A GaAs MMIC-based coupling RF MEMS power sensor with both detection and non-detection states

doi:10.1016/j.sna.2011.03.039

Sensors and Actuators A: Physical

Volume 168, Issue 1, July 2011, Pages 30-38

https://doi.org/10.1016/j.sna.2011.03.039 Get rights and content

Abstract

This paper first presents the detection and non-detection function of an inline RF MEMS power sensor by employing two shunt capacitive MEMS switch structures. It solves a problem that regardless of whether the power sensor needed to detect the power, a certain microwave power will always be detected, which results in the unnecessary power loss. This power sensor is based on sensing a certain percentage of the incident microwave power coupled by a MEMS membrane. The effect of an impedance matching structure for improving microwave characteristics, a capacitance compensating structure for obtaining the wideband response, and the two shunt capacitive MEMS switch structures for achieving both states conversion together associated in this sensor, on the performance of the power sensor is proposed in this paper, and verified by the simulation and measurement. This power sensor offers the compatible capability with GaAs MMIC technology. In the detection state, experiments demonstrate that the design of the improved power sensor has resulted in the reflection loss of less than −17 dB, the insertion loss of less than 0.8 dB, and the flatness of the frequency response at X-band. And a sensitivity of more than 36 μV mW⁻¹ and a resolution of 0.316 mW are obtained at 10 GHz under the normal ambient temperature. Yet in the non-detection state, the design has resulted in the reflection loss of less than −19 dB and the insertion loss of less than 0.6 dB. The measured actuation voltage of MEMS switches is about 42 V.

Introduction

Radio frequency (RF) power sensors play an important role in wireless applications like power detection, gain control or circuit protection. Nowadays, the commercially available RF power sensors must dissipate all incident microwave power for the purpose of the power detection based on thermocouples, thermistors and diodes, which are usually called the terminating power sensors [1], [2]. Their largest shortcoming is that the incident microwave signal is not available after the power detection. With the rapid development of RF integrated circuits, most of modern personal communication and radar systems require that the RF signal is still available during power detection. And these power sensors are called the inline or through power sensors. Recently, three kinds of typical inline microwave power sensors have been proposed based on MEMS technology. They mainly include (a) the inline inserted power sensors [3], [4], [5]; (b) the inline capacitive power sensors [6], [7], [8], [9], [10]; (c) the inline coupling power sensors [11], [12], [13]. However, these three kinds of power sensors embedded into RF circuits for inline power detection cannot achieve the conversion of detection and non-detection states on the chips, and then lead to a waste of the microwave power when the circuits are not required to be detected.

In order to reduce the effect of the MEMS membrane on the microwave performance and obtain the wideband frequency response of the RF MEMS power sensor, an impedance matching method by modifying the gap size of the CPW line before and after the MEMS membrane, as well as an capacitance compensating method by adding an open-circuital transmission line has been reported in our lab [13]. On this basis, this paper proposes two shunt capacitive MEMS switches added in the coupling branches of this RF MEMS power sensor for achieving the conversion of detection and non-detection states. When the actuation voltage is not applied to MEMS switches, the switches are in the up state and the power sensor is in the detection state. It means that a certain percentage of the incident microwave power coupled by the MEMS membrane will be dissipated by termination resistors for microwave power measurement. When the actuation voltage is applied to MEMS switches, the switches are in the down state and the power sensor is in the non-detection state. It means that a certain percentage of the incident microwave power coupled by the MEMS membrane will be reflected and not dissipated by termination resistors, thus the total microwave power is not almost attenuated. Moreover, in this paper, the effect of the impedance matching structure, the capacitance compensating structure, and two shunt capacitive MEMS switch structures together associated in this power sensor, as a whole, on the performance of this power sensor is given and verified by the simulation and measurement. And the coupling RF MEMS power sensor with both detection and non-detection states is accomplished with GaAs MMIC technology. Finally, this paper offers the measurement comparison of the power sensor with the improved structures and with the basic structure, further demonstrating the validity of the design theory.

Section snippets

Basic structure

The principle of the coupling RF MEMS power sensor consists of: (a) a coupling step: the microwave power coupler couples a certain percentage of the incident microwave power into two inputs of the thermoelectric microwave power sensors by a suspended MEMS membrane, based on the capacitive coupling MEMS technology; and (b) a measurement step: the two thermoelectric microwave power sensors convert the coupled microwave power into heat by termination resistors and then result in the output

Design of improved structures

In order to reduce the effect of the MEMS membrane on the microwave performance and improve the frequency response of the output thermovoltage, and achieve the detection and non-detection function, an impedance matching method by modifying the gap size of the CPW line before and after the MEMS membrane and a capacitance compensating method by adding an open-circuital transmission line, and a state-conversion method by employing two shunt capacitive MEMS switches in two coupling branches,

Measurement results

In this paper, coupling RF MEMS power sensors are fabricated using GaAs MMIC process [11], [12]. The microwave performance and power handling are measured for the characterization of the coupling RF MEMS power sensors. To further verify the accuracy of impedance matching and open-circuital transmission line compensating capacitance methods, measurement results of power sensors with improved structures and the basic structure are given together.

Conclusions

In order to improve microwave characteristics and the frequency response of the output thermovoltage, and achieve the conversion of detection and non-detection states, a wideband 8–12 GHz inline coupling RF MEMS power sensor with the impedance matching and capacitance compensating structures and the shunt capacitive MEMS switch structures is presented in this paper. The design model of this power sensor is given and verified. And the experiments prove that the power sensor with the improved

Acknowledgment

This work is supported by the National Natural Science Foundation of China (NSFC: 60976094, 61076108, 60676043) and the National High Technology Research and Development Program of China (863 Program, 2007AA04Z328).

Zhiqiang Zhang was born in China in 1983. He received the B.S. degree in 2006 from Hefei University of Technology, Hefei, China. He was admitted in 2007 for the M.S. degree by the Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing, China, and then became a Ph.D. candidate in 2009. Now he is currently working toward the Ph.D. degree in the Key Laboratory of MEMS of Ministry of Education, Southeast University.

His current research interests include RF MEMS power

References (16)

Z.Q. Zhang et al.
A coupling RF MEMS power sensor based on GaAs MMIC technology
Sens. Actuators A: Phys.
(2010)
A.W. Van Herwaardena et al.
Thermal sensors based on the seebeck effect
Sens. Actuators
(1986)
A. Dehe et al.
High-sensitivity microwave power sensor for GaAs-MMIC implementation
Electron. Lett.
(1996)
A. Dehe et al.
Integrated microwave power sensor
Electron. Lett.
(1995)
A. Dehe et al.
Broadband thermoelectric microwave power sensors using GaAs foundry process
A. Dehe et al.
GaAs monolithic integrated microwave power sensor in coplanar waveguide technology
L.J. Fernandez et al.
Capacitive MEMS application for high frequency power sensor
L.J. Fernandez et al.
Radio frequency power sensor based on MEMS technology

There are more references available in the full text version of this article.

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A lumped model with phase analysis for inline RF MEMS power sensor applications
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The other is the decrease of the fabricated MEMS membrane in height. According to [8,9,11], the membrane with the original height of 1.6 μm is lowered due to the stress and adhesion effects after wet-removing the polyimide layer and its height can decrease hundreds of nanometers by the calculation of the coupled power and the SEM observation, which leads to the increase in the capacitance between the membrane and the signal line of the CPW. In this paper, the height of the MEMS membrane is considered to be 1.6 μm in the calculations, without the decrease of the membrane height.
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In Fig. 1, it consists of three design techniques: an impedance matching structure for reducing the effect of the MEMS membrane and the switch beams on the microwave performance, a capacitance compensating structure for obtaining the wideband frequency response of the output, and two shunt capacitive MEMS switches for achieving the conversion of both detection and non-detection states. The detailed design methods of these structures have been developed in Ref. [2]. To depress the generation of higher modes, CPW ground lines that are separated by the coupling branches and the capacitance compensating structure are together connected by air bridges.
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His current research interests include RF MEMS power sensors and passive filters.

Xiaoping Liao was born in China in 1966. He received the B.S and Ph.D. degrees in electronic engineering from Southeast University, Nanjing, China, in 1987 and 1998, respectively.

He was a Postdoctoral researcher at Hong Kong University of Science and Technology, Kowloon, Hong Kong, in 2002, where his research involved RF SOI power MOSFETs. He is currently a full Professor with the Key Laboratory of MEMS of Ministry of Education, Southeast University. He focuses on RF MEMS devices and circuits, particularly on RF MEMS switches and microwave power sensors.

Lei Han was born in China in 1982. He received the B.S. degree in 2003 from Hefei University of Technology, Hefei, China, and the M.S. degree in 2006 from Southeast University, Nanjing, China, where he is currently working toward the Ph.D. degree, with interests in design and fabrication of micromachined RF/MW devices on GaAs substrate.

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A GaAs MMIC-based coupling RF MEMS power sensor with both detection and non-detection states

Abstract

Introduction

Section snippets

Basic structure

Design of improved structures

Measurement results

Conclusions

Acknowledgment

Sens. Actuators A: Phys.

Thermal sensors based on the seebeck effect

Sens. Actuators

High-sensitivity microwave power sensor for GaAs-MMIC implementation

Electron. Lett.

Integrated microwave power sensor

Electron. Lett.

Broadband thermoelectric microwave power sensors using GaAs foundry process

GaAs monolithic integrated microwave power sensor in coplanar waveguide technology

Capacitive MEMS application for high frequency power sensor

Radio frequency power sensor based on MEMS technology