepped-impedance ring resonator (SIRR). The relation and design graphs between the differential-mode (DM) and common-mode (CM) characteristics with different physical parameters are analyzed. It reveals that the proposed SIRR has more degrees of freedom in controlling DM and CM characteristics for tri-band design with excellent out-of-band performances and high CM suppression. Moreover, the SIRR is loaded by open stubs with different lengths to further improve the CM suppression. Finally, a balanced tri-band BPF prototype is fabricated and measured. Good agreement between simulated and experimental results verifies this design method.

A wideband power divider with bandpass response

In this paper, a new configuration embedded with two filters and one resistor is proposed, which has the dual function of power splitting and filtering. The filter is based on stepped impedance ring resonator. All the even- and odd-mode resonant frequencies and transmission zeroes of the stepped impedance ring resonator are derived based on the even- and odd-mode analysis. Three interdigital-coupled lines are applied at the input port and output ports to achieve a bandpass response and suppress the second harmonic. For verification, a sample operating at the central frequency of 2 GHz is fabricated and tested. The measured results show the power divider has good performance on impedance matching, frequency selectivity, and isolation over the operating band.

Dual-Band Bandpass Filter With Wide Stopband Using One Stepped-Impedance Ring Resonator With Shorted Stubs

A novel stepped-impedance ring resonator (SIRR) with two pairs of shorted stubs is proposed to design a dual-band bandpass filter. The proposed resonator is a quad-mode resonator, and one resonator can realize a dual-band filter. The frequency space between two passbands and bandwidths of two passbands can be controlled by the shorted stubs. Wide out-of-band rejection can be achieved by selecting the desired impedance and length ratios and suitable feeding point to suppress some spurious resonant frequencies. A prototype filter centered at 1.395 and 1.825 GHz is designed with the first spurious response occurring at 7.84 GHz or $5.7f_{01}$ ( $f_{01}$ is the center frequency of the first passband). Good agreement between the simulated and measured results can be observed.

DUAL-BAND BANDPASS FILTER WITH INDEPENDENTLY TUNABLE PASSBANDS AND WIDE STOPBAND

This paper presents a dual-mode stub loaded ring resonator (SLRR) to design a tunable dual-band bandpass filter (BPF) with two independently controllable passbands. The proposed resonator principally comprises a stepped-impedance ring resonator (SIRR) loaded with three stubs and two varactor diodes. Two independently tunable passbands are implemented by employing two varactors to control the dominant even-mode resonant frequency and odd-mode resonant frequency, respectively. Moreover, a new stub loaded double-ring resonator (SLDRR) is proposed to design the second tunable dual-band filter by shorting two stubs of the SLRR. With the same tuning method, the second filter can achieve two independently controllable passbands. In order to suppress the harmonics, defected ground structures (DGSs) are introduced at input and output feeding lines without degrading the passbands characteristics. The measured results are in good agreement with the simulated ones.

TRANSMISSION ZERO DESIGN GRAPH FOR DUAL-MODE DUAL-BAND FILTER WITH PERIODIC STEPPED-IMPEDANCE RING RESONATOR

Compact dual-mode dual-band bandpass fllters are realized with a single periodic stepped-impedance ring resonator. Neither extra resonator nor substrate layer is required for implementing the second passband. Based on the transmission line theory, a transmission zero design graph consisting of the transmission zeros together with the resonant frequencies of the resonator is developed against the space separation angle between the input and output ports. Based on this graph, when the line-to-ring feed structure is implemented, the space angle can be determined for the dual-mode dual-band design with designated zeros near the two passbands. It is believed that this is the flrst design graph for designating the transmission poles and zeros of a dual-mode ring resonator fllter before the excitation structure is realized. Three dual-mode dual-band bandpass fllters are carried out for demonstration. All circuits occupy only 60% of the area of the conventional ring resonator bandpass fllter

스텝 Perturbation의 영향에 따른 주기적 스텝 임피던스 링 공진기의 해석 및 이중 모드 대역 통과 필터의 적용

Dual-mode bandpass filter was designed by using periodic stepped impedance ring resonator with step perturbation. The periodic stepped impedance ring resonator has the effects of size reduction and harmonic suppression by changing characteristic impedance ratio. The perturbation for dual-mode generation was also easily controlled by characteristic impedance ratio, and the variation of dual-mode resonant frequencies and attenuation pole frequencies were analyzed by the effect of step perturbation. Chip capacitors were used for input/output coupling, and the variation of center frequency by the coupling capacitance and step perturbation was also considered. From the results, two types of 2 GHz dual-mode bandpass filter were fabricated in size of , those have different attenuation poles and bandwidths. The measured results of proposed bandpass filters showed a good agreement with the calculated estimations, and those have insertion loss of 2.52, 0.52 dB and 3 dB bandwidth of 4.03, 15.02 %, respectively.

Miniaturized Rat Race Coupler With Suppression of Spurious Passband

A new hybrid ring coupler design is devised for circuit miniaturization based on the periodic stepped-impedance ring resonator structure. The circuit has an area of 21.5% of a conventional rat race coupler and no passband up to the sixth harmonic of the design frequency. The designs are validated by comparing measured four-port parameters with the simulated results

Periodic stepped-impedance ring resonator (PSIRR) bandpass filter with a miniaturized area and desirable upper stopband characteristics

A periodic stepped-impedance ring resonator (PSIRR) is proposed to design dual-mode bandpass filters with a miniaturized area and desirable upper stopband characteristics. Design parameters of a PSIRR include impedance ratio R of the hi-Z to low-Z sections, their lengths, and number of impedance steps 2N. The resonant characteristics of PSIRRs with various N and R values are investigated by both the transmission-line theory and electromagnetic simulation. Proper choice of the above parameters leads to an optimal reduction of circuit area and extension of upper rejection bandwidth. Two extra transmission zeros exist in the upper stopband and are tunable via changing the arm lengths of the line-to-ring coupling structure. Realized by the standard microstrip technology, the dual-mode PSIRR bandpass filter has not only the first spurious response at higher than 3.7/spl times/ the passband frequency, but also an area reduction of better than 60% against a conventional ring filter. Experimental results of several fabricated circuits validate the analysis and theoretical prediction.

Microstrip Dual-Mode Bandpass Filter with Ultra-Broad Stopband Using Aperture-Backed Stepped-Impedance Ring Resonator

A novel microstrip dual-mode bandpass filter with ultra-broad stopband is proposed using the aperture-backed stepped-impedance ring resonator (SIRR). This SIRR consists of low-impedance strips in the four bended comers and high-impedance strips in the four straight sides. With the cross-shaped aperture placed on the ground underneath the SIRR, the upper stopband is significantly broadened. In particular, the 2nd resonant frequency of this proposed SIRR is confirmed to exceed the four times of its 1st counterpart. The dual-mode filter with the passband of 7.5% at 1.59 GHz is then designed and implemented, demonstrating the measured stopband of 1.70-5.80 GHz and size reduction of 56.0%.

Microstrip dual-mode filters with miniaturized size and broadened stopband using meander-shaped stepped-impedance ring resonator

An improved class of microstrip dual-mode bandpass filter is proposed using the meander-shaped stepped-impedance ring resonator (SIRR). This meander SIRR, together with a uniform impedance ring resonator (UIRR), is at first studied to demonstrate its attractive features of harmonic-resonance suppression and overall-size miniaturization. A pair of squared notches is then etched out on the corners along either of diagonal lines of this symmetrical SIRR that is capacitively driven by the two perpendicular feed lines. Two SIRR-based dual-mode filters are therefore designed, simulated and fabricated. The overall size of this filter finds to be reduced by about 50% in area. The 1st harmonic passband of this filter is raised to 5.30GHz that exceeds the three times of its fundamental passband at 1.52GHz as verified by experiment.

Dual-mode stepped-impedance ring resonator for bandpass filter applications

It is well known that two orthogonal resonant modes exist within a one-wavelength ring resonator. In this paper, we focus on a ring resonator possessing an impedance step as a form of perturbation. A convenient analyzing method for obtaining the resonance characteristics of this resonator structure is presented. Furthermore, generation of attenuation poles obtained by the dual-mode ring resonator is discussed. In addition, a filter design method based on this resonator is explained, followed by experimental results, which prove the validity of the proposed design method.