CN102569951A - Micro electronic mechanical system (MEMS) load line type 2-bit phase shifter based on left-handed transmission line - Google Patents

Abstract

The invention discloses a micro electronic mechanical system (MEMS) load line type 2-bit phase shifter based on a left-handed transmission line, and particularly relates to an MEMS load line type 2-bit phase shifter in order to solve the problems of small phase shift amount and large switching quantity of MEMS switches in the 2-bit phase shifter. A microstrip line comprises a ground plate, a base and a signal wire, wherein a metal layer is covered on the ground plate; the signal wire is fixed on the upper surface of the base and positioned at a middle position of the base along the width direction, and is divided into four sections, and each two adjacent sections are electrically connected with each other through a phase-shifting unit; the phase-shifting unit comprises stub lines, an interdigital capacitor, MEMS switches and a cylindrical metal through hole; and a stub line and an MEMS switch are arranged at two ends of the interdigital capacitor respectively, one end of the stub line is connected with the center of one end of the interdigital capacitor, and a cube contact point is arranged in the middle of the lower surface of a bridge of the MEMS switch and is suspended above the stub line. The MEMS load line type 2-bit phase shifter is used for controlling phase changes of signals.

Description

MEMS load line type 2 phase shifter based on left-handed transmission line

technical field

The invention relates to a MEMS load line type 2 phase shifter, in particular to a MEMS load line type 2 phase shifter based on a left-hand transmission line.

Background technique

The phase shifter is used to control the phase change of the signal. It is the basic component of the wireless communication system and the key component of the phased array radar, microwave and millimeter wave receiver and transmitter. According to the different signal delay mechanism, it can be divided into reflection linear phase shifter, switch linear phase shifter and load linear phase shifter. Among them, the load linear phase shifter controls the phase difference under different load conditions by adjusting the load impedance value. Currently, traditional phase shifters are generally implemented based on PIN diodes, EFT switches or ferrite materials. With the development of information technology, the operating frequency of communication systems such as mobile communication and satellite communication continues to increase. Due to the shortcomings of large size and high power consumption, traditional phase shifters cannot well meet the increasingly stringent performance indicators of communication systems.

Micro-Electro-Mechanical Systems (MEMS) is a new type of interdisciplinary technology developed in recent years, involving microelectronics, mechanics, materials science, mechanics, optics, thermal and other disciplines. It uses the combination of microelectronics technology and micromachining technology to manufacture various microelectronic devices with excellent performance and low price. Compared with traditional PIN diodes and EFT switches, MEMS switches have the advantages of low insertion loss, high isolation, high linearity, and wide operating frequency band. The disadvantages are low reliability and short working life. If the MEMS switch is applied to the design of the phase shifter, it will make the phase shifter have lower loss at any frequency. In addition, because the MEMS switch has good compatibility, it can be integrated with other devices on a chip, which makes the product integrated and miniaturized, and greatly reduces the cost and size. According to the published literature, the number of MEMS switches used in the 2-bit MEMS phase shifter reported so far is relatively large. For example, the 2-bit distributed MEMS phase shifter made by Juo-Jung Hung et al., University of Michigan, USA requires 24 MEMS switches. This will undoubtedly reduce the reliability of the MEMS phase shifter and shorten its working life. Therefore, the current 2-bit MEMS phase shifter has the problems of small MEMS switch phase shift and large number of switches.

Contents of the invention

The purpose of the present invention is to provide a MEMS load line type 2 phase shifter based on the left-hand transmission line in order to solve the problems of small MEMS switch phase shift and large number of switches in the 2-bit MEMS phase shifter.

The MEMS load line type 2 phase shifter based on the left-hand transmission line of the present invention includes a microstrip line and three groups of phase shifting units; the microstrip line includes a ground plate covered with a metal layer, a base and a signal line, and the signal line is fixed on the base and located in the middle of the substrate along the width direction, the signal line is divided into four sections, and the electrical connection is realized through a phase shifting unit between each adjacent two sections;

The phase-shifting unit includes stubs, interdigitated capacitors, MEMS switches and cylindrical metal vias; the stubs and interdigitated capacitors constitute the structural unit of the left-hand transmission line;

A stub and a MEMS switch are respectively set at both ends of the interdigitated capacitor, one end of the stub is connected to the center of one end of the interdigitated capacitor, and the other end of the stub is connected to the ground plate through a cylindrical metal via hole connection, the stub and the interdigitated capacitor are coplanar and vertical;

The two ends of the MEMS switch are respectively fixed on both sides of the corresponding stub line, the position where the two ends of the MEMS switch are connected to the substrate is an anchor area, and each anchor area is provided with a cylindrical metal via, and the cylindrical metal via connects the MEMS One end of the switch is connected to the ground plate, the bridge of the MEMS switch is suspended above the stub, and a cube contact point is arranged in the middle of the lower surface of the bridge, the cube contact point is located directly above the stub, and the cube contact point There is a gap from the stub.

The advantage of the present invention is that each group of phase-shifting units adopts interdigitated capacitors and a pair of through-hole grounded stubs as series capacitors and parallel inductances respectively, and constructs a periodic structural unit of the left-hand transmission line. The grounded stubs of the left-hand transmission line Load the MEMS switch on the top, use its left-hand characteristic and backward wave characteristic, increase the phase shift amount caused by a single MEMS switch, and then reduce the number of MEMS switches used, which helps to improve the reliability of the MEMS phase shifter; through MEMS The switches are opened at the same time, or closed at the same time to adjust the load impedance value of the left-hand transmission line. A group of phase shifting units can achieve a phase shift of 90° at 25GHz; three groups of phase shifting units can be cascaded regularly, and there can be 4 at 25GHz. phase shift states, which are 0°, 90°, 180° and 270° respectively, which realizes the function of 2 phase shifters; in addition, at 25GHz, the insertion loss of the phase shifter in 4 phase shift states is better than -2.1dB, the return loss is less than -10dB. In summary, the MEMS phase shifter based on the left-handed transmission line of the present invention has the advantages of small size, low loss, high phase shifting precision and fewer switches.

Description of drawings

Figure 1 is a top view of the present invention.

Fig. 2 is a schematic diagram of the three-dimensional structure of the present invention.

Fig. 3 is a schematic structural diagram of the phase shifting unit of the present invention.

Fig. 4 is a top view of the structural schematic diagram of the MEMS switch of the present invention when it is closed.

Fig. 5 is a front view of a structural schematic diagram of the MEMS switch of the present invention when it is closed.

Fig. 6 is the phase characteristic curve of phase shifter of the present invention, and wherein, curve A represents the phase characteristic curve of phase shifter when 3 pairs of MEMS switches are closed, and curve B represents when the 1st pair and the 2nd pair of MEMS switch closure, The phase characteristic curve of the phase shifter when the third pair of MEMS switches is off, the curve C represents the phase characteristic curve of the phase shifter when the first pair of MEMS switches are closed, and the second pair and the third pair of MEMS switches are off, and the curve D represents The phase characteristic curve of the phase shifter when all 3 pairs of MEMS switches are off.

Fig. 7 is the insertion loss of phase shifter and the schematic diagram of return loss curve, wherein, four curves indicated by E respectively represent the insertion loss curve schematic diagram of phase shifter of the present invention in four kinds of situations shown in Fig. 6, F indicated The four indicated curves respectively represent the schematic diagrams of the return loss curves of the phase shifter of the present invention under the four situations shown in FIG. 6 .

Detailed ways

Specific Embodiment 1: This embodiment is described in conjunction with Fig. 1, Fig. 2, Fig. 3, Fig. 4 and Fig. 5. The MEMS load line type 2 phase shifter based on the left-hand transmission line described in this embodiment includes a microstrip line 1 and three groups of phase shifting units 2; the microstrip line 1 includes a ground plate 1-1 covered with a metal layer, a substrate 1-2 and a signal line 1-3, and the signal line 1-3 is fixed on the upper surface of the substrate 1-2, And located in the middle of the substrate 1-2 along the width direction, the signal line 1-3 is divided into four sections, and the electrical connection is realized through a phase shifting unit 2 between each adjacent two sections;

The phase shifting unit 2 includes a stub 2-1, an interdigitated capacitor 2-2, a MEMS switch 2-3 and a cylindrical metal via 2-4; the stub 2-1 and the interdigitated capacitor 2-2 form a left-hand transmission line structural unit;

A stub 2-1 and a MEMS switch 2-3 are respectively arranged at both ends of the interdigitated capacitor 2-2, and one end of the stub 2-1 is connected to the center of one end of the interdigitated capacitor 2-2, and the short The other end of the stub 2-1 is connected to the ground plate 1-1 through a cylindrical metal via 2-4, and the stub 2-1 is coplanar and vertical to the interdigitated capacitor 2-2;

The two ends of the MEMS switch are respectively fixed on both sides of the corresponding stub line 2-1, the position where the two ends of the MEMS switch are connected to the substrate 1-2 is an anchor area, and each anchor area is provided with a cylindrical metal via hole 2-4, The cylindrical metal via 2-4 connects one end of the MEMS switch to the ground plate 1-1, and the bridge 2-3-1 of the MEMS switch 2-3 is suspended above the stub 2-1, and the bridge 2 - The middle of the lower surface of 3-1 is provided with a cube contact point 2-3-2, the cube contact point 2-3-2 is located directly above the stub line 2-1, and the cube contact point 2-3-2 is connected to There is a gap between the stubs 2-1.

Each group of phase-shifting units uses interdigitated capacitors 3-2 and a pair of via-grounded stubs 3-1 as series capacitors and parallel inductances, respectively, to construct a periodic structural unit of the left-hand transmission line. According to the working principle of the load line phase shifter, the length of the grounding stub 3-1 is changed through the MEMS switch 3-3, so as to accurately control the phase difference under different load conditions and realize the phase shifting function.

The pair of stub wires 3-1 are connected to the metal ground plate of the base through the technology of cylindrical metal vias to form a shunt inductor. When the MEMS switch 3-3 is applied with a DC drive voltage, the MEMS switch 3-3 is closed due to the electrostatic force, so that the cube contact point 3-3-2 of the MEMS switch 3-3 is connected to the grounded stub 3- 1 contact, so as to change the load impedance value of the left-hand transmission line by adjusting the length of the ground stub to achieve the effect of phase shifting.

Embodiment 2: The difference between this embodiment and the MEMS load line type 2 phase shifter based on the left-hand transmission line described in Embodiment 1 is that the distance between the centers of adjacent single phase shifting units 2 is 800 μm.

Embodiment 3: This embodiment is different from the MEMS load line type 2 phase shifter based on the left-hand transmission line described in Embodiment 1 in that the length of the phase shifter is 3.0mm, the width is 1.8mm, and the height is 0.234mm .

Embodiment 4: The difference between this embodiment and the MEMS load line type 2 phase shifter based on the left-hand transmission line described in Embodiment 1 is that the width and thickness of the signal lines 1-3 of the microstrip line 1 are 200 μm and 200 μm respectively. 2 μm, the material of the signal lines 1-3 of the microstrip line 1 is gold or copper.

Embodiment 5: The difference between this embodiment and the MEMS load line type 2 phase shifter based on the left-hand transmission line described in Embodiment 1 is that the thickness of the ground plate 1-1 is 2 μm, and the material of the metal layer for gold or copper.

Embodiment 6: The difference between this embodiment and the MEMS load line type 2 phase shifter based on the left-hand transmission line described in Embodiment 1 is that the substrate 1-2 is made of silicon with a dielectric constant of 11.9 and a thickness of 230 μm.

Embodiment 7: This embodiment is described in conjunction with FIG. 3 . The difference between this embodiment and the MEMS load line type 2 phase shifter based on the left-hand transmission line described in Embodiment 1 is that the interdigitated capacitance of the phase shifting unit 2 is 2- 2. It consists of 10 metal strips arranged in a staggered manner. The length of each metal strip is 188 μm, the width is 11 μm, and the thickness is 2 μm. The distance between the metal strips is 10 μm; The signal line 1-3 of the microstrip line 1 is connected, and the distance between the other end and the signal line 1-3 of the microstrip line 1 on the other side of the interdigitated capacitor is 2 μm; The distance between the signal lines 1-3 of the microstrip line 1 on one side is 2 μm, and the other end is connected to the signal lines 1-3 of the microstrip line 1 on the other side of the interdigitated capacitor; the material of the metal strip is gold or copper.

Embodiment 8: The difference between this embodiment and the MEMS load line type 2 phase shifter based on the left-hand transmission line described in Embodiment 1 is that the stub 2-1 of the phase shifting unit 2 has a length of 320 μm and a width of 10μm, the thickness is 2μm; the stub material is gold or copper.

Embodiment 9: The difference between this embodiment and the MEMS load line type 2 phase shifter based on the left-hand transmission line described in Embodiment 1 is that the inner diameter of the cylindrical metal via hole 2-4 is 30 μm, and the cylindrical metal via hole The material of 2-4 is gold or copper.

Embodiment 10: This embodiment is described in conjunction with FIG. 4 and FIG. 5. The difference between this embodiment and the MEMS load line type 2 phase shifter based on the left-hand transmission line described in Embodiment 1 is that the cube of the MEMS switch 2-3 The straight-line distance between the center of the contact point 2-3-2 and one end of the stub 2-1 is equal to 30 μm, and one end of the stub 2-1 is the end connected to the interdigitated capacitor 2-2; the bridge 2-3 -1 has a length of 100 μm, a width of 20 μm, and a thickness of 2 μm; a cube contact point 2-3-1 has a length of 4 μm, a width of 4 μm, and a thickness of 2 μm; the cube contact point 2-3-1 is connected to the stub 2- The gap between 1 is 2 μm.

The working principle of the present invention is as follows: at 25GHz, for each group of phase shifting units, a pair of MEMS switches are in two states of opening and closing at the same time to realize a 90° phase shift. When all three pairs of MEMS switches are off, the phase is -76.3°; when the first pair of MEMS switches is closed, and the second and third pairs of MEMS switches are off, the phase is 12.4°; the first pair and the second pair of MEMS switches When the third pair of MEMS switches is closed, the phase is 105.1°; when all three pairs of MEMS switches are closed, the phase is 195.5°. At 25GHz, the insertion loss of these four cases is better than -2.1dB and the return loss is lower than -10dB. Therefore, the four phase shift states are 0°, 90°, 180° and 270° respectively, which is a 2-phase shifter.

The structure of the MEMS load line type 2-phase shifter based on the left-handed transmission line of the present invention is not limited to the specific structures described in the above-mentioned embodiments, but may also be a reasonable combination of the technical features described in the above-mentioned embodiments.

Claims (10)

1. The MEMS load line type 2 phase shifter based on left-handed transmission line, it comprises microstrip line (1) and three groups of phase shifting units (2); Microstrip line (1) comprises the ground plate (1- 1), the base (1-2) and the signal line (1-3), the signal line (1-3) is fixed on the upper surface of the base (1-2), and is located in the middle of the base (1-2) along the width direction position, the signal line (1-3) is divided into four sections, and the electrical connection is realized by a phase shifting unit (2) between every adjacent two sections; it is characterized in that, The phase shifting unit (2) comprises a stub (2-1), an interdigitated capacitor (2-2), a MEMS switch (2-3) and a cylindrical metal via (2-4); the stub (2- 1) and the interdigitated capacitance (2-2) constitute the structural unit of the left-hand transmission line; A stub (2-1) and a MEMS switch (2-3) are respectively arranged at the two ends of the interdigitated capacitor (2-2), and one end of the stub (2-1) is connected to the interdigitated capacitor (2-2). 2) is connected at the center of one end, the other end of the stub (2-1) is connected to the ground plate (1-1) through a cylindrical metal via (2-4), and the stub (2-1) Coplanar and perpendicular to the interdigitated capacitor (2-2); The two ends of the MEMS switch are respectively fixed on both sides of the corresponding stub line (2-1), the position where the two ends of the MEMS switch are connected to the substrate (1-2) is an anchor area, and each anchor area is provided with a cylindrical metal via hole (2-4), the cylindrical metal via hole (2-4) connects one end of the MEMS switch to the ground plate (1-1), and the bridge (2-3-1) of the MEMS switch (2-3) Suspended above the stub line (2-1), the middle of the lower surface of the bridge (2-3-1) is provided with a cube contact point (2-3-2), and the cube contact point (2-3-2) Located directly above the stub line (2-1), there is a gap between the cube contact point (2-3-2) and the stub line (2-1). 2. The MEMS load line type 2 phase shifter based on left-handed transmission line according to claim 1, characterized in that the distance between the centers of adjacent single phase shifting units (2) is 800 μm. 3. The MEMS load line type 2 phase shifter based on left-hand transmission line according to claim 1, characterized in that the length of the phase shifter is 3.0mm, the width is 1.8mm and the height is 0.234mm. 4. The MEMS load line type 2 phase shifter based on the left-handed transmission line according to claim 1, characterized in that the width and the thickness of the signal line (1-3) of the microstrip line (1) are respectively 200 μm and 2 μm, The material of the signal lines (1-3) of the microstrip line (1) is gold or copper. 5. the MEMS load line type 2 phase shifter based on left-handed transmission line according to claim 1, is characterized in that, the thickness of described ground plate (1-1) is 2 μ m, and the material of described metal layer is gold or copper . 6. The MEMS load line type 2 phase shifter based on the left-handed transmission line according to claim 1, characterized in that the substrate (1-2) is made of silicon with a dielectric constant of 11.9 and a thickness of 230 μm. 7. the MEMS load line type 2 phase shifter based on left-hand transmission line according to claim 1, is characterized in that, the interdigitated capacitance (2-2) of phase shift unit (2) is formed by staggered arrangement of 10 metal strips, The length of each metal strip is 188 μm, the width is 11 μm, and the thickness is 2 μm. The distance between the metal strips is 10 μm; one end of the metal strips arranged in an odd number and the signal line of the microstrip line (1) on the side of the interdigitated capacitor (1-3) connection, the distance between the other end and the signal line (1-3) of the microstrip line (1) on the other side of the interdigitated capacitor is 2 μm; The distance between the signal lines (1-3) of the microstrip line (1) is 2 μm, and the other end is connected to the signal line (1-3) of the microstrip line (1) on the other side of the interdigitated capacitance; the material of the metal strip for gold or copper. 8. The MEMS load line type 2 phase shifter based on the left-handed transmission line according to claim 1, characterized in that the length of the stub (2-1) of the phase shifting unit (2) is 320 μm, the width is 10 μm, and the thickness is 2 μm; the stub (2-1) is made of gold or copper. 9. the MEMS load line type 2 phase shifter based on left-handed transmission line according to claim 1, is characterized in that, the internal diameter of cylindrical metal via hole (2-4) is 30 μ m, and cylindrical metal via hole (2-4 ) is gold or copper. 10. the MEMS load line type 2 phase shifter based on left-handed transmission line according to claim 1, is characterized in that, the center of the cube contact point (2-3-2) of MEMS switch (2-3) and stub line The linear distance of one end of (2-1) is equal to 30 μ m, and one end of described stub line (2-1) is an end connected with interdigitated capacitance (2-2); The length of bridge (2-3-1) is 100 μm, width 20 μm, thickness 2 μm; cube contact point (2-3-1) has length 4 μm, width 4 μm, thickness 2 μm; cube contact point (2-3-1) and stub (2- 1) The gap between them is 2 μm.

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