Mobile phone radio waves need to be emitted, and the frequency must be high to a certain degree, such as the current GSM 900MHZ and 1800MHZ. The frequency of sound is very low, only 20HZ-20KHZ, the signal of this frequency can not be directly transmitted, it must be modulated to the high frequency, which is the radio frequency to be transmitted, which is the meaning of radio frequency. In order to achieve good communication between the mobile phone and the base station, the radio frequency emitted by the mobile phone must have sufficient strength. When the mobile phone is close to the base station, the communication can be maintained with a small power. When the mobile phone is far away from the base station, the mobile phone must increase its own transmission power to maintain a good communication level. Therefore, the RF power in the mobile phone is automatically adjustable. Because the current mobile phone for the appearance of small, many of the antenna integrated in the mobile phone, which has a certain impact on the radio frequency emission, in order to achieve good results, mobile phones have to further increase the radio frequency power to maintain normal work, sometimes, this power exceeds the national standard specified value, it will have a certain impact on the human body.
The characteristics of the receiver are also important for the overall mobile phone system.
Poor receiver characteristics can cause the user to receive a very low quality sound signal, and even lose the user's base station information and cause the termination of the call.
Poor receiver sensitivity is often caused by internal noise and stray signals emitted by the transmitter feeding back into the receiver.
Therefore, the CTIA standard requires that receiver sensitivity be measured at the transmitter's maximum transmit power.
Mobile radio frequency refers to the function module of receiving, transmitting and processing high-frequency radio waves, which is based on ITU specifications.
The frequency planning of 3G is as follows: China Mobile TD-SCDMA is 1880-1900mhz and 2010-2025mhz; China Telecom CDMA2000 is 1920-1935mhz and 2110-2125mhz; China Unicom WCDMA is 1940-1955mhz and 2130-2145mhz.