Showing papers on "Prototype filter published in 2012"

A Survey on Multicarrier Communications: Prototype Filters, Lattice Structures, and Implementation Aspects

Abstract: Due to their numerous advantages, communications over multicarrier schemes constitute an appealing approach for broadband wireless systems. Especially, the strong penetration of orthogonal frequency division multiplexing (OFDM) into the communications standards has triggered heavy investigation on multicarrier systems, leading to re-consideration of different approaches as an alternative to OFDM. The goal of the present survey is not only to provide a unified review of waveform design options for multicarrier schemes, but also to pave the way for the evolution of the multicarrier schemes from the current state of the art to future technologies. In particular, a generalized framework on multicarrier schemes is presented, based on what to transmit, i.e., symbols, how to transmit, i.e., filters, and where/when to transmit, i.e., lattice. Capitalizing on this framework, different variations of orthogonal, bi-orthogonal, and nonorthogonal multicarrier schemes are discussed. In addition, filter design for various multicarrier systems is reviewed considering four different design perspectives: energy concentration, rapid decay, spectrum nulling, and channel/hardware characteristics. Subsequently, evaluation tools which may be used to compare different filters in multicarrier schemes are studied. Finally, multicarrier schemes are evaluated from the view of the practical implementation issues, such as lattice adaptation, equalization, synchronization, multiple antennas, and hardware impairments.

1 € filter: a simple speed-based low-pass filter for noisy input in interactive systems

Abstract: The 1 € filter ("one Euro filter") is a simple algorithm to filter noisy signals for high precision and responsiveness. It uses a first order low-pass filter with an adaptive cutoff frequency: at low speeds, a low cutoff stabilizes the signal by reducing jitter, but as speed increases, the cutoff is increased to reduce lag. The algorithm is easy to implement, uses very few resources, and with two easily understood parameters, it is easy to tune. In a comparison with other filters, the 1 € filter has less lag using a reference amount of jitter reduction.

Architectural Evolution of Integrated M-Phase High-Q Bandpass Filters

Abstract: -phase bandpass filters (BPFs) are analyzed, and variations of the structure are proposed. For values of that are integer multiples of 4, the conventional -phase BPF structure is modified to take complex baseband impedances and frequency-translate their complex impedance response to the local oscillator frequency. Also, it is demonstrated how the -phase BPF can be modified to implement a high quality factor (Q) image-rejection BPF with quadrature RF inputs. In addition, we present high-Q BPFs whose center frequencies are equal to the sum or difference of the RF and IF (intermediate frequency) clocks. Such filters can be useful in heterodyne receiver architectures.

Novel Wideband Differential Bandpass Filters Based on T-Shaped Structure

Abstract: Two novel wideband differential bandpass filters based on a T-shaped structure are proposed in this paper. Broad passband and wideband harmonic suppression for the differential/common mode can be easily achieved for the wideband differential filter without cross coupling, due to the controlled resonator frequencies of the shorted/open T-shaped structure. In addition, another more compact differential filter using cross coupling is proposed with two transmission zeros close to the passband to improve the selectivity for the differential mode. To verify the presented concept, two prototypes (er = 2.65, h = 0.5 mm) with 3-dB fractional bandwidth of 70% and 70.7% for the differential mode and insertion loss greater than 13.5 dB for common mode (0-19 GHz) are designed and fabricated. Good agreement can be observed between measured results and theoretical expectations.

WR-3 Band Waveguides and Filters Fabricated Using SU8 Photoresist Micromachining Technology

Abstract: This paper demonstrates a two-layer SU8 photoresist micromachining technology that has similar performance to conventionally machined metal. The technology is demonstrated in the WR-3 band (220-325 GHz). Three different WR-3 band circuits, namely a WR-3 band straight through waveguide, a bandpass filter and a dual-band filter are demonstrated. For the measurements, a conventionally precision machined metal block was used for the WR-3 band waveguide and the bandpass filter to achieve good calibration and accurate interconnection with standard waveguide flanges; whereas, for the dual-band filter, two back-to-back right-angle bends are added in order to achieve accurate, reliable waveguide interconnection without using the metal block. A measured average insertion loss of 0.03 dB/mm has been achieved for the 14.97 mm long straight through waveguide. This is comparable to the loss of around 0.02 dB/mm for a standard metal waveguide at this frequency. The fifth-order waveguide filter exhibits an 8% 3 dB bandwidth at a central frequency of around 300 GHz. The minimum passband insertion loss was measured to be around 1 dB and the return loss was better than 10 dB throughout the passband. The filter results showed a notable improvement over those obtained from the separate SU8 layer technique that was also used to make the same devices for comparison. To further demonstrate the advantages of the new two-layer SU8 micromachining technique, the dual-band filter included isolated regions in the waveguide channels that would have not been possible for micromachining using the previous separate single layer technique. The performance of the micromachined dual band filter was excellent in terms of very low insertion losses on both passbands.

Frequency-Reconfigurable Monopole Antennas

Abstract: A novel coplanar-waveguide (CPW) bandpass filter using short-circuit slotlines and varactor diodes is introduced. This bandpass filter, when integrated with a CPW wideband antenna, produces frequency agility with a wideband mode and a continuous narrowband mode. The design of another CPW filter based on a square-ring resonator with switches is also shown and applied to a wideband antenna, making it reconfigurable. Both filters are based on controlling two stop bands far enough apart so that there is a passband between them. When the stop band frequencies are altered using switches or varactors, the passband is altered. Complete working and design principles along with simulated S-parameter results of the filters are presented. The simulated and measured reflection coefficients of the antennas incorporating the filters are also shown. Good monopole-like radiation characteristics are observed for both antennas. The filters are small in size and can be incorporated in any CPW antenna design to make it reconfigurable. The benefits of the novel varactor filter antenna over the switch filter antenna are also described.

A $Ka$ -Band Fully Tunable Cavity Filter

Abstract: A TE011Ka-band tunable filter with a stable and continuous tuning performance is presented in this paper. Both bandwidth and center-frequency tunability are demonstrated by cascading six-pole pseudo-low-pass and pseudo-high-pass tunable filters. A novel mode-splitter resonator and coupling configuration enabling cross-coupled planar TE011 filter realization is introduced in this paper. The concept can be applied to back-to-back coupled TE011 resonators as well. The filter design is verified through fabrication of multiple tunable filters that demonstrates 500 MHz of tuning range with a stable RF tuning performance.

Switchless Tunable Bandstop-to-All-Pass Reconfigurable Filter

Abstract: The theory of a new type of bandstop-to-all-pass reconfigurable filter is developed in this work. A bandstop filter structure with both source-to-load and inter-resonator coupling is implemented. The synthesis equations are manipulated such that the signals in the filter's resonators and source-to-load transmission line can be made to constructively or destructively interfere at the output port through tuning of the resonant frequency of the filter's resonators. The relationship between resonator quality factor, filter bandwidth, and the all-pass response state is shown for the first time. The theory is proven through fabrication of a bandstop-to-all-pass filter with resonator unloaded quality factors greater than 500. Measured results show that the filter can continuously tune from insertion loss of 2.1 dB in the all-pass state to insertion loss of 69 dB in the bandstop state at the center frequency of the filter. Analog tuning of the attenuation level is also shown. The capability to switch from an all-pass to a variable-attenuation bandstop response enables a spectrally aware system to operate over wide bandwidths when interference levels are low and to dynamically add bandstop responses when interference affects its performance or signal equalization is required.

Novel Second-Order Dual-Mode Dual-Band Filters Using Capacitance Loaded Square Loop Resonator

Abstract: This paper presents a novel approach for designing dual-mode dual-band bandpass filters using capacitance loaded square loop resonators (CLSLR). The CLSLR features compactness and spurious response suppression because of the loaded capacitance. A dual-band response is obtained via an extremely large perturbation in a single resonator and second-order dual-mode dual-band filters are realized by a new cascading principle. Coupling coefficients between two resonators in both bands can be controlled independently and external quality factors are also controlled by a particularly-designed coplanar waveguide (CPW) feed line. Three types of filters are designed to validate the analysis. They are direct coupling dual-mode dual-band filter, source-load coupling dual-mode dual-band filter with a better band-to-band isolation and CPW-feed dual-mode dual-band filter with a wider bandwidth. Measured results show good agreement with the design specifications.

Miniaturised multi-band substrate integrated waveguide filters using complementary split-ring resonators

Abstract: A novel method for designing miniaturised multi-band filters using the complementary split-ring resonators (CSRRs) is proposed and demonstrated on the basis of substrate integrated waveguide (SIW) technology. By loading different types of CSRRs on the waveguide surface, multiple passbands propagating below the waveguide cutoff frequency can be generated separately. The proposed structures allow relatively independent control over the centre frequency and the coupling coefficient. The working principle is illustrated by the equivalent circuit and the filter coupling methodology is introduced for design purpose. Two types of dual-passband filters, a triple-band and a quadruple-band filter are designed and fabricated to validate the proposed concept. These filters are showing advantages in terms of compact size, good selectivity and stopband rejection, as well as the easy integration capability with other circuits.

Intrinsically Switched Varactor-Tuned Filters and Filter Banks

Abstract: Intrinsically switched tunable filters are switched on and off using the tuning elements that tune their center frequencies and/or bandwidths, without requiring an increase in the tuning range of the tuning elements. Because external RF switches are not needed, substantial improvements in insertion loss, linearity, dc power consumption, control complexity, size, and weight are possible compared to conventional approaches. An intrinsically switched varactor-tuned bandstop filter and bandpass filter bank are demonstrated here for the first time. The intrinsically switched bandstop filter prototype has a second-order notch response with more than 50 dB of rejection continuously tunable from 665 to 1000 MHz (50%) with negligible passband ripple in the intrinsic off state. The intrinsically switched tunable bandpass filter bank prototype, comprised of three third-order bandpass filters, has a constant 50-MHz bandwidth response continuously tunable from 740 to 1644 MHz (122%) with less than 5 dB of passband insertion loss and more than 40 dB of isolation between bands.

Radiation Suppression for Cable-Attached Packages Utilizing a Compact Embedded Common-Mode Filter

Abstract: A compact and wideband common-mode filter is newly proposed to embed in a cable-attached printed circuit board (PCB) or packages for the suppression of the common-mode noise and its resulting electromagnetic interference (EMI) emission from the attached cable. The proposed filter consists of a pair of distributed signal lines on the top of a mushroom-like structure. Owing to its symmetry, an equivalent circuit model is developed and applied efficiently for this filter design. As an example, a filter prototype is designed and fabricated on a multilayer PCB. The filter prototype shows that it can greatly reduce the common-mode noise over 10 dB from 1.65 to 5.2 GHz. In addition, the corresponding fractional bandwidth is over 100% while the electrical size of the prototype is only 0.11 × 0.11 λg, where λg is the wavelength of the central frequency of its stopband. Also in the time domain, this filter prototype can reduce over 60% of the unintended noise. More importantly, the differential-signal integrity, in terms of the insertion loss in the frequency domain and the eye diagram in the time domain, is maintained up to 7 GHz. To the best of our knowledge, it is the first embedded common-mode filter proposed for gigahertz differential signals with such a large bandwidth and the most compact size. To further demonstrate the ability of the filter to suppress the common-mode current on the attached cable and the corresponding EMI emission, a test board design is also introduced and realized. From the experimental results related to this test board, a 10-dB suppression on average is indeed achieved.

Miniaturized UWB Filters Integrated With Tunable Notch Filters Using a Silicon-Based Integrated Passive Device Technology

Abstract: This paper reports on the implementation of miniaturized ultra-wideband filters integrated with tunable notch filters using a silicon-based integrated passive device technology An ultra-wideband bandpass filter is realized on a micromachined silicon substrate, showing an insertion loss of 11 dB, return loss of better than 15 dB, and attenuation of more than 30 dB at both lower and upper stop-bands, with a spurious-free response up to 40 GHz The filter occupies only 29 mm 24 mm of die area To address the in-band interference issues associated with ultra-wideband communication, very compact tunable notch filters are monolithically integrated with the bandpass filters A two-pole tunable notch filter integrated with an ultra-wideband filter provides more than 20 dB rejection in the 5-6 GHz range to reject U-NII interferences, with a total footprint of 48 mm 29 mm The power handling, linearity, and temperature stability of filters are characterized and presented in this paper

A High-Performance Continuously Tunable MEMS Bandpass Filter at 1 GHz

Abstract: This paper reports a continuously tunable lumped bandpass filter implemented in a third-order coupled resonator configuration. The filter is fabricated on a Borosilicate glass substrate using a surface micromachining technology that offers hightunable passive components. Continuous electrostatic tuning is achieved using three tunable capacitor banks, each consisting of one continuously tunable capacitor and three switched capacitors with pull-in voltage of less than 40 V. The center frequency of the filter is tuned from 1 GHz down to 600 MHz while maintaining a 3-dB bandwidth of 13%-14% and insertion loss of less than 4 dB. The maximum group delay is less than 10 ns across the entire tuning range. The temperature stability of the center frequency from -50°C to 50°C is better than 2%. The measured tuning speed of the filter is better than 80 s, and the is better than 20 dBm, which are in good agreement with simulations. The filter occupies a small size of less than 1.5 cm × 1.1 cm. The implemented filter shows the highest performance amongst the fully integrated microelectromechanical systems filters operating at sub-gigahertz range.

Synthesis Methodology Applied to a Tunable Patch Filter With Independent Frequency and Bandwidth Control

Abstract: A new methodology for the synthesis of tunable patch filters is presented. The methodology helps the designer to perform a theoretical analysis of the filter through a coupling matrix that includes the effect of the tuning elements used to tune the filter. This general methodology accounts for any tuning parameter desired and was applied to the design of a tunable dual-mode patch filter with independent control of center frequency and bandwidth (BW). The bandpass filter uses a single triangular resonator with two etched slots that split the fundamental degenerate modes and form the filter passband. Varactor diodes assembled across the slots are used to vary the frequency of each degenerate fundamental mode independently, which is feasible due to the nature of the coupling scheme of the filter. The varactor diode model used in simulations, their assembling, the dc bias configuration, and measured results are presented. The theory results are compared to the simulations and to measurements showing a very good agreement and validating the proposed methodology. The fabricated filter presents an elliptic response with 20% of center frequency tuning range around 3.2 GHz and a fractional BW variation from 4% to 12% with low insertion loss and high power handling with a 1-dB compression point higher than .

Coupled-Resonator Waveguide Filter in Quadruplet Topology With Frequency-Dependent Coupling – A Design Based on Coupling Matrix

Abstract: This letter presents an application of a recently developed coupling matrix synthesis technique to design of coupled-resonator filters with dispersive inter-resonator couplings. This technique is used to design a novel coupled-cavity bandpass filter. Measurements validate the design and confirm effectiveness of the synthesis method. The filter is a four-pole generalized Chebyshev filter with three transmission zeros. Resonators are arranged in a quadruplet configuration and employ a single dispersive cross coupling to produce an extra zero in comparison to classical approaches. Frequency-dependent coupling was realized via a rectangular waveguide iris with an incomplete height conducting post.

Lumped-Element Realization of Absorptive Bandstop Filter With Anomalously High Spectral Isolation

Abstract: In this paper, we show a new absorptive banstop filter topology that is capable of creating large attenuation using low-Q small-size resonators. In addition, the implementation of a lumped-element absorptive bandstop filter is shown for the first time. Compared with the conventional absorptive filter structure, the new absorptive filter structure is smaller in size because there is no quarter-wavelength transmission line between two resonators and the resonators are lumped elements. For verification of the new topology, a lumped-element low-temperature co-fired ceramic (LTCC) bandstop filter with low-Q resonators has been designed and measured. Theory, simulation, and measurement showed good agreement between them, and the measurement showed 60-dB attenuation level at the center frequency. This attenuation level of the absorptive bandstop filter is 50 dB larger than the one obtained from the reflective bandstop filter with the same Q-factor and bandwidth. The small size and absorptive nature of the filter allow us to cascade the filters to create many different filter responses. It is shown that the lumped-element implementation makes the filter very amenable to realization of higher order responses in small form factors.

Some applications of fractional order calculus to design digital filters for biomedical signal processing

Abstract: The goal of this paper is to describe some applications of fractional order calculus to biomedical signal processing with emphasis on the ability of this mathematical tool to remove noise, enhance useful information, and generate fractal signals. Three types of digital filters are considered, namely, lowpass differentiation filter, smoothing filter, and 1/fβ-noise generation filter. The filter impulse responses are functions of the fractional order and the sampling period only, and thus can be computed easily. Application examples are presented for illustrations.

Design of compact microstrip lowpass filter with ultra-wide stopband

Abstract: A new microstrip lowpass filter with compact size and an ultra-wide stopband is proposed. To achieve compact size and ultra-wide band rejection, both triangular patch resonators and radial patch resonators are introduced in the filter. To reduce the circuit size of the filter further, meander transmission lines are also adopted in the design. A demonstration filter with 3 dB cutoff frequency at 1 GHz has been designed, fabricated and measured. Results indicate that the proposed filter can suppress the sixteenth harmonic response referred to a suppression degree of 15 dB. Furthermore, the proposed filter exhibits a small size of 0.111 λg×0.091 λg, where λg is the guided wavelength at 1 GHz.

8-Path tunable RF notch filters for blocker suppression

Abstract: The huge growth of the number of wireless devices makes wireless coexistence an increasingly relevant issue. If radios operate in close proximity, blockers as strong as 0dBm may occur, driving almost any receiver in compression (note that 0dBm in 50Ω corresponds to a peak-to-peak voltage of half a 1.2V supply). Thus RF blocker filtering is highly wanted. However, fixed filters are undesired when aiming for multiband, software-defined or cognitive radio transceivers. Passive LC filters show limited Q and tunability. Recently frequency translated filtering has been proposed as a potential solution direction for high-Q filtering [1–5]. In [1,2] we showed that by applying the “N-path concept” [6], more than a decade of center frequency range with good linearity, compression point (P 1dB >0dBm, IIP3 >14dBm) and low noise is feasible for a bandpass (BP) filter. In [3] a notch filter with a combination of active and passive mixers is applied in a feedforward path realizing a BP filter. Moreover in [5] the low input impedance of a transimpedance amplifier with feedback is upconverted to create a notch filter at low frequencies (80MHz) suppressing TX leakage in an FDD system. In this work we explore the possibility to realize a notch filter applying the N-path concept at RF frequencies and in a completely passive way. A single-ended (SE) and a differential 8-path notch filter with passive frequency mixing are presented. The filters are power-matched in the input and output in the passband and provide a low insertion loss, high compression point and also low noise property, thus they can be utilized in front of a receiver to provide rejection of high-power blockers with a large frequency tuning range.

A Substrate Integrated Waveguide (SIW) Bandpass Filter in A Box Configuration With Frequency-Dependent Coupling

Abstract: This letter presents the design of a microwave bandpass filter with frequency-dependent coupling implemented in substrate integrated waveguide (SIW) technology. The proposed filter implements a four-pole generalized Chebyshev filtering function with two transmission zeros. Resonators are arranged in an extended box configuration with dispersive coupling on a main signal path, which produces an extra zero in comparison to classical approaches. The frequency-dependent coupling is implemented as a shorted stub with an additional septum made from via-holes. Such modification allows better control of the positions of the resonant frequencies of coupled SIW cavities, as well as of the position of the transmission zero. The filter was fabricated in SIW technology and good agreement was achieved between the simulated results and those measured.

Triple-Conductor Combline Resonators for Dual-Band Filters With Enhanced Guard-Band Selectivity

Abstract: Novel combline resonators and filters with enhanced dual-band characteristics are introduced in this paper. The proposed resonator is made up of three metallic conductors: an inner post, an intermediate conductor, and an enclosure. This structure provides two asynchronous resonant modes that can be used for realizing compact microwave dual-band filters. Such dual-band filters offer the low cost, compact size, and ease of manufacturing features of traditional combline resonator filters, with additional size reduction due to the fact that a single physical cavity provides two electrical resonators. In addition, the new cavity introduces a transmission zero in the guard-bands enhancing the filter selectivity, while keeping a simple and compact inline topology. The design of filters based on this novel resonator is discussed, starting with the resonator circuit model, the coupling scheme, and the complete filter design methodology. Simulations as well as experimental results of a tenth-order (2 × 5) dual-band filter with a measured rejection level in excess of 100 dB in the guard-band are presented to show the concept.

Analytical Design of Two-Mode Dual-Band Filters Using E-Shaped Resonators

Abstract: This paper presents a novel analytical approach for designing two-mode dual-band bandpass filters using E-shaped resonators. Based on the dual-band coupling matrix, the dimensions of the filter configuration are extracted via even- and odd-mode analysis of E-shaped resonators. The back-to-back E-shaped resonators provide the out-of-phase property by coupling at specific edges, and it produces good selectivity for dual-band characteristics. The proposed filters have the advantage of compact size and satisfy various requirements of filter orders and coupling coefficients at both passbands. The transmission zeros are successfully introduced into each passband in both filters. To verify the proposed method, two filters are implemented using microstrip technology. The measured results exhibit two-mode dual-band bandpass responses and agree well with simulations.

Compact lowpass filter based on coupled-line hairpin unit

Abstract: A compact lowpass filter (LPF) with sharp cutoff frequency response and wide rejection bandwidth is proposed. The proposed LPF has a simple structure and comprises one microstrip coupled-line hairpin unit, one spiral slot and two open stubs. A demonstration filter with 3 dB cutoff frequency at 2.0 GHz has been designed and fabricated. Theoretical and simulated results are presented, which are in good agreement with the measured results.

Extended Passband Bandstop Filter Cascade With Continuous 0.85–6.6-GHz Coverage

Abstract: This paper presents a cascade of tunable bandstop filters with a wide spurious-free upper passband, which is completely spanned by the tuning range of the notch responses. A collection of resonators is shown to be able to provide bandstop filter responses over a 7.8 to 1 tuning range. By using spurious-free upper passband aperture-coupled cavity bandstop filters, multiple resonators, each with octave tuning, can cover a multioctave frequency range in a cascade. It is shown that the upper passband of this type of filter is limited by the reactance of the coupling apertures, which produce an unwanted in-band resonance unless designed properly. The details of this design process are explained and used to design a six-resonator bandstop filter cascade that is able to provide a bandstop filter response with up to 55 dB attenuation over the continuous band of 0.85-6.6 GHz. Through dynamic allocation of the cascade circuit's transmission zeros, one-, two-, three-, and four-pole bandstop filter responses of variable bandwidth can be realized over different frequency ranges, offering numerous bandwidth-attenuation level tradeoff combinations.

Tunable high quality-factor absorptive bandstop filter design

Abstract: A two-pole, substrate-integrated, high quality(Q)-factor absorptive bandstop filter is demonstrated that exhibits enhanced selectivity over traditional reflective bandstop filter designs and higher Q-factor components than previous absorptive designs. With a Q-factor of 729, the presented filter has a peak isolation of 30 dB, a narrow 10-dB rejection bandwidth of 3.9 MHz that is tunable over 3.4–3.8 GHz, and an out-ofband insertion loss of 0.3 dB, exhibiting the same attenuation of a standard two-pole reflective notch filter with a Q-factor of 3100. These features enable channel-select isolation of high power interfering signals from closely separated receive bands without impacting receiver noise figure.

FS-FBMC: A flexible robust scheme for efficient multicarrier broadband wireless access

Abstract: An alternative implementation of the filter bank multicarrier (FBMC) concept is introduced. It is based on an FFT whose size is the length of the prototype filter. The approach clarifies the connection with OFDM and its main benefit is in the receiver, where high performance sub-channel equalization and timing offset compensation are achieved in a straightforward manner without additional delay. The scheme is particularly appropriate for broadband wireless access, to cope with fragmented frequency bands and to optimize the utilization of the spectrum, for example with the help of water-filling based sub-channel loading algorithms. The context of TV white spaces is taken for illustration. An issue with the proposed scheme is the computational complexity in the receiver and an approach having the potential for substantial savings is mentioned.

Design of microstrip lowpass filter with compact size and ultra-wide stopband

Abstract: A new microstrip lowpass filter with compact size and ultra-wide stopband is presented. To achieve a compact design and ultra-wide band rejection, both triangular patch resonators and polygonal patch resonators are introduced in the filter. To reduce the circuit size of the filter further, the meander transmission line is also adopted in the design. A demonstration filter with 3 dB cutoff frequency at 0.85 GHz has been designed, fabricated and measured. Results indicate that the proposed filter is able to suppress the 14th-harmonic response referred to a suppression degree of 15 dB, together with a small size of 0.089 λg × 0.081 λg, where λg is the guided wavelength at 0.85 GHz.