CN200979907Y - A novel built-in antenna system for a mobile phone - Google Patents

Abstract

The utility model discloses a new mobile phone IFA built-in antenna device, the radiator of which is directly printed on the main board, the signal is fed by the radio frequency front end of the mobile phone, a part of the radiator is connected in parallel with the ground and short-circuited, and is generated according to the shape of the radiator and the mutual coupling between the vibrators. Different lengths of bypass currents result in different frequency bands. The antenna is at the same height as the main board of any standard mobile phone, the length and relative position of the antenna vibrator can be adjusted, and dual-band, triple-band and broadband can be realized by changing the current control. Compared with common conventional built-in antennas, the antenna of the utility model has stronger index stability and high performance. Compared with common monopole antennas, the utility model has higher radiation resistance, and compared with common PIFA antennas, it saves space.

Description

A new mobile phone built-in antenna device

Technical field

The utility model belongs to the technical field of mobile communication terminals, and mainly relates to a new built-in antenna device of the IFA type for an ultra-thin mobile phone.

Background technique

The rapid development of mobile communication has effectively promoted the development of mobile phones in the direction of miniaturization and high performance.

So far, the radio frequency (RF) part and the baseband part have achieved a high degree of IC integration, which effectively promotes the miniaturization and low cost of mobile terminals. As for mobile phone antennas, due to further high requirements for shape and radio frequency performance, antenna designers have also presented unprecedented challenges. It can meet the requirements for beautiful appearance, but also meet the frequency bandwidth and efficiency indicators.

As a mobile terminal with complex and changeable usage environment, mobile phone designers need to face how to overcome various problems to optimize antenna performance. These problems include:

The shape of the mobile phone requires the size and position of the antenna;

Proximity effect of mobile phone circuit components;

Mobile phone users often use it in buildings or cars, and require antenna directivity;

When the human body carries the mobile phone, the human body senses the requirements for the impact on the antenna.

The emergence of the built-in antenna of the mobile phone has made a great breakthrough in the shape, but the impact of the built-in antenna on the antenna index and the requirements for the overall layout of the mobile phone are also problems faced by various mobile phone manufacturers.

At present, there are two types of built-in antennas: monopole antenna and planar inverted F antenna (PIFA). The quarter-wavelength monopole antenna is the basic mobile antenna. The prototype of the PIFA antenna is a typical inverted F planar antenna. Depending on the shape of the sheet, different lengths of winding currents are generated, thereby forming different frequency bands. The basic configuration method of the antenna is: turn the quarter-wavelength antenna installed on the ground plane into an L shape, and feed at a point away from the installation point. It is easy to realize the impedance matching of the antenna by choosing a suitable feed point.

When using a conventional PIFA antenna, in order to achieve the required frequency bandwidth and radiation efficiency, the height of the antenna from the motherboard shielding cover should be about 8mm for the CDMA and GSM frequency bands, and about 6mm for the PHS frequency band. When the monopole built-in antenna is used, it needs to be placed away from metals and devices. Due to the existence of the coupling capacitance of the antenna to adjacent devices, the radiation efficiency will be seriously affected. It is necessary to leave a clean area for the antenna on the main board, which is The whole machine needs to give it a large space for matching, so as to increase the antenna reactance and generate frequency bandwidth. These requirements are not conducive to the development of mobile phones in the direction of miniaturization and ultra-thin.

Contents of Invention

The purpose of this utility model is to design a new type of inverted F antenna (IFA), which can not only optimize the electrical performance of the built-in antenna, but also reduce the conventional height and space of the current built-in antenna, so that the mobile phone with the built-in antenna can be ultra-thin in shape design. , to achieve multi-frequency performance.

In the analysis of the basic planar built-in small antenna, it can be seen that due to the reduction in size, the radiation resistance of the antenna becomes significantly smaller or the equivalent reactance becomes larger, which leads to the mismatch of the antenna. The general practice is to insert a matching network with centralized parameters at the front end of the antenna to improve the matching, but at higher frequencies, the Q value of the matching network is very low, which introduces a large insertion loss and reduces the efficiency of the antenna. We need to find a suitable distribution structure to match the electrically small antenna.

In the antenna device of the utility model, the radiator is directly printed on the main board, the signal is fed by the radio frequency front end of the mobile phone, and a part of the radiator is connected in parallel with the ground and short-circuited. The meander line and the short vibrator constitute two different resonant circuits. The length of the short vibrator corresponding to the high-frequency resonance frequency is proportional to its corresponding free space wavelength and inversely proportional to the dielectric constant of the material. The length of the meander line corresponding to the low-frequency resonance frequency is also related to the shortening rate of the meander line. According to the shape of the radiator and the mutual coupling between the vibrators, the antenna generates winding currents of different lengths, thereby generating different frequency bands.

The built-in antenna of the utility model can be level with the main board on any standard mobile phone.

When determining the length of the zigzag line, the shortening rate of the zigzag line is generally taken as about 35%.

The built-in antenna of the utility model can realize dual-frequency, triple-frequency and broadband by adjusting the length of the meander line and the short vibrator, and the relative position between the meander line and the short vibrator. The meanders can be long dipoles or other types.

At present, the antenna directly printed on the main board is in the form of a monopole antenna, and there is no ground below it. Although the height of the antenna is reduced, the antenna in the form of a monopole has strict requirements on the processing of the ground around the main board. Compared with the existing antenna technology printed on the main board, the IFA antenna of the utility model can adjust the ground pin to reduce the influence of the surrounding ground on the antenna, and can effectively improve the radiation resistance compared with the monopole antenna.

Compared with the inverted F antenna, the antenna structure of the present utility model has the advantage that there must be a ground at a strict distance below the antenna required by the non-inverted F antenna, which can be flush with the main board, reducing the height of the antenna.

The antenna of the utility model can change the current control by adjusting the length and relative position of the antenna vibrator, thereby realizing dual-frequency, triple-frequency and broadband.

Description of drawings

Figure 1 is an L-shaped antenna diagram.

Figure 2 is an impedance circle diagram of an L-shaped antenna.

Figure 3 is an admittance circle diagram of an L-shaped antenna.

Figure 4 is a branch diagram of an L-shaped antenna plus a short circuit to ground.

Fig. 5 is a schematic structural diagram of the antenna of the first embodiment of the present invention.

Fig. 6 is a schematic structural diagram of the antenna of the second embodiment of the present invention.

Detailed ways

Further describe the utility model below in conjunction with accompanying drawing and embodiment.

First, we study the matching of the L-shaped antenna, which is shown in Figure 1. Observe the Smith chart of the L-shaped antenna: the impedance chart is shown in Figure 2, and the admittance chart is shown in Figure 3. We can see that the first resonance point is the fundamental mode frequency point of the antenna, which is a matching point that can be considered. It can be seen that when f<f0, the antenna has a large capacitive reactance, we can increase the parallel reactance of the antenna to the ground by adding a short-circuit branch to the ground, thereby increasing the real part of the input impedance, as shown in Figure 4 .

On the basis of the above research, the mobile phone built-in antenna device designed by the utility model prints the radiator directly on the main board, the signal is fed by the radio frequency front end of the mobile phone, and a part of the radiator is connected in parallel with the ground and shorted. The meander line and the short vibrator constitute two different resonant circuits. The length of the short vibrator corresponding to the high-frequency resonance frequency is proportional to its corresponding free space wavelength and inversely proportional to the dielectric constant of the material. The length of the meander line corresponding to the low-frequency resonance frequency is also related to the shortening rate of the meander line. According to the shape of the radiator and the mutual coupling between the vibrators, the antenna generates winding currents of different lengths, thereby generating different frequency bands.

Specifically, the radiator includes a first radiator 4 and a second radiator 5. The first radiator 4 and the second radiator 5 can be used as signal inlets or ground connections, one of which is connected to the radio frequency signal port, and the other One is connected to the ground of the main board, and a part of the radiator is connected in parallel with the ground for short circuit.

Fig. 5 and Fig. 6 are two different structures of the mobile phone built-in antenna device designed according to the utility model. Figure 5 is a pure dual oscillator structure. The antenna from the antenna feed point is divided into two paths. The meander line 2 achieves low frequency, and the short vibrator 3 achieves high frequency. The positions of meander line 2 and short vibrator 3 can be adjusted interchangeably. Figure 6 is a structure of the integrated design of the antenna, which can also be understood as a short vibrator 3 and a meander line 2, but the meander line 2 and the short vibrator 3 are not separated into two branches. This structure is reversed through the detour in the vibrator current to achieve dual frequency.

Referring to Figure 5 and Figure 6, the meander line 2 and the short vibrator 3 constitute two different resonant circuits, where the high-frequency resonance frequency corresponds to the length of the short vibrator 3 ${\mathrm{<figure-callout\; id="3"\; label="L"\; filenames="Y20062014827300091.png"\; state="\{\{state\}\}">L</figure-callout>}}_3=\mathrm{\&lambda;}/4\sqrt{(1+\mathrm{\&epsiv;\&gamma;})/2},$ λ is the free space wavelength corresponding to the high-frequency resonance frequency, εγ is the dielectric constant of the material; the length of the meander line 2 corresponding to the low-frequency resonance frequency $L_{}$${}_2=\mathrm{\&lambda;}/4\sqrt{(1+\mathrm{\&epsiv;\&gamma;})/2}(1-\mathrm{SR}),$ λ is the free space wavelength corresponding to the low frequency resonant frequency, SR represents the shortening rate of the meander line, and the shortening rate is generally about 35%, and εγ is the dielectric constant of the material. By selecting appropriate structural parameters and material permittivity, a corresponding antenna device can be obtained. Wherein, the meander 2 is a long vibrator, and of course it can also be of other types.

The above-mentioned antenna device generates winding currents of different lengths according to the shape of the radiator and the mutual coupling between the vibrators, thereby generating different frequency bands. By adjusting the length of the meander line 2 and the short vibrator 3 and the relative position of the meander line 2 and the short vibrator 3, dual-frequency, triple-frequency and broadband can be realized.

The utility model utilizes the IFA antenna to effectively improve the radiation resistance. Compared with the inverted F antenna, the two IFA antenna structures of the present utility model have the advantage that there must be a ground at a strict distance below the antenna required by the non-inverted F antenna, which can be flush with the main board and reduce the height of the antenna. The structure can be directly applied and printed on the main board without structural parts and installation process.

Claims (9)

1. A new type of mobile phone built-in antenna device, including a radiator, a vibrator and a main board, characterized in that: the radiator is directly printed on the main board (1), the signal is fed by the radio frequency front end of the mobile phone, and a part of the radiator is connected in parallel with the ground for short circuit; The line (2) and the short oscillator (3) constitute two different resonant circuits, in which the length of the short oscillator (3) corresponding to the high-frequency resonance frequency is proportional to its corresponding free space wavelength and inversely proportional to the dielectric constant of the material The length of the zigzag line (2) corresponding to the low-frequency resonance frequency is also related to the shortening rate of the zigzagging line; the antenna device generates detour currents of different lengths according to the shape of the radiator and the mutual coupling between the vibrators, thereby generating different frequency bands. 2. The mobile phone built-in antenna device according to claim 1, characterized in that: the radiator includes a first radiator (4) and a second radiator (5), one of which is connected to the radio frequency signal port, and the other is connected to the radio frequency signal port. The main board is connected to the ground, and a part of the radiator is connected in parallel with the ground for short circuit. 3. The mobile phone built-in antenna device according to claim 1 or 2, characterized in that: the length of the short vibrator (3) $L_3=\mathrm{\&lambda;}/4\sqrt{(1+\mathrm{\&epsiv;\&gamma;})/2},$ λ is the free-space wavelength corresponding to the high-frequency resonance frequency, and εγ is the dielectric constant of the material; the length of the meander line (2) $L_2=\mathrm{\&lambda;}/4\sqrt{(1+\mathrm{\&epsiv;\&gamma;})/2}(1-\mathrm{SR}),$ λ is the free space wavelength corresponding to the low frequency resonant frequency, SR represents the shortening rate of the meander line, and the shortening rate is generally about 35%, and εγ is the dielectric constant of the material. 4. The mobile phone built-in antenna device according to claim 1 or 2, characterized in that the antenna is at the same height as the main board (1) on any standard mobile phone. 5. The mobile phone built-in antenna device according to claim 3, characterized in that the antenna is at the same height as the main board (1) on any standard mobile phone. 6. The mobile phone built-in antenna device according to claim 1 or 2, characterized in that: the length and relative position of the meander line (2) and the short vibrator (3) can be adjusted, and dual-frequency, three-frequency frequency and broadband. 7. The mobile phone built-in antenna device according to claim 1 or 2, characterized in that: the meander line (2) can be a long vibrator or other types. 8. The mobile phone built-in antenna device according to claim 3, characterized in that: the meander line (2) and the short vibrator (3) are separated into two paths from the antenna feed point. 9. The mobile phone built-in antenna device according to claim 3, characterized in that: the meander line (2) and the short vibrator (3) are an integrated structure.

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