Microwave Power Sensor Research Articles

Study on Static Deflection Model of MEMS Capacitive Microwave Power Sensors

Study on Static Deflection Model of MEMS Capacitive Microwave Power Sensors

Research on MEMS dual-channel microwave power sensor with fixed beam structure

To improve the sensitivity and dynamic range of microwave power sensors, a micro-electromechanical system (MEMS) dual-channel microwave power sensor is proposed in this study. The sensor is designed and manufactured using the GaAs monolithic microwave integrated circuit` (MMIC) process and MEMS technology. The microwave performance, overload power and sensitivity are theoretically studied. At 8–12 GHz, the return loss of the sensors with three different fixed beam sizes are approximately −10 dB, which is good microwave performance. The sensitivities for capacitive detection channel of the two sensors with larger sizes are 2.4 fF W−1 @10 GHz and 14.5 fF W−1 @10 GHz, respectively, and the sensitivities of the thermoelectric detection channel of the three sensors is 25.7 mV W−1, 24.9 mV W−1 and 24.2 mV W−1, respectively. Compared with traditional microwave power sensors, the sensor proposed takes into account the advantages of microwave power sensors in both thermoelectric and capacitive structures. This work helps lay the foundation for the design of microwave power sensors with a fixed beam structure and thermoelectric microwave power sensors.

A High-Performance Dual-Channel MEMS Microwave Power Sensor With Cantilever Beam

In order to optimize the sensitivity and overload power of microwave power sensor, a dual-channel MEMS microwave power sensor with cantilever beam is proposed in this paper. GaAs MMIC process and MEMS technology are used for design and manufacturing. The theoretical model of MEMS dual-channel microwave power sensor with cantilever beam is established. The influence of the size of the cantilever beam on the microwave performance, overload power and sensitivity of the sensor is studied. The microwave performance and sensitivity of three sensors with different cantilever beam sizes were tested. At 8-12 GHz, the return loss of three sensors are -10.6 dB~-57.2 dB@ 200 μm beam length, -10.6 dB~-62.4 dB@300 μm beam length, and -12.0 dB~-62.3 dB@400 μm beam length, respectively. They all show good microwave performance. At 10 GHz, the sensitivities of capacitive detection channel of three sensors are 16.3 fF/W, 65.6 fF/W and 144.4 fF/W respectively. And the sensitivities of thermoelectric detection channel are 142.3 mV/W, 109.5 mV/W and 82.9 mV/W respectively. The sensitivities of dual-channel MEMS microwave power sensors with cantilever beam are improved compared with the traditional microwave power sensor, which has certain reference value for the design of MEMS microwave power sensors.

Highly Linear RMS Microwave Power Sensor Joule-Heating-Based Using CMOS Technology

This article presents the design and implementation of a high-power handing capacity, wideband, and excellent microwave-dc linearity root-mean-square (rms) microwave power sensor (PS) in 180-nm standard RF CMOS technology. The detection technique utilizes two well-matched microwave power absorbers and a balanced Wheatstone full bridge (WFB) with thermistors to produce a dc output proportional to incident microwave power. The lateral spacing between the hot and cold zones of WFB with 80, 100, 120, 140,and 160 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mu}$</tex-math> </inline-formula> m has been investigated experimentally, which provides insight into the proper adjustment of the layout parameters. The experimental result of the vector network analyzer (VNA) shows that the input reflection loss is less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 22.3 dB in the frequency range of 0–20 GHz. This indicates that the designed microwave PSs have good impedance matching characteristics. Moreover, it is demonstrated that the inherent linear relationship between the output dc voltage and the incident microwave power is less than 1.6% over a dynamic range of 1–500 mW. The proposed microwave PS can be further integrated in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{X}$</tex-math> </inline-formula> -band RF transceivers, offering high microwave-dc linearity, acceptable sensitivity, small size, and low cost for improving power transfer efficiency and optimizing the performance of the transmitting and receiving chain.

Resistive Power Splitter-Based Direct Comparison Technique for Microwave Power Sensor Calibration from 1 MHz to 50 GHz at CSIR-NPLI

Resistive Power Splitter-Based Direct Comparison Technique for Microwave Power Sensor Calibration from 1 MHz to 50 GHz at CSIR-NPLI

A Novel Capacitive Microwave Power Sensor Based on Double MEMS Cantilever Beams

In order to improve the sensitivity characteristic and the fabrication reliability, a novel capacitive power sensor based on double MEMS cantilever beams is proposed in this work. It is designed and fabricated using GaAs MMIC process and MEMS technology. A lumped circuit model is built to study the microwave characteristic of this capacitive microwave power sensor. The influence of impedance value and electric length of the coplanar waveguide on the microwave performance of the double MEMS beams are studied. The microwave characteristic of both ports are measured. The return loss of port A is from −11.5dB to −14.6dB, and the return loss of port B is from −12.1dB to −14.3dB at 8-12GHz. The insertion loss of port A is from −3.6 dB to −2.8dB, and the insertion loss of port B is from −3.7 dB to −2.9dB at 8-12GHz. The measured results show that this capacitive power sensor has a good microwave characteristic. The measured sensitivity of this capacitive microwave power sensor is about 51.6 fF/W @10 GHz, and the theoretical sensitivity is 55.97 fF/W. The relative error is 7.8%. Compared with the capacitive microwave power detection system based on single cantilever beam, the sensitivity characteristics have been greatly improved. It is valuable to realize the multiple beams detection technology and enable further interesting possibilities in the field of microwave power detection.

Improved Method for Calibration and Nonlinearity Correction of Microwave Power Sensor

Improved Method for Calibration and Nonlinearity Correction of Microwave Power Sensor

A Thermoelectric MEMS Microwave Power Sensor with Inline Self-Detection Function.

In this paper, the design, fabrication and measurement of a thermoelectric MEMS microwave power sensor with the terminal load inline self-detection function is proposed. The structure of the sensor mainly includes a coplanar waveguide, a thermopile, two terminal load resistors and two calibration resistors. In order to realize the inline self-detection function, the load and calibration resistors are designed to form a voltage divider circuit. The fabrication of this sensor is compatible with the GaAs MMIC technology. The on-chip performance is tested by using a microwave experimental platform. The measured reflection loss is less than −10 dB at 0.1–10 GHz. When the bias voltage is not applied, the sensitivity of the sensor is 47.39 μV/mW@5 GHz and 32.58 μV/mW@10 GHz, respectively, and when the bias voltage is applied, the sensitivity is 47.50 μV/mW@5 GHz and 32.73 μV/mW@10 GHz, respectively. The difference between the two cases is less than 0.5% at the same frequency, which indicates that whether or not to apply the bias voltage has little effect on the sensitivity. In addition, when the calibration resistance is increased from 50 to 100 Ω, the current flowing through the load resistance is decreased under the same bias voltage. Therefore, the DC power consumed on the load resistance will be significantly reduced. This makes the measured and theoretical results show better agreement, thus verifying the validity of the design.

Power Sensor Characterization From 110 to 170 GHz Using a Waveguide Calorimeter

This article proposes a new calorimetry-based measurement method to measure absolute microwave power obtained through dc substituted power from 110 to 170 GHz (WG 29, WR 6/7, or D-band) using a custom-designed thin-film microwave power sensor. This method complements traditional microcalorimetry techniques used to provide traceability for microwave power in this band while diversifying the potential applications and accessibility to such traceability. The thermopile of the measurement system was characterized using a known dc power with the microwave sensor and the thermopile coefficient obtained. Absolute microwave power on the microwave sensor was calculated using the thermopile coefficient and was used to remove the effect of a thermal isolation section (TIS) and calorimeter unbalance effect. To transfer the power traceability from the calorimeter to microwave power measurement applications, the effective efficiency of a device under test (DUT), consisting of a power sensor/meter combination, was defined using the calorimeter’s absolute microwave power and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> -parameters of the measurement system and the DUT. The effective efficiency (EE) of the DUT was obtained between 0.9386 and 0.9815 for the whole frequency band.

A novel study of the resistance of thermopile for thermoelectric MEMS microwave power sensors

In order to study the effect of the resistance of thermopile on the output performance of thermoelectric microelectromechanical system (MEMS) microwave power sensors, the relationship of the electron mobility and the resistance in n+-type GaAs is studied, and the reason why the resistance of thermocouple changes with the input microwave power and frequency is analyzed. The experimental results show that in the range of 8 ∼ 12 GHz, the return loss of the sensor is less than −27.75 dB, and the sensitivity of the sensor is 0.055 mV/mW@10 GHz. The resistance of thermopile shows a downward trend with the frequency. With the input power range from 0 to 300 mW, the resistance of thermopile increases from 55.51 to 71.17 kΩ, and it has good linearity. Therefore, this work has a certain reference value for improving the output performance of thermoelectric microwave power sensors.

A Novel 3-D Equivalent Circuit Model of Thermoelectric MEMS Microwave Power Sensors

In this work, a novel 3-D equivalent circuit model of thermoelectric microelectro-mechanical system (MEMS) microwave power sensor is proposed. According to the model, the 3-D temperature distribution and the response time of the thermoelectric MEMS microwave power sensor are obtained. The thermoelectric MEMS microwave power sensor is designed and fabricated based on GaAs monolithic microwave integrated circuit (MMIC) technology. The measured results show that the sensitivity of the sensor is 0.06 mV/mW at 10 GHz and the time constant is $85~\mu \text{s}$ . The theoretical results of the model show that the sensitivity is 0.076 mV/mW at 10 GHz and the time constant is $56.24~\mu \text{s}$ . The measured results are relatively consistent with the theoretical results. Furthermore, the heat dissipation in the substrate can be obtained accurately, and the transient response of the sensor can be further studied according to the 3-D equivalent circuit model. Therefore, this work has a certain reference value and guiding significance for the research of thermoelectric MEMS microwave power sensors.

Structural Optimization of Capacitive MEMS Microwave Power Sensor

In this work, a pivoted mechanical model of capacitive MEMS microwave power sensor is established to optimize the relative position of the measuring electrode. The pivoted model is divided into four sections in order to more accurately study the vibration of the cantilever beam. The model of the sensitivity and the overload power are obtained. According to the established model, the structure of the sensor is analyzed and optimized, the relationship of the sensitivity and the overload power with the relative position of the measuring electrode is obtained. ${x}_{3}/{l}=0.9$ is the optimal solution for the overload power, ${x}_{3}/{l}=0.8$ is the optimal solution for the sensitivity, and ${x}_{3}/{l}=0.5$ is taken as the trade-off value to verify the accuracy of the model. Finally, the measured results show that this work has certain reference value and guiding significance for capacitive MEMS power sensors.

High-power electro-mechanical behavior of a capacitive microwave power sensor with warped cantilever beam

In this paper, high-power up to 4000 mW electro-mechanical behavior of a capacitive micro-electromechanical systems (MEMS) microwave power sensor using cantilever beam is investigated. Due to residual stress gradients, the power sensor is proposed for a warped cantilever beam connected to coplanar waveguide (CPW) structure. The proposed sensor is fabricated using the GaAs monolithic microwave integrated circuit (MMIC) process. It is demonstrated that the output response of this sensor exhibits non-linear characteristics under high power levels (more than 1000 mW). The measurement results can be classified as three regions: linear region (1–1000 mW), saturated region (1000–2500 mW), and over-saturated region (2500–4000 mW). Their corresponding sensitivities are 2.8 fF/W, 1.03 fF/W, and 0.32 fF/W at 10 GHz, respectively. The non-linear output response of the power sensor is mainly caused by impedance mismatch at X-band (8–12 GHz). Furthermore, an electro-mechanical model of power sensor based on warped cantilever beam is proposed. The results are well in agreement with the calculated ones using this model by software that employs the finite element method (FEM), which provides the potential prospect for the design of capacitive power sensor.

A novel gradient thermoelectric microwave power sensors based on GaAs MMIC technology

A novel gradient thermoelectric microwave power sensor is designed to improve the performance in this work. The thermocouples are designed with different lengths based on the thermal distribution of resistance. It is fabricated using GaAs MMIC technology, and it can be integrated with other planar circuit structures. The thermal distribution of the gradient thermoelectric microwave power sensor is simulated by ANSYS finite element software. The performances of the gradient thermoelectric microwave power sensors are measured. The result shows that return loss is better than − 25 dB at 8–12 GHz. It reveals that this structure has a low reflection loss and a good matching characteristic. The sensitivity is 9.6 mV/W@8 GHz, 8.7 mV/W@10 GHz and 7.8 mV/W@12 GHz, respectively, and an excellent linear relationship of the output voltage with the input microwave power is obtained. Therefore, this optimized design of thermocouples has certain reference value for thermoelectric microwave power sensors.

Microwave Power Sensors With Integrated Filtering Function for Transfer Power Standards

This letter presents a bolometric power sensor for transfer power standards in a waveguide. This is a novel design of the microwave power sensor with an integrated filter function. An analytical power sensor synthesis technique using the coupling matrix is presented here for the first time. An ${X}$ -band power sensor with the integrated third-order Chebyshev filter function was designed and manufactured. The filtering sensor uses a small bead thermistor as a sensing element. Measurements are in good agreement with simulation and theoretical expectations.

Research on a Ka‐Band MEMS Power Sensor Investigated with an MEMS Cantilever Beam

In this work, a novel high overload Ka-band power sensor with a Micro-electro-mechanical system (MEMS) cantilever beam is investigated in order to improve the measurement dynamic range and the bandwidth. The fabrication of the Ka-band power sensor is divided into front side and back side processing with a combination of surface and bulk micromachining of GaAs. The low-power measurement reveals that the terminating-type sensitivity is close to 0.081, 0.076 and 0.072mV/mW at 34, 35 and 36GHz, respectively. The high-power measurement indicates that the capacitivetype sensitivity is around 4.9fF/W at Ka-band. The overload power measurements show that the MEMS cantilever beam can improve the dynamic range by increasing the top end of the range into no less than 200mW, and enhance the bandwidth by increasing the top end of the range into no less than 36GHz. There is an important reference value to achieve the high overload and wide frequency band for the thermoelectric microwave power sensors.

Research on Measurement Accuracy of the Double‐Channel Microwave Power Sensors Based on an MEMS Cantilever Beam

A thermopile-based microwave power sensor and a double-channel microwave power sensor are compared in order to research the measurement accuracy of microwave power. The relationship of the displacement of MEMS cantilever beam with the measured microwave power is researched, and the reason that the microwave power consumed by the MEMS cantilever cannot be ignored at low power level is explained. The ratio of microwave power consumed by the MEMS cantilever with the microwave frequency is obtained, and the measured results show that the percentage is 51.96%@8GHz, 52.31%@10GHz and 55.11%@12GHz on the average, respectively. There is an important reference value to achieve the accurate microwave power measurement of the double-channel microwave power sensors.

Design of LTE-Band Microwave Power Detection System Based on Schottky Diode

In this paper, a novel microwave power detection system based on Schottky diode is constructed in order to measure microwave power in the LTE-band (1.8~2.7 GHz). The proposed detection system is consisted of three modules: a collecting module, a measuring module, and a processing module. Among them, a microwave power detection circuit based on Schottky diode is developed to realize the high-quality conversion of microwave power signal to voltage signal. The experimental results reveal that the presented system has good linearity. In the range of 1.8~2.7 GHz, the incident microwave power is increased from 1 uW to 50 mW, and the sensitivity of the detection system is 1.86 mV/uW at 2.0 GHz, 1.61 mV/uW at 2.3 GHz, and 1.2 mV/uW at 2.6 GHz, which is much better than other microwave power sensors. Therefore, the microwave power detection system based on Schottky diode provides an effective solution for microwave power detection in the LTE-band.

Accuracy improvement of micro‐electro‐mechanical system microwave power sensor based on self‐reference algorithm

AbstractThis article presents a self‐reference algorithm to improve the accuracy of micro‐electro‐mechanical system thermoelectric microwave power sensor (5‐15 GHz). The output thermovoltage of the sensor is not only a function of the input signal power, but also relates to the signal frequency, resulting in low accuracy of the sensor. In this article, a mathematical model is established for the sensor to analyze the reasons for frequency dependence. Moreover, an algorithm is derived from analyzing the characteristics of the model and the experimental results. The algorithm relieves the dependence on the thermovoltage and frequency. Experiments show that the relative error of the sensor based on the proposed self‐reference algorithm decreases from 22% to 1.6%, and the SD is smaller than 0.4 mW. This self‐reference algorithm plays critical role in the practical application of microwave power sensors.

MEMS microwave power sensor with thermovoltage compensation and transformation

An MEMS microwave power sensor with thermovoltage compensation and transformation is presented. The sensor obtains a thermovoltage which is linear to the input power, thanks to the Seebeck effect. However, the thermovoltage decreases as the frequency of input power increases due to the loss. The novelty is that the variation of thermovoltage has been compensated by an algorithm, and a transformation line is obtained to transform the thermovoltage to measured power displayed on liquid crystal display. The result indicates that the relative error is smaller than 1.5%. This system has practical applications in precise power measuring instruments.