## 1 Introduction  
Global Navigation Satellite Systems (GNSSs) are described as satellite constellations strategically placed to provide positioning, navigation, and timing (PNT) data. Specifically, the systems called Galileo, Compass, GLOASS, and GPS are the four most well-known PNT providers, and each of them has provider-specific operational frequency bands from 1.164 to 1.610 GHz [1]. This diversity in GNSSs increases the demand for advanced GNSS receiver systems using different frequency bands of various GNSSs. The multi-band receivers improve the positioning accuracy and reliability while reducing jamming vulnerability of the system [2]. The all-band antennas are the indispensable parts of multi-band GNSS receivers to maximize the operational capability by receiving signals from all operating bands provided by each GNSS using just a single antenna. Thus, the number of antennas, interference problems between antennas, and the antenna placement difficulties can be easily reduced. This is especially advantageous for space platforms that are subject to severe size and weight limitations. Moreover, if the all-band antenna has a stable gain performance over the entire frequency band, it provides another significant advantage by reducing the design complexity of the amplifier network used in multi-mode GNSS receivers. GNSSs operate in circular polarization to mitigate ionospheric losses, and receiving GNSS antennas are typically designed to provide right-hand circularly polarized (RHCP) radiation characteristics to decrease the polarization mismatch to as low a level as possible in order to increase the efficiency of data transmission as high as possible [3]. Particularly for space applications where weight and size are strictly limited, a good candidate for an all-band GNSS antenna must have high-compactness while ensuring its performance remains constant under all operational frequency bands. However, theoretically the fundamental limitation of antenna bandwidth is directly related with its electrical size [4]. These two conflicting requirements are the major challenge of all-band GNSS antenna designs for applications where size and weight are limited including space platforms. A wide variety of antennas are used in GNSS receiver studies, but most of these types are not suitable for direct utilization in practical space implementations. One of the candidates is quadrifilar helix antennas (QHA) because of their satisfactory axial ratio performance in circular polarization, whereas these antennas operate in resonant modes and have inherently narrow bandwidth [5]. Recently, some new versions of QHA have been presented that are aimed at obtaining wider bandwidth or multi-band behavior [6; 7; 8]. However, they require an additional broadband four-way hybrid feed to cover all GNSS bands, which complicates their feeding networks. Additionally, QHA needs a relatively large ground plane to provide the expected high gain performance. Patch antennas are another popular type of antenna that are easy to manufacture and offer a low-volume (planar) option for some GNSS applications [9]. Nevertheless, they are also resonant structures with limited bandwidth, and various methods have been presented to overcome their narrow-band characteristics, such as stacked structure [10], U-shaped slot [11], and L-probe [12]. The designed structures using these bandwidth enhancement methods require additional complex feed networks and are quite poor in resistance to vibration, which is vital in space applications. Although the operational bandwidth is not wide enough to operate in all GNSS bands, another study that is suitable for utilizing in space applications is on the dielectric resonator antenna (DRA) type [13]. Thanks to its monolithic structure, vibration resistance is sufficient, but it only has satisfactory performance in the lower and upper GNSS bands. Another space application-compatible antenna study presents dual/triple band designs and an antenna array for GPS [14].