A MEMS microwave phase detector with broadband performance operable at X‐band

Abstract

This letter presents the design, fabrication, and measurement of a broadband MEMS microwave phase detector for X-band, 8-12 GHz. In order to realize the broadband performance, a two-section power combiner is designed and utilized for the configuration of the phase detector. Stable sensitivities of phase detection are revealed by measurements within the bandwidth 8-12 GHz. The sensitivities are all better than 7.1, 22.1, 33.4, 42.0, and 51.2 mV/mW at 10, 50, 100, 150, and 200 mW input power, respectively. Moreover, the discrepancies are less than 1. 8, 5.1, 7.3, 9.3, and 10.9 mV/mW at the above powers for different frequencies. The measured output voltage versus the phase difference at 200 mW, 10 GHz is normalized and compared to the theoretical value. The relative error is less than 8.5%. The response times of this presented phase detector are also obtained by measurement. . However, they suffer from small dynamic range, large power consumption, and difficulties to fabricate as an IC, respectively. The MEMS technology provides a solution to these problems. A MEMS microwave phase detector fabricated by micromachining processes have been presented by our group [5]. It consists of a power combiner operator based on vector combination and a thermoelectric power sensor based on Seebeck effect. However, this phase detector was designed and optimized at the center frequency of 10 GHz and suffers from performance degradation at the other frequencies of X-band. Thus, it cannot satisfy the urge for broadband phase detection components in modern communication systems.For these reasons, this paper presents the design, fabrication, and measurement verification of a MEMS microwave phase detector with broadband detection range for the whole X-band, 8-12 GHz. The novelty of this phase detector is that, a twosection power combiner is designed and utilized in order to realize the broadband performance. The fabrication process is completely compatible with the GaAs MMIC technology. Measurements are performed for this phase detector over 8-12 GHz. The output responses of phase detection show cosine relationship versus the phase differences, which is in accordance with the theory. The phase detection sensitivities within the measured bandwidth are rather stable at low frequencies and show slight variation when the frequency increases. Moreover, this letter presents an experimental study of the response time at different input powers. DESIGN AND FABRICATIONA MEMS microwave phase detector is composed of a power combiner and a thermoelectric power sensor, among which the power combiner is the factor element in determining the phase detection bandwidth. Thus, it is essential to adopt a power combiner that can maintain good performance over X-band instead of the traditional power combiner which is matched and optimized at one signal center frequency [6]. According to the study in Ref. 7, the bandwidth of a power combiner can be broadened by cascading multi-section matching networks.Thus, the basic idea for the architecture of...

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