Low-loss Bandpass Research Articles

Electronically Reconfigurable Microwave Bandpass Filter

A new class of reconfigurable bandpass filter based on parallel-coupled switched delay line approach is presented in this paper. The approach allows both center frequency and passband bandwidth to be reconfigured electronically. In contrast to conventional approach, the effects of the switch losses are relatively insignificant and can be treated as an auxiliary effect and therefore the filter has low passband loss. Despite the loss performance, the filter provides excellent linearity performance with large power handling capability. Theoretical analysis is presented and the feasibility of the approach has been experimentally verified with microstrip circuit prototypes. The first filter prototype provides narrowband quasi-elliptic filter response with constant bandwidth (50-MHz) tuning across 45% tuning range. The minimum stopband rejection level is 45 dB. The second filter possesses passband-width 3:1 ratio tunability. The third filter provides both functionalities which allow center frequency and passband bandwidth to be reconfigured. All filters have a < 4-dB passband loss with an OIP3 of >20 dBm and are immune from power saturation effect. The measured results demonstrate improved performance in terms of linear and nonlinear characteristic compared with prior works.

Microstrip ring resonator bandpass filters using ceramic substrate

AbstractThe miniaturization of ring bandpass filters by employing high‐permittivity ceramic substrates (with respective dielectric constants of 9.7 and 23.5) are investigated. Microwave dielectric ceramics with high permittivity are commonly applied in several microwave communication components. With the advantages of compact size, high‐permittivity ceramics can be used as the substrate for bandpass filters. Moreover, the fundamental characteristics of newly developed compact square‐ring resonators have also been described and applied to the design of bandpass filters. In this paper, the designed square‐ring resonators structures are simulated using an IE3D simulator. The responses of the fabricated bandpass filters using Al2O3 (εr = 9.7, tan δ = 0.000036) and 0.875Mg0.95Zn0.05TiO3‐0.125Ca0.8Sm0.4/3TiO3 (εr = 23.5, tan δ = 0.000021) ceramic substrates are designed at the center frequency of 2.4 GHz. This compact size, low loss bandpass filter should be useful in many wireless communication systems. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 218–220, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24847

An improved asymmetric defected ground structure cell and its application to lowpass filter

AbstractAn improved asymmetric defected ground structure cell is presented and analyzed. Based on this structure, a microstrip lowpass filter with low passband loss and high stopband suppression is designed and fabricated. Measured passband losses are below 1 dB, and a sharp slop is obtained at passband frequency fringe. The suppression is no &lt;30 dB in stopband from 2.98 to 10 GHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2933–2935, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24778

Left-handed behavior and low-loss passband in a ferromagnetic sandwich structure

The electromagnetic properties of a ferromagnetic-dielectric-ferromagnetic sandwich structure were studied by experiment and simulation. In the transmission spectra, an obvious passband emerges in the broad forbidden band of ferromagnetic resonance because the strong coupling of two resonating ferrite slabs excites a propagating mode. The passband has ultralow loss (∼−1 dB) due to the feature of surface wave and the bias magnetic field pump. A negative phase evolution of propagating wave occurs in the second slab only based on the magnetic resonance. The ultralow insertion loss of passband and magnetotunability endow the sandwich structure a promising application future.

구형 공진기와 계단 임피던스 개방 스터브를 사용한 고효율 광대역 대역 통과 필터 특성

본 논문에서는 구형 공진기와 SIOS(Step-Impedance-Open-Stub)를 사용하여 삽입 손실이 적고, 차단 특성이 아주 좁고, 광대역 특성을 갖는 대역 통과 필터를 연구하였다. SIOS는 일반 <TEX>$0.25\;{\lambda}$</TEX> 개방 스터브보다 약 30 %의 길이를 줄일 수 있고, 또한, SIOS의 길이에 따라 임피던스 값을 조정함으로써 필터의 특성 개선에 적용할 수 있다. 본 논문의 객관성을 입증하기 위해서 이중 모드 구형 공진기를 사용한 최적화된 광대역 대역 통과 필터를 구현하였다. 전송 선로 모델을 사용하여 계산한 주파수 특성 결과는 실험값과 아주 잘 일치하였다. 본 논문에서 구현된 필터의 주파수 특성은 필터의 3 dB 대역폭은 51.75 %(3.206 GHz)이고, 삽입 손실은 0.44 dB, 30 dB 차단 특성은 저 주파수 대역에서 221 MHz(<TEX>$4.326{\sim}4.587\;GHz$</TEX>), 고주파수 대역에서 181 MHz(<TEX>$7.739{\sim}7.954\;GHz$</TEX>)이다. 최대 차단 특성은 저주파 대역에서 -61.8 dB, 고주파 대역에서 -76.3 dB이다. This paper presents a compact, low insertion loss, sharp rejection and wide band microstrip band pass filter that is composed rectangular loop resonator and Step-Impedance-Open-Stub(SIOS). The SIOS can be reduce length about 30 % more than general 0.25 <TEX>$\lambda$</TEX> open stub. And the stub can the advantage of tuning impedance magnitude. In order to demonstrate agrement of this paper prove, the optimized wide band pass filters are realized and experimented. A transmission line model used to calculate the frequency response of the new filters shows good agreement with measurements. The filter has 3 dB fractional bandwidth of 51.75 %(3.206 GHz), an insertion loss of better than 0.44 dB from 4.587 GHz to 7.793 GHz, and two rejection of greater than 30 dB within 221 MHz(<TEX>$4.326{\sim}4.587\;GHz$</TEX>) at low frequency band, 181 MHz(<TEX>$7.739{\sim}7.954\;GHz$</TEX>) at high frequency band. Maximum rejection characteristics of the filter are -61.8 dB at low frequency and -76.3 dB at high frequency.

A New Class of Low-Loss High-Linearity Electronically Reconfigurable Microwave Filter

A novel electronically reconfigurable microwave bandpass filter based on a switched delay-line approach is presented. In contrast to conventional tunable filters, the approach enables the lossy and nonlinear switching elements to be used as part of the coupling elements rather than within the resonators. Therefore, the filter distinguishes itself through its ability to provide a wide tuning bandwidth with low passband loss and high linearity. Theoretical analysis of the approach is presented in this paper. The feasibility of the approach has been experimentally verified with microstrip circuit prototypes. The filter produced a maximum passband loss of 1.7 dB and a third-order intercept point of >32 dBm with 35% tuning bandwidth.

Novel Folded Waveguide Resonator Filter Using Slot Technique

This letter presents a primary investigation into developing a compact and low-loss bandpass filter using novel folded-waveguide resonators with a footprint reduction. A slot coupling between adjacent resonators is introduced, which is characterized using full-wave electromagnetic simulations and verified experimentally. Two two-pole folded-waveguide resonator filters of this type have been designed, fabricated and tested. Simulation and measurement results are presented to validate the design and to show the advantages of this type of filter.

Reduced-size dual-mode slotted patch resonator for low-loss and narrowband bandpass filter applications

A compact, low-loss and narrowband dual-mode microstrip filter is proposed using degenerate modes of a microstrip patch resonator loaded with two narrow slots. The resonator structure is fed by inset lines connected directly to the centre of adjacent edges of a microstrip patch with two notches. The dual-mode filter is verified by both simulation and measurement.

Low-loss bandpass filter using higher mode strip line for millimetre-wave integrated circuits

A technique to construct a low-loss printed bandpass filter was demonstrated by using a higher mode strip line at 30 GHz. A three-pole, 0.1 dB Chebyshev ripple bandpass filter with a 2% relative bandwidth was designed and fabricated. The insertion loss was found to be 0.7 dB.

Surface-acoustic-wave devices for the 2.5–5 GHz frequency range based on longitudinal leaky waves

The recently discovered “longitudinal leaky” surface acoustic wave on YZ-cut lithium niobate has been used to implement low-loss bandpass filters operating in the 2.5-GHz Bluetooth frequency range. The filter is of the ladder type, employing synchronous resonators as building blocks. Resonator Q-values above 300 have been measured. The filter features a center frequency of 2491 MHz, a minimum insertion loss of 3.5 dB, and a fractional 3-dB bandwidth as wide as 6.2%.

Low-loss and high-selectivity bandpass filter with harmonic suppression and piezoelectric transducer tuning

A low-loss and high-selectivity bandpass filter with harmonic suppression and piezoelectric transducer (PET) tuning is presented. At the 3.5 GHz passband, the insertion loss is 1.48 dB, and the transmission zeros at 3.05 and 4.08 GHz have rejection of 55 dB. The rejection at the 7 GHz second harmonic is 50 dB. A PET tunes the bandstop sections to obtain a tunable suppression (>45 dB) around the second harmonic from 5.35 to 7.8 GHz.

New wide-band DC-block cymbal bandpass filter

A new low-loss dc-blocking parallel-cascaded bandpass filter is presented. The filter is much easier to use and fabricate, more compact, and simpler to design than the conventional end- or parallel-coupled line filters. The filter has a wide passband with a 2:1 voltage standing-wave ratio bandwidth of around 10% and an insertion loss of 0.5 dB at 10 GHz. Simulated results agree very well with experimental results.

Two-layer mm-wave FSS of linear slot elements with low insertion loss

The performance of a very low loss frequency selective surface (FSS) comprising two air spaced planar arrays of linear slot elements is reported. The beamsplitter generates a low loss passband response with a very sharp transmission roll-off with frequency. Simulated and measured results in the 30 GHz and 300 GHz wavebands are used to quantify the performance improvement compared to a conventional multilayer dielectrically backed conducting ring FSS. The paper also discusses the effect of the array dimensions on the passband width and filter roll-off rate.

High-Q inductors and low-loss bandpass filters on Al2O3 substrates by thin-film technology

High-Q spiral inductors were designed and fabricated on high-resistivity Al2O3 substrates with an air-bridge technology. A maximum Q-value of 36 was achieved for a 2.74 nH inductor at 2.5– 5.5 GHz. Detailed broadband models for inductors and interdigital capacitors have been developed based on measured results, which enable us to build a low insertion loss 2.4 GHz bandpass filter with a size of 2 mm×2 mm. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 20: 322–326, 1999.

Dense WDM multiplexer and demultiplexer with 0.4nm channel spacing

The authors report high performance dense WDM multiplexers and demultiplexers with a 0.4 nm channel spacing. Special apodised FBGs and low loss bandpass WDM filters are utilised. The demonstrated cost effective eight-channel dense WDM devices have a high channel isolation of &gt; 25 dB and an insertion loss of ~7.5 dB. The WDM devices can be expanded to 32 or 64 channels in the same structures.

Computer optimization of transducer transfer functions using constraints on bandwidth, ripple, and loss

Transducers, having one piezoelectric layer near its half-wave resonance and N quarter-wave layers, are designed using computer optimization to adjust the thicknesses and impedances of the various layers so as to fit the resulting transfer function to a target function. An augmented Mason model is used to evaluate the transducer. Optimization of fit is by a steepest descent algorithm. Essentially error-free fits are achieved for target functions that match the underlying dynamics. By applying classical filter theory to a lumped-element transducer model, the transducers dynamics are identified as all-pole filters, which are characterized by polynomials of order N to N+1. The design methodology is tested by designing a series of low-loss transducers that explore fractional bandwidths from 45 to 116%. From these studies there appears to be constraints on the minimum Q of the poles, and other properties. Typical power transfer efficiencies of -1 dB are achieved by impedance scale matching. Using a second-order Fano bound, it is shown that the matching layers function as an optimal compensation network for low-loss flat bandpass transducers. Finally, by the inclusion of loss, lower Q poles are demonstrated with a Bessel transducer.

A compact, high power notch filter with adjustable F/sub 0/ and bandwidth

The network described is a notch filter, synthesized as a capacitively-coupled short circuited shunt stub design. A well-known equivalence between open circuited, quarter wavelength high-impedance stubs, and capacitively coupled short-circuited stubs of lower impedance, is used iteratively to achieve a design with some innovative features: The shunt stubs are all the same impedance; typically; 50 /spl Omega/. The series 90 degree coupling lines are also the same impedance (again typically 50 /spl Omega/). Dimensions and components may thus be easily selected for high-power and low-loss operation. The coupling capacitors (which are in series with the stubs) are adjustable without compromising Q. Re-entrant stubs are used which allow a mixed lumped-distributed stub response and easy adjustment of stub lengths. A rugged coaxial construction is adopted with nothing cantilevered or unsupported. These features result in a design which is quite compact, tunable over a wide range of center frequencies, allows for adjustable bandwidth and thus selectivity, while intrinsically exhibiting high-power capability, low passband loss, and suitability for operation in demanding environments.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Ka-band slot-fed higher order-mode low-loss Fabry-Perot filters

Low-loss bandpass filters consisting of Fabry-Perot resonators excited by slots which couple to higher order resonator modes are demonstrated. For close reflector spacings, the slots efficiently couple power from rectangular waveguide to the TEM/sub 400/ and TEM/sub 300/ modes of the resonator. At Ka-band the filters have insertion losses less than 1 dB in general and less than 0.5 dB in some cases. The unloaded Q values of the filters range from 1500 to 3000. The filters are mechanically tunable over a 25% bandwidth.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Slot-fed higher order mode Fabry-Perot filters

Low-loss bandpass filters consisting of Fabry-Perot resonators excited by waveguide-fed slots coupling to higher-order resonator modes are demonstrated. For close reflector spacings, the waveguide couples efficiently through the slots to the TEM/sub 400/ and TEM/sub 300/ modes. The characteristics of both rectangular and circular waveguide feeds with various slot lengths and widths are presented. At X-band the filters have unloaded Q values which range from 1000 to 7000 with insertion losses less than 1 dB. The filters which have the rectangular waveguide feeds are mechanically tunable over a 20% bandwidth. >

Development of a High-Q Multilayer Ceramic Resonator

It has been discovered that multilayer ceramic resonators, manufactured by a cofiring method at a temperature above the melting point of the inner conductor, have an improved Q-factor. The increase in Q-factor enabled the realization of an S-band multilayer low-loss bandpass filter (BPF). In this paper the insertion loss of the cofired BPFs is examined, and a relationship between firing temperature and Q-factor is established.