A helicon wave current drive is proposed as an efficient off-axis current drive in the high electron β plasmas that are expected in fusion reactors. A high frequency helicon wave coupling was analyzed using the surface impedance at a plasma boundary. A slow wave coupling, which may compete with the helicon wave coupling at a frequency of 500 MHz, is estimated to be lower than the fast wave coupling by an order of magnitude in the KSTAR edge plasma density and in practical Faraday shield misalignment with the magnetic pitch. A traveling wave antenna, which is a two port combline antenna, was analyzed using a simplified lumped element model. The results show that the traveling wave antenna provides load resiliency because of its insensitivity to loading resistance, provided that the loading resistance at a radiating element is limited within a practical range. The combline antenna is attractive because it does not require a matching system and exhibits a high selectivity of parallel refractive index. Based on the analysis, a seven element combline antenna was fabricated and installed at an off-mid-plane offset of 30 cm from the mid-plane in KSTAR. The low power RF characteristics measured during several plasma discharges showed no evidence of slow wave coupling. This is consistent with the expectation made through the surface impedance analysis which predicted low slow wave coupling. The wave coupling to the plasma is easily controlled by a radial outer-gap control and gas puffing. No plasma confinement degradation was observed during the radial outer-gap control of up to 3 cm in H-mode discharges. In a ELMy plasmas, only a small reflection peak was observed during a very short portion of the ELM bursting period. If the number of radiating elements is increased for high power operation, then complete load resiliency can be expected. A very large coupling can be problematic for maintaining a parallel refractive index, although this issue can be mitigated by increasing the number of elements.
Abstract-A compact multiband handset antenna including MIMO antenna operation for LTE 13 band (746 ∼ 787 MHz) applications is proposed. The proposed antennas are separately located on the top and bottom portions of a mobile handset in order to use the antenna area more effectively. The proposed antenna achieves isolations of higher than 14 dB, enveloped correlation coefficients (ECC) of less than 0.25, and total efficiencies of greater than 40%. The operating frequency bands of Antenna 1 and Antenna 2 include the LTE 13 (746 ∼ 787 MHz)/DCS/PCS/UMTS (1710 ∼ 2170 MHz) bands and the LTE 13 (746 ∼ 787 MHz)/GSM850/900 (824 ∼ 960 MHz) bands, respectively.
A compact handset multiple-input multiple-output (MIMO) antenna for long-term evolution (LTE) 700 band (746∼787 MHz) applications is proposed. The proposed antenna consists of two symmetrical PIFAs. Without the usage of any additional coupling elements between closely mounted antennas, a high isolation (>15 dB) and a low enveloped correlation coefficient (ECC < 0.35) are achieved by the optimum location and arrangement of MIMO antenna elements.
A compact (8 × 62 × 5 mm3; 2.48 cc) frequency reconfigurable antenna that uses electrical switching with PIN diodes is proposed for the low frequency LTE band (699 MHz–862 MHz), high frequency LTE band (2496 MHz–2690 MHz), GSM850/900 bands (824 MHz–960 MHz), and DCS/PCS/WCDMA bands (1710 MHz–2170 MHz). The penta-band PIFA is first designed for GSM850/900/DCS/PCS/WCDMA bands by using two slits and ground pins within a limited antenna volume (8 × 54.6 × 5 mm3; 2.18 cc). The frequency reconfigurable antenna based on this penta-band PIFA is thus proposed to additionally cover all LTE bands. The proposed antenna has two PIN diodes with an optimal location. For State 1 (PIN diode 1: ON state, PIN diode 2: OFF state), the proposed antenna covers the low frequency LTE band, DCS/PCS/WCDMA bands, and high frequency LTE band. For State 2 (PIN diode 1: OFF state, PIN diode 2: ON state), the antenna covers the GSM850/900 bands. Simulated and measured results show that the total efficiency of the proposed antenna was greater than 40% for all operating frequency bands.
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