CN103048540A - Online microwave frequency detector and detecting method thereof based on cantilever beam and direct-type power sensor - Google Patents

Abstract

The invention discloses an online microwave frequency detector and a detecting method thereof based on a cantilever beam and a direct-type power sensor. The detector is prepared on a GaAs substrate and comprises coplanar waveguide (CPW) transmission lines, four micro-electromechanical system (MEMS) cantilever beam structures of the completely same structure, a power combiner and three MEMS direct-type microwave power sensors of the completely same structure. The micro-electronic mechanical online microwave frequency detector provided by the invention not only has the advantages of being novel in structure and smaller in size, but also can realize online detection on a microwave signal frequency, and can be compatible with a GaAs single wafer microwave integrated circuit.

Description

Online microwave frequency detector and detection method thereof based on semi-girder and direct-type power sensor

Technical field

The invention belongs to microelectromechanical systems MEMS technical field, be a kind of online microwave frequency detector and detection method thereof based on semi-girder and direct-type power sensor.

Background technology

In research of microwave technology, amplitude, phase place and frequency are the three basic parameters that characterizes microwave signal, wherein, frequency has very important effect in the research of microwave signal, and frequency detector all can be used in the fields such as military and national defense, business correspondence and scientific research.Process of heterodyning, counting method and resonance method principle are mainly adopted in the design of microwave frequency detector, and outstanding advantage is that precision is higher, frequency band is wider, but common complex structure can't be realized the online detection of microwave frequency.Along with the development of science and technology, require more and more higher to modern PCS Personal Communications System and radar system: simple in structure, circuit size microwave frequency detector little and that can detect online becomes new study hotspot.In recent years, along with the fast development of MEMS technology, and the MEMS cantilever beam structure conducted in-depth research, make the online microwave frequency detector based on semi-girder and direct-type power sensor become possibility.

Summary of the invention

The problem to be solved in the present invention is: existing microwave signal frequency detects and has the shortcoming that can't detect online, and the user needs simple structure, less volume and the microwave frequency detector that can detect online.

Technical scheme of the present invention is: based on the online microwave frequency detector of semi-girder and direct-type power sensor, be provided with the measured signal transmission line at the GaAs substrate, four identical MEMS cantilever beam structures of structure, a merit is closed device and three the identical MEMS direct-type of structure microwave power detectors, the measured signal transmission line is the CPW transmission line, described CPW transmission line is made of signal wire and ground wire, microwave signal to be measured is by the measured signal transmission line, four MEMS cantilever beam structures are divided into two pairs, symmetry is suspended from the signal wire top of measured signal transmission line, two the MEMS cantilever beam structures in signal wire the same side that wherein are positioned at the measured signal transmission line connect respectively a MEMS direct-type microwave power detector, two MEMS cantilever beam structures of opposite side symmetry are connected to respectively merit and close device, and the output terminal that merit is closed device connects a MEMS direct-type microwave power detector.

As preferably, along measured signal transmission line direction, centered by the distance L between the two pairs of MEMS cantilever beam structures 1/4 of Frequency point institute corresponding wavelength, described center frequency points refers to the center frequency points of the frequency detecting scope of described microwave frequency detector.

The MEMS cantilever beam structure closes between device and the MEMS direct-type microwave power detector with merit and is connected by the CPW transmission line, and merit is closed between device and the MEMS direct-type microwave power detector and is connected by the CPW transmission line; Cantilever beam structure comprises semi-girder and anchor district, is provided with insulating medium layer between the signal wire of the measured signal transmission line of semi-girder and below.

Merit is closed device and is comprised asymmetric coplanar stripline ACPS signal wire, ground wire and isolation resistance, and merit is closed and is asymmetric coplanar stripline ACPS signal wire between the input end of device and the output terminal, and isolation resistance is arranged between two input ends.

A kind of detection method of above-mentioned online microwave frequency detector based on semi-girder and direct-type power sensor, microwave signal to be measured from the measured signal transmission line through out-of-date, two MEMS cantilever beam structures that are positioned at signal wire the same side of measured signal transmission line are coupled out the microwave signal that two amplitudes equate, exist certain phase differential online, input respectively a MEMS direct-type microwave power detector, measure the microwave signal power P that is coupled out separately by cantilever beam structure ₁, P ₂Two MEMS cantilever beam structures that are positioned at described signal wire opposite side are coupled out two same microwave signals online, and input work is closed device, and to carry out vector synthetic, inputs a MEMS direct-type microwave power detector again, measures the power P by composite signal ₃There is a phase differential that is directly proportional with microwave signal frequency to be measured in described two microwave signals

Merit is closed the power P of the composite signal of device ₃With this phase differential

The relation that has a cosine function:

MEMS direct-type microwave power detector is based on Seebeck principle detection power P ₁, P ₂And P ₃Size, and with DC voltage V ₁, V ₂And V ₃The formal output measurement result, based on formula (1), the frequency of microwave signal to be measured is:

$f=\frac{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="HDA00002770275300011.png,HDA00002770275300012.png"\; state="\{\{state\}\}">c</figure-callout>}}{2\mathrm{\&pi;L}\sqrt{{\mathrm{\&epsiv;}}_{\mathrm{er}}}}\arccos \frac{V_3-\frac{1}{2}{V}_1-\frac{1}{2}{V}_2}{\sqrt{V_1{V}_2}}---\left(2\right)$

Wherein, c is the light velocity, ε _ErEffective dielectric constant for the CPW transmission line.

The invention provides a kind of online microwave frequency detector and preparation method based on semi-girder and direct-type power sensor, be positioned at CPW transmission line top and equate, exist the microwave signal of a phase differential at a distance of the identical MEMS semi-girder of four structures of a segment distance two pairs of amplitudes that are coupled out online, a supported signal of getting every centering wherein closes device through merit, and to carry out vector synthetic.Detected the watt level of synthetic rear microwave signal and other two microwave signals by three the identical MEMS direct-type of structure microwave power detectors.According to the size of the DC voltage of exporting, infer the frequency of measured signal.Online microwave frequency detector based on semi-girder and direct-type power sensor of the present invention not only has novel structure, the advantage that is easy to measure, and can realize online detection to microwave signal frequency, be easy to integrated and with the advantage of GaAs monolithic integrated microwave circuit compatibility.

Description of drawings

Fig. 1 is the structural representation that the present invention is based on the online microwave frequency detector of semi-girder and direct-type power sensor.

Fig. 2 is the A-A' sectional view among Fig. 1.

Fig. 3 is the B-B' sectional view among Fig. 1.

Embodiment

The present invention is produced on the GaAs substrate 1, has co-planar waveguide CPW transmission line, four the identical MEMS cantilever beam structures of structure, merits to close device and three the identical MEMS direct-type of structure microwave power detectors thereon.The CPW transmission line is as the signal transmssion line of frequency detector of the present invention, be used for the transmission of microwave signal to be measured, and the transmission of closing signal between device and the MEMS direct-type microwave power detector of MEMS cantilever beam structure, merit, the CPW transmission line is made of signal wire and ground wire.

Four identical MEMS semi-girders of structure are positioned at the top of the insulating medium layer 6 on the signal wire 2 of measured signal transmission line.When microwave signal process measured signal transmission line to be measured, it is identical but have the microwave signal of certain phase differential to be coupled out two amplitudes along measured signal transmission line two cantilever beam structures separated by a distance, it is synthetic to close the device vector through merit again, the poor cosine function relation that exists of the power of composite signal and microwave signal phase to be measured.In order to measure the size of the microwave signal power that is coupled out by cantilever beam structure, opposite side at the signal wire of measured signal transmission line has designed two identical cantilever beam structures of structure symmetrically, respectively be connected to MEMS direct-type microwave power detector, measure the signal power that cantilever beam structure is coupled out thereafter.Utilize the direct-type microwave power detector to detect the size of synthetic power, finally realize the detection of microwave signal frequency to be measured.

The specific embodiments of the online microwave frequency detector based on semi-girder and direct-type power sensor of the present invention is as follows:

Such as Fig. 1, the present invention includes: GaAs substrate 1, CPW signal wire 2, ground wire 3, MEMS semi-girder 4, anchor district 5, insulating medium layer 6, power splitter isolation resistance 7, ACPS signal wire 8, semiconductor thermocouple arm 9, terminal resistance 10, direct current IOB 11, isolated dc capacitor 12.Fig. 2 and Fig. 3 are the side cut away view of Fig. 1.

The CPW transmission line comprises signal wire 2 and ground wire 3.The measured signal transmission line adopts the CPW transmission line, and microwave signal to be measured enters the CPW transmission line from the input end of measured signal transmission line, is exported by output terminal again.

The MEMS cantilever beam structure comprises semi-girder 4 and anchor district 5.Along the measured signal transmission line, the two pairs of semi-girders 4 at a distance of certain distance L are suspended from the top of insulating medium layer 6 on the signal wire 2 of measured signal transmission line, as preferably, centered by the distance L 1/4 of Frequency point institute corresponding wavelength, described center frequency points refers to the center frequency points of the frequency detecting scope of described microwave frequency detector.When measured signal from the signal wire of measured signal transmission line through out-of-date, four identical MEMS semi-girders 4 of structure are coupled out the microwave signal that two pairs of amplitudes equate, exist certain phase differential online, getting a input work in every pair of microwave signal, to close the device vector synthetic.In order to measure the microwave signal power that is coupled out by semi-girder 4, another in the every pair of microwave signal connects respectively a MEMS direct-type microwave power detector.

Merit is closed device and is comprised asymmetric coplanar stripline ACPS signal wire 8, ground wire 3 and isolation resistance 7.The effect that merit is closed device is that two microwave signal vectors that the MEMS cantilever beam structure is coupled out are synthesized.When microwave signal to be measured is passed through the signal wire of measured signal transmission line, because two semi-girders of the same side on the signal wire have certain distance L, there is a phase differential that is directly proportional with microwave signal frequency to be measured in two microwave signals that are coupled out, described phase differential be that L is corresponding, L fixedly the time phase differential be a definite value, merit is closed the power P of the composite signal of device output ₃Relation with a cosine function of this phase differential existence:

Wherein, P ₁, P ₂Be respectively the power of the microwave signal that the opposite side MEMS semi-girder on the signal wire is coupled out.So the power that MEMS direct-type microwave power detector obtains is corresponding with microwave signal to be measured.

MEMS direct-type microwave power detector comprises semiconductor thermocouple arm 9, terminal resistance 10, direct current IOB 11 and isolated dc capacitor 12.MEMS direct-type microwave power detector is based on Seebeck principle detection power P ₁, P ₂And P ₃Size, and with DC voltage V ₁, V ₂And V ₃The formal output measurement result.Based on equation (1), the frequency of measured signal can be expressed as,

$f=\frac{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="HDA00002770275300011.png,HDA00002770275300012.png"\; state="\{\{state\}\}">c</figure-callout>}}{2\mathrm{\&pi;L}\sqrt{{\mathrm{\&epsiv;}}_{\mathrm{er}}}}\arccos \frac{V_3-\frac{1}{2}{V}_1-\frac{1}{2}{V}_2}{\sqrt{V_1{V}_2}}---\left(2\right)$

Wherein, c is the light velocity, ε _ErEffective dielectric constant for the CPW transmission line.

The preparation method who the present invention is based on the online microwave frequency detector of semi-girder and direct-type power sensor is:

1) prepares gallium arsenide substrate: select the semi-insulating GaAs substrate of extension, wherein extension N ⁺The doping content of gallium arsenide is 10 ¹⁸Cm ^-3, its square resistance is 100～130 Ω/;

2) photoetching and isolate the N of extension ⁺Gallium arsenide, the figure of the semiconductor thermocouple arm of formation thermoelectric pile;

3) anti-carve N ⁺Gallium arsenide, forming its doping content is 10 ¹⁷Cm ^-3The semiconductor thermocouple arm of thermoelectric pile;

4) photoetching: removal will keep the photoresist in tantalum nitride place;

5) sputter tantalum nitride, its thickness are 1 μ m;

6) peel off;

7) photoetching: removal will keep the photoresist in the place of ground floor gold;

8) evaporation ground floor gold, its thickness is 0.3 μ m;

9) peel off, form CPW signal wire and ground wire, the anchor district of MEMS semi-girder;

10) anti-carve tantalum nitride, form terminal resistance and isolation resistance, its square resistance is 25 Ω/;

11) deposit silicon nitride: with plasma-enhanced chemical vapour deposition technique (PECVD) growth

Thick silicon nitride medium layer;

12) photoetching and etch silicon nitride dielectric layer: be retained in the silicon nitride on the CPW signal wire of MEMS semi-girder below, and the medium silicon nitride of the isolated dc capacitor of direct-type power sensor;

13) deposit and photoetching polyimide sacrificial layer: apply the thick polyimide sacrificial layer of 1.6 μ m in gallium arsenide substrate, pit is filled up in requirement, and the thickness of polyimide sacrificial layer has determined that MEMS semi-girder and its below are in the distance between the silicon nitride medium layer on the main line CPW; The photoetching polyimide sacrificial layer only keeps the sacrifice layer of semi-girder below;

14) evaporation titanium/gold/titanium, its thickness is

Evaporation is used for the down payment of plating;

15) photoetching: removal will be electroplated local photoresist;

16) electrogilding, its thickness are 2 μ m;

17) remove photoresist: removing does not need to electroplate local photoresist;

18) anti-carve titanium/gold/titanium, the corrosion down payment forms CPW signal wire, ground wire, MEMS semi-girder and direct current IOB;

19) with this gallium arsenide substrate thinning back side to 100 μ m;

20) discharge polyimide sacrificial layer: developer solution soaks, and removes the polyimide sacrificial layer under the MEMS semi-girder, and deionized water soaks slightly, and the absolute ethyl alcohol dehydration is volatilized under the normal temperature, dries.

Above-mentioned steps adopts the processes well known in the MEMS technology, no longer describes in detail.

Distinguish whether to be the standard of structure of the present invention as follows:

The online microwave frequency detector of microelectron-mechanical of the present invention has four identical MEMS cantilever beam structures and three identical MEMS direct-type microwave power detectors.When microwave signal process CPW transmission line to be measured, it is identical but have the microwave signal of certain phase differential that two identical semi-girders separated by a distance and that be suspended from CPW transmission line signals line top are coupled out two amplitudes, close device through a merit again, there are the cosine function relation in the power of composite signal and phase differential.In order to measure the size of the microwave signal power that is coupled out by semi-girder, designed symmetrically two identical cantilever beam structures of structure at the opposite side of signal wire, be connected to respectively thereafter MEMS direct-type microwave power detector.Utilize the direct-type microwave power detector to detect the size of coupled power and synthetic power, finally realize the detection of microwave signal frequency to be measured.

The structure that satisfies above condition namely is considered as online microwave frequency detector and the detection method based on semi-girder and direct-type power sensor of the present invention.

Claims (6)

1. based on the online microwave frequency detector of semi-girder and direct-type power sensor, it is characterized in that being provided with the measured signal transmission line at the GaAs substrate, four identical MEMS cantilever beam structures of structure, a merit is closed device and three the identical MEMS direct-type of structure microwave power detectors, the measured signal transmission line is the CPW transmission line, described CPW transmission line is made of signal wire and ground wire, microwave signal to be measured is by the measured signal transmission line, four MEMS cantilever beam structures are divided into two pairs, symmetry is suspended from the signal wire top of measured signal transmission line, two the MEMS cantilever beam structures in signal wire the same side that wherein are positioned at the measured signal transmission line connect respectively a MEMS direct-type microwave power detector, two MEMS cantilever beam structures of opposite side symmetry are connected to respectively merit and close device, and the output terminal that merit is closed device connects a MEMS direct-type microwave power detector.

2. the online microwave frequency detector based on semi-girder and direct-type power sensor according to claim 1, it is characterized in that along measured signal transmission line direction, centered by the distance L between the two pairs of MEMS cantilever beam structures 1/4 of Frequency point institute corresponding wavelength, described center frequency points refers to the center frequency points of the frequency detecting scope of described microwave frequency detector.

3. the online microwave frequency detector based on semi-girder and direct-type power sensor according to claim 1 and 2, it is characterized in that MEMS cantilever beam structure and merit are closed between device and the MEMS direct-type microwave power detector is connected by the CPW transmission line, and merit is closed between device and the MEMS direct-type microwave power detector and is connected by the CPW transmission line; Cantilever beam structure comprises semi-girder and anchor district, is provided with insulating medium layer between the signal wire of the measured signal transmission line of semi-girder and below.

4. the online microwave frequency detector based on semi-girder and direct-type power sensor according to claim 1 and 2, it is characterized in that merit closes device and comprise asymmetric coplanar stripline ACPS signal wire, ground wire and isolation resistance, merit is closed and is asymmetric coplanar stripline ACPS signal wire between the input end of device and the output terminal, and isolation resistance is arranged between two input ends.

5. the online microwave frequency detector based on semi-girder and direct-type power sensor according to claim 3, it is characterized in that merit closes device and comprise asymmetric coplanar stripline ACPS signal wire, ground wire and isolation resistance, merit is closed and is asymmetric coplanar stripline ACPS signal wire between the input end of device and the output terminal, and isolation resistance is arranged between two input ends.

6. the detection method of each described online microwave frequency detector based on semi-girder and direct-type power sensor of a claim 1-5, it is characterized in that microwave signal to be measured from the measured signal transmission line through out-of-date, two MEMS cantilever beam structures that are positioned at signal wire the same side of measured signal transmission line are coupled out the microwave signal that two amplitudes equate, exist certain phase differential online, input respectively a MEMS direct-type microwave power detector, measure the microwave signal power P that is coupled out separately by cantilever beam structure ₁, P ₂Two MEMS cantilever beam structures that are positioned at described signal wire opposite side are coupled out two same microwave signals online, and input work is closed device, and to carry out vector synthetic, inputs a MEMS direct-type microwave power detector again, measures the power P by composite signal ₃There is a phase differential that is directly proportional with microwave signal frequency to be measured in described two microwave signals

Merit is closed the power P of the composite signal of device ₃With this phase differential

The relation that has a cosine function:

MEMS direct-type microwave power detector is based on Seebeck principle detection power P ₁, P ₂And P ₃Size, and with DC voltage V ₁, V ₂And V ₃The formal output measurement result, based on formula (1), the frequency of microwave signal to be measured is:

$f=\frac{c}{2\mathrm{\&pi;L}\sqrt{{\mathrm{\&epsiv;}}_{\mathrm{er}}}}\arccos \frac{V_3-\frac{1}{2}{V}_1-\frac{1}{2}{V}_2}{\sqrt{V_1{V}_2}}---\left(2\right)$

Wherein, c is the light velocity, ε _ErEffective dielectric constant for the CPW transmission line.

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