I understand the working principle of antennas in RF radio
The type and selection of antennas in the RF RF circuit
Antenna parameters
Some key parameters for antenna performance are provided below.
▪ Echo loss: The echo loss of the antenna represents how the antenna matches the transmission line (TL) of the impedance, which is displayed as the signal feed in Figure 7. Typically, the impedance value of this TL is 50Ω, but it can also be other values. For industrial standards, commercial antennas and its test equipment resistance
50Ω, so it is recommended that you prefer this value.
Echo loss display: due to mismatch, the incident power size reflected in the antenna (Equation 1). An ideal antenna will transmit all power without any reflection.
If the echo loss is unlimited, the antenna is considered to match TL, such as shown in FIGURE 7. S11 is the reciprocal of the return loss, and its unit is DB.
In most cases, if the return loss is ≥ 10 dB (ie S11 ≤ -10 dB), it is large enough. Table 1 shows the echo loss (DB) and reflection power (%) of the antenna. When the return loss is 10 dB, 90% of the incident power is transmitted to an antenna for transmission.
Table 1 Antenna Echo Loss and Reflection Power
▪ Bandwidth: refers to the frequency response of the antenna. It indicates how the antenna and 50 Ω transmission line match each other in the entire frequency band employed, ie in the range of 2.40 GHz to 2.48 GHz.
Figure 8. Bandwidth
As shown in Figure 8, on the bandwidth of 2.33 GHz to 2.55 GHz, the return loss is greater than 10 dB. Therefore, the bandwidth used is about 200 MHz.
In most cases, a wider bandwidth is preferred because it minimizes the exhaustive effect of the product caused by the environment around the actual use of the antenna (for example, placed on the mouse on wood / metal / plastic table, around the mouse Hand, etc.). )
▪ Radiation efficiency: refers to a part of non-reflective power consumption (see figure 7) being consumed into heat in the antenna. The generating heat is due to dielectric losses in the FR4 substrate, as well as conductor losses in the copper wire. This information acts as radiation efficiency. When the radiation efficiency is 100%, all non-reflected power consumption has been sent
Shoot within the space. For small PCB shape factors, the heat dissipation is minimal.
▪ Radiation diagram: This pattern represents the directionality of radiation, that is, the radiation in which direction is larger, which is smaller in which direction is smaller. This helps to accurately determine the direction of the antenna in the application. The non-directional antenna can be equivalently transmitted in all directions in all directions perpendicular to the axis. But most antennas do not meet this ideal performance. For more details, see the radiation map of the PCB antenna shown in Figure 9. Each data point represents RF field strength, which can be measured by an indicator (RSSI) for receiving signal intensity in the receiver. As the case, the contour image obtained is not circular because the antenna is not part of the sameness.
Figure 9. Radiation map
▪ Gain: The gain provides information on the radiation in the direction of the adopted direction to compare the same - sex antennas (ie, emit to all directions). The gain unit is "DBI", i.e., the field strength of radiation when compared with an ideal unconventional antenna.
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