Miniature Long-Term Evolution (LTE) MIMO Ferrite Antenna

A long-term evolution (LTE) MIMO ferrite antenna was fabricated on Ni
_0.5
Mn
_0.2
Co
_0.07
Fe
_2.23
O
₄
ferrite substrate (14 × 7 × 3 mm
³
) and characterized for antenna performance. Measured return loss and isolation were -26 and -16.4 dB at 720 MHz, respectively. Correlation coefficient calculated from experimental S-parameters (S
₁₁
, S
₂₂
, S
₁₂
, and S
₂₁
) was less than 0.02 in the LTE band. Three-dimensional peak gain at 746 MHz was measured to be -8.83 dBi for antenna 1 and -8.32 dBi for antenna 2. These low antenna gains are attributed to high magnetic loss of ferrite substrate. Performance simulation suggests that antenna gain can be further improved up to -3.14 dBi with the use of low-loss ferrite.