CN102074786B - Dual frequency printed circuit antenna for electronic devices - Google Patents

Abstract

The invention discloses a dual-frequency printed circuit antenna for an electronic device, which comprises a substrate, a first monopole antenna and a grounding metal sheet. The first monopole antenna is formed on the substrate and has an electrical length approximately equal to one quarter of a wavelength of a first frequency band and three quarters of a wavelength of a second frequency band. The grounding metal sheet is formed on the substrate and used as a grounding end of the first monopole antenna. A feed end of the first monopole antenna is formed at a first side of the grounding metal plate, and the first side is divided into a first edge and a second edge, and the lengths of the first edge and the second edge are approximately one quarter of the wavelength of the second frequency band.

Description

Dual frequency printed circuit antenna for electronic devices

technical field

The present invention is a dual-frequency printed circuit antenna for an electronic device, especially a dual-frequency printed circuit antenna realized by using a monopole antenna whose length is a quarter wavelength of low frequency and three-quarter wavelength of high frequency .

Background technique

Electronic products with wireless communication functions, such as USB wireless network card (WLAN USB Dongle), transmit or receive radio waves through antennas to transmit or exchange radio signals, and then access wireless networks. Therefore, in order to allow users to access wireless communication networks more conveniently, the bandwidth of an ideal antenna should be increased as much as possible within the allowable range, while the size should be reduced as much as possible to match the trend of shrinking electronic products.

In addition, with the continuous advancement of wireless communication technology, the number of antennas configured on electronic products may increase. For example, the wireless local area network standard IEEE 802.11n supports multiple-input multiple-output (Multi-input Multi-output, MIMO) communication technology, that is, related electronic products can transmit and receive wireless signals synchronously through multiple sets of antennas, so as not to increase the bandwidth Or in the case of total transmit power consumption (TransmitPower Expenditure), the data throughput (Throughput) and transmission distance of the system are greatly increased, thereby effectively improving the spectral efficiency and transmission rate of the wireless communication system, and improving communication quality.

In general, printed antennas have the advantages of light weight, small size, and high compatibility with various circuits. Therefore, they have been widely used in various wireless communication products in recent years. In traditional electronic products, in order to realize a printed dual-frequency antenna in a limited space, the high-frequency radiating element and the low-frequency radiating element of the dual-frequency antenna are often arranged in parallel, resulting in the radiation impedance of the high-frequency radiating element being affected by the low-frequency radiating element Decrease, so that high-frequency antenna characteristics (such as bandwidth) deterioration. In addition, since the high frequency signal attenuates faster in the substrate and air than the lower frequency signal, if the high frequency radiation element fails to provide sufficient radiation efficiency, the radiation distance of the high frequency signal will be greatly reduced.

On the other hand, in an electronic device supporting MIMO technology, multiple antennas may interfere with each other when transmitting signals simultaneously, which reduces antenna efficiency and fails to fully utilize the advantages of MIMO.

Contents of the invention

Therefore, the main objective of the present invention is to provide a dual-band printed circuit antenna for an electronic device.

The invention discloses a dual-frequency printed circuit antenna for an electronic device. The dual-frequency printed circuit antenna includes a substrate, a first monopole antenna and a grounded metal sheet. The first monopole antenna is formed on the substrate and has an electrical length approximately one quarter of a wavelength of a first frequency band and three quarters of a wavelength of a second frequency band. The ground metal sheet is formed on the substrate and serves as a ground terminal of the first monopole antenna. Wherein, a feeding end of the first monopole antenna is formed on a first side of the ground metal sheet, and divides the first side into a first edge and a second edge, and the first edge and the The length of the second edge is approximately a quarter of the wavelength of the second frequency band.

Description of drawings

FIG. 1 is a schematic diagram of a dual-frequency printed antenna according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a dual-band printed antenna according to a preferred embodiment of the present invention.

FIG. 3 is a Smith chart of the dual-frequency printed antenna in FIG. 2 .

FIG. 4 is a reflection coefficient diagram of the dual-frequency printed antenna in FIG. 2 .

FIG. 5 is a coupling coefficient diagram of the dual-frequency printed antenna in FIG. 2 .

6A to 6C are radiation pattern diagrams of the dual-frequency printed antenna in FIG. 2 .

FIG. 7 is a radiation efficiency diagram of the dual-frequency printed antenna in FIG. 2 .

8 to 11 are schematic diagrams of other embodiments of the present invention.

Description of main component symbols

10, 20 Dual frequency printed antenna

11, 21 Substrate

12, 14, 22, 24 monopole antenna

13, 23 Ground metal sheet

F1, F2 Feed-in terminal

S1, S2 side

E1, E2, E3, E4 Edge

Detailed ways

Please refer to FIG. 1 , which is a schematic diagram of a dual-band printed antenna 10 according to an embodiment of the present invention. The dual-frequency printed antenna 10 is used in an electronic device of a multiple-input multiple-output wireless communication system (such as IEEE 802.11n) for synchronous transmission and reception of wireless signals. The dual-band printed circuit antenna 10 includes a substrate 11 , a monopole antenna 12 and a grounded metal sheet 13 . The monopole antenna 12 is a meander-line monopole antenna realized by a metal wire, which is formed on the substrate 11, and its electrical length is approximately 1/4 of the wavelength of a first frequency band, which is also equal to a second frequency band. Three-quarters of the band wavelength. Wherein, the frequency of the second frequency band is higher than the frequency of the first frequency band. The ground metal sheet 13 is also formed on the substrate 11 and serves as a ground terminal of the monopole antenna 12 . A feeding end F1 of the monopole antenna 12 is formed on a first side S1 of the ground metal sheet 13 and is divided into a first edge E1 and a second edge E2 . Wherein, the lengths of the first edge E1 and the second edge E2 are approximately a quarter of the wavelength of the second frequency band.

In order to support MIMO wireless communication systems, the dual-band printed antenna 10 further includes a monopole antenna 14 . Monopole antenna 14 is formed on substrate 11 and has the same structure as monopole antenna 12 . A feeding end F2 of the monopole antenna 14 is formed on a second side S2 of the ground metal sheet 13 and is divided into a third edge E3 and a fourth edge E4 . Wherein, the lengths of the third edge E3 and the fourth edge E4 are approximately a quarter of the wavelength of the second frequency band.

As shown in FIG. 1 , the first side S1 and the second side S2 are opposite sides of the ground metal sheet 13 , and the first edge E2 is adjacent to the third edge E3 . In other words, in the embodiment of the present invention, there are two monopole antennas 12 and 14 on the substrate 11 , and the antennas are separated by the ground metal sheet 13 . Each monopole antenna has two frequency bands: a first frequency band and a second frequency band, which respectively correspond to a low frequency band and a high frequency band. The electrical length of a monopole antenna is approximately one-quarter wavelength at low frequencies and three-quarters wavelength at high frequencies. The feed-in ends F1 and F2 of the monopole antenna respectively divide the two sides S1 and S2 of the ground metal sheet 13 into two edges. The length of each edge is about a quarter wavelength of the high frequency. For the design principle of the dual-band printed antenna 10 , please continue to refer to the following description.

As known to those skilled in the art, the real part of the input impedance of a center-fed half-wavelength dipole antenna is about 75 ohms (Ω); rather than a center-fed 1-wavelength dipole antenna (signal line 3/4 wavelength, ground wire 1/4 wavelength) The real part of the input impedance has been simulated and is close to 100 ohms. Assuming that the radiation impedance of the antenna is Ra and the ohmic loss resistance is Rohm, the radiation efficiency of the antenna is proportional to Ra/(Ra+Rohm). Since the ohmic loss resistance of the antenna is approximately equal to 10 ^-3 ohms, it can be known from the formula for calculating the radiation efficiency of the dipole antenna that the greater the radiation impedance, the higher the radiation efficiency. Among them, for a monopole or dipole antenna, the radiation impedance of the antenna is approximately proportional to the real part of the input impedance of the antenna.

Generally speaking, the printed monopole antenna is limited by the size of the substrate, making it very close to the ground, resulting in a very small radiation impedance (about 10 ohms). In this case, after impedance matching is performed on the antenna, the bandwidth of the antenna becomes very small. Therefore, if the initial radiation impedance of the antenna can be as close as possible to 50 ohms, the bandwidth of the antenna will increase a lot after impedance matching. In the embodiment of the present invention, since the monopole antenna whose electrical length is approximately three-quarters of the high-frequency wavelength and the ground edge whose length is approximately one-fourth the high-frequency wavelength, it is similar to a non-intermediately fed 1-wavelength dipole The antenna, therefore, can be used to increase the radiation impedance of the high frequency, thereby increasing the bandwidth of the high frequency band.

In addition, the feed-in ends F1 and F2 of the monopole antenna divide the ground metal sheet 13 into two edges. The length of the ground edge below the feed-in terminals F1 and F2 is about a quarter wavelength of the high frequency (ie, edges E2 and E4 ). When feeding in here, the high-frequency current is the maximum and the bandwidth is the widest. In addition, the antenna itself is three-quarters of the wavelength, so the high-frequency signal can be resonated. Similarly, the edge length above the feed-in ports F1 and F2 is approximately 1/4 wavelength of the high frequency band (ie edges E1 and E3 ), so that high frequency signals can be resonated. In this case, the edges E1 and E3 are like a reflector, which is used to isolate the ground current of the high frequency band of the two antennas, so as to reduce the current flowing to the adjacent antennas. In this way, the monopole antennas 12 and 14 have good isolation.

Preferably, according to the embodiment of the present invention, the lengths of the edges E1 and E3 can be appropriately adjusted according to the requirement of impedance matching, so that they are slightly larger than a quarter of the wavelength of the high-frequency band. In this way, the embodiment of the present invention can further increase the bandwidth of the high frequency band.

Please refer to FIG. 2 , which is a schematic diagram of a dual-band printed antenna 20 according to a preferred embodiment of the present invention. The operating frequency of the dual-band printed antenna 20 is 2.4GHz and 5GHz, and it is implemented in a USB wireless network card (WLAN USB Dongle) supporting the IEEE802.11n wireless local area network standard. As shown in FIG. 2 , the dual-band printed antenna 20 includes two monopole antennas 22 and 24 . The antenna lengths of the monopole antennas 22 and 24 are approximately one-quarter wavelength of 2.45 GHz and three-quarter wavelength of 5.5 GHz. The length of the ground edge below the feed point is a quarter wavelength (7.5mm) of 5.5GHz, and the length of the ground edge above the feed point is greater than 1/4 wavelength (11mm) of 5G.

For the antenna characteristic simulation results of the dual-band printed antenna 20 , please refer to FIG. 3 to FIG. 7 . Fig. 3 is the Smith chart (Smith Chart) of dual-frequency printed antenna 20, Fig. 4 is the reflection coefficient figure of dual-frequency printed antenna 20, Fig. 5 is the coupling coefficient (Coupling Coefficient) figure of dual-frequency printed antenna 20, Fig. 6A to Fig. 6C is a radiation pattern diagram of the dual-frequency printed antenna 20 , and FIG. 7 is a radiation efficiency diagram of the dual-frequency printed antenna 20 .

As shown in FIG. 3 , at high frequencies, the real part impedance of the dual-frequency printed antenna 20 falls near the characteristic impedance of the transmission line, so that the high frequency band has a very wide bandwidth. FIG. 4 shows the reflection coefficients of the monopole antennas 22 and 24, respectively. Based on -10dB, the low-frequency bandwidth of the dual-band printed antenna 20 falls between 2.4GHZ-2.6GHz, and the high-frequency bandwidth falls between 5.15GHz-6GHz.

Fig. 5 shows the coupling coefficient between monopole antennas 22 and 24, which is plotted by using monopole antennas 22 and 24 as signal input and signal output respectively, by measurement or simulation transmitted by a monopole antenna (or coupled) to the energy ratio of another monopole antenna. Since the length of the ground edge above the feeding point of the two antennas is greater than a quarter wavelength of 5GHz, the coupling coefficients in the 5GHz band are all below -15dB, so the two adjacent antennas have good isolation in the high frequency band.

6A to 6C show the radiation pattern diagrams of the monopole antenna 22 at three different cut planes. When drawing the radiation pattern of the monopole antenna 22 , the embodiment of the present invention couples the monopole antenna 24 to a 50-ohm load to simulate the mutual interference between the two antennas. As shown in Fig. 6A and Fig. 6C, since the edge above the feeding point of the two antennas will cause reflection of the high-frequency band signal, therefore, the radiation pattern of the monopole antenna 22 in the XY plane and the YZ plane will be pushed to 180- The half plane of 270-360 degrees makes the monopole antennas 22 and 24 have good isolation. In this case, the dual-frequency printed antenna 20 can also maintain good radiation efficiency, and the radiation efficiency in the high-frequency band is as high as 60-80%, as shown in FIG. 7 .

Please note that in the embodiment of the present invention, the monopole antennas 22 and 24 are formed on the same surface of the substrate, and in other embodiments, the monopole antennas 22 and 24 can also be formed on the upper and lower surfaces of the substrate respectively, and are not limited to this . In addition, the shape, size, or material of the monopole antenna and the ground metal sheet can also be adjusted according to actual needs, as long as the relevant electrical lengths meet the limitations of the present invention, they all fall within the scope of the present invention. 8 to 11 are schematic diagrams of other embodiments of the present invention.

In summary, the present invention provides a dual-band printed circuit antenna for USB wireless network devices, which utilizes a monopole antenna whose length is 1/4 of the wavelength of the low frequency and 3/4 of the wavelength of the high frequency to increase the high-frequency signal In the case of multiple antennas sharing the same ground, the position of the feed point is selected so that the high frequency band has very good isolation, radiation efficiency and bandwidth.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the present invention shall fall within the scope of the present invention.

Claims (12)

1. double-frequency printed circuit antenna that is used for an electronic installation comprises:

One substrate;

One first unipole antenna is formed on this substrate, has 3/4ths of 1/4th and 1 second band wavelength that an electrical length is similar to one first band wavelength; And

One grounded metal sheet is formed on this substrate, is used as a ground end of this first unipole antenna;

Wherein, one feed side of this first unipole antenna is formed on a first side of this grounded metal sheet, and this first side is divided into one first edge and one second edge, the length at this first edge and this second edge is similar to 1/4th of this second band wavelength.

2. double-frequency printed circuit antenna according to claim 1, wherein this first unipole antenna is a dioptric type unipole antenna.

3. double-frequency printed circuit antenna according to claim 1, wherein this first unipole antenna is a metal wire.

4. double-frequency printed circuit antenna according to claim 1, it separately comprises one second unipole antenna, be formed on this substrate, have the structure identical with this first unipole antenna, one feed side of this second unipole antenna is formed on a second side of this grounded metal sheet, and this second side is divided into one the 3rd edge and one the 4th edge, the length at the 3rd edge and the 4th edge is similar to 1/4th of this second band wavelength.

5. double-frequency printed circuit antenna according to claim 4, wherein this first side and this second side are the relative edge of this grounded metal sheet.

6. double-frequency printed circuit antenna according to claim 4, wherein this first edge is adjacent to the 3rd edge.

7. double-frequency printed circuit antenna according to claim 6, wherein the length at this first edge and the 3rd edge is slightly larger than 1/4th of this second band wavelength.

8. double-frequency printed circuit antenna according to claim 4, wherein this first unipole antenna and this second unipole antenna are respectively formed at the upper and lower surface of this substrate.

9. double-frequency printed circuit antenna according to claim 4, wherein this first unipole antenna and this second unipole antenna are formed on the same face of this substrate.

10. double-frequency printed circuit antenna according to claim 1, wherein this first frequency range and this second frequency range correspond respectively to the frequency of operation of IEEE 802.11b/g and IEEE 802.11a.

11. double-frequency printed circuit antenna according to claim 1, wherein this electronic installation is a USB wireless network card.

12. double-frequency printed circuit antenna according to claim 1, wherein this electronic installation is supported a multiple input, multiple output wireless communication system.

Images