Three dimensional capacitance and inductance of MM

With the development of the information age, higher requirements are put forward for the miniaturization, low power consumption and portability of some external discrete components in wireless communication equipment. Nowadays, monolithic microwave integrated circuit (MMIC) technology is usually used to make microwave circuit devices. The characteristics of traditional MMIC technology are: using semi insulating material (GaAs) as insulating substrate; The back of the substrate is metallized and used as the ground. However, MMIC technology also has its inevitable disadvantages: due to the high cost of GaAs, the cost of microwave devices made by MMIC technology is also relatively high; When the frequency is greater than 12GHz, the device must use a through hole to fully contact the ground, and the millimeter wave makes the circuit performance worse through the through hole; In addition, the area of passive devices made by MMIC technology accounts for the vast majority of the whole device; Finally, the Q value of passive components made by MMIC technology is also relatively low

in order to overcome the shortcomings of MMIC technology, people began to have great interest in the research of microelectromechanical system (MEMS) technology. MEMS is a new application basic technology with broad application prospects. Using MEMS technology, the external discrete components in wireless communication equipment can meet the requirements of miniaturization, low power consumption and portability. MEMS adopts deep etching technology to realize the three-dimensional structure of macro machinery, which makes it possible to miniaturize the previous passive devices, while greatly reducing the layout area and making it easier to integrate; Sacrificial layer technology is a very important technology of MEMS, which is the key to making movable and adjustable devices; MEMS devices mainly use Si as the processing material, so we want to deal with this kind of shortcomings, which will greatly reduce the cost of devices made by MMIC technology compared with the traditional ones, and the integration of MEMS is possible due to the support of microelectronics technology. These characteristics of MEMS also determine its continuous development towards miniaturization, diversity and microelectronic technology

according to the characteristics of MEMS and (4) cyclic torque stage MMIC technology, we hope to make a device or circuit that combines the advantages of the two technologies. Because microwave devices and circuits have high requirements for frequency, frequency matching must be carried out before their use, and the individual differences between devices and circuits are large, so the matching work is cumbersome and there is no unified law to follow. The traditional filter has a large layout area and low frequency, so it is ready to design and make a filter made of MEMS technology, which adopts three-dimensional capacitance and high-Q inductance devices, so that the natural frequency of the circuit can be adjusted accurately and conveniently, and the layout area can be effectively reduced to reflect its high integration characteristics

I. design and calculation of filter

filter, as one of the indispensable and important devices in microwave communication, has always been the object of people's efforts to optimize the design. Considering that the filter designed this time will be mainly used in wireless communication equipment, its low-pass cut-off frequency is designed near 2GHz, and the input and output impedance is 50. The following mainly analyzes the design process of Chebyshev filter and Butterworth filter

● the topological diagram of Chebyshev filter is shown in Figure 1 (omitted), and its parameter values are RS =50 (), rl=50 (), c1=2.1 (PF), c2=1.3 (PF), l1=4.4118 (NH), l2=7.0441 (NH) through MATLAB programming and calculation, and the simulation results are shown in Figure 2 (omitted)

● the topological diagram of Butterworth filter is shown in Figure 3 (omitted), and its parameter values are rs=50 (), rl=50 (), c1=1.6 (PF), c2=1.6 (PF), l1=7.9577 (NH) through MATLAB programming and calculation. The simulation results are shown in Figure 4 (omitted)

although the passband of Butterworth filter is relatively stable, the attenuation at the cut-off frequency is large, so it is considered to achieve low attenuation at 2GHz by increasing the cut-off frequency. Through Pspice simulation, we can get that when the cut-off frequency is 4GHz, the attenuation at f=2ghz is small, as shown in Figure 5. 4) the analysis value of the finite element method is in good agreement with the measured value (omitted), so the design parameters obtained by using this cut-off frequency are rs=50, rl=50, c1=0.8pf, c2= 0.8pf, l1=4.0nh. Compared with Chebyshev filter, Butterworth filter has more outstanding advantages after increasing the cut-off frequency. Therefore, this paper will use Butterworth filter for design and calculation

design and calculation of two-dimensional and three-dimensional capacitors

because the performance of capacitors determines the performance of the whole circuit, adjustable capacitors and capacitors whose capacitance values are easy to change have become the development trend of capacitors. A method of adding electrostatic bias voltage to the two plates of the capacitor to change the distance between the plates is proposed, and the two plates of the capacitor can be made into a comb structure to increase its capacity and its change. Due to the large area of passive components in integrated circuits, and it is inconvenient to change its size. Some materials have proposed a stacked capacitor. Although its area has decreased a lot, it is difficult to use multi-layer technology, so this paper proposes a three-dimensional capacitor

considering that the thickness of side medium is thinner than that of horizontal plane, Side medium thickness D3 is

d3=k*d2 (0 K1)

the capacitance value of the three-dimensional capacitor is:

the meaning of the parameters are:

SiO2: dielectric constant of SiO2

L1: width of the groove

L2: width of the boss

W: length of the groove

D1: depth of the groove

D2: thickness of the medium on the horizontal plane

n: number of grooves

A: angle between the side and the bottom of the groove.

k: the ratio of the thickness of the side medium of the groove to the thickness of the bottom medium

can be simplified:

for mining Using the traditional planar capacitor, its capacity value is

, so we can get that under the same area, the competitive advantage of the three-dimensional market depends on the ratio y between the capacitance value of the capacitor and the capacity value of the traditional planar capacitor established in the building and decoration industry

from the section of filter design, it can be seen that when the cut-off frequency is f=4ghz, the calculated capacitance value is 0.8pf, the selected dielectric thickness is 0.3 m, the dielectric constant of SiO2 is 3.8, k=0.8, the steepness is 85o, the selected slot width is 6 m, the boss width is 4 m, the slot depth is 20 m, the number of slots is 4, the transverse width is 35 m, and the two tables on the side are