A new design of multi-bit RF MEMS distributed phase shifters for phase error reduction

2020

Circuit Theory & Apps

A phase shifter is one of the main components of radars and phased array systems. In this paper, a novel three-state two-bridge unit cell is presented for a compact low-loss six-bit distributed microelectromechanical systems (MEMS) transmission line (DMTL) phase shifter. The proposed unit cell includes a coplanar waveguide (CPW) transmission line, a MEMS bridge on the signal line, two metal-air-metal (MAM) capacitors on a glass substrate, and two additional electrodes under the MEMS bridge, near the signal line. Using these electrodes, it is possible to generate two different phase states employing the MEMS bridge, and the third state is produced by a metal-air-metal (MAM) bridge. Hence, the designed structure can generate three different phase shifts per unit cell (i.e., 5.625 , 11.25 , and 22.5 phase shifts). The novelty of this design is that the number of unit cells is considerably reduced from 64 in a conventional six-bit phase shifter to only 17 in our design. Therefore, the total length of the six-bit phase shifter and average loss are considerably reduced. The designed structure is calculated and simulated at 32 GHz using MATLAB and ANSOFT HFSS, respectively. According to the calculation and simulation results, the lateral size of the phase shifter is only 8.5 mm, the root mean square (RMS) phase error is 1.38 , and the average loss is 1.1 dB. The feasibility of the proposed design is investigated using the proposed fabrication process. The designed phase shifter can be easily scaled to other frequencies for radar and satellite applications with more bits. K E Y W O R D S DMTL phase shifter, phased array antennas, return loss, unit cell 1 | INTRODUCTION Radio frequency (RF) microelectromechanical systems (MEMS) as a new interesting area in MEMS technology enable us to design and use high-performance devices and systems for broadband communication applications. 1-3 In recent years, nano-electromechanical systems (NEMS) have also developed and have found some new applications. 4-10 RF MEMS-based devices include switches, inductors, capacitors, varactors, and phase shifters. Phase shifters are the main components of the phased array antennas for radar applications and are classified into analog and digital types. 11-14 Analog MEMS phase shifters change the phase from 0 to 360 continuously, and their structure contains MEMS varactors. 15 Digital MEMS phase shifters contain only a discrete set of phase shifts and usually employ MEMS

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“…Borgioli et al 25a Chen et al 26a Du et al 27 Afrang et al 31 Gharekhani and Abbaspour-sani 32 This work…”

Section: References Hayden and Rebeiz 24amentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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A low‐loss compact six‐bit DMTL phase shifter for phased array antenna applications

2020

Circuit Theory & Apps

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“…The MEMS phase shifters are generally designed and fabricated based on four basic methods such as reflected type, 13,14 switched line, 15,16 loaded line 17,18 and distributed MEMS transmission line (DMTL) 19–32 . Many studies have focused on DMTL phase shifters because of the simplicity of their modeling, very wideband performance and high frequency operation.…”

Section: Introductionmentioning

confidence: 99%

Ka‐band distributed microelectromechanical systems transmission line phase shifter using metal air metal switch

2021

Circuit Theory & Apps

A new approach for designing a two‐state unit cell for a six‐bit distributed coplanar waveguide microelectromechanical systems (MEMS) phase shifter is proposed in this study. The proposed structure includes metal air metal (MAM) capacitors as switches and consists of a unit cell with one MEMS and two MAM switches to produce two phase shifts per unit cell. In the first state, the MAM switches are pulled down and a 5.625° phase shift is achieved, and in the second state, the MEMS switch is actuated to yield a phase shift of 11.25°. The designed structure is modeled using equivalent transmission line circuit model and simulated in the Ka‐band at 34 GHz, employing advanced design system (ADS), ANSOFT HFSS and COMSOL software. Based on the modeling and simulation results, the root‐mean‐square (RMS) phase error is 1.4°, and maximum return loss and minimum insertion loss for all 64 states are better than −10.1 and −1.45 dB, respectively. The main advantages of the designed structure are its small size, low loss, low phase error and a simple phase shift mechanism. A fabrication process is also proposed for the distributed MEMS transmission line (DMTL) phase shifter that shows the feasibility of the proposed design. The proposed structure can be easily scaled to other bands and used in applications with more bits as complex as phased array antennas.

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A Compact Low-Loss 6-bit DMTL Phase Shifter Using a Novel Three-State Unit Cell

Circuits Syst Signal Process

2022