In-band Ripple Research Articles

An 8-way series-parallel combiner based power amplifier for mm-wave 5G communication in 40-nm CMOS

This paper presents a power amplifier (PA) with an 8-way series–parallel power combiner for 5G communication. By theoretical analysis of the S-parameters matrix and the equivalence of the impedance network, the design of the multi-port combiner is transformed into a dual-port on-chip transformer, and the bandwidth expansion is achieved without increasing the in-band gain ripple based on the mismatch-consistent magnetically coupled resonator (MCR) technique. As a validation of the methodology, the 8-way series–parallel power combiner PA is implemented in 40-nm CMOS Bulk process. The large-signal performances of the PA at 31 GHz are 21.36 dBm, 17.1 dBm, and 25.7 % for Psat, OP1dB, and PAEmax, respectively. The proposed PA has a peak S21 of 25.1 dB and a 3-dB bandwidth of 23.5–46.4 GHz, which fully covers the 5G new radio (NR) frequency range2 (FR2) operating band, and the S21 ripple is less than 1-dB in the range of 26.0–42.3 GHz, which achieves a broadband flat frequency response and supports the feasibility of the design.

Investigation of spurious mode suppression in 3.8 GHz shear-horizontal mode surface acoustic wave resonators based on LiNbO3/SiO2/Si multilayer structure

LiNbO3(LN)/SiO2/Si multilayer structures have recently attracted much attention due to their superior performance in realizing wideband radio-frequency acoustic filters. However, the spurious modes, which are commonly found in LN-on-insulator (LNOI) resonators, often cause in-band ripples and a deteriorated out-of-band suppression level. Although much research work has been done on the suppression of spurious modes in LNOI resonators operating in the <3 GHz region, little has been reported for >3 GHz devices. This work investigates the spurious mode suppression techniques for a 3.8 GHz shear-horizontal mode 36° YX-LNOI surface acoustic wave (SAW) device based on an LN/SiO2/Si multilayer structure. Specifically, we explore different techniques based on apodized electrodes, dummy electrodes and a double busbar structure. The measured results show that the effect of spurious mode suppression can be improved by combining the benefits of these techniques, which provides a promising solution for designing spurious-free LNOI SAW resonators operating above 3 GHz.

Synthesis and Design of Shunt Resonator-Based Phase Shifters With Reduced Phase Error and In-Band Magnitude Ripple

Synthesis and Design of Shunt Resonator-Based Phase Shifters With Reduced Phase Error and In-Band Magnitude Ripple

A 6 to 18 GHz flat high gain power amplifier using mismatch-consistent MCR technique in 40-nm CMOS

This paper presents a power amplifier (PA) based on the mismatch-consistent magnetically coupled resonator (MCR) technique, which employs adjustable dual-pole to achieve a wide operating frequency range. The in-band no gain ripple condition of the proposed mismatch-consistent MCR is systematically analyzed and derived. By applying this condition to the mismatch-consistent MCR technique, the in-band gain flatness in broadband is improved. An ultra-wide wiring method for the power-combining structure is proposed to further improve the in-band gain flatness by reducing parasitic effects. Meanwhile, an active broadband matching network without any on-chip inductor is used to obtain a -11 dB input return loss (S11) across the whole bandwidth. Implemented in 40-nm CMOS process, the proposed PA achieves a saturated output power of 19.2 dBm, an output 1 dB compression point of 17.8 dBm, a peak power added efficiency of 29.7 %, and only 0.5 dB in-band gain ripple at 8.2-16.2 GHz. The amplifier achieves a 3 dB bandwidth from 6 to 18 GHz while the fractional bandwidth reaches 100 %, realizing wideband and flat frequency response.

SAW Filters on LiNbO3/SiC Heterostructure for 5G n77 and n78 Band Applications.

The 5G communication system has experienced a substantial expansion of the spectrum, which poses higher requirements to radio frequency (RF) filters in enhancing their operating frequencies and bandwidths. To this end, this work focused on solving the filtering scheme for challenging 5G n77 and n78 bands and successfully implemented the corresponding spurious-free surface acoustic wave (SAW) filters exploiting large-coupling shear horizontal (SH) modes based on X-cut LiNbO3 (LN)/silicon carbide (SiC) heterostructure. Here, we initially investigated the suppression methods for spurious modes theoretically and experimentally and summarized an effective normalized LN thickness ( [Formula: see text] range of 0.15-0.30 for mitigating Rayleigh modes and higher order modes, as well as tilted interdigital transducers (IDT) by about 24° for eliminating transverse modes. Resonators with wavelengths ( λ) from 0.95 to [Formula: see text] were also fabricated, showing a scalable resonance from 2.48 to 4.21 GHz without any in-band ripple. Two filters completely meeting 5G n77 and n78 full bands were finally constructed, showing center frequencies ( fc) of 3763 and 3560 MHz, 3-dB fractional bandwidths (FBW) of 24.8% and 15.6%, and out-of-band (OoB) rejections of 18.7 and 28.1 dB, respectively. This work reveals that X-LN/SiC heterostructure is a promising underpinning material for SAW filters in 5G commercial applications.

Design of a New Capacitive Load Cross-Coupled Cavity Filter

This paper presents a new design method for a capacitor-loaded cross-coupled cavity filter, which significantly increases the power capacity of the cavity filter while improving out-of-band rejection. The filter uses a coaxial resonator at the open end of the donut capacitive-load. A triangular form of cavity structure is used for the full-cavity arrangement to reduce the size of the filter. In order to validate the design, a filter with a center frequency of 2.08 GHz and bandwidth of 80 MHz was designed, processed, and tested. The measured insertion loss was ≤0.97 dB, and the return loss was &gt;20 dB in the range of 2040 MHz to 2120 MHz; the rejection was as high as 80 dB, and in-band ripple was 0.06 dB in the upper and lower stopband-range, which was only 30 MHz away from the sideband. After a simulation of the model using HFSS software (HFSS 2021, Canonsburg, PA, USA), the measured results matched the simulation results, which verified the correctness and practicality of the design. Compared with the ordinary-disc-load resonant cavity, the new donut capacitively loaded cavity-bandpass-filter has a 13.2% reduction in height and a 29.7% increase in power capacity.

Ultraflat bandpass, high extinction, and tunable silicon photonic filters.

We report on the design and the demonstration of silicon photonic ultraflat bandpass filters with low insertion loss and high out-of-band rejection for an operation near the 1550 nm wavelength band. These filters are based on cascading low (2nd) order Ring-Assisted Mach-Zehnder Interferometer (RAMZI) filter stages. The cascade design enables high out-of-band rejection while keeping the unit cells of each stage low order to be more tolerant to fabrication imperfections. The characterization of filters shows an insertion loss of ∼1 dB, an in-band ripple of <0.1 dB, an out-of-band rejection of >50 dB for a filter 3-dB bandwidth of ∼1.1 nm, and tunable up to ∼6 nm. We also investigate the filter's spur-free dynamic range at high input optical powers, which is important for RF photonics applications, and quantify a dynamic range of >60 dB for a laser power as high as ∼11.6 mW sent to the filter. Such integrated filters are promising for applications in pump wavelength rejection in four-wave mixing photon pair generation, and in RF antenna remoting where multiple RF signals are carried on different coarse wavelengths to be separated.

Large-Range Spurious Mode Elimination for Wideband SAW Filters on LiNbO₃/SiO₂/Si Platform by LiNbO₃ Cut Angle Modulation.

A LiNbO3 (LN)/SiO2/Si multilayered structure was recently reported as a new platform for achieving wideband radio frequency (RF) filters. However, the in-band ripples in filters resulting from the spurious Rayleigh mode lead to deteriorated performance, and thus, a wide Rayleigh elimination window (REW) is highly desired for realizing spurious-free wideband surface acoustic wave (SAW) filters with a wide design space and good process tolerance. Here, we investigated the spurious mode suppression on the LN/SiO2/Si platform theoretically and experimentally through modulating the cut angle ( θ ) of LN. The K2 dispersion characteristics of the main mode (shear-horizontal wave) and spurious mode (Rayleigh wave) on LN/SiO2/Si substrates were systematically analyzed by the finite-element method (FEM), along with bulk LN for comparison. It is found that the REW is wider on LN/SiO2/Si than bulk LN, as Rayleigh wave can be totally eliminated with Cu electrode normalized thickness ( [Formula: see text]) ranging from 0.1 to 0.19 when θ is between 19° and 22° on the LN/SiO2/Si platform, in contrast to the quite narrow REW on bulk LN restricted to some specific [Formula: see text]. To verify the simulation results, resonators were prepared on 15°YX-LN/SiO2/Si, 20°YX-LN/SiO2/Si, bulk 15°YX-LN, and bulk 20°YX-LN. In addition, the typical spurious-free wideband SAW filter with [Formula: see text] nm based on the 20°YX-LN/SiO2/Si platform demonstrates high performance with a center frequency ( [Formula: see text]) of 1.27 GHz, a minimum insertion loss (ILmin) of 0.7 dB, and a 3-dB fractional bandwidth (FBW) of ~20.1%. This work provides a workable solution in fabricating spurious-free wideband and low-loss SAW filters for fifth-generation (5G) applications.

Methods of solving in‐band ripples and out‐of‐band suppression for yarn tension sensor based on surface acoustic wave

The two key problems of the in-band ripples and out-of-band suppression are proposed in the design of the SAW yarn tension sensor and the methods of decreasing them are achieved. The unbalanced split-electrode interdigital transducers (IDT) are designed so that the total phase of the regenerated reflection wave and mass load feedback is close to 180°, leading to an effective reduction of the in-band ripples effect characterised by the sensor frequency response. The engraved bi-directional slots on the back of the substrate can block the propagation path of the bulk acoustic wave (BAW) to a certain extent, reducing the influence of BAW propagation and suppressing the out-of-band suppression of the frequency response. The experimental results show that the SAW yarn tension sensor with the unbalanced split-electrode IDT can reduce the in-band ripples from 23.34 to 0.93 dB, and the engraved bi-directional slots can suppress the out-of-band suppression from 28.03 to 7.71 dB.

Proposal and Synthesis of Wideband Multilayer Planar Magic-T With Independent In-Phase and Out-of-Phase Chebyshev Filtering Responses

A wideband planar multilayer filtering magic-T is proposed and developed. The proposed magic-T uses coupled microstrip slotlines (CMSs) and microstrip-slot transitions. With the orthogonality of even and odd modes of the CMS, the Chebyshev filtering responses of both the in-phase divider part (H-T) and out-of-phase divider part (E-T) are independent of each other. The microstrip-slot transitions act as a part of filtering structures to realize vertical transmission of energy. With equivalent impedance transformer models, the synthesis processes of a four-pole Chebyshev filtering H-T and a three-pole Chebyshev filtering E-T are derived and analyzed. To verify the proposed concept, a prototype with an operating center frequency of 3 GHz, a 100% equal ripple fractional bandwidth, and a different H-T and E-T in-band ripple are synthesized and implemented on a three-layer printed circuit board. The synthesized, simulated, and measured results show good agreements among them, verifying the feasibility of the proposed planar magic-T.

Ultra-compact wideband filter with sidelobe suppression based on double modulated grating-assisted microring resonator

In this paper, we propose an ultra-compact wideband filter (WBF) with high sidelobe suppression. The filter consists of a single microring resonator incorporated with a proposed new structure of double modulated subwavelength gratings. The double modulated subwavelength gratings are obtained via two different fill factors with the same period. The ultra-compact WBF achieved FSR-free, flat response with a 3 dB bandwidth of 1.0734 THz and a sidelobe suppression of 19.79 dB. In addition, a low insertion loss of &lt;0.6 dB and a low in-band ripple of less than 0.2 dB were obtained. The filter has a compact device footprint of 380 μm2.

Equiripple design of low‐pass filter using stub‐loaded Z‐shaped coupled‐line section

Design procedure of a novel transmission line low-pass filter is presented. The filter has a flexible rejection response for a prescribed cut-off frequency and an in-band ripple factor. It is compact by using a Z-shaped coupled-line section, which is loaded with open-circuited stubs. All of the transmission line elements are identical in electrical length, and the impedances can be calculated by solving certain specific equations according to prescribed in-band specifications. The simulated results show that the circuit can generate low-pass responses with third-, fifth-, and seventh-order filtering functions. The filter order depends on the number and position of the loading stubs. For verification, two sample filters with cut-off frequency of 0.5/0.3 GHz are fabricated using a three-/five-layer PCB process, which generate seventh-order low-pass filtering responses with good selectivity. The experimental results agree well with the predictions.

6.7–15.3 GHz, High-Performance Broadband Low-Noise Amplifier With Large Transistor and Two-Stage Broadband Noise Matching

This letter presents a fully integrated wideband, ultralow average noise figure (NF), low power consumption, compact, and electrostatic discharge protected 6.7-15.3-GHz low-noise amplifier (LNA). A peak-gain distribution technique with a large transistor and two-stage broadband noise matching technique are proposed. For verification, a two-stage common source LNA is implemented in a 65-nm bulk complementary metal-oxide-semiconductor technology. The fabricated LNA achieved an average NF of 2.08 dB and an average gain of 19.1 dB with in-band gain ripple of ±0.75 dB in the frequency range of 7.6-14.7 GHz. It has a 3-dB fractional bandwidth of 78% and the third-order input intercept point is -9.0 dBm at 10 GHz. It consumes a 16 mA at a 0.8-V supply and has an area of 0.144 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

A General Variable Bandwidth Microring Filter for Lossless Bandwidth Tuning

We propose a general variable bandwidth filter of arbitrary even order based on the sum-difference microring filter architecture. The filter bandwidth can be varied by tuning only the resonant frequencies of the microrings and thus do not require additional controls other than those used to tune the filter center frequency. In addition, we show that there exists a bandwidth tuning range over which the filter exhibits no extra insertion loss and no degradation in the filter shape. We demonstrated a 4 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> -order variable bandwidth filter in Silicon-on-Insulator, achieving a bandwidth tuning range from 0.3 nm to 1.35 nm with a maximum in-band ripple of 3 dB. The proposed variable bandwidth filter could serve as a key element in elastic optical networks which can support variable data bandwidth allocation on demand.

X-Band Miniature Filters Using Lithium Niobate Acoustic Resonators and Bandwidth Widening Technique

This work presents a class of micro-electromechanical system (MEMS)-driven radio frequency filters in the X-band. The X-band center frequencies are achieved by resorting to the third-order antisymmetric Lamb wave mode (A3) in a 650-nm-thick Z-cut lithium niobate thin film. A novel bandwidth (BW) widening technique based on using the self-inductance of the top interdigital transducers and bus lines is proposed to overcome the limitations set by the electromechanical coupling (k <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> ) and satisfy the demands in miniaturization and wide BW. Four different designs of the filters are designed and fabricated to show the trade-off among BW, insertions loss (IL), out-of-band rejections, and footprint. Due to the spurious-free and highQ performance of the A3 lithium niobate resonators, the fabricated A3 lithium niobate filters have demonstrated small in-band ripples and sharp roll-offs. One of these fabricated has demonstrated a 3-dB BW of 190 MHz, an IL of 1.5 dB, and a compact footprint of 0.56 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Another design is fabricated to demonstrate a 3-dB BW of 170 MHz, an IL of 2.5 dB, an outof-band rejection of 28 dB, and a compact footprint of 1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

5th-Order Continuous-Time Low-Pass Filter Achieving 56 MHz Bandwidth 30.5 dBm IIP3 With a Novel Low-Distortion Amplifier

This brief presents a highly linear and high-speed operational amplifier that consists of a double-recycling folded cascode input stage and an adaptive biasing with a flipped voltage follower to boost slew-rate and unity-gain frequency. In addition, frequency compensation is performed by an input cross-coupled phase-lead passive compensation scheme and hybrid Miller-cascode compensation. A 56 MHz -3 dB bandwidth fifth-order programmable gain continuous-time active low pass filter is fabricated in 180 nm CMOS to validate the proposed scheme. The filter achieves 30.5 dBm of third-order interception point at 38 MHz and occupies 0.215 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The filter consumes 14.7 mW with 1.8 V supply and has 0.2 dB in-band ripple.

A Millimeter-Wave Receiver Using a Wideband Low-Noise Amplifier With One-Port Coupled Resonator Loads

This article presents design techniques to facilitate the use of the driving point impedance (Z 11 ) of one-port transformer-coupled resonators as wideband loads of millimeter-wave amplifier stages for a 28-GHz receiver front end. While the use of both the Z 11 of a one-port and the transimpedance (Z 21 ) of a two-port coupled resonator is considered to achieve a wideband response, it is shown that under conditions of low magnetic coupling and constrained network quality factor, the use of Z 11 can result in a higher gain-bandwidth product of low-noise amplifier (LNA) amplifier stages. The effect of the complex zero in the Z 11 response on the in-band gain ripple is shown to be alleviated merely by lowering the quality factor of the transformer's secondary coil; this strongly motivates the use of compact, nested-inductor transformer layouts. Implemented in a 65-nm CMOS process, a three-stage LNA (with Z 11 wideband loads in two stages) achieves a 24.4-32.3-GHz bandwidth (27.9 % fractional bandwidth), a peak S 21 of 24.4 dB (20.4 dB), a minimum noise figure (NF) of 4 dB (4.6 dB), and an input-referred P1dB of -23 dBm (-22 dBm) while consuming 22-mW (9.9 mW) power from a 1.1-V (0.85 V) supply. The use of compact transformers limits the LNA's footprint to only 0.12 mm2. A 26.5-32.5-GHz quadrature receiver prototype employing the LNA achieves a 29.5-dB peak conversion gain, a 5.3-dB minimum NF, and a -26-dBm inputreferred P1dB while consuming 33 mW from a 1.1-V supply.

Ultra-compact on-chip optical filters with narrow bandwidth

A novel scheme for integrated optical filters with narrow bandwidth is proposed to dramatically improve its compactness on the basis of slow-light waveguide, which provides a large optical path in a short geometry length. By introducing the one-dimensional grating waveguide (ODGW), a kind of slow-light waveguide, into a micro-ring resonator (MRR), the area of MRR is reduced by three orders of magnitude compared to the MRR without ODGW. As a proof of concept, an ultra-compact on-chip filter with narrow bandwidth of 2.1 pm (263 MHz) is conceived by cascading six MRRs with ODGW. Additionally, the designed optical filter shows excellent performances of roll-down speed, out-of-band signal suppression, and in-band ripple. Our proposal offers a promising solution to miniaturize the integrated optical filters with narrow bandwidth, and hence improve the integration density of on-chip photonic networks.

Explicit Solution to Exact Synthesis of Cross-Coupled Quadruplet Filter With a Real-Frequency Zero Pair

Explicit solution is derived for the exact synthesis of cross-coupled quadruplet filters with a real-frequency zero pair. Through a comparison of two-port S-parameters of the low-pass prototype circuit with the canonical generalized Chebyshev insertion loss function, a univariate quadratic function is formulated, and all element values of the circuit are explicitly expressed in terms of the designated zero and in-band ripple levels. The analytical expression of the sidelobe attenuation level is also obtained in terms of the zero, and vice versa. Results are checked against those from the existing literature.

A LNA-merged RF front-end with digitally assisted technique for gain flatness and input-match compensation

In this paper, a wideband LNA-merged RF receiver front-end (RFE) with digital assist (DA) for conversion gain flatness and input-match compensation is presented. It employs a novel common gate $$g_m$$ -stage with multiple feedback, double-balanced Gilbert-type switches and active loads to form stacking topology. The conversion gain boost factor and input-match compensation factor can be controlled by DA. Theory and simulation results show that DA broaden the RF bandwidth of the proposed RFE and improve the conversion gain flatness. A prototype of the presented RFE is designed and fabricated in the SMIC 40-nm CMOS process, the active area is just $$0.03\,{\hbox {mm}}^2$$ . From measurement results, the proposed RFE achieves conversion gain of 7.5 dB, 10.0 dB and 12.5 dB from 0.5 to 3.5 GHz with 0.3 dB inband ripple. The best IIP3 is 1.5 dBm. The minimum SSB NF is 11.3 dB. The average DC power is only 3.2 mW from a 1.1 V supply.