# Testing and Analysis of MOSFET-Based Absorber Integrated Antenna for 5G/WiMAX/WLAN Applications
## 1 Introduction  
The fast expansion of wireless and mobile communication sectors places significant demands on RF front-end systems that are small in size and high in efficiency [1; 2; 3; 4; 5]. While trying to meet these demands, there are numerous challenges, especially during the design stage of these systems [6; 7]. These challenges have been solved with the introduction of active integrated designs. Active antennas became an intriguing study topic because of advancements in Microwave Integrated Circuit (MIC) technology. The use of active antenna arrays in mobile communication and beam control has solved the channel capacity limitation problems by increasing the data rate. The advancement of smart antennas is just one of the many advantages of incorporating an active device into a passive antenna. Other benefits include increasing the effective length of short antennas, increasing the bandwidth, improving the noise factor, impedance matching, and increasing receiver antenna sensitivity. One such integrated design is the active integrated antenna (AIA), a novel technology that combines microstrip antennas with active solid-state electronics and microwave components to provide a variety of useful functionalities [8; 9; 10; 11; 12]. Integrated antenna design has been introduced to improve the efficiency of front-end systems and exists in recent times in the form of filtering antennas, rectifying antennas, power amplifier antennas, and low noise amplifier (LNA) antennas [13; 14; 15; 16; 17]. Compact fifth-mode and eighth-mode balanced substrate integrated waveguide (SIW) band-pass filters for 39 GHz were constructed and evaluated by _[PERSON]_ and _[PERSON]_[18; 19]. A third-order SIW filter/antenna was designed and presented by [PERSON] et al. [20]; the filter/antenna comprises two cavity resonators, one of which has a slot antenna. Theslot antenna maintains the radiation characteristics of the antenna while the excitation of two modes in the slot cavity produces a third-order filtering response. The integrated filter/antenna design had a center frequency of 3.71 GHz, 8.29% fractional bandwidth, and an antenna gain of 5.10 dBi. [PERSON] et al. [21] presented a miniaturization approach to designing. The initial stage in this concept was to reduce the size of a cavity filter while maintaining a high-quality factor for reduced insertion loss. A second-order filter was used to achieve downsizing by combining a high dielectric permittivity ceramic with a capacitive effect induced by inserting a post in the center of each resonator. Even when the load was greater than 50, the filter performance was maintained. Additionally, [PERSON] et al. [22] created a ring-type filtering patch antenna that combines a ring patch and a dual-mode microstrip ring resonator. Within the pass-band, two patch modes were created, and two radiation nulls were formed on both sides of the pass-band. This integrated design reduced the overall size and power loss of the front-end system. From the experiment, the max gain of the proposed filtering antenna was above 10 dBi. [PERSON] et al. [23] developed a wideband circularly polarized filtering patch antenna with three minima in the axial ratio response. In that arrangement, the patch antenna was processed in the same manner as the output port and final resonator of the filter network. In a far-field study, the amplitude and phase responses of a circular polarized (CP) wave were mapped to its axial ratio (AR). An 8.8% AR bandwidth was attained on a low profile of 0.028 \(\lambda\), and the resultant gain demonstrated strong filtering characteristics. Furthermore, for the operating frequency of 1575.42 MHz of the GPS band, a microstrip antenna with a low noise amplifier was designed by [PERSON] et al. [24]. This consists of a single passive antenna and an LNA. According to the simulation, it had a gain of 28.4 dBi; however, the measured gain was 14.77 dBi. The simulation yielded a circular polarization bandwidth of 60 MHz, while the experiment yielded 25 MHz.