With the high-speed development and deep popularization of wireless communication technology, users have already been able to deeply feel wireless mobile life styles brought by high speed and convenience of high technology. Mobile terminal products such as function phones, smart phones, data cards and portable WiFi hot spots oriented to the users have been widely popularized and used.
Mobile communication experiences a long development and evolution process from 2G to 3G and from 3G to 4G. At present, Long Term Evolution (LTE) networks are being comprehensively popularized and all countries have carried out large-scale network construction. As a standard technology of 4G mobile communication technologies, LTE introduces key transmission technologies such as the Orthogonal Frequency Division Multiplexing (OFDM) technology and Multiple-Input Multiple-Output (MIMO) antennas, which effectively increase the spectrum efficiency and data transmission rate Under a Cat3 technical specification frame, a peak rate of the LTE technology can reach to 50 Mbit/s on uplink and 100 Mbit/s on downlink, and various bandwidth allocation such as 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz is supported. Thus, the spectrum allocation can be more flexible and the system capacity and coverage are obviously improved. LTE wireless network architecture is more flattened, the system time delay is reduced, the network construction cost and maintenance cost are reduced, and interoperation with a 3rd Generation Partnership Project (3GPP) system can be supported.
The Time Division-Long Term Evolution (TD-LTE) technology is an important branch in 4G, and corresponds to Frequency Division Duplexing-Long Term Evolution (FDD-LTE) technology. Different from FDD-LTE uplink and downlink functions which work at paired symmetrical frequency bands, uplink and downlink functions of TD-LTE are realized by using the same frequency band, and thus the utilization rate of resources can be improved. In addition, during actual use of TD-LTE, by adjusting uplink and downlink frame structure proportions according to actual needs of users, the utilization rate of LTE networks and system resources is improved and the flexibility is higher.
However, most Power Amplifiers (PA) used by mobile terminals at present are single-chip integrated amplifiers, and an input/output matching network, a direct-current biasing circuit and an amplifier tube core are integrated on a very small chip using GaAs as a substrate. Although this kind of power amplifiers has the features of small volume, light weight, high reliability, low cost and the like, and can exempt a user from designing an input/output matching network and a static working point and thus design time is saved, since an inductor L and a capacitor C in the matching network respectively consist of a gold wire and a gold foil, the tolerable power is comparatively small; and due to the small volume, the direct-current consumption power is comparatively large, the thermal resistance from the tube core to an element surface is large and consequently heat emission is comparatively serious. As a result, the maximum output power of this kind of power amplifiers is about 28-30 dBm and it is difficult to reach higher output power; and in consideration of 1 dB compression point factor, the actually usable output power of this kind of power amplifier is only about 27-29 dBm.
In addition, in countries and regions in which 4G networks have been constructed or are under construction, with respect to actual requirements of operators on mobile terminals, besides referring to standards and specifications that are made by 3GPP, related standards and specifications are also made according to factors in multiple aspects such as network deployment features and actual user demands in the countries and regions, wherein a very important factor is an Over The Air (OTA) index of shielding darkrooms of the mobile terminals, including Total Radiated Power (TRP) and Total Isotropic Sensitivity (TIS). This index has a direct relationship with actual user experience and is an important standard for selecting mobile terminal products by the operators. In a general sense, on the premise that the conducted power and receiving sensitivity specified by 3GPP are reached, it is expected to have higher TRP and TIS.
At present, there are two ways to improve TRP, wherein one way is to, when the power from a radio frequency link to an antenna port is fixed, debug an antenna to enable it to have higher radiating efficiency, such that TRP can be improved; and the other way is to, when the radiating efficiency of the antenna is fixed, increase output power of the radio frequency link or decrease link insertion loss such that TRP can also be improved. Comparatively, after the antenna design is finalized, it is an easier and simpler measure to adjust the output power of the radio frequency link.
With respect to the improvement of TIS, similarly there are two ways, wherein one way is to, when receiving sensitivity from the radio frequency link to the antenna port is fixed, debug the antenna to improve the efficiency, such that TIS can be improved; and the other way is to, when the efficiency of the antenna is fixed, decrease link insertion loss, such that TIS can also be improved. Comparatively, after the antenna design is finalized, it is an easier and simpler measure to decrease the insertion loss of the radio frequency receiving link. On the premise that the conducted power and receiving sensitivity specified by 3GPP are reached, products with higher TRP and TIS can improve the transmitting power of the transmitting link and the receiving sensitivity of the receiving link.