Antenna system and mobile terminal implemented with the antenna system

An antenna system for a mobile terminal, the mobile terminal comprising a metal frame and a system grounding spaced apart from the metal frame, wherein

• the antenna system comprises at least a first antenna module, a second antenna module, a third antenna module and a fourth antenna module;
• the first antenna module comprises a radiating body formed in the metal frame and a parasitic element coupled to the radiating body, the radiating body is configured to generate a main harmonic, and the parasitic element is configured to generate a parasitic harmonic;
• the first antenna module further comprises a first tuning circuit and a second tuning circuit, the first tuning circuit is connected in series between the radiating body and the system grounding, the second tuning circuit is connected in series between the parasitic element and the system grounding;
• the antenna system is characterized in that, the antenna system comprises at least four operation modes, wherein
• in a first operation mode, the first tuning circuit of the first antenna module switches among multiple operation states such that the main harmonic covers an LTE low frequency and switches among multiple wave bands of the LTE low frequency, the second tuning circuit is configured to keep one operation state such that the parasitic harmonic covers an LTE medium frequency and an LTE high frequency, the second tuning circuit comprises at least one small-capacitance capacitor, a capacitance of the small-capacitance capacitor is less than 0.8 pF, the first antenna module and the second antenna module cooperatively consist a 2*2MIMO system covering the LTE low, medium and high frequencies in this mode;
• in a second operation mode, the first tuning circuit of the first antenna module switches among multiple operation states such that the main harmonic covers the LTE low frequency and switches among multiple wave bands of the LTE low frequency, the second tuning circuit switches among multiple operation states such that the parasitic harmonic covers the LTE medium frequency and switches among multiple wave bands of the LTE medium frequency, the first antenna module, the second antenna module, the third antenna module and the fourth antenna module cooperatively consist a 4*4MIMO system covering the LTE medium frequency in this mode;
• in a third operation mode, the first tuning circuit switches among multiple operation states such that the main harmonic covers the LTE low frequency and switches among multiple wave bands of the LTE low frequency, the second tuning circuit switches among multiple operation states such that the parasitic harmonic covers the LTE high frequency and switches among multiple wave bands of the LTE high frequency, the first antenna module, the second antenna module, the third antenna module and the fourth antenna module cooperatively consist a 4*4MIMO system covering the LTE high frequency in this mode;
• in a fourth operation mode, the first tuning circuit is configured to keep one operation state such that the main harmonic covers the LTE medium and high frequencies, the second tuning circuit is configured to keep one operation state such that the parasitic harmonic covers the LTE medium and high frequencies, the first antenna module, the second antenna module, the third antenna module and the fourth antenna module cooperatively consist a 4*4MIMO system covering the LTE medium and high frequencies.