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In this work, the nonlinearity of PIN diode on frequency reconfigurable patch antenna is investigated. To perform frequency reconfiguration, the proposed design makes use of the switching capabilities of a PIN diode. The antenna has a dimension of 41 × 44 mm2 corresponding to 0.33 λ0 × 0.35 λ0, where λ0 represents the wavelength in free space at 2.4 GHz fabricated on Rogers Duroid RO3003TM material. In the OFF state of the PIN diode, a single resonance (ISM 5.8 GHz) is achieved. However, in the ON state of the PIN diode, a dual‐resonance (ISM 5.8 GHz and 2.4 GHz) is achieved. A directional and bidirectional radiation pattern can be observed in the E‐plane at 5.8 GHz and 2.4 GHz, respectively, and omnidirectional radiation patterns can be viewed in the H‐plane for both 5.8 GHz and 2.4 GHz. The gain is measured to be 4.84 dBi at 2.4 GHz and 5.87 dBi at 5.8 GHz, with total efficiencies of 91.8% and 92.5% at 5.8 GHz and 2.4 GHz, respectively. Two‐tone nonlinear measurements at 2.4 GHz and 5.8 GHz are used to evaluate the PIN diode. Several third‐order intermodulation distortion products (IMD3) frequencies are observed with input powers between 0 and 20 dBm. The IMD3 at 2.4 GHz is −36.18 dBm, while at 5.8 GHz is −47.19 dBm and the third‐order input intercept point (IIP3) of +66.65 dBm is obtained at 2.4 GHz, while +22.69 dBm at 5.8 GHz. Additionally, at 2.4 GHz, the 1‐dB gain compression (P1‐dB) could not be identified, showing that the antenna behaves linearly within the spectrum of input power. Similarly, the P1‐dB is detected at 14.8 dBm input power at 5.8 GHz. The proposed antenna works in the linear region up to an input power level of 15 dBm, where the received signal strength of the IMD3 is minimal, according to the measurement of the nonlinearity caused by the PIN diode. The nonlinearity results confirm that the active reconfigurable antenna designed and implemented in this work is suitable for use in the 2.4 GHz and 5.8 GHz bands for indoor and short‐range communication applications. Furthermore, the assessment of nonlinearity provides a deeper understanding of and helps mitigate the negative effects of nonlinearity on the proposed antenna. This measurement assists in refining biasing, selecting suitable linearization methods, improving the design, and evaluating performance at the system level. Ultimately, it enhances antenna performance and expands frequency reconfigurability by enabling optimization across multiple aspects. [ABSTRACT FROM AUTHOR]

In this study, a novel reconfigurable triple-band monopole antenna for LoRa IoT applications is fabricated on an FR-4 substrate. The proposed antenna is designed to function at three distinct LoRa frequency bands: 433 MHz, 868 MHz, and 915 MHz covering the LoRa bands in Europe, America, and Asia. The antenna is reconfigurable by using a PIN diode switching mechanism, which allows for the selection of the desired operating frequency band based on the state of the diodes. The antenna is designed using CST MWS® software 2019 and optimized for maximum gain, good radiation pattern and efficiency. The antenna with a total dimension of 80 mm × 50 mm × 0.6 mm (0.12 λ 0 × 0.07 λ 0 × 0.001 λ 0 at 433 MHz) has a gain of 2 dBi, 1.9 dBi, and 1.9 dBi at 433 MHz, 868 MHz, and 915 MHz, respectively, with an omnidirectional H-plane radiation pattern and a radiation efficiency above 90% across the three frequency bands. The fabrication and measurement of the antenna have been carried out, and the results of simulation and measurements are compared. The agreement among the simulation and measurement results confirms the design's accuracy and the antenna's suitability for LoRa IoT applications, particularly in providing a compact, flexible, and energy efficient communication solution for different LoRa frequency bands. [ABSTRACT FROM AUTHOR]