November 26, 2020
The market demand for multiband NB-IoT and LTE coverage is increasing rapidly. Furthermore, products tend to decrease in size. To meet these demands, Proant presents a tunable antenna solution, using the patented Niche antenna concept with active switching. Proant proves the Niche antenna concept works well for multiband purposes by active switching.
Summery white paper “Tunable Antenna for Global NB-IoT and LTE Coverage
The market demand for wireless communication with multiband NB-IoT and LTE coverage is increasing. Furthermore, products tend to decrease in size, which implies less available space for the antenna. To meet these demands, Proant presents a tunable antenna solution using the patented Niche antenna concept with active switching. By utilizing the method of active switching, Proant has reached a return loss better than -3dB and efficiency maximum of -3dB over the global NB-IoT and LTE ranges. With this, Proant proves that the Niche antenna concept is suitable to be used with active switching for extended frequency coverage.
Solution
Since the operational frequency of the Niche antenna is determined by the capacitance on the top load. A neat solution is to use a single SP4T switch to change the capacitance value, hence tune the antenna to extend the frequency range and maintain performance.The complete evaluation board is shown in the bottom right figure. The antenna tuner, including the SP4T switch and the antenna top load, is marked in red. A detailed electrical schematic of the top load tuning functionality is displayed in the top right figure. Four capacitors in parallel, each connected to an output of the switch. The switch can combine the capacitive loads in different combinations or states. In this study, five states were utilized to cover the intended bands.
Results, Active Switching
The top right figure shows the return loss for different output states of the SP4T switch. The bottom right table summarizes the return loss data.The table below shows which NB-IoT and LTE communication bands that are covered with a return loss of at least -3dB.
Results, Performance
The figure shows the total efficiency for the lowest (State 1) and highest (State 5) output state of the SP4T switch. Datapoints are added to indicate points of importance.
The Niche Antenna Concept
The Niche antenna concept is a patented antenna technology by Proant. The antenna is a triangular cutout with two reactive loads crossing the cutout, the feed and the top load. The unique shape and reactive loads gives the antenna magnetic radiation properties.In implementation, the antenna should be “open” towards an edge of the application board and the preferable placement is in the center of the longest side. The size of the application board and the Niche antenna cutout together with its reactive loads, determine the operational frequency, bandwidth and efficiency.
Proant has proved that active switching of the Niche antenna concept is a viable method to extend the antenna frequency range. In this study, global NB-IoT and LTE bands. The Niche antenna is highly efficient, require a small area and have unique placement options. Due to its magnetic radiating properties it is very frequency stable close to dielectric materials such as potting or plastic. The Niche concept is a Proantpatented technology available for multiple applications such as Bluetooth, WiFi, GNSS, LoRA, 868 MHz, 915 MHz, 2G, 3G, LTE, NB-IoT and 5G and is available through license.
