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Journal of ZheJiang University (Engineering Science)  2021, Vol. 55 Issue (7): 1399-1406    DOI: 10.3785/j.issn.1008-973X.2021.07.019
    
Design of 0~21 GHz wideband silicon-based digital attenuator with high accuracy
Mei-shan LIU(),Wei ZHANG*(),Dong-ning HAO
School of Microelectronics, Tianjin University, Tianjin 300072, China
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Abstract  

A new switch embedded attenuator structure based on capacitive correction network was presented, in order to solve the problem of unstable broadband performance in the RF front-end transceiver system. The capacitive correction network saving the core circuit area by adjusting the influence of the zero and pole to the frequency response, expanded the working band, which satisfied the cross-band, wide frequency domain RF design requirements for communication transceiver front end. A 6-bit digital step attenuator with the correction network based on HHNEC 0.18 μm SiGe BiCMOS process was designed, the digital step attenuators had 6-bit digital control inputs with 64 attenuation states, the maximum attenuation of 31.5 dB and the least attenuation step of 0.5 dB. Simulation results show that in the bandwidth of 0~21 GHz, the 64-state root mean square (RMS) of attenuation error is less than 0.23 dB, the RMS of phase variation is less than 4.38°, the maximum insertion loss at 21 GHz is ?11.05 dB, the minimum insertion loss is ?4 dB, the 1 dB compression point at the center frequency is 17.3 dBm. The layout area of core circuit is 0.86 mm×0.2 mm.



Key wordsdigital step attenuator      phased array radar      high precision attenuation      low additional phase shift      ultra wide band      body-float technology     
Received: 24 June 2020      Published: 05 July 2021
CLC:  TN 433  
Corresponding Authors: Wei ZHANG     E-mail: ms03@tju.edu.cn;tjuzhangwei@tju.edu.cn
Cite this article:

Mei-shan LIU,Wei ZHANG,Dong-ning HAO. Design of 0~21 GHz wideband silicon-based digital attenuator with high accuracy. Journal of ZheJiang University (Engineering Science), 2021, 55(7): 1399-1406.

URL:

https://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2021.07.019     OR     https://www.zjujournals.com/eng/Y2021/V55/I7/1399


0~21 GHz高精度宽带硅基数字衰减器设计

针对射频前端收发系统中衰减结构宽带性能不稳定的问题,提出具有双重电容补偿的新型开关内嵌式衰减结构。该结构基于容性校正网络,在节约核心电路面积的同时通过调节零、极点对频率响应的影响,达到拓展衰减单元工作频带的目的,以满足跨频段、宽频域射频通信收发前端的设计需求. 基于HHNEC 0.18 μm SiGe BiCMOS工艺,采用新型电容补偿结构设计6位步进式数字衰减电路,该衰减器通过6位数控开关实现64种衰减状态,衰减步进0.5 dB,衰减范围0~31.5 dB. 仿真结果表明,在0~21 GHz工作频带内衰减误差均方根小于0.23 dB,附加相移均方根小于4.38°,插入损耗最大为?11.05 dB,最小为?4 dB,中心频率处1 dB压缩点17.3 dBm,核心电路版图面积0.86 mm×0.2 mm.


关键词: 数字步进式衰减器,  相控阵雷达,  高精度衰减,  低附加相移,  超宽带,  体悬浮技术 
Fig.1 Structures of digital step attenuator
Fig.2 Simplified small-signal equivalent circuits
Fig.3 Amplitude response and pole-zero distribution of 4 dB bridge-T cell
参数 单位 数值 参数 单位 数值
R1 Ω 44.00 RM1,on Ω 9.84
R2 Ω 38.00 CM1,off fF 43.36
R3 Ω 56.00 RM2,on Ω 23.00
Z0 Ω 50.00 CM2,off fF 20.66
Tab.1 Device parameters of 4 dB bridge-T attenuation unit
Fig.4 Phase response and pole-zero distribution of 4 dB bridge-T cell
Fig.5 Pole-zero distribution of 4 dB bridge-T cell with Cs
Fig.6 Amplitude and phase response of 4 dB bridge-T cell with Cs
Fig.7 Attenuator structure with double capacitor
Fig.8 Comparison of amplitude response of two capacitors compensation structures
Fig.9 Comparison of ordinary π-topology attenuation cell and two improved structures
Fig.10 Body-float switch circuit and cross section of deep N-type well
Fig.11 Design of whole circuit and final layout
Fig.12 Simulation result of 6 bit digital step attenuator
设计结构 D/μm f/GHz RA/dB SA/dB IL/dB RL/dB RMSA'/dB RMSθ/(°) IP1dB/dBm S/mm2
*为核心电路面积
文献[5] 0.130 0~20 0~31.50 0.5 1.7-7.2 <?12 0.37 <4.0 10 0.14*(1.00×0.14)
文献[6] 0.350 14~18 0~31.50 0.5 8±0.6 <?10 0.29 <3.9 >10 0.27*(0.80×0.34)
文献[8] 0.180 3~22 0~31.00 1 5.53~13.07 <?11 0.53 <6.3 18.4
文献[10] 0.130 3~13 0~31.75 0.25 <6.6 <?9 0.17 <2.8 16.8 1.57(1.59×0.79)
文献[19] 0.065 8~18 0~31.50 0.5 6.1~8.6 <?10 0.1 <5.5 12 0.273*(0.91×0.3)
文献[20] 0.180 0~18 0~31.50 0.5 2.9~6.1 <?11 0.39 <2.4
本文 0.180 0~21 0~31.50 0.5 4~11.05 <?8.35 0.23 <4.38 17.3 0.172*(0.86×0.02)
Tab.2 Key performance comparison of capacitor compensation structure digital step attenuator
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