Group Delay Variation Research Articles

A Stagger-Tuned Transimpedance Amplifier

A new transimpedance amplifier (TIA) design procedure using stagger tuning with inverted transformer coils is described in this paper. A broadband TIA, realized using the proposed staggered design technique that enhances the transimpedance limit and the bandwidth while only adding small passband gain ripple, was implemented in a 0.13- ${\mu }\text {m}$ standard CMOS process. The TIA achieves a 3-dB bandwidth of 33 GHz with a 150 fF photodiode capacitance. The TIA transimpedance gain is $43.8~{\text {dB}}\Omega $ with ±8 ps group-delay variation over the entire bandwidth. The circuit occupies an active area of ${250~\mu }\text {m}\times 260~\mu \text {m}$ and consumes 9 mW from a 2 V supply. Despite operating with much larger photodiode capacitance, the TIA achieves the highest figure of merit, and occupies smaller area while consuming the least amount of power among previously published TIAs designed for the same data rate in similar technologies.

Compact UWB bandpass filter based on grounded square patch resonator

A novel UWB bandpass filter based on a grounded square patch resonator with slots is proposed. Owing to this specific geometry, three fundamental resonances of the resonator can be independently controlled and by their even distribution within the UWB range, an UWB passband can be formed. An UWB filter with in-band insertion loss <0.9 dB, group delay variation of 0.25 ns, and very small size of only 0.26λ g × 0.26λ g has been designed and fabricated, and measurement results are in good agreement with simulations.

Modified antipodal Vivaldi antenna for ultra‐wideband communications

In this study, a modified antipodal Vivaldi antenna (AVA) with low cross-polarisation is proposed for ultra-wideband communications. The bandwidth offered by conventional single petal AVA is enhanced by adding another petal. This dual petal antenna occupies a small volume of 60 × 60 × 0.8 mm 3 and provides operating bandwidth from 2.4 GHz to frequencies >14 GHz. The proposed antenna configuration provides low cross-polarisation level which is 5 dB and an average group delay variation of 0.5 ns. The prototype antenna is fabricated and tested to validate the simulation results.

CPW-Fed 8-Shaped Monopole Antenna for Ultra Wideband Applications

AbstractA CPW-fed 8-shaped monopole antenna for ultra wideband applications is presented. It consists of a 8-shaped monopole and two quarter elliptical coplanar waveguide ground planes. An impedance bandwidth from 5.4 GHz to 23.83 GHz is achieved. The radiation patterns are observed to be omnidirectional and bidirectional in E-and H-plane respectively at lower resonances. At higher frequencies, the radiation patterns are found to be nearly omnidirectional in both planes. The group delay variation is also observed to be constant in the operating frequency range. A good agreement is found between the simulation and experimental results. The designed antenna structure has miniaturized dimensions and wider bandwidth as compared to other already reported monopole structures.

Application of Multiobjective Topology Optimization to Miniature Ultrawideband Antennas With Enhanced Pulse Preservation

This letter presents an application of multiobjective topology optimization to ultrawideband (UWB) antenna design. The design of UWB antennas is very challenging because it involves multiple design goals including miniaturization, a wide impedance bandwidth, uniform gain variation, and enhanced time-domain pulse preservation. Although topology optimization has been a popular approach for UWB antenna design, a multiobjective version that systematically copes with all the design details is critically lacking, and the early attempts have not been very successful. In this letter, we propose a Pareto-based technique for multiobjective topology optimization, showing that the proposed methodology facilitates the development of a UWB antenna with compact size, a wide bandwidth, uniform gain variation, and high fidelity factors. The optimized UWB antenna occupies a small area of $15 \times 15~\hbox{mm}^2$ , showing excellent impedance matching and stable broadside gains throughout 3.1–10.6 GHz. In addition, the variation of group delay drops dramatically from 0.94 to 0.40 ns, and the fidelity factor is enhanced from around 0.80 to 0.92. The simulated and measured results are exhibited, confirming the validity of multiobjective topology optimization.

22–27 GHz 11 dB inductive feedback cascode amplifier with 12 picoseconds group delay variation

22–27 GHz 11 dB inductive feedback cascode amplifier with 12 picoseconds group delay variation

Band‐rejected UWB antenna based on two‐pole band‐stop filter

AbstractThis study proposes a design method of proper two‐pole band‐rejection characteristics on a UWB antenna. This method has advantage of easy accomplishment of the required band‐rejection characteristics of an UWB antenna, such as skirt characteristic, bandwidth, and ripple by directly applying the well‐known band‐rejection filter design procedure without hard iteration or optimization process using an EM‐Simulator. A designed and fabricated antenna by the design method satisfied broad and sharp band‐rejection characteristic at 5 GHz WLAN band with the full UWB band specifications with return losses less than −10 dB. The group delay variations are within 1.0 ns except the rejection band. The band‐stop filter was placed around the radiating patch without degradation on the operation of the main UWB antenna so that it does not need any extra space for the adoption. The proposed method could be useful for designing various wideband antennas with excellent band rejection properties. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:406–409, 2016

Design of Bessel low-pass filter using DGS for RF/microwave applications

ABSTRACTA synthesis method to design a defected ground structures (DGS)-based Bessel low-pass filter (LPF) using a triangular and an open-square (OS)-type DGS is reported. For the five-pole Bessel LPF at fc = 2.5 GHz, we get 10.6 dB/GHz selectivity using the triangular DGS; while the OS-type DGS provides 39 dB/GHz selectivity. For these two filters, the 10 dB impedance matching BW is 76% and 84%, respectively. It is a much wider BW that is obtained for a lumped element Bessel LPF. The maximum group delay (GD) variation within the pass band is 25pS and 28pS, respectively. The 20 dB rejection BW can be increased from 5.8 GHz to 18.8 GHz with increase in the order of filter from 5 to 11. We have also presented the design of a compact five-pole DGS-based elliptic filter with selectivity 38.2 dB/GHz and 17.8 dB return loss. Results on the DGS-based elliptic filter, Butterworth and Chebyshev filters are also presented. The experimental results are compared against the recently reported LPFs. Our reported filters perform better with respect to selectivity and group delay variation. The flatter GD and high selectivity, along with a wide 10 dB impedance matching BW, make the DGS Bessel filter a candidate for high-speed data communication, front end of a wideband communication system and efficiency improvement of a power amplifier.

Compact Integrated Bluetooth UWB Antenna with Quadruple Bandnotched Characteristics

In this paper,a compact printed dualband antenna for Bluetooth and UWB applications with WiMax(3.3-3.7 GHz), C-band satellite downlink(3.7-4.2GHz), WLAN(5.15-5.825GHz) and DSRC(5.5-5.925GHz) bandnotched characteristics is proposed and investigated. By etching two half-wavelength L-shaped slots in the radiating patch and an inverted U-shaped slot in the microstrip feedline quadruple bandnotched characteristics is obtained. Further, by embedding quarter wavelength parasitic strip at two edges of U-shaped radiating patch dualband characteristics with desired bandwidth is obtained. the proposed antenna is designed and fabricated on a FR4 substrate of dimensions 24mm X 35mm that operates over a 2.4-11GHz with S11&amp;lt;-10dB except over notch bands of 3.3-3.7GHz, 3.7-4.2GHz,5.15-5.625GHz and 5.625-6GHz. Directional pattern in E-plane and nearly omnidirectional pattern in H-plane are observed over a UWB band except at desired bandnotched freqencies. Less variation in group delay and pulse deformation shows good time domain characteristics. In addition, the structure exhibits stable gain over the desired band.

Widely bandwidth-tunable silicon filter with an unlimited free-spectral range.

Next-generation high-capacity optical networks require flexible allocation of spectrum resources, for which low-cost optical filters with an ultra-wide bandwidth tunability beyond 100 GHz are desired. We demonstrate an integrated band-pass filter with the bandwidth continuously tuned across 670 GHz (117-788 GHz) which, to the best of our knowledge, is the widest tuning span ever demonstrated on a silicon chip. The filter also features simultaneous wavelength tuning and an unlimited free spectral range. We measured an out-of-band contrast of up to 55 dB, low in-band ripples of less than 0.3 dB, and in-band group delay variation of less than 8 ps. This result was achieved using cascaded Bragg-grating-assisted contra-directional couplers and micro-heaters on the 220 nm silicon-on-insulator platform with a very compact footprint of less than 7000 μm2. Another design with the bandwidth continuously tunable from 50 GHz to 1 THz is also presented.

Digital All-Pass Filter Modeling Based on Desired Group Delay Using Advanced Material: A Review on the Signal Processing Part

This paper presents a review on three types of techniques in designing digital all-pass filters based on group delay. All the three methods use the same basic concept rooting back to the requirement of a stable transfer function of the filter which should be a minimum-phase type, and the denominator group delay. The most optimized of the three is chosen to be implemented in MATLAB in order to decrease the group delay variation of a 5th order Chebyshev low-pass filter with cut-off frequency of 160 MHz. The digital transfer function of the low-pass filter is obtained from the analog transfer function by means of bilinear transformation. The sampling frequency of the digital LPF is 100 times the cut-off ffrequency to retain the response of the analog LPF. Both of the filters are then cascaded together and the overall group delays variations are analyzed. The variations of group delay shows a reduction but the price paid is the increase of the overall group delay of the system.

Compact wideband bandpass filter using fish spear‐shaped multimode resonator

ABSTRACTA compact wide‐band pass filter (BPF) with sharp band rejection characteristics and wide upper stopband is presented in this article. The proposed bandpass filter is designed using a fish spear‐shaped multimode resonator (MMR). This fish spear‐shaped MMR has four arms and have five resonant modes, out of which three are even modes and the remaining two modes are odd. These modes lie in the wide frequency spectrum and they are used to realize the wideband passband of the filter. These five modes are brought closer by optimizing the dimensions of fish spear‐shaped MMR to get the desired passband. To improve out‐of band performance, a stepped impedance resonator is added at the central plane. The proposed wideband BPF filter have fractional bandwidth better than 85%. Moreover, to verify the proposed concept the designed filter is fabricated and measured. The measured bandwidth of proposed filter is 6.82 GHz and is from 2.55 to 9.37 GHz with an insertion loss of 2 dB. The measured return loss of the filter is better than 10 dB in the entire designed wideband. Measured results are validated with the simulated results. The group delay variation is less than 0.25 ns. A wide stopband with 15 dB attenuation is extended up to 20 GHz is obtained. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2833–2837, 2015

Miniaturized HTS linear phase filter based on neighboring CQ units sharing resonators

This paper presents a method for using neighboring cascaded quadruplet (CQ) units sharing resonators to decrease the order of filter so as to reduce the size of a high temperature superconducting (HTS) linear phase filter. The main advantage is that it will not reduce the number of the filter’s transmission zeros, and will not increase the difficulty of circuit design and tuning. Based on this method, this paper presents a 10-order HTS linear phase filter with two pairs of transmission zeros on double-sided YBCO/LaAlO3/YBCO films with a size of 20.3 mm × 20.92 mm, a thickness of 0.5 mm and a dielectric constant of 24.04. At 77 K, the filter’s measured center frequency is 830.03 MHz with a bandwidth of 10 MHz, an edge out-of-band rejection greater than 30 dB MHz−1, and a group delay variation of less than ±10 ns over 60% of the filter bandwidth.

10-Gb/s 0.13-&lt;formula formulatype="inline"&gt; &lt;tex Notation="TeX"&gt;$\mu{\rm m}$&lt;/tex&gt;&lt;/formula&gt; CMOS Inductorless Modified-RGC Transimpedance Amplifier

This paper presents an inductorless 0.13- $\mu{\rm m}$ CMOS TIA structure that is a modified version of a regulated cascode (RGC) TIA. An immittance converter is incorporated to reduce power consumption while increasing transimpedance gain. Measured 3-dB bandwidth is 7 GHz, sufficient for 10-Gb/s operation, in the presence of 250 fF capacitance at the TIA input, representative of typical CMOS photodiode capacitance. The transimpedance gain of the single-stage TIA is 50 ${\rm dB}\Omega$ , and the group-delay variation is less than $\pm$ 19 ps over the 3-dB bandwidth. The circuit occupies an active area of $180 \mu{\rm m}\times 90 \mu{\rm m}$ and consumes 7 mW from a 1.5-V supply. The measured average input-referred current noise of the TIA is 31 ${\rm pA}/\sqrt{\rm Hz}$ . Simulations and analysis show that the proposed single-stage TIA architecture is capable of achieving improvement in the transimpedance limit over a single-stage RGC TIA designed for the same data rate and the same input photodiode capacitance. A comparison of measurement results to published TIAs also demonstrates the competitive performance of the proposed TIA in terms of the TIA transimpendance gain, bandwidth, area, and power consumption.

A compact modified U-shaped UWB bandpass filter

ABSTRACTA compact ultra wideband bandpass filter (BPF) with sharp rejection and wide upper stopband is proposed in this letter. The proposed bandpass filter is constructed using modified U‐shaped multimode resonator (MMR). The U‐shaped MMR is loaded with two open stubs on the symmetrical locations. This proposed resonator has five resonant modes, out of which two are odd modes and the remaining are even modes. These modes are present in the UWB band and are used to realize the wideband passband of the filter. By optimizing the dimensions of the stubs, the five resonant modes of the resonator can be brought into the desired passband. This bandpass filter with fractional bandwidth better than 110% is simulated, fabricated, and measured. The measured impedance bandwidth of filter is from 3.75 to 13.75 GHz with an insertion loss of 2 dB and return loss better than 11 dB. The simulated and measured results show a good agreement. The group delay variation is less than 0.25 ns. A wide stopband bandwidth with 16 dB attenuation is up to 19 GHz is obtained in the proposed filter. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2172–2175, 2015

A CMOS Low-Power Cross-Coupled Immittance-Converter Transimpedance Amplifier

This letter presents a low-power transimpedance amplifier (TIA) that employs an immittance converter, which provides both a negative input resistance to increase the input pole frequency and a negative inductance to improve the circuit stability. These allow for a significant bandwidth enhancement with low power consumption. Two TIAs, TIA1 with 6 GHz and TIA2 with 8.8 GHz 3 dB bandwidths, were fabricated in a standard 0.13- μm CMOS technology and were designed to operate with a 250 fF photodiode capacitance at 10 Gb/s. The transimpedance gains of the single-stage TIAs, followed by near-unity-gain output-matching buffers, are ~ 54 dBΩ, the group-delay variations and average input-referred noise currents are ±3 ps and 24 pA/√{Hz} (TIA1) and ±70 ps and 28 pA/√{Hz} (TIA2) over their 3 dB bandwidths. The TIAs occupy an active area of 250 μm× 160 μm, and without the output-matching buffer each consumes 2 mW.

An ultra flat phased array Ku-band antenna with integrated receivers in SiGe BiCMOS

A highly integrated Ku-band (10.7–12.75 GHz) planar phased array receiver of 64 antenna elements is presented. It features instantaneous reception of the full Ku-band (2.05 GHz wide) in two orthogonal polarizations with wide scan angles by using time delay instead of phase shift. The receiver is part of a system for satellite broadcast TV reception on board of moving vehicles. Two SiGe radio frequency integrated circuits (RFICs) were developed, packaged in ceramic BGAs and assembled onto a 15-layer printed circuit board (PCB) which integrates the antenna elements. An outline of the system is given along with a detailed description. It sets a new standard in integration density. The receiver has extensive analog signal processing at intermediate frequency (IF)-level. A novel bipolar implementation for true time delay is proposed, with a continuous programmable delay range of 0…80 ps with less than 2.5 ps group-delay variation in 2 GHz bandwidth (BW). The wide BW calls for a constant group-delay implementation in the IF chain. The receiver (RFIC) consumes only 132 mW per channel. Each channel has 40 dB gain.

High‐performance suspended stripline wideband bandpass filter with new miniaturisation technology

A simple wideband tubular suspended stripline (SSL) bandpass filter using novel miniaturisation technology is presented. In this design, the equivalent circuit of the proposed filter is considered as the conventional tubular bandpass filter circuit. A new miniaturisation technology called ‘different height of cavity’ is applied to the filter design. A SSL filter is designed and fabricated with the passband from 0.6 to 1 GHz. The insertion loss is better than 0.6 dB in the passband while the return loss is mostly higher than 20 dB. The group delay variation is <0.2 ns. Good agreement between the simulated and measured result is observed, which proves the validity of the technique.

A low power and high gain CMOS LNA for UWB applications in 90 nm CMOS process

This paper presents a two stage low noise amplifier (LNA) to achieve low power and high gain for 3.1–10.6GHz ultra-wide band (UWB) applications. Its first stage yields exceptionally wideband input matching because of the input impedance Zin=1/gm1≈50Ω of the common-gate (CG) input matching transistor. A source degenerated common source (CS) topology with the shunt peaking inductor Ld2 is designed as the second stage to improve the overall gain response. Using a standard 90nm CMOS process, the proposed LNA achieves a gain S21 approximately equal to 20dB, while consuming only 4.33mW power from a 0.6V supply voltage. With the aid of source degenerated inductor, the simulation results show input return loss S11<−10dB in the frequency range of 3.1–9.7GHz, a noise figure (NF) less than 1.41dB, and the minimum noise figure (NFmin) below 1.034dB in the frequency range of 3.1–10.6GHz. When a two tone test is performed with a frequency spacing of 2MHz, the third order input intercept point (IIP3) of −22dBm is achieved. The other advantages of the proposed LNA are its small group-delay variation and gain variation of ±28ps and ±0.39dB, respectively.

Very compact UWB antenna with group delay improvement

In this paper, very compact (12mm?17mm) and simple UWB antenna is proposed. The achieved bandwidth of the presented antenna is from 3.05 GHz to 12.5 GHz and in the most of the bandwidth, the return loss is less than -20dB. In addition to frequency characteristics, time characteristics such as group delay variations for three different antenna positions, namely, front to front, back to back and side by side using CST MW studio are simulated and discussed. To improve the group delay variations, by changing the radius of the circle on the back side of the antenna, the antenna gain in different frequencies will be tuned, therefore, the time domain characteristics of the proposed antenna are greatly improved.