High-isolation miniaturized quasi side-fed microstrip antenna suitable for double-sided board

Abstract

A main body comprises the double-sided board, an antenna oscillator is arranged in the middle of the surface layer of the double-sided board, and a ground copper foil is laid on the whole bottom layer of the double-sided board; the center of the antenna oscillator is provided with a grounding via hole. A feeding point deviating from a corresponding inner angle is arranged near each of two adjacent inner angles on the right side of the antenna oscillator, the two feeding points are sequentially connected with a linear feeder line, an arc-shaped microstrip line and a curved microstrip line, and a chip pin is arranged at the tail end of the curved microstrip line; ground wires similar to the circular-arc-shaped micro-strip lines in outline are evenly distributed on the two sides of any circular-arc-shaped micro-strip line, and a plurality of via holes are evenly distributed in any ground wire. The utility model can be used for low-cost radars, Wi-Fi transceivers and other scenes. Through the design of miniaturization and double panels, the requirements of low cost and high performance of the product can be met, through reasonable grounding, static accumulation is eliminated, the reliability of a chip connected with the antenna is improved, and miniaturization and low cost of the product are facilitated.

Description

Technical Field

[0001] The utility model relates to the field of electronic equipment and electronic devices, in particular to a high-isolation miniaturized quasi-edge-fed microstrip antenna suitable for double-sided boards. Background Art

[0002] Antennas are often used in the transmitting and receiving ports of SOC chips with integrated radio frequency. For situations where cost requirements are relatively high, double-sided boards are a favorable choice. However, conventional double-sided board antennas are large in size and have poor isolation, resulting in their cost being comparable to that of four-layer boards, and they have no size advantage. If the circuit boards are the same size, the transmit-receive isolation of double-sided board antennas is poor. Doppler sensing radar is a self-mixing system, where transmission and reception are performed simultaneously. Because the system's transmit-receive isolation is limited, part of the transmit signal will directly return to the receiving section, forming a self-mixing DC level. Although the DC level can be eliminated by a DC blocking capacitor, because the Doppler frequency is very low, the phase noise of the frequency source will form low-frequency noise through the self-mixing effect, becoming the main noise source of the radar system. Although this low-frequency noise is partially derived from the 1 / f noise of the mixer and intermediate frequency amplifier, the main source of noise is still the near-end phase noise of the voltage-controlled oscillator. Even if the phase-locked loop technology is used, the noise in the loop at a slightly farther position can be greatly improved, but the near-end noise depends on the crystal oscillator. Doppler sensing radar chips with phase-locked loops consume a lot of power and are expensive, and require external crystal oscillators, which put them at a cost and power disadvantage in low-end applications of smart lighting. For example, for a 5.8GHz Doppler radar module, when a person walks at 1 meter per second, the Doppler frequency is 38Hz. This low-frequency phase noise is difficult to improve by optimizing the voltage-controlled oscillator. The main method in the industry is to improve the isolation between the transmitter and receiver, which results in a double-sided board module with an integrated transmitter-receiver antenna having greater noise than a four-layer board module of the same size, and a much shorter sensing distance.

[0003] In addition, due to the inherent characteristics of the double-layer board transceiver antenna, the range of standing wave and isolation is particularly narrow, which easily leads to the mismatch between the antenna's operating frequency and the chip's transmitting frequency, seriously affecting the module performance. Because the dielectric constant of the circuit board has a certain fluctuation range, the optimal operating frequency band of the antenna will vary from batch to batch. In serious cases, the software code can only be rewritten after testing the actual operating frequency band of the antenna to set the chip's transmitting frequency to the antenna's optimal frequency point, which makes software burning difficult and increases production and management costs. Although thickening the circuit board can alleviate this situation, thickening the circuit board is not a regular circuit board, and the cost is greatly increased, which is not a good solution. Summary of the invention

[0004] The purpose of the utility model is to provide a high-isolation miniaturized quasi-edge-fed microstrip antenna suitable for double-sided boards, which can be used in multiple scenarios such as low-cost radars, RFID transceivers, etc. After miniaturization and double-sided board design, the low-cost and high-performance requirements of the product can be met. This design eliminates static electricity accumulation through reasonable grounding, improves the reliability of the chip connected to the antenna, and realizes the electrical interconnection between the double-sided board antenna and the chip through two-stage impedance transformation using a combination of coplanar waveguides and microstrip lines, which is conducive to the miniaturization and low cost of the product.

[0005] The utility model is realized by the following technical scheme: a high-isolation miniaturized quasi-edge-fed microstrip antenna suitable for double-sided boards, characterized in that: a main body comprises a double-sided board, a square copper foil area is provided in the middle area of ​​the surface layer of the double-sided board to form an antenna vibrator, and the entire bottom layer is paved with ground copper foil; a ground via is provided in the center of the antenna vibrator;

[0006] A feeding point is provided near each of two adjacent inner corners on the right side of the antenna vibrator, and the two feeding points are symmetrical about the horizontal central axis of the antenna vibrator, and the two feeding points are respectively located on the upper and lower opposite sides of the antenna vibrator; one of the feeding points is a receiving feeding point, and the other feeding point is a transmitting feeding point;

[0007] Any feeding point is connected to a straight feed line extending outward, and the angle between the straight feed line and the horizontal central axis of the antenna element is 45°; the length of the straight feed line is 0.25-0.5 times the side length of the antenna element;

[0008] The outer end of any straight feed line is connected with a circular arc microstrip line, and the two circular arc microstrip lines are bent toward each other;

[0009] The end of any arc-shaped microstrip line is connected to a curved microstrip line, the line width of the curved microstrip line increases from the beginning to the end, and a chip pin is provided at the end of the curved microstrip line; wherein the chip pin connected to the receiving feed point is a chip receiving pin; and the chip pin connected to the transmitting feed point is a chip transmitting pin;

[0010] Ground wires with a similar outline to the circular arc microstrip line are arranged on both sides of any circular arc microstrip line, and a plurality of via holes are arranged on any ground wire.

[0011] Compared with the previous technology, the beneficial effects of the utility model are:

[0012] 1. The high-isolation miniaturized double-panel circularly polarized microstrip antenna proposed in this design not only provides a small size, but also improves the isolation of the antenna, greatly reduces the noise of the radar module, and greatly improves the sensing distance; this design reduces the Q value of the antenna, which is conducive to improving the working bandwidth of the antenna and can solve the problem of mismatch between the transmitting frequency of the radar chip without a phase-locked loop and the antenna working frequency. The center of the antenna is grounded, eliminating the possibility of static electricity accumulation. In addition, due to the use of conventional double-panel panels, the production cost is greatly reduced while reducing the volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural schematic diagram of the utility model.

[0014] Explanation of reference numerals: 1 double-sided board, 2 antenna element, 21 ground via, 31 receiving feed point, 32 transmitting feed point, 4 straight feed line, 5 arc-shaped microstrip line, 6 curved microstrip line, 71 chip receiving pin, 72 chip transmitting pin, 8 ground wire, 81 via. DETAILED DESCRIPTION

[0015] The utility model is described in detail below with reference to the accompanying drawings:

[0016] like Figure 1 As shown: a high-isolation miniaturized quasi-edge-fed microstrip antenna suitable for double-sided boards, the main body includes a double-sided board 1, a square copper foil area is provided in the middle area of ​​the surface layer of the double-sided board 1 to form an antenna vibrator 2, and the bottom layer is covered with ground copper foil; a ground via 21 is provided in the center of the antenna vibrator 2;

[0017] A feeding point is provided near two adjacent inner corners on the right side of the antenna element 2, each of which is offset from the corresponding inner corner. The two feeding points are symmetrical about the horizontal central axis of the antenna element 2, and the two feeding points are respectively located on the upper and lower opposite sides of the antenna element 2; one of the feeding points is a receiving feeding point 31, and the other feeding point is a transmitting feeding point 32;

[0018] Any feeding point is connected to an outwardly extending straight feed line 4, and the straight feed line 4 forms an angle of 45° with the horizontal central axis of the antenna element 2; the length of the straight feed line 4 is 0.25-0.5 times the side length of the antenna element 2;

[0019] The outer end of any straight feed line 4 is connected to a circular arc microstrip line 5, and the two circular arc microstrip lines 5 are bent toward each other;

[0020] The end of any arc-shaped microstrip line 5 is connected to a curved microstrip line 6, the line width of the curved microstrip line 6 increases from the beginning to the end, and a chip pin is provided at the end of the curved microstrip line 6; wherein the chip pin connected to the receiving feed point 31 is a chip receiving pin 71; and the chip pin connected to the transmitting feed point 32 is a chip transmitting pin 72;

[0021] Ground lines 8 with a similar profile to the circular arc microstrip line 5 are evenly arranged on both sides of any circular arc microstrip line 5 , so that the circular arc microstrip line 5 forms a coplanar waveguide transmission line, and a plurality of vias 81 are evenly arranged on any ground line 8 .

[0022] The antenna of the present invention adopts a coplanar waveguide transmission line (that is, ground wires are provided on both sides of the microstrip line to achieve the effect of different characteristic impedances) and a microstrip line to form a two-stage impedance transformation, which corresponds to the bias of the two corners of the antenna vibrator 2 respectively, which is different from the traditional feeding method of directly accessing the corner.

[0023] In the utility model, the distance between the two antenna feed lines is increased due to the increase in the length of the feed line, thereby increasing the isolation. In addition, since the copper foil at the right-angle vertex has a certain shielding effect, the transmitted signal is not easy to be directly coupled from the transmitting feed point to the receiving feed point. The antenna vibrator 2 of the utility model offsets the right-angle vertex of the square antenna, further enhancing the isolation of the two ports, so that the antenna achieves a good effect in terms of isolation. By setting a grounding via 21 at the center position of the antenna vibrator 2, static electricity can be eliminated. The antenna is made of a double-sided board, which can effectively reduce production costs. Figure 1 The area around the middle antenna element 2 is a blank area, without copper paving, and nothing else except green oil and silk screen; the bottom layer is a whole layer of ground copper foil.

[0024] The antenna vibrator is a square, and its side length is close to half the wavelength of the electromagnetic wave corresponding to the working frequency. It is slightly less than half the wavelength because the parasitic capacitance causes the frequency to become lower, and the theoretical frequency needs to be slightly increased. The specific side length is determined by the antenna design software simulation. In addition, a transmitting feeding point and a receiving feeding point are respectively set near the two adjacent corners of the antenna vibrator. Since the antenna of the utility model is a circularly polarized antenna, the feeding point is not like the conventional square horizontally polarized and vertically polarized antennas, where the feeding point is located at the midpoint of the two adjacent sides of the square, and there is no groove to reduce the impedance.

[0025] The length of the linear feeder 4 is 0.25-0.5 times the side length of the antenna vibrator 2; the currently implemented solution is 0.25-0.5 times the side length; its purpose is to increase the distance between the bending position and the antenna vibrator to improve isolation. In theory, the longer the straight length of the linear feeder 4, the higher the isolation, but too long will increase the transmission insertion loss and reception insertion loss. In addition, it cannot be too long due to the size limit of the module circuit board.

[0026] In addition, the line width of the linear feed line 4 determines the impedance of the microstrip line. Since the antenna presents high impedance and the transceiver port of the chip is generally 50 ohms, the line width of the linear feed line 4 is transformed according to the antenna impedance. Therefore, the linear feed line 4 is not designed for 50 ohms.

[0027] The distance between the feeding point and the corresponding inner corner is the width of the linear feeder 4. Compared with the traditional solution, the connection point between the linear feeder 4 and the antenna element of the utility model is not at the adjacent corners of the rectangle, but needs to be deviated from the outside by one line width, in order to improve the transmit and receive isolation of the overall antenna.

[0028] The linear feed line 4 is then connected with an arc-shaped microstrip line 5, and then connected with a curved microstrip line 6 with gradually increasing line width, until the line width of the curved microstrip line 6 increases to the line width of the microstrip line designed for 50 ohms. Finally, because the pad width of the chip pin of the chip is not necessarily the width of the microstrip line for 50 ohms impedance, the curved microstrip line designed for 50 ohms is gradually reduced in a teardrop manner to the same width as the pad of the chip pin and connected together.

[0029] On both sides of the curved microstrip line 6, the ground wire is isolated in a shape exactly the same as the curved microstrip line 6. The line width of the ground wire is first designed according to the line width of 50 ohms, and then the vias are evenly punched. The diameter of the via 81 does not exceed the line width of the corresponding ground wire 8. The distance between the midpoints of any two adjacent vias 81 is not greater than three times the line width of the corresponding ground wire 8. The ground wires on both sides of the curved microstrip line 6 will participate in impedance matching, so the ground wires should be as close to the curved microstrip line 6 as possible to reduce the line width of the curved microstrip line 6 and avoid the size of the circuit board from becoming larger. The design is determined according to the minimum line spacing of the PCB board factory. The impedance design is calculated based on the dielectric constant and board thickness given by the PCB board factory. The ground wire will reduce the coupling between the transmitting RF line and the receiving RF line and the antenna, and improve the isolation between sending and receiving. The ground wire will reduce the coupling between the transmitting RF line and the receiving RF line and other routings, reducing interference.

[0030] In addition, the receiving feed point 31 and the straight feed line 4, arc-shaped microstrip line 5, and curved microstrip line 6 chip receiving pin 71 connected to the receiving feed point 31 are symmetrical with the transmitting feed point 32 and the straight feed line 4, arc-shaped microstrip line 5, and curved microstrip line 6 chip receiving pin 71 connected to the transmitting feed point 32 about the horizontal central axis.

[0031] That is to say, the antenna described in the present invention is symmetrical, so the transmitting feeding point and the receiving feeding point can be interchanged.

[0032] It should also be noted that the directions or positional relationships indicated by “upper”, “lower”, “left”, “right”, etc. that appear in the description of the present invention are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0033] The utility model can be mainly applied to multiple scenarios such as low-cost radars, RFID transceivers, etc.

[0034] Take the 5.8GHz motion-triggered radar module as an example. The motion-sensing radar trigger chip designed and manufactured using CMOS technology is small in size, low in cost and low in power consumption. It is made into a radar module with a PCB board antenna and can be installed in LED lamps to realize intelligent lighting that turns on the light when people come and turns off the light when people leave, saving overall social electricity consumption. At present, the infrared sensing automatic lights installed in the corridors of buildings rely on Fresnel lenses to partition the space and use differential input thermopiles to identify human infrared thermal radiation. Although the cost is low, the infrared sensing probe needs to be installed independently because the LED emits light and heat, which interferes with the work of the infrared detector. Infrared sensing lamps are only suitable for installation when new houses and new buildings are renovated, and are not convenient for entering thousands of households. In addition, the Fresnel lens made of organic glass is prone to aging over time, which will reduce the sensitivity of the infrared sensor. In addition, in summer, the ambient temperature in buildings in the south is close to the human body temperature, which can easily lead to the inability to recognize human movement and make it difficult to turn on the light when people come.

[0035] The radar sensing module is manufactured by using the motion sensing chip based on the Doppler speed measurement principle. It has the advantage of working around the clock and can be placed directly in the lamp. In particular, the radar module is placed in the bulb. Although the performance of the double-layer circuit board radar module in this solution is slightly lower than that of the 4-layer board radar module, it is not much lower. Under the condition of appropriate performance of the radar chip, it is easy to meet the application requirements of a hanging height of 3 meters and a sensing radius of more than 3 meters. Since the radar module in this case can place all devices on the same side, it reduces power frequency interference, improves the test distance and stability, reduces material costs and patch costs, and allows the radar module to be used more widely.

[0036] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-isolation miniaturized quasi-edge-fed microstrip antenna suitable for double-sided boards, characterized in that: The main body comprises a double-sided board (1), a square copper foil area is provided in the middle area of ​​the surface layer of the double-sided board (1) to form an antenna vibrator (2), and the entire bottom layer is paved with ground copper foil; a ground via (21) is provided in the center of the antenna vibrator (2); A feeding point is provided near two adjacent inner corners on the right side of the antenna element (2), each of which is offset from the corresponding inner corner. The two feeding points are symmetrical about the horizontal center axis of the antenna element (2), and the two feeding points are respectively located on the upper and lower opposite sides of the antenna element (2); one of the feeding points is a receiving feeding point (31), and the other feeding point is a transmitting feeding point (32); Any feeding point is connected to a straight feed line (4) extending outward, wherein the straight feed line (4) forms an angle of 45° with the horizontal central axis of the antenna vibrator (2); the length of the straight feed line (4) is 0.25-0.5 times the side length of the antenna vibrator (2); The outer end of any straight-line feed line (4) is connected to a circular arc microstrip line (5), and the two circular arc microstrip lines (5) are bent toward each other; The end of any arc-shaped microstrip line (5) is connected to a curved microstrip line (6), the line width of the curved microstrip line (6) increases from the beginning to the end, and a chip pin is provided at the end of the curved microstrip line (6); wherein the chip pin connected to the receiving feed point (31) is a chip receiving pin (71); and the chip pin connected to the transmitting feed point (32) is a chip transmitting pin (72); Ground lines (8) having a similar profile to the circular arc-shaped microstrip line (5) are evenly arranged on both sides of any circular arc-shaped microstrip line (5), and a plurality of vias (81) are evenly arranged on any ground line (8).

2. According to claim 1, a high-isolation miniaturized quasi-edge-fed microstrip antenna suitable for double-sided boards, characterized in that: The distance between the feeding point and the corresponding inner corner is the width of the straight feed line (4).

3. The high-isolation miniaturized quasi-edge-fed microstrip antenna suitable for double-sided boards according to claim 1, characterized in that: The length of the linear feed line (4) is 0.25-0.5 times the side length of the antenna element (2).

4. The high-isolation miniaturized quasi-edge-fed microstrip antenna suitable for double-sided boards according to claim 1, characterized in that: The diameter of the via hole (81) does not exceed the line width of the corresponding ground line (8), and the distance between the midpoints of any two adjacent via holes (81) is not greater than three times the line width of the corresponding ground line (8).

5. The high-isolation miniaturized quasi-edge-fed microstrip antenna suitable for double-sided boards according to claim 1, characterized in that: The receiving feed point (31) and the straight feed line (4), arc-shaped microstrip line (5), curved microstrip line (6) and chip receiving pin (71) connected to the receiving feed point (31) are symmetrical with the transmitting feed point (32) and the straight feed line (4), arc-shaped microstrip line (5), curved microstrip line (6) and chip receiving pin (71) connected to the transmitting feed point (32) about a horizontal central axis.

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