Frequency tracking circuit of CMUT resonant biochemical sensor

Abstract

The invention discloses a frequency tracking circuit of a CMUT resonant biochemical sensor, and the circuit comprises a bias network, an impedance matching network, a CMUTs network, a load capacitancenetwork and a BJT amplification feedback network, wherein the bias network provides DC voltage for the CMUTs and avoids current overload; the impedance matching network tunes to make the CMUTs form aseries-parallel resonant region; and positive feedback of an oscillating signal is formed based on the BJT and the load capacitance network to realize real-time output of the oscillating signal of the CMUTs parallel resonance point. The frequency tracking circuit provided by the invention enables the CMUTs to form a series-parallel resonant region at a low voltage, and the resonant circuit is simple and convenient, the starting time is microsecond, and the CMUTs resonant frequency can be output in real time, which is of great significance for portable and real-time detection applications based on CMUTs resonant biochemical sensors.

Description

technical field [0001] The invention belongs to the technical field of MEMS sensor electronic measurement, and in particular relates to a frequency tracking circuit of a CMUTs (Capacitive Micromachined Ultrasonic Transducers, capacitive micromachined ultrasonic transducer) resonant biochemical sensor. Background technique [0002] In recent years, CMUTs have been applied in the field of resonant biochemical substance detection, which has the characteristics of high quality factor. After coating with functional materials, the detection sensitivity of CMUTs resonant biochemical sensors can reach ppt level. The cell size of CMUTs based on MEMS technology is only tens of μm, and large-scale arrays can be realized. Designing a frequency tracking circuit for real-time output is the key to the real-time monitoring application of CMUTs resonant biochemical sensors. [0003] Foreign research institutions have carried out some research on CMUTs frequency tracking circuit, but there is...

AI Technical Summary

Problems solved by technology

North Carolina State University designed a CMUTs resonant circuit based on the Colpitts oscillation theory. The CMUTs bias voltage is 35V, and the thickness of the functionalized material is 100nm. It realizes the real-time output of the working frequency of 4.35MHz, but the circuit is not loaded with an impedance matching network. It can only work above the bias voltage at the phase zero crossing point, limited by the bias voltage, and the oscillation startup time is long (millisecond level)

2015 Based on this theory, the research group designed a multi-channel CMUTs resonant circuit with a bias voltage as high as 40V, which met the resonant conditions and detected toluene, but the power consumption was huge

However, when the loaded DC bias voltage is low, its vibration amplitude is small, the influence of capacitance parasitics is large, and the reactance is capacitive in the series and parallel resonance regions, which directly makes it difficult to resonate at low voltage and cannot work normally.

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