Differential Bandpass Filter Research Articles

Compact differential bandpass filter with a narrow notched band using APCL structure suitable for UWB application

A compact differential band pass filter with asymmetric parallel-coupled lines (APCL) and center frequency of 5.6GHz is proposed in this paper. The APCL suppresses unwanted RFID signals by introducing a fully tunable notched band at 6.8GHz. By combining the concept of transmission matrix with modal analysis and extracting a novel model for symmetric three parallel coupled lines (SPCL), role of each resonant frequency is clearly explained. Measurement results in the differential mode show a pass band from 3.1 to 8.1GHz and a wide stop band from 9.1 to 16GHz with attenuation of more than 20dB. In addition, S21 in common mode is lower than −10.5dB over the pass band.

Low‐loss differential bandpass filter using TE 01 δ ‐mode dielectric resonators

A novel differential bandpass filter (BPF) based on a TE01δ -mode dielectric resonator (DR) is proposed. By utilising the inherent electromagnetic properties of the TE01δ -mode ring-shaped DR, the TE01δ mode, as a dominate mode of the DR, can be differentially excited for constructing the fundamental differential passband of the BPF. To validate the proposed idea, a second-order differential BPF is designed, fabricated and measured. Good agreement is obtained between simulated and measured results, showcasing good performance such as low insertion loss and high common-mode suppression in the differential passband.

A novel ±0.8 V high-performance voltage-tunable CDTA with enhanced bandwidth

In this article, we propose a novel high-performance complementary metal oxide semiconductor (CMOS) current differencing transconductance amplifier (CDTA) with a transconductance gain (GM) that can be linearly tuned by a voltage. By using a high-speed, low-voltage, cascaded current mirror active resistance compensation technique, the proposed CDTA circuit exhibits wide frequency bandwidths, high current tracking precisions as well as large output impedances. The linear-tunable GM of the CDTA is designed with the use of linear composite metal oxide semiconductor field-effect transistor as basic cells in the circuit. Combining these two approaches, several design concerns are studied, including: impedance characteristic, tracking errors, offset and linearity and noise. The prototype chip with a 0.25 mm2 area is fabricated in a GlobalFoundries’0.18 μm CMOS process. The simulated results and measured results with ±0.8 V DC supply voltages are presented, and show extremely wide bandwidths and wide linear tuning range. In addition, a fully differential band-pass filter for a high-speed system is also given as an example to confirm the high performance of the proposed circuit.

A Second Differential Bandpass Filter with Tuning Center Frequency and Constant Q

A second order differential filter with Q-enhancement and tunable active inductor is presented. The design technique for a tunable Q-enhancement SiGe HBT active inductor operating in the wide RF-band for the filter is described. Multi-regulated Cascode circuit is employed to enhance the quality factor Q by increasing the output impedance. Tunable active resistor is introduced to boost the tuning ability of the active inductor. Employing the proposed active inductor, the center frequency of the filter is tuned in the frequency of 1.05~2.45GHz by adjusting the bias current, Q reducing with different bias current can be compensated via tuning the feedback effective resistance of the active inductor, and Q has almost constant value of 209~225 at the frequency of 2.15GHz.

Dual-band differential bandpass filter using stepped impedance resonators

In this article, a novel dual-band differential bandpass filter using (SIRs) is designed. To demonstrate the design ideas, the differential and common mode equivalent half circuits are built and studied. Two resistors are connected between the two ends of the SIRs to consume the power in common mode. A capacitor is connected between the Ground and Center of the SIR to adjust the spurious frequencies, also strength the coupling of the two SIRs. The theoretical analysis shows the second band can be obtained by the proper impedance ratios of the resonances and the capacitor connected to the resonator. Two through ground vias (TGVs) connecting the top and bottom sides of the SIR filter, are used to realize the common mode rejection. To investigate the proposed filter in detail, a set of design equations are derived based on the circuit theory and transmission line theory. A phototype dual-band differential filter operating at 1.5 and 2.75 GHz has been realized to validate the proposed concept and theory. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:468–473, 2015.

Dual-Band SIW Differential Bandpass Filter With Improved Common-Mode Suppression

A dual-band differential bandpass filter with controllable differential-mode (DM) center frequencies, and high common-mode (CM) suppression as well as band-to-band isolation, is proposed in this letter. The presented filter is implemented based on the substrate integrated waveguide (SIW) technology. The first DM passband can be derived by the dominant modes, while the second DM passband response can be obtained by employing the higher order modes. The center frequencies of two DM passbands can be tuned by changing the dimension parameters. To improve the CM suppression, four slotlines with different locations are etched on the top metal plane. The measured and simulated results are in good agreement.

COMPACT DIFFERENTIAL BANDPASS FILTERS BASED ON COUPLED-LINE RESONATORS WITH IMPROVED PERFORMANCE AND MINIATURIZED SIZE

Two compact differential bandpass filters (BPFs) based on coupled-line resonators and loaded capacitors are proposed in this work. By properly designing the coupled resonator and the loaded capacitance of original filter model, differential-mode (DM) passband responses and common- mode (CM) rejection can be obtained. For validation, two differential BPFs named Filter I and Filter II are discussed and experimentally characterized. One more DM transmission zero generated by out- of-phase cross-coupling is employed to control the DM bandwidth and sharpen the selectivity in Filter I while lumped capacitors are loaded in Filter II to replace capacitive coupled resonators for miniaturized size. Both filters are centered at 4.5 GHz with about 9% DM fractional bandwidth (FBW), less than 1.5 dB insertion loss, more than 15 dB return loss, and wideband CM suppression with more than 18 dB rejection. Furthermore, the size of Filter II is substantially smaller than Filter I and previously reported differential BPFs.

HIGH SELECTIVITY DIFFERENTIAL BANDPASS FILTER USING DUAL-BEHAVIOR RESONATORS

A high selectivity differential bandpass filter (BPF) using two pairs of dual-behavior resonators (DBRs) is proposed in this letter. A high selectivity passband for the differential mode with second harmonic suppression is achieved, by utilizing shorted coupled lines with two short stubs. For the commonmode (CM) circuit, the CM responses can be suppressed over a wide frequency band by the loaded open/shorted stubs. To validate the feasibility of the proposed filter, a planar differential BPF (3-dB fractional bandwidth 4.9%) with good CM suppression is designed and fabricated. The theoretical and measured results agree well and show good in-band filtering performances and out-of- band harmonic suppression performances.

A Wideband Differential BPF With Multiple Differential- and Common-Mode Transmission Zeros Using Cross-Shaped Resonator

Wideband differential bandpass filter (BPF) with multiple differential-mode (DM) and common-mode (CM) transmission zeros (TZs) is presented in this letter. This filter is designed based on Cross-Shaped Resonator (CSR) alone that is intrinsically attributed by three DM transmission poles (TPs), four DM TZs and one CM TZ. Adding loaded coupled structures, two extra DM and CM TZs are generated respectively. A prototype differential BPF centered at 3.5 GHz with 40% fractional bandwidth (FBW) is designed and experimentally characterized. The experimental results are in good agreement with theoretical and simulated results. Allocating three CM TZs in the DM passband, the suppression is better than 40 dB in average, and the maximum rejection is as high as 80 dB, while the DM passband is sharpened by two extra DM TZs.

Analysis of Coupled Cross-Shaped Resonator and Its Application to Differential Bandpass Filters Design

Analysis and applications of coupled cross-shaped resonator (CCSR) for fixed and fully reconfigurable differential bandpass filters (BPFs) design are focused in this paper. CCSRs with open and capacitive terminations are presented and discussed. One differential BPF named Filter I centered at 4.5 GHz with fixed differential-mode (DM) and common-mode (CM) responses using CCSR with open termination; and another one named Filter II using capacitive termination and loaded lumped capacitors offers fully reconfigurable DM center frequency, bandwidth and intuitive CM suppression control are proposed with very compact size (0.01λ0 2 ). Such that ultra-wide DM center frequency tuning range of 82% fractional tuning range with both constant absolute bandwidth (ABW) and constant fractional bandwidth (FBW), easy control of CM suppression level and rejected range are achieved, respectively. Their experimental characterizations are in good agreement with theoretical analysis validating a simple approach of fixed and fully reconfigurable differential BPFs design.

Analytical Design of Wire-Bonded Multiconductor Transmission-Line-Based Ultra-Wideband Differential Bandpass Filters

A systematic design process of ultra-wideband differential bandpass filters based on wire-bonded multiconductor transmission lines is presented. The topology is thoroughly analyzed by means of analytical design equations that provide some insights into the physical behavior of the proposed structure. Single- and double-section configurations are introduced and exact closed-form design equations are derived to design differential filters with either a Butterworth or Chebyhsev frequency response. To validate the design procedure, two differential filters are designed and fabricated with an equal-ripple fractional bandwidth (FBW) of 100% and 60% (3-dB FBW of 145% and 97%), respectively. The measured differential-mode responses show a good in-band flatness with insertion losses lower than 1 dB and with high common-mode rejection levels greater than 20 dB. Experimental results demonstrate a good agreement with theory and prove that the proposed design methodology is useful for accurate and fast ultra-wideband differential filter synthesis.

Compact dual‐mode differential bandpass filter using stepped impedance resonators

ABSTRACTA compact dual‐mode differential bandpass filter using a pair of identical stepped impedance resonators connected by a short microstrip line is presented in this letter. The proposed filter showcases good differential‐mode (DM) bandpass response centered at 2.5 GHz (f0) while possesses inherent bandstop effect across the differential passband for the common‐mode (CM) signal. In addition, there is a transmission zero for the CM operation located within the DM passband. Accordingly, the loaded lumped element or stub for the CM suppression is not required in this design. In addition, compact size and wide stopband of the differential filter are both achieved, and the DM stopband rejection is more than 30 dB up to 8.0 GHz (3.2 f0). © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2055–2058, 2014

Compact wideband balanced bandpass filter with high common‐mode suppression based on cascade parallel coupled lines

A novel differential bandpass filter based on the cascaded parallel coupled lines is proposed, which takes the features of wide passband, high common-mode suppression and compact size. Six transmission zeros are created and located at the frequency range of 0-2f 0 ( f 0 is centre frequency of the passband), which helps realise the wide passband performances. The balanced bandpass filter consists of the four-stage parallel coupled lines, and the even- and odd- mode characteristic impedances can be adjusted to achieve the desired bandwidth of the passband while the positions of four transmission zeros can be conveniently adjusted by changing the impedance ratio of the asymmetrical stepped impedance resonator (SIR) structures in the proposed filter. By applying the differential and common modes analysis method, the two-port bisections of the filter become a bandpass and all-stop filter topologies under differential- and common-mode excitations, respectively. For performance demonstration of the proposed differential filter, a prototype operating at the frequency band of 2.15-3.85 GHz (with fractional bandwidth of 56.7%) was designed and fabricated on a commercial printed circuit board (PCB) substrate. The insertion loss and return losses of the differential-mode filter are 15 dB in the passband and the common-mode suppression is higher than 30 dB. Good agreements between the simulated and measured results have been observed.

Differential Wideband Bandpass Filters With Enhanced Common-Mode Suppression Using Internal Coupling Technique

A differential wideband bandpass filter (WBPF) with enhanced common-mode (CM) suppression is presented. The study about this modified branch-line structure with internal coupling sections shows that the proposed filter demonstrates a good wideband bandpass filtering response under the differential mode (DM) operation, meanwhile it also functions as a CM bandstop filter with wide and high rejection owing to the multiple transmission zeros brought by the internal coupling mechanism. To verify the design concept, one filter example has been designed, fabricated and measured. The fabricated differential WBPF has a DM 3 dB fractional bandwidth (FBW) of 59.5%. Moreover, it demonstrates an ultra-wide CM stopband from 0.82 to 2.8 GHz over 40 dB, representing a 40 dB FBW of 109.4%.

S-Shaped Complementary Split Ring Resonators and Their Application to Compact Differential Bandpass Filters With Common-Mode Suppression

This letter presents an S-shaped complementary split ring resonator (S-CSRR) for application in compact differential filters. The working principle of the proposed S-CSRR is explained and a circuit model is developed and validated through electromagnetic simulations. It is shown that an S-CSRR-loaded differential microstrip line with series gaps can be used in the design of compact differential bandpass filters (BPFs) with common-mode suppression. The filter design procedure is explained and the theoretical concept is validated through fabrication and measurement of a compact (0.09λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ×0.25 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ) third-order differential BPF with common-mode suppression.

Common-mode suppressed differential bandpass filter based on open complementary split ring resonators fabricated in microstrip technology without ground plane etching

A differential (or balanced) bandpass filter based on open complementary split ring resonators (OCSRRs) coupled through admittance inverters is presented in this article. Pairs of OCSRRs are symmetrically placed in a mirror configuration between the strips of the differential line and are modeled by means of two series connected parallel resonators. For the differential (odd) mode, there is a virtual ground at the connecting plane between the OCSRR pairs, and the structure is roughly described by the canonical model of a bandpass filter, consisting of a cascade of shunt resonators coupled through admittance inverters. It is demonstrated that, through a proper design of the OCSRR stages, the common mode noise in the vicinity of the differential filter pass band can be efficiently suppressed. Due to the differential mode operation of the filter, it is not necessary to incorporate metallic vias to ground the OCSRRs. Moreover, as compared to other differential filters based on OCSRRs, defected ground structures are not present in the proposed filters. To illustrate the potential of the approach, two balanced bandpass filters are designed, fabricated, and characterized. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:910–916, 2014

X‐band differential bandpass filter with high common‐mode suppression using substrate integrated waveguide cavity

A novel X-band differential bandpass filter based on substrate integrated waveguide is proposed. By making an aperture etched in the middle common ground of the vertically stacked cavities, the common-mode (CM) signals can be highly suppressed. Compared with conventional structures, the proposed design possesses a relatively simple and effective measure for the rejection of the CM signals. Based on simulated and measured results, good differential-mode responses can be observed along with a CM rejection of more than 45 dB in a wide frequency range.

COMPACT WIDEBAND DIFFERENTIAL BANDPASS FILTER USING A MARCHAND BALUN

A novel compact wideband differential bandpass filter with wideband common mode suppression using a Marchand balun is presented in this paper. Open/shorted coupled lines and stubs are used to improve the selectivity for the differential mode and common mode suppression. The demonstrated filter with a compact size of 50 mm × 30 mm exhibits a fractional bandwidth of 53% centered at 3.0 GHz and 13 dB common-mode suppression from 0 to 9 GHz. The theoretical and measured results agree well with each other and show good in-band performances.

Differential Wideband Bandpass Filter With High-Selectivity and Common-Mode Suppression

A circuit for differential wideband bandpass filter (BPF) is presented. The circuit works as a bandpass and bandstop filter under differential- and common-mode excitation, respectively. Under differential-mode, two transmission zeros are generated by the short-ended parallel-coupled stubs and supply a very sharp differential passband. The circuit parameters are analyzed and given to show the circuit characteristics. Finally, the circuit is implemented using microstrip technology and a differential wideband BPF is designed, simulated and measured. Simulated and measured results are well agreed.

Compact Low-Loss Wideband Differential Bandpass Filter With High Common-Mode Suppression

Compact low-loss wideband differential bandpass filters are presented in this letter. The proposed filters are constructed by a pair of multilayer differential microstrip-slotline transitions (MDMSTs) and microstrip line resonators. Wideband common-mode suppression and low insertion loss can be easily achieved by employing the MDMSTs. Wideband differential-mode passband and sharp notched band can be obtained by combining the microstrip resonators at the middle and the two sides with the pair of MDMSTs, respectively. The demonstrated filters with a compact size of 24 mm × 12 mm (0.56λg × 0.28 λg) exhibits a fractional bandwidth of 115% centered at 4.25 GHz (f0) with minimum insertion loss of 0.43 and 20 dB common-mode suppression from 1 to 10 GHz (2.35 f0).