Wireless communication apparatus and control method therefor
a communication apparatus and wireless technology, applied in electrical apparatus, spatial transmit diversity, diversity/multi-antenna systems, etc., can solve the problems of large scale of the circuit around the antenna, deterioration of performance, control circuit in the antenna circuit, etc., and achieve the effect of reducing the amount of radio wave radiation
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first embodiment
[0038][First Embodiment]
[0039]FIG. 4 is a schematic view showing a case in which a body moves close to an antenna 1 of a wireless communication apparatus including a plurality of antennas 1 to 4 arranged at physically different positions. In this case, a transmission radio wave from the antenna 1 radiates the body close to it, and is absorbed by the body.
[0040]At this time, the body absorbs the transmission radio wave, and also absorbs a received radio wave, thereby reducing received power. Furthermore, the resonance frequency of the antenna 1 close to the body changes due to the influence of the dielectric constant of the body, which changes the input impedance of the antenna 1, resulting in a return loss. If the body moves close to the antenna 1, the received power of the antenna decreases by the sum of the return loss of the antenna and an absorption loss by the body. As will be described below, according to the embodiment, if the amount of radiation of the radio wave to the body...
case 1
[0053]In case 1, the body is in contact with the exterior covering, and the received power variation and the transmitted reflected power exceed the received power variation threshold ΔPth (a first threshold) and the transmitted reflected power threshold RLth (a second threshold), respectively. In this case, the absorption degree of the radio wave by the body is highest, and it is thus determined to switch the antenna.
[0054]In case 2, the distance between the exterior covering and the body is 3 mm. The body is not in contact with the exterior covering of the housing but is sufficiently close to it, and the transmitted reflected power and the received power variation exceed the thresholds RLth and ΔPth, respectively. In this case, it is determined that the absorption degree of the radio wave by the body is high, thereby determining to switch the antenna.
[0055]In case 3, the distance between the exterior covering and the body is 4 mm. Since the transmitted reflected power and the recei...
second embodiment
[0071][Second Embodiment]
[0072]The relationship between transmitted reflected power and the distance between an antenna and a body when using an antenna in which a change in transmitted reflected power due to the proximity of the body is relatively small and an antenna in which it is relatively large will be described with reference to FIG. 15. A general pattern antenna, ceramic chip antenna, or the like presents a change in transmitted reflected power due to the proximity of the body, as indicated by a broken line. For a patch antenna or the like, however, a change in transmitted reflected power is small as indicated by a solid line even if the body moves close to the antenna. It is difficult to detect the proximity of the body to such an antenna by only detecting a change in transmitted reflected power. It is, however, possible to perform an antenna switching determination operation based on the fact that a received power variation changes as the absorption degree of a radio wave ...
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