How Do I Choose the Best Hidden Antenna?

Bluetooth antenna is an important necessary component for transmitting and receiving electromagnetic wave energy in wireless communication systems.

Bluetooth antenna

Because the current technology cannot integrate the antenna into the chip of the semiconductor process, in addition to the core system chip in the Bluetooth module, the antenna is another key component that has an impact on the transmission characteristics of the Bluetooth module. The antenna design methods and materials used in various Bluetooth applications are also different. In addition to choosing an appropriate antenna, it helps to match the appearance of the product and improve the transmission characteristics of the Bluetooth module, and can further reduce the cost of the entire Bluetooth module.

1)

For users of handheld Bluetooth devices, it is one of the ultimate purposes of Bluetooth to be able to smoothly use Bluetooth for short-distance transmission regardless of the location or direction of use, and an appropriate Bluetooth antenna

Design will help achieve such transmission quality. In terms of radiation field, the antenna of the handheld Bluetooth product should be omnidirectional and can be interconnected with other Bluetooth products from all directions; in terms of antenna gain, due to Bluetooth

The ISM frequency band used has a short operating wavelength, and the energy loss caused by obstacles or conductors in the transmission medium or transmission path is relatively increased. Therefore, although Bluetooth products are advertised as short-range transmission devices, it should still be considered that there will be electromagnetic wave obstacles such as furniture, room walls, and even the human body when used in an indoor environment. Therefore, the gain of the Bluetooth antenna cannot be too small. Since the Bluetooth antenna on the AP device needs to cover a large area, its antenna gain must be much higher than that of handheld products. In addition, in terms of the radiation field type, it is necessary to consider the installation location of the AP and the scope to be covered to determine the design of a suitable directional antenna. In addition to the design requirements discussed above, for various Bluetooth products, Bluetooth antennas still have to meet the primary requirements of low cost. From the perspective of product application, because the antenna is very sensitive to the surrounding ground plane, such as the ground plane on the circuit board or the shielding metal sheet on the circuit board to prevent static electricity, it will seriously affect the antenna radiation characteristic. Taking a notebook computer as an example, there are currently two ways to install a Bluetooth module: In terms of the PCMCIA card external connection method, since the motherboard of the notebook computer is covered with a shielded metal shell and a grounded metal surface, the end of the PCMCIA card must be Prominent outside the laptop, and the Bluetooth antenna is designed on the internal circuit board in a built-in concealed manner or as an external antenna via a adapter (as shown in Figure 7) and fixed on the PCMCIA card; in addition, the Bluetooth antenna is on the laptop There will also be differences in characteristics due to different placement positions. Generally speaking, the operating bandwidth and antenna gain of placing a Bluetooth antenna around an LCD screen is greater than installing it around a keyboard.

The Bluetooth transmission mode is based on a piconet. A piconet can have seven Bluetooth slaves and one master simultaneously. All slaves in the same piconet The Frequency Hopping Sequence must cooperate with the active device. As shown in Figure 5, on the basis of the piconet, multiple transmission modes of point to point (Point to Point), point to multipoint (PointtoMultipoint, and several piconets can be linked to each other). Among these modes, Whether it is a master or slave device in a piconet, because it needs to be connected with a slave or master device that changes its position at any time in the network, the antenna radiation pattern used by these devices must be approximately omnidirectional, if it is Using a highly directional antenna for transmission or reception will cause the signal between the two Bluetooth devices to not transmit properly at certain relative angles. Figure 6 shows a fixed access device (Access Point) for indoor environments. , AP) to transmit with other Bluetooth devices. Since the access device AP has been fixed in some suitable locations indoors for data transmission to indoor Bluetooth devices, the antenna used on the AP device does not necessarily need to be fully equipped. Directivity, on the contrary, the antenna with high directivity in a fixed direction is designed according to the installation position and transmission range to obtain the best transmission effect. As for other Bluetooth devices An omni-directional antenna still best meets its needs.