Two-way type frequency reconfigurable meander line antenna
Technical Field
The invention discloses a two-way type frequency reconfigurable meander line antenna, which can be switched among eight different working frequency bands, and belongs to the technical field of basic electrical elements.
Background
The quality requirement of wireless communication is continuously increasing, and the antenna is an indispensable part in the wireless communication system, so that the communication quality of the whole wireless communication system can be greatly influenced by improving the antenna. The conventional antenna is generally designed to be used with a single function, and nowadays, the antenna which tends to be more and more multifunctional cannot meet the frequency requirements under different mobile communication systems. The reconfigurable antenna becomes a better solution for a series of problems caused by diversified frequency requirements and shortage of spectrum resources. The reconfigurable antenna can improve the main performance index of the antenna to meet various frequency requirements of different mobile communication systems, improve the system performance, reduce the occupied space of the system, simplify the system structure, and ensure that the antenna is matched with an adjacent module and is flexible and adjustable. In addition, the antenna with the reconfigurable characteristic can not only reduce the number of antennas in a communication system, but also be used under complex environmental conditions. The miniaturization of communication systems generally has the characteristics of good concealment, convenient movement, easy integration and convenient arrangement, and generally depends on the miniaturization of antennas, so the miniaturization of antennas is very important.
In 1981, d.schaubert et al first proposed a "reconfigurable antenna" in "frequency reconfigurable, polarization diversity antenna and frequency swept array". The frequency reconfigurable antenna has the name that the working frequency can be adjusted according to different use conditions on the premise that other parameters are not changed, so that the multiband or ultra-wideband characteristic of the antenna is realized. Generally, a way to achieve frequency reconfiguration is to add a switch element in the antenna layout, change the equivalent structure of the antenna by controlling the on and off of the switch, achieve different working states, and then change the electrical performance parameters of the antenna. For example, Huda a.majid et al published 2012 a article "a Compact Frequency-Reconfigurable multirow band micro Slot Antenna" also implements Frequency reconfiguration by changing the effective electrical length of a ground Slot on the basis of a Microstrip monopole sub-line Antenna, but each operating bandwidth is narrow, and up to 5 PIN diode switches are used, and only 6 different operating states are implemented. In addition, I-Fong Chen et al 2011 published a "Compact Modified penta band and means-Line Antenna for Mobile Handsets" which designed a small five-band Antenna on the basis of a small Meander-Line Antenna, but did not have frequency-reconfigurable characteristics.
The microstrip antenna has the characteristics of miniaturization and easiness in integration, and the PIN diode is used for the lumped design of the microstrip antenna to realize the working states of the exponential antenna and further realize frequency reconstruction.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a two-way frequency reconfigurable meander line antenna, which adopts a simpler microstrip meander line antenna as a basic structure and realizes eight different working states by only using 3 PIN diode switches, thereby solving the technical problems of more lumped elements and less reconfigurable states of the traditional frequency reconfigurable antenna.
The invention adopts the following technical scheme for realizing the aim of the invention:
a frequency reconfigurable meander line antenna of the two-way type includes: the metal floor board comprises an upper-layer microstrip structure, a middle-layer dielectric substrate and a bottom-layer metal floor board, wherein the upper-layer microstrip structure comprises a section of shorter microstrip feeder line, a longer main microstrip line with a bent structure and a shorter impedance matching stub extending out of the main microstrip line. The main microstrip line is folded for three times, the three bending structures have certain gaps and are connected through the shorter microstrip line, and 3 PIN diodes are placed in the gaps of the bending structures. The effective electrical length of the antenna is changed by controlling the conduction of the PIN diodes with the three bending structures at different longitudinal positions, so that the length of a current path is reduced, and the binary frequency reconfigurable characteristic is realized.
In the above scheme, on the basis of the monopole meander line antenna, in order to reduce the frequency points of operation and reduce the repeatability of frequency bands in different operating states while maintaining a better standing wave, the two-way frequency reconfigurable meander line antenna has an additional microstrip line connected to the end of the last meander structure to implement impedance matching. And a third middle-layer dielectric plate is arranged below the microstrip structure, and a metal floor with the same length as the microstrip feeder is arranged right below the microstrip feeder.
The two-way type frequency reconfigurable meander line antenna provided by the invention has eight different working states, so that the antenna realizes the switching of different working frequency bands in a wider working frequency band range, the working frequency bands in the working states are not overlapped, the working frequency bands in all the working states cover the wider working frequency band, the electrical size is small, and the size of the antenna at the lowest central frequency is only 0.16 lambda0。
By adopting the technical scheme, the invention has the following beneficial effects:
(1) on the basis of a basic monopole bent antenna, a PIN diode is connected into a gap of a bent structure to serve as a switch, the effective electrical length of the antenna is adjusted by controlling the on-off of the PIN diode, the length of a current path is further adjusted, eight different working states are achieved with a small number of switches, working frequency bands in each working state are not overlapped, the resonant frequency in each working state tends to increase along with the change of the on-off state of the switch, the antenna has the advantage of small number of lumped elements, the parasitic effect and the manufacturing cost are greatly reduced, and the antenna is very suitable for reducing the number of antennas in a wireless communication system and achieving antenna multi-functionalization.
(2) The two-way type frequency reconfigurable folded antenna has the frequency reconfigurable characteristic that the working frequency band gradually increases along with the change of the switch state, meanwhile, the impedance matching performance of each part is good, the directional diagram and the gain under all the states are similar to those of a half-wave oscillator antenna, the omnidirectional radiation on the H surface is realized, and the application range is wider.
(3) The invention adopts a planar circuit structure, is suitable for the integration of other devices in a wireless communication system, and has small antenna electrical size and high space utilization rate.
Drawings
Fig. 1 is a schematic structural diagram of a basic monopole meander line antenna according to the present invention.
Fig. 2 is a schematic diagram of an upper-layer microstrip structure of a frequency reconfigurable meander line antenna according to the invention.
Fig. 3 is a schematic diagram of a frequency reconfigurable meander antenna bias circuit in the present invention.
Fig. 4 is a detailed illustration of the dimensions of each part of the frequency reconfigurable meander line antenna of the two-way type according to the present invention.
Fig. 5 is a simulation result of reflection characteristic curve S11 of each state of the frequency reconfigurable meander line antenna of the two-way system of the invention.
FIG. 6 shows a frequency-reconfigurable meander line antenna of the two-way system of the present invention at f0674MHz, E-plane, H-plane pattern at the resonant frequency of 000 states.
The reference numbers in the figures illustrate: 1. the microstrip feed line, 2, a bottom metal floor, 3, a middle-layer dielectric substrate, 4, a first bending structure, 5, a second bending structure, 6, a third bending structure, 7, an impedance matching stub, 8, a first metal via hole, 9, a first inductor, 10, a second metal via hole, 11, a first bias line, 12, a second bias line, 13, a third bias line, 14, a first resistor, 15, a second resistor, 16, a third resistor, 17, a first DC blocking capacitor, 18, a second DC blocking capacitor, 19, a third DC blocking capacitor, 20, a first PIN diode, 21, a second PIN diode, 22, a third PIN diode, 23, a fourth DC blocking capacitor, 24, a second inductor, 25 and a fourth bias line.
Detailed Description
The technical scheme of the invention is explained in detail in the following with reference to the attached drawings.
The invention discloses a two-way frequency reconfigurable meander line antenna as shown in figure 2, which is designed based on the basic monopole meander line antenna shown in figure 1, and comprises an upper microstrip structure, a middle layer dielectric substrate and a bottom layer metal floor, wherein the upper microstrip structure and the bottom layer metal floor 2 are respectively attached to the upper and lower surfaces of the middle layer dielectric substrate 3. The upper microstrip structure is shown in fig. 2 and includes: the monopole antenna comprises a microstrip feed line 1, a main microstrip line with a bent structure and an impedance matching branch 7, wherein the main microstrip line is provided with a first bent structure 4, a second bent structure 5 and a third bent structure 6, gaps for placing PIN diodes are reserved among the bent structures, the length of a bottom metal floor 2 is the same as that of the microstrip feed line 1, the length of a current path is reduced by controlling the conduction of the PIN diodes at different longitudinal positions of the three bent structures, 1 represents conduction, 0 represents disconnection, the effective electrical length of the antenna is changed by controlling the on-off of the PIN diodes, and therefore the three-position binary frequency reconfigurable characteristic is achieved.
As shown in fig. 3, the first PIN diode 20 placed in the slot of the first folded structure 4 and the third PIN diode 22 placed in the slot of the third folded structure 6 are placed in the same direction, and the cathode faces the feed port; the third PIN diode 21 placed in the slot of the second meander structure 5 is opposite to the other two PIN diodes. The first bias line 11 is connected with the first bending structure 4 through a first resistor 14, the second bias line 12 is connected with the second bending structure 5 through a second resistor 15, the third bias line 13 is connected with the third bending structure 6 through a third resistor 16, the first blocking capacitor 17 is connected in the first bending structure 4, the second blocking capacitor 18 is connected in the second bending structure 5, the third blocking capacitor 19 is connected in the third bending structure 6, the fourth blocking capacitor 23 is connected at the connection position of the first bending structure 4 and the second bending structure 5, and four large capacitors which are 100pF simultaneously block the influence of direct current on each PIN diode and do not influence the passing of alternating current. A first inductor 9 and a second inductor 24 which are 150nH are respectively arranged near the microstrip feed line 1 and the second bent structure 5, the first inductor 9 is directly grounded through the first metal via hole 8, and the second inductor 24 is grounded after being connected with the second metal via hole 10 through the fourth bias line 25, so that the antenna is biased. The on-off of 3 PIN diodes is controlled by adding forward direct current voltage at the tail ends of a first bias line 11, a second bias line 12 and a third bias line 13, meanwhile, the first bias line 11 applies direct current voltage to a first bending structure through a first resistor 14 with the resistance value of 1k omega, the second bias line 12 applies direct current voltage to a second bending structure through a second resistor 15 with the resistance value of 1k omega, the third bias line 13 applies direct current voltage to a third bending structure through a third resistor 16 with the resistance value of 1k omega, and the three resistors play a role in preventing the PIN diodes from being broken down due to overlarge current. When the antenna is in a 000 state, the three PIN diodes are in a turn-off state, and at the moment, the part which is not short-circuited in the bending structure is at the maximum, the effective electrical length of the antenna is at the maximum, and the resonant frequency is at the minimum; when the antenna is in a 001 state, the 6s part of the third bending structure is short-circuited due to the conduction of the third PIN diode 22, the effective electrical length of the antenna is reduced, and the resonant frequency is increased; when the antenna is in the 010 state, the 5s portion of the second folded structure is short-circuited by conduction of the second PIN diode 21; when the antenna is in a 111 state, the 4s part of the first bent structure is short-circuited due to conduction of the first PIN diode 20, the 5s part of the second bent structure is short-circuited due to conduction of the second PIN diode 21, and the 6s part of the third bent structure is short-circuited due to conduction of the third PIN diode 22, so that the effective electrical length of the antenna is minimum and the resonant frequency is highest; the short-circuited portions of the bent structure in the other states of the antenna are shown in table 2. The bias circuit is specially designed for the binary 3-bit frequency reconfigurable microstrip antenna disclosed by the invention, can well control the switching of eight working frequency bands, and has the advantages of simple circuit structure and relatively few lumped elements.
In this embodiment, the dielectric constant of the middle dielectric substrate is 3.55, and the thickness is 0.508 mm. The length and width of each part of the design are indicated in fig. 4, and the specific values are detailed in the table below. (unit: mm)
TABLE 1
FIG. 5 is a reflection curve S of a binary frequency-reconfigurable meander-line antenna according to the present invention11Simulation result graph of (1), S11In the frequency band range of 668-951MHz, the working frequency range of the antenna in each working state is distinct, the frequency reconfigurable characteristic is good, and in the process that the on-off state of the PIN diode switch is gradually changed from '000' to '111', namely the working frequency band in each working state is gradually increased along with the change of the on-off state of the switch, and the resonant frequency is also gradually increased. The operating band and resonant frequency for each particular state are shown in table 2.
TABLE 2
The simulation result of the E-plane and H-plane directional diagrams at the resonant frequency corresponding to the '000' working state of the frequency reconfigurable meander line antenna of the two-in-one system of the invention is shown in fig. 6, the E-plane and H-plane directional diagrams of other states have characteristics basically similar to '000', and the E-plane directional diagrams basically keep '8' shape between the working frequency bands, thereby conforming to the radiation characteristics of the traditional monopole antenna. From the simulation results, the frequency reconfigurable meander line antenna of the two-input system of the invention only uses 3 PIN diodes to realize eight different working states, can meet the frequency requirements under different mobile communication systems, has directional patterns and gains similar to those of a half-wave oscillator antenna in all states, realizes omnidirectional radiation on an H surface, is very suitable for reducing the number of antennas in a wireless communication system and realizing the multifunction of the antennas, has very small antenna electrical size, and is beneficial to the miniaturization of the system.
The foregoing is only a preferred embodiment of this invention and it should be noted that modifications can be made by those skilled in the art without departing from the principle of the invention and these modifications also fall within the scope of the invention.