# Design of a Compact Microstrip Decoupled Array
## 1 Introduction  
With the rapid advancement of wireless communication systems and radar technologies [1], the demand for compact and high-performance antennas has grown exponentially. Conventional antennas have become impractical due to their size, weight, power consumption, and limited flexibility. In response to this need, miniaturized mono-pulse antennas have emerged as a great solution, offering a compact dimension factor while maintaining excellent performance. A one-dimensional miniaturized mono-pulse antenna is suggested in this research. It is smaller than typical designs but still retains good radiation patterns. By minimizing the antenna's physical dimensions and array spacing, the proposed antenna achieves miniaturization. However, coupling is inevitable as antenna spacing is shrunk. As a result, the antenna's performance degrades and its radiation efficiency decreases. Therefore, to achieve the decoupling function, the feed network needs to be upgraded. Researchers have focused on various decoupling methods to reduce antenna coupling. In [2], a technique of decoupling dielectric stubs (DDS) [3] was applied to a 4 \(\times\) 4 dual-polarized and wideband antenna array. The DDS can achieve all port-to-port isolations over 25 dB from 4.4 to 5.0 GHz for all the coupling paths, which are 7 dB higher than their counterparts without the DDS. In [4], the neutralization line [5] is used to design a UWB MIMO antenna that covers the 3.1-5 GHz band with isolation greater than 22 dB. In [6], a tunable decoupling and matching network [7, 8] (DMN) for a two-element closely spaced antenna array is presented. It uses only one varactor to achieve a tuning range of 18.8% with both return loss and isolation better than 10 dB. In [9], a self-decoupling structure was designed to present a new decoupling concept for dual-band shared-aperture base station antenna arrays. This approach provides the antenna array with both in-band and in-band decoupling capabilities. The co-polarized in-band coupling between the designed high-band antennas is reduced by about 9 dB to 26.9 dB. In [10], a new decouplingmethod for phased array antenna units is proposed. The decoupling of the antenna units is achieved by embedding non-radiating coupled resonators between the antenna units. A mutual coupling reduction of more than 10 dB is achieved over the entire operating bandwidth. A decoupling method for slit antenna arrays is proposed in [11]. The array antenna decoupling surface consists of partially reflective metal patches. In [12], a quadratic slit antenna array based on ADS is simulated, and the mutual coupling is less than \(-15\) dB over the impedance bandwidth of 2.35-2.545 GHz. Microstrip antennas can be miniaturized by slotting the antenna surface or ground plane or by loading shorting probes. In [13], [PERSON] et al. proposed a compact circularly polarized microstrip antenna with square-ring slots and loaded shorting probes [14]. The overall size is 0.33 \(\lambda\)\(\times\) 0.33 \(\lambda\)\(\times\) 0.04 \(\lambda\) with a 3 dB measured gain. In [15], the antenna achieved high gain by incorporating a shorted probe loaded with a strip line. The antenna has dimensions of 0.57 \(\lambda\)\(\times\) 0.57 \(\lambda\)\(\times\) 0.09 \(\lambda\) and achieves a high gain of 8.5 dB. In [16], a defected ground structure (DGS) [17] was used to design a small decoupled MIMO antenna array. It etches cross slots on a metal ground plane to alter the distributed capacitance and inductance of the transmission lines, achieving decoupling. The dimensions of the designed antenna unit are 0.23 \(\lambda\)\(\times\) 0.27 \(\lambda\)\(\times\) 0.0058\(\lambda\), and the isolation at 5.8 GHz is greater than 20 dB. In [18], a compact CPMA was designed with the use of an artificial magneto-dielectric material [19]. The antenna has an overall size of 0.303 \(\lambda\)\(\times\) 0.303 \(\lambda\)\(\times\) 0.01 \(\lambda\) with a measured peak gain of \(-3.75\) dBic over the frequency band [20]. These methods generally result in a size reduction of about 30-50%.