Low-Profile Two-Port MIMO Terminal Antenna for Low LTE Bands with Wideband Multimodal Excitation

<div>Multiple-input multiple-output (MIMO) is a key</div><div>enabler for high data rates in mobile communications. However, it is challenging to design MIMO terminal antennas for LTE bands below 1 GHz, due to the conventional chassis offering only one resonant characteristic mode (CM). Recently, it was shown that minor structural changes can yield up to two additional resonant modes for designing two-port MIMO antennas. Nonetheless, the resulting bandwidth for the second port is relatively small. To simultaneously meet bandwidth and other practical requirements (including low profile and no off-ground clearance), a step-by-step approach for structural changes and feed design is applied in this work to exemplify the use of physical insights from CM analysis to achieve a competitive wideband two-port solution. The main novelty is that an entirely new mode is identified and appropriately tuned by structural modification for creating an additional resonance below 1 GHz. Moreover, two simple probe-feed ports are designed to jointly excite different subsets of four modes over frequency. In addition, far-field pattern orthogonality is guaranteed by the different phase shifts of the characteristic electric fields at the port locations. Furthermore, bulkier self-resonant antenna elements are avoided. To show design flexibility, a three-port version is also demonstrated.</div>

Low-Profile Two-Port MIMO Terminal Antenna for Low LTE Bands with Wideband Multimodal Excitation

<div>Multiple-input multiple-output (MIMO) is a key</div><div>enabler for high data rates in mobile communications. However, it is challenging to design MIMO terminal antennas for LTE bands below 1 GHz, due to the conventional chassis offering only one resonant characteristic mode (CM). Recently, it was shown that minor structural changes can yield up to two additional resonant modes for designing two-port MIMO antennas. Nonetheless, the resulting bandwidth for the second port is relatively small. To simultaneously meet bandwidth and other practical requirements (including low profile and no off-ground clearance), a step-by-step approach for structural changes and feed design is applied in this work to exemplify the use of physical insights from CM analysis to achieve a competitive wideband two-port solution. The main novelty is that an entirely new mode is identified and appropriately tuned by structural modification for creating an additional resonance below 1 GHz. Moreover, two simple probe-feed ports are designed to jointly excite different subsets of four modes over frequency. In addition, far-field pattern orthogonality is guaranteed by the different phase shifts of the characteristic electric fields at the port locations. Furthermore, bulkier self-resonant antenna elements are avoided. To show design flexibility, a three-port version is also demonstrated.</div>

Low-Profile Two-Port MIMO Terminal Antenna for Low LTE Bands with Wideband Multimodal Excitation

It is challenging to design multiple-input multiple-output (MIMO) terminal antennas for LTE bands below 1 GHz, due to the conventional chassis offering only one resonant characteristic mode. Recently, it was shown that minor structural changes can yield additional resonant mode(s), which were used to design two-port MIMO antennas. However, the resulting bandwidth for the second port does not cover the low LTE bands. Herein, a new approach to structural changes and feed design is proposed for the design of a low profile (4 mm) two-port MIMO antenna that covers all common low LTE bands (0.75-0.96 GHz) with total efficiency of above 67%. The large symmetric bandwidth (25%) is achieved using three additional resonant modes obtained by structural changes as well as two simple probe-feed ports jointly exciting weighted combinations of the four modes over frequency. The envelope correlation coefficient of below 0.15 is facilitated by the different phase shifts of the characteristic electric fields at the port locations. Moreover, the design requires no ground clearance, no decoupling structure and the two ports are separated by only 0.2 wavelength. Finally, to show design flexibility, a third antenna is added to the top of the chassis to create a three-port MIMO antenna

Design and fabrication of a novel single-layer Ka-band reflectarray antenna

A novel dual-polarization, single-layer reflectarray has been designed and manufactured to operate at receive (20 GHz) and transmit (30 GHz) frequencies for Ka-band terminal antennas. The reflectarray unit cell is composed of several types of resonant elements printed on the upper side of a conductor-backed substrate, which are designed to produce a collimated beam at 20 and 30 GHz in dual polarization. Cross-shaped loops are used to provide the required phases at 20 GHz, while crossed dipoles and modified truncated rings are used to control the phasing at 30 GHz. The resonant lengths of the proposed elements have been adjusted cell by cell by means of a two-dimensional interpolation method to achieve the required phase shift at each frequency. Two different feeds have been used to illuminate the reflectarray at 20 and 30 GHz. The measured gain is 28.02 dBi at 20 GHz and 32.14 dBi at 30 GHz. The measurement results show that the radiation patterns of the designed single-layer reflectarray antenna are in good agreement with those achieved from the simulations.

User’s hand effect on efficiency of 2-port 5 GHZ mobile terminal antennas

In this paper, the influence of user’s hand on mobile terminal antenna when it placed approximately on top of Multiple Input Multiple Output radiating element antennas (PIFAs) is studied extensively. The antenna is designed to operate at 5 GHz with 1.5 GHz of -6 dB bandwidth. The effect of user’s hand with different finger positions are studied at seven positions on slit at the ground plane, seven differences height above the antenna and nine different locations around the radiating element at 2 mm height from antenna. The losses due to presence of hand are studied in terms of scattering parameters, radiation efficiency and matching efficiency. The maximum loss in term of isolation in the presence of user’s hand is found at 6 mm on the slit and it decreased as the hand move away from the slitted area on the ground plane. The maximum efficiency loss is observed when the finger is placed right on top of the radiating element with -5.85 dB compare to antenna without the presence of user’s hand. On the other hand, the result for matching efficiency indicates approximately 0.2 dB losses occurred when the fingers are varied at different height and position.