Design and electromagnetic analysis of pyramidal and conical horn antenna for X-band satellite communication systems

1 Introduction

Horn antennas are among the most common microwave antenna structures due to their simple geometry and ease of implementation. Although the concept was introduced in the late nineteenth century, their development accelerated during the 1930s with the emergence of microwave engineering and waveguide-based transmission systems. During World War II, horn antennas became an important component of radar and microwave communication systems, leading to their widespread adoption in numerous applications. Today, they are used in radio astronomy, satellite tracking systems, ground stations, and satellite communication systems, where their high gain, predictable radiation characteristics, and broad operational bandwidth are particularly advantageous.

Horn antennas have been widely investigated in the literature, with detailed analyses presented by Balanis (Sunny Dayal, 2015), Milligan (Samaneh and Mallahzadeh, 2011), and Kraus and Marhefka (Xiao et al., 2022), covering design methodologies, radiation characteristics, and practical implementations. The extensive use of horn antennas is largely due to their simple construction, the availability of multiple geometric configurations adapted to different applications, ease of excitation, structural flexibility, high gain and ability to operate at high power levels (Sunny Dayal, 2015; Samaneh and Mallahzadeh, 2011). Owing to these characteristics, honr antennas are frequently employed as radiating elements in a variety of microwave and satellite communication systems.

Several studies have reported the design and analysis of pyramidal horn antennas for X-band applications. Pendurthy (Patnaik and Basavarajappa, 2014) presented a design procedure for an X-band pyramidal horn antenna and reported high gain together with stable radiation characteristics suitable for satellite communication systems. Other horn antenna configurations have also been investigated, including wideband planar horn antennas based on substrate integrated waveguide technology (Investigation of Circular Horn, 2023) and designs incorporating frequency selective surfaces to improve gain de directivity in X-band radar and satellite applications (Patnaik and Basavarajappa, 2014). Recent studies have also considered conical horn antennas for X-band radar and satellite uplink systems, reporting stable circular polarization and good impedance matching over the operating bandwidth (Investigation of Circular Horn, 2023).

Beyond their extensive use in terrestrial systems, horn antennas play an important role in space technologies, particularly in satellite communication systems. For example, the communication satellite OneSat, developed by Airbus for geostationary orbit applications, operates in the KU-band and Ka-band and is designed to allow flexible reconfiguration according to evolving mission requirements. The satellite employs an advanced reflector antenna system developed by ArianaGroup, known as the SPIRIT reflector antenna, whose radiating element is a corrugated horn antenna (Advanced Microwave Technologies, 2025). Similarly, satellites developed by BlackSky employ reflector antenna systems in which the radiating element is a horn antenna operating in the S-band and X-band frequency ranges. Another relevant example is represented by horn antennas integrated into the communication systems of CubeSat microsatellites, which frequently operate in the Ku-band and Ka-band. These examples highlight the versatility and continued relevance of horn antennas as reliable radiating elements in modern satellite communication systems.

Although numerous studies have examined individual horn antenna configurations, fewer works have presented a direct comparison between pyramidal and conical horn antennas under the same design and simulation conditions. In particular, the influence of circular polarization capability on antenna selection for satellite communication applications has received limited attention. The present study addresses this aspect by comparing the electromagnetic performance of both antenna types operating in the X-band frequency range (8–12GHz), which is widely used in radar, satellite communication, and space observation systems (Sunny Dayal, 2015; Investigation of Circular Horn, 2023).

The comparison between pyramidal and conical horn antennas in motivated by differences in their geometric and electromagnetic characteristics and by their potential use in satellite communication systems. The rotational symmetry of the conical horn antenna facilitates the generation of circular polarization, which is commonly employed in satellite communications. In addition, its geometry is well suited for the illumination of parabolic reflector antennas, contributing to a more uniform field distribution across the reflector antennas, contributing to a more uniform field distribution across the reflector aperture. The conical horn antenna also serves as the geometric basis for the conical corrugated horn antenna, a configuration frequently used as a feed for reflector systems because of its symmetric radiation pattern, low cross-polarization levels, and good polarization performance (Olver et al., 1994; Mihai, 2008). For these reasons, a comparison with the pyramidal horn antenna provides useful insight into the advantages and limitations of both configurations for X-band satellite communication applications.

The objective of this study is to compare the electromagnetic performance of pyramidal and conical horn antennas and to evaluate the suitable of the smooth-wall conical horn antenna for satellite communication applications. The analysis provides a characterization of the conucal horn antenna. The obtained results serve as a reference for a subsequent study focused on the design and analysis of a conical corrugated horn antenna within the framework of a broader doctoral research project.

The feeding of horn antennas is achieved through waveguide transmission line structures, which guide electromagnetic signals efficiently with very low radiation losses and high immunity to external interference (Nicolaescu, 1997; Pozar, 2011). In the present study, two waveguide types were selected as feeding structures for the designed horn antennas.

For the pyramidal horn antenna, the WR-90 rectangular waveguide was selected, with standard dimensions a = 22.86 mm and b = 10.16 mm, operating in the dominant TE₁₀ propagation mode within the X-band frequency range. The guided wavelength within the WR-90 waveguide at the central frequency of 10 GHz is λ g = 39.707 mm, calculated as λ g = λ 1 − λ / 2 a 2, where λ = 30 mm represents the free-space wavelength at 10 GHz.

For the conical horn antenna, the BY89 circular waveguide was selected, with a diameter of d = 23.825 mm and wall thickness of 1.65mm, operating in the dominant TE₁₁ propagation mode, with a cutoff frequency of 8.67 GHz, confirming stable single-mode propagation within the operational frequency band.

Both waveguide structures were modeled using copper as the conductive material, ensuring minimal ohmic losses and accurate electromagnetic simulation results in both Ansys HFSS and CST Studio Suite environments (Pozar, 2011; Constantine, 2005).

The transition from each feeding waveguide to the corresponding horn aperture was designed without steps, ensuring a smooth impedance transformation and avoiding discontinuities that cloud excite higher-order modes in the throat region (Nicolaescu, 1997; Constantine, 2005). For the BY89 circular waveguide, the next higher-order mode above the dominant TE₁₁ is TM₀₁, with a cutoff frequency f_c (TM₀₁)=(2.405/1.841) · f_c (TE₁₁) = 11.32GHz, calculated from the standard roots of the Bessel function for circular waveguide modes (Constantine, 2005); since the conical horn antenna operates within the 9–12 GHz band, single-mode TE₁₁ propagation is preserved across most of this range. The mismatch component, derived from S₁₁, is below 0.01 dB for both antennas, while the ohmic component is approximately 0.27dB for the pyramidal horn and 0.18dB for the conical horn, confirming efficient power transfer from the feeding port to the radiating aperture in both configurations.

The simulations and determination of the characteristic antenna parameters were carried out using two electromagnetic simulation environments, namely, Ansys HFSS and CST Studio Suite. The purpose of employing both platforms was to ensure accurate validation of antenna performance and to minimize potential numerical errors through cross-platform verification. The remainder of this paper is organized as follows: Section 3 presents the design and analysis of the pyramidal horn antenna; Section 4 describes the conical horn antenna design and simulation results; Section 5 provides a comparative discussion of both configurations; and Section 6 summarizes the main conclusions.

2 Design and analysis of pyramidal horn antenna parameters specification

Pyramidal horn antennas are widely used in satellite communication systems, radar applications, and antenna measurement facilities due to their simple structure and favorable radiation characteristics. Their geometry enables efficient radiation of electromagnetic waves while providing high gain and good directivity. The performance of a pyramidal horn antenna depends strongly on its geometric dimensions, which influence the impedance matching bandwidth, gain and radiation pattern. Consequently, the selection and optimization of these parameters represent an important stage in the antenna design process (Pozar, 2011; Constantine, 2005).

The aperture dimensions and flare angle are among the most important design parameters of horn antenna, as they directly influence its gain, beamwidth, impenace matching, and radiation efficiency. The dimensions of the aperture directly affect the antenna gain: a larger aperture results in higher gain and a more directive beam. The flare angle of the aperture also directly impacts both antenna gain and impedance matching. A steeper flare angle can introduce unwanted reflections and standing waves, whereas a gradual flare may result in unnecessarily large aperture dimensions. Appropriate selection of the aperture dimensions and flare angle allows the horn antenna to achieve gains of up to approximately 25dB while maintaining a voltage standing wave ratio VSWR<1.5:1 over the operating frequency band (Nicolaescu, 1997; Constantine, 2005).

The antenna is fed through a waveguide that provides the transition between the external circuitry and the radiating structure. The waveguide dimensions and material properties influence the propagation characteristics and transmission losses and therefore must be selected according to the operating frequency range and performance requirements. To maximize energy transfer to the antenna, this section must be smooth so that expansion does not create discontinuities that could generate reflections or higher-order modes. As discussed in the previous subsection, waveguide sections are commonly manufactures from brass or aluminum alloys because of their good electrical conductivity, mechanical strength and corrosion resistance. The method used to couple electromagnetic energy into the waveguide and subsequently into the horn antenna influence the overall antenna performance. Consequently, the feeding structure should be positioned along the waveguide axis and designed according to the operating waveguide axis and designed according to the operating wavelength and waveguide dimensions (Nicolaescu, 1997; Constantine, 2005; Thomas, 2005).

The polarization characteristics of an antenna are critical from the design stage, as they define the antenna’s suitability for integration into the intended system. Linear polarization is the most common and easiest to implement; however, it can be sensitive and may introduce polarization mismatch losses, resulting in partial reception of the information-carrying electromagnetic waves. Structural circular polarization is more challenging to implement, yet it is essential in applications such as satellite communications and weather radar systems (Nicolaescu, 1997; Constantine, 2005; Thomas, 2005).

Thus, in order to calculate and implement methods for determining the geometric parameters of the antenna, the aforementioned properties and the operating frequency band must be known. In this study, a pyramidal horn antenna will be designed to operate in the X-band (8–12 GHz). This frequency band was selected following an analysis of various satellite systems, concluding that this band is commonly used in practice, as illustrated by the examples presented in the Introduction chapter of this work.

First, to define the geometric parameters of the antenna, one starts from the waveguide standards corresponding to the desired frequency band. For the X-band, the most suitable waveguide is WR-90. Based on the target frequency band, the desired gain provided by the chosen waveguide in this case, G = 22.70dB, and the WR-90 waveguide dimensions (a = 22.86 mm and b = 10.16 mm), the parameters on the pyramidal horn antenna are calculated using the following mathematical formulas. These parameters are then input for analysis and simulation in the Ansys HFSS software (Hansen, 2009; Kraus and Marhefka, 2002).

The first step is to convert the gain G from dB to linear value, as follows (Constantine, 2005):

G dB = 10 · ⁡ log ⁡ G (1)

G 0 = 10 G dB / 10 = 186.208 (2)

Next, χ is calculated, a dimensionsless geometric parameter used in horn antenna design according to Balanis (1982), Constantine (2005):

χ = G 0 2 π 2 π = 11.823 (3)

The horn slant lengths correspomding to the two principal planes (the electric field plane E and the magnetic field plane H) are then computed (Kraus and Marhefka, 2002):

ρ e = χ · λ = 354.446 (4)

ρ h = G 0 2 · λ 8 π 3 · χ = 354.446 (5)

The two lengths of the antenna along the respective planes are calculated as follows (Constantine, 2005):

A = 3 λ ρ h = 178.544 mm (6)

B = 2 λ ρ e = 145.781 mm (7)

The horn antenna apertures are set equal (p_h = p_e), calculated as (Constantine, 2005):

ph = pe = b 1 ‐ b ρ e b 1 2 − 1 4 1 / 2 = 322.696 mm (8)

It should be noted that these dimensions were calculated for the central frequency of 10 GHz.

With the geometric parameters illustrated in Figure 1 and defined for analysis in the two simulation programs, Ansys HFSS and CST Studio, the next step was to design the pyramidal horn antenna and analyze the parameters of interest in both software environments. The purpose of this analysis was to evaluate whether the antenna operates optimally within the X-band frequency range. To provide a clearer overview of the mathematical quantities used in the antenna design and their definitions, as well as to better illustrate their influence on the antenna profile, the following parameters are presented in Table 1.

TABLE 1. Geometrical parameters of the pyramidal horn antenna.

As shown in Figure 2 the reflection coefficient S₁₁ remains well below −10dB across the entire X-band frequency range, indicating that the pyramidal horn antenna operates optimally throughout the initially defined band.

In Ansys HFSS simulation, the maximum reflection coefficient is −19.05dB at 9.14GHz, while the minimum value, corresponding to the lowest losses, occurs at 8.22GHz with S11 = −39.43dB. This demonstrates excellent impedance matching, low reflection losses, and optimal energy transfer from the input port to the antenna. In the CST Studio simulation, as shown in Figure 2 , the maximum reflection coefficient is 25.18dB at 9.42GHz and the minimum, corresponding to the lowest losses, occurs at 8.07GHz with S₁₁ = −56.18dB. Therefore, both simulation programs confirm that the studied antenna exhibits optimal matching with the feeding line and minimal energy losses.

It is also noteworthy from the results presented in Figure 3 that the variations of the reflection coefficient in both simulation programs follow the same trend, indicating that antenna maintains optimal matching with the feeding lines across the entire desired frequency band. To confidently assert that excellent matching is achieved, the normalized impedance values presented in the Smith chart can be observed. The vertical ring value are around 1, while the horizontal ring corresponding to the reactance is approximately 0.1, which approximates the input impedance as Z_in≈(50 ± 3)+j (±5)Ω. This indicates optimal matching of the antenna with the feeding line, compatibility with a 50Ω system, and stable impedance with near-ideal VSWR values. Comparing these results with those obtained in the CST Studio simulation, the studied antenna exhibits the same variations in input impedance.

The radiation pattern obtained in both Ansys HFSS and CST Studio indicates a main lobe with a maximum gain of approximately 23.63dB, as shown in Figure 4. This gain aligns with the values expected from the initial design phase. It should be noted that if the measured gain were significantly lower than the design predictions, it would indicate that the antenna is not properly matched to the feeding line and that the obtained geometric dimensions are not appropriate.

A symmetry in the antenna gain distribution in evident, along with a narrow -3dB beamwidth. Specifically, the -3dB beamwidth is 6° in the HFSS simulation and 10° in the CST Studio simulation, ensuring high directivity and optimal antenna selectivity. Additionally, Figure 5 shows the electric field amplitude distribution across the surface of the pyramidal horn antenna, calculated using Ansys HFSS.

It can be observed that the electric field limits shown in Figure 5 reach maximum values of approximately 400v/m. The TE₁₀ propagation mode is present within the waveguide, which transforms into a plane wave at the antenna aperture as the horn expands, causing the field to spread. The region closer to the feeding line exhibits a more uniform amplitude distribution and straighter phase contours, indicating a smooth and uniform energy transfer without abrupt variations.

The electric field distribution shoe lower field intensity near the horn walls and a maximum value along the antenna axis. The reduced field concentration at the metallic surfaces is associated with lower conductor losses, while the field distribution at the aperture remains nearly uniform in phase. As illustrated in Figure 5, the transition from the TE₁₀ waveguide mode to free-space propagation is achieved with limited field distortion. These characteristics are consistent with the obtained gain and the low side-lobe levels observed in the radiation pattern.

The performance parameters of the pyramidal horn antenna were estrablished in accordance with the standard specifications associated with the WR-90 rectangular waveguide used as the feeding structure. THE waveguide standard inherently defines certain electromagnetic performance constraints, from which a target gain of 22.7dB was derived analytically using the expression G = 10 · ⁡ lg ⁡ 0.51 · A · B / λ 2, where A = 178.5 mm, B = 145.8 mm and λ = 30 mm. The geometric dimensions of the antenna were selected so that the analytical design and the numerical simulation performed in Ansys HFSS and CST Studio Suite would yield consistent and optimal results. The simulation results were evaluated with the aim of achieving a practical engineering compromise: good impedance matching across a defined portion of the X-band, low reflection losses, and a -3dB beamwidth in both th E and H planes that is sufficiently narrow to concentrate the radiated energy along the principal rqadiation axis, ensuring high directivity and beam selectivity. It should be noted that these trade-offs between the analytically computed values and the simulation results are directly governed by the geometric profile of the antenna structure. To illustrate the relationship between the analytical calculations and the corresponding simulated performance, the relevant parameters are summarised in Table 2.

TABLE 2. Pyramidal horn antenna design parameters and performance trade-off.

Bold values indicate the row corresponding to the actual simulated (HFSS) result, shown for direct comparison with the analytical design target.

3 Design and analysis of conical horn antenna parameters specification

In the following paragraphs, the analyze and design of the conical horn antenna are described, with particular emphasis on its capability to suport circular polarization. The antenna is designed to operate within the X-band frequency range (8–12 GHz), and its feeding is achieved using a circular waveguide of type BY89 with a wavelength of λ = 30mm, which was also analyzed in Section 1.

The conical horn antenna can operate over a wide frequency band and achieve relatively high gain values; therefore, it is widely used in applications such as radio astronomy, satellite communications, television broadcasting, and radar systems. In addition to its broad operational bandwidth, when properly designed, it can also operate at very high frequencies, extending up to the terahertz range. However, its primary structural advantage, as previously mentioned, lies in the ease of implementing circular polarization. From a geometric standpoint, the antenna facilitates the formation of circularly polarized electromagnetic waves; nevertheless, it requires the inclusion of polarizer in the feeding line to introduce a 90° phase shift between the input signals in order to generate circularly polarized signals (Mihai, 2008).

The definition of the geometric parameters of a conical horn antenna differs slightly from that of pyramidal horn antenna, following the methodology described by Al-Asaslih (2016). Initially, a circular waveguide of type BY89 was selected as the feeding waveguide. According to the relevant standards, this Waveguide has a diameter of d = 23.825 mm and a material thickness of 1.65 mm (Güney, 2001). Based on these two defined values, the following formulas are used to determine the antenna aperture diameter and the horn length, which are essential parameters for achieving proper impedance matching and the desired gain. These calculated values are subsequently introduced into electromagnetic simulation and design software in order to analyze the operating behavior of the antenna.

The aperture diameter of the antenna, d_m is calculated, where the length l is selected in the range 2 λ ≤ l ≤ 3 λ (Sunny Dayal, 2015; International Electrotechnical Commission, 2022):

d m = 3 · l · λ = 73.4 mm (9)

The flare angle of the antenna aperture is defined as follows (International Electrotechnical Commission, 2022):

φ = arctg d m − d 2 l = arctg 0.4134 = 22.5 ° (10)

The length of the antenna is determined as follows (Sunny Dayal, 2015) (International Electrotechnical Commission, 2022):

L = l cos ⁡ φ = 65.5 mm (11)

The obtained values were modeled and implemented in the electromagnetic analysis and simulation software Ansys HFSS and CST Studio, resulting in the geometric configuration presented in Table 3.

TABLE 3. Geometrical parameters of the conical horn antenna.

To evaluate whether the conical horn antenna satisfies the required operating conditions, the analysis begins with the determination of the reflection coefficient S₁₁. As illustrated in Figure 6, across the entire analyzed frequency band (9–12GHz), the reflection coefficient values remain below the −10dB threshold, indicating effective impedance matching and efficient power transfer from the feeding line to the antenna with low reflection losses. Electromagnetic simulations performed using Ansys HFSS indicate an effective operating bandwidth of approximately 3 GHz, within which the conical horn antenna ensures stable signal transmission with minimal losses. The minimum reflection coefficient value is S₁₁ = -43dB, corresponding to frequency of 11.22GHz. These results confirm the well-known characteristic of horn antennas to operate over wide frequency bands, which represents a significant advantage for satellite communication applications. To validate these findings, the same antenna structure was also analyzed in the CST Studio simulation environment, using identical geometric dimensions and simulation conditions. The obtained results show a similar variation of the reflection coefficient, with a minimum value of S₁₁ = -39.70dB, occurring at a frequency slightly shifted by approximately 1GHz compared to the value obtained in Ansys HFSS.

The comparative analysis of the obtained results reveals a good agreement between the two simulation environments, demonstrating that the conical horn antenna exhibits very good impedance matching across the entire analyzed frequency band (9–12GHz). In both cases, the reflection coefficient values remain below the −10dB threshold, confirming the high performance of the antenna and the efficient energy transfer between the feeding line and the radiating structure.

The results obtained in Ansys HFSS and CST Studio Suite are in close agreement, indicating consistent performance of the proposed antenna design. In addition, the cutoff frequency was evaluated since it determines the lower frequency limit for electromagnetic wave propagation within the waveguide.

As illustrated in Figure 7, the cutoff frequency corresponding to the conical horn antenna defines the lower operational limit of the horn structure. Ideally, in order to ensure stable propagation of the dominant TE₁₁ mode, the operating frequency should be sufficiently higher than the cutoff frequency (fop≥ 1.3 · fcut). This condition is satisfied in the present design, where the cutoff frequency is 8.67GHZ, resulting in an ideal operating frequency of approximately 11.27GHz, which lies within the initially defined frequency band of 8–12GHz. It should be noted that as the operating frequency approaches the cutoff frequency, reflections and degradations in radiation performance may occur. According to the results illustrated in the figure, it can be concluded that the optimal operating frequency should be higher than 11.27 GHz, ensuring reduced reflection and radiation losses, high gain, and minimal impedance variations. Under these conditions, maximum power transfer can be achieved through proper impedance matching.

Nevertheless, it can also be stated that the antenna operates in the dominant TE₁₁ propagation regime even though the central frequency of the operating band and the frequency used for defining the geometric parameters remain relatively close to the cutoff frequency.

AS shown in Figure 8, the waveguide impedance exhibits a rapid variation in the vicinity of the cutoff frequency 8.67GHz, which is characteristic of circular waveguides and consistent with the theoretical behavior of the dominant TE₁₁ mode. Above the cutoff frequency, within the 9–12GHz operating band, the impedance becomes relatively stable, indocating the propagation of the dominait TE₁₁ mode throughout the antenna structure.

The relatively high impedance values observed in this region are characteristic of the modal propagation regime of the waveguide and do not indicate a mismatch with the 50Ω system. Instead, they correspond to the characteristic impedance associated with the propagating TE mode in the circular waveguide.

The results obtained from the CST Studio simulation confirm the same type of impedance variation and the same behavior near the cutoff frequency. This agreement between the two simulation environments supports the validity of the antenna operation within the 9–12GHz frequency band.

The 3D radiation pattern presented in Figure 9 highlights a maximum gain of 16.43dB and beamwidth of approximately 30°, values that are consistent with the theoretical relationships between directivity and beamwdth for circular aperture antennas. The symmetric shape of the main lobe and the absence of pronounced side lobes indicate stable operation in the dominant TE₁₁ mode and good aperture efficiency, which is an essential aspect when the antenna is used as a feed element in a parabolic reflector system or within a microstrip antenna array.

It can also be observed that the antenna beamwidth is consistent with the typical characteristics of the antennas employed in satellite communication applications, which generally exhibit beamwidths in the range of 20°–30°. Consequently, the antenna analyzed in this manuscript enables efficient illumination of the reflector while minimizing excessive edge losses.

By comparing the results with those obtained using the CST Studio simulation environment, it can be observed that the spatial distribution of the electromagnetic waves remains consistent, while the obtained directivity values are very similar. The beamwidth obtained from the second simulation environment is approximately 29.6°, which is nearly identical to the value obtained in Ansys HFSS. Furthermore, the antenna gain calculated using CST Studio is 14.8dB, a value very close to that obtained in the initial simulation. These results indicate that the antenna analyzed in both simulation environments exhibits consistent operating characteristics and comparable performance parameters, thereby confirming the validity of the design and the optimal operation of the antenna within the 9–12GHz frequency band. The antenna was excited using a multimodal wave port, enabling the two orthogonal fundamental TE₁₁ modes of the circular waveguide. This Configuration was facilitated by the circular geometry of the antenna, in contrast to the previously analyzed pyramidal horn structure. By imposing a 90° phase difference between the two modes and maintaining equal amplitudes, circular polarization was achieved. The Axial Ratio diagram shown in Figure 10 indicates values lower than 3dB over an angular region of approximately 30°, corresponding to the beamwidth of the main lobe. This agreement confirms the presentation of modal orthogonality and the absence of polarization degradation in the region of maximum radiation. The obtained performance demonstrates that the analyzed antenna exhibits characteristics suitable for implementation in satellite communication applications.

The electric field distribution illustrated in Figures 11, 13 confirms that stable propagation of the dominant TE₁₁ mode occurs inside the horn antenna, without the excitation of higher-order modes. The progressive expansion of the wavefront and the gradual field uniformity at the antenna aperture indicate a smooth impedance transition and high aperture efficiency. The electric field distribution remains uniform, without abrupt variations or parasitic modal excitations, while the wavefront becomes progressively flatter as it approaches the antenna aperture. The axial symmetry of the electric field distribution validates the preservation of the orthogonality of the excited modes and supports the obtained performance metrics, namely, a gain of 16.43dB and an Axial Ratio AR<3dB within the angular region corresponding to the main lobe beamwidth.

The performance parameters of the pyramidal horn antenna were estrablished in accordance with the standard specifications associated with the WR-90 rectangular waveguide used as the feeding structure. THE waveguide standard inherently defines certain electromagnetic performance constraints, from which a target gain of 22.7dB was derived analytically using the expression G = η_ap·(π·d_m/λ)² where η_ap is the aperture efficiency, d_m is the aperture diameter and λ = 30 mm.The geometric dimensions of the antenna were selected so that the analytical design and the numerical simulation performed in Ansys HFSS and CST Studio Suite would yield consistent and optimal results. The simulation results were evaluated with the aim of achieving a practical engineering compromise: good impedance matching across a defined portion of the X-band, low reflection losses, and a -3dB beamwidth in both th E and H planes that is sufficiently narrow to concentrate the radiated energy along the principal rqadiation axis, ensuring high directivity and beam selectivity. It should be noted that these trade-offs between the analytically computed values and the simulation results are directly governed by the geometric profile of the antenna structure. To illustrate the relationship between the analytical calculations and the corresponding simulated performance, the relevant parameters are summarised in Table 4.

TABLE 4. Conical horn antenna design parameters and performance trade-off.

Bold values indicate the row corresponding to the actual simulated (HFSS) result, shown for direct comparison with the analytical design target.

4 Discussion

A comparison between the two analyzed configurations highlights several advantages and limitations that significantly influence the selection of the appropriate antenna type depending on the specific application and the operational requirements of the system. The pyramidal horn antenna provides high directivity, wide operational bandwidth, a relatively simple mechanical structure, and effective beam control in both the E-plane and H-plane. However, a notable limitation of this configuration is that circular polarization is difficult to implementation directly, which may restrict its use in communication systems requiring circular polarization, as this mismatch can lead to signal degradation and potential information loss. Nevertheless, it remains highly suitable as a feed for reflector antennas, as a calibration antenna, or in applications where linear polarization is required (Tele communications Industry Association). Table 5 provides a quantitative summary of the key performance parameters obtained for both antenna configurations, enabling a direct comparison of their electromagnetic characteristics.

TABLE 5. Comparative performance summary of the pyramidal and conical horn antennas.

In comparison with the pyramidal horn antenna, the conical horn antenna presents a significant advantage regarding the implementation of circular polarization, as its geometric configuration naturally supports the generation of circularly polarized electromagnetic waves. In addition to this advantage, several other important characteristics can be highlighted, including the axial symmetry of the electromagnetic field distribution, uniform illumination of reflector antennas, and a high stability of the dominant TE₁₁ propagation mode (Tele communications Industry Association).

Radiation efficiency represents the ratio between the power radiated into free space and the power accepted at the antenna input port. The difference between the two quantities correspondts to the power dissipated as through ohmic losses in the antenna walls. The results obtained confirm that the chosen conductor material introduces a radiation efficiency reduction of approximately 4% which has a negligible impact on the overall antenna performance. The conical horn antenna achieves a radiation efficiency approximately 2% higher than the pyramidal horn, owing to its smaller inner surface area, which reduces the total ohmic loss. Both configurations exceed 90% radiation efficiency and the difference between them is not practically significant for the intended application.

Aperture efficiency characterizes how effectively the physical aperture area contributes to coherent radiation in the desired direction. A low aperture efficiency implies that a large physical aperture is used without a proportional increase in radiated power, resulting in wasted volume, increased structural dimensions, or distortion of the principal radiation direction if the aperture field distribution is non-uniform. The 10% difference in aperture efficiency between the two configurations indicates that the conical geometry makes more effective use of the aperture surface for coherent radiation, reducing the contribution of peripheral aperture regions. In satellite systems, the aperture efficiency of the feed element directly influences the total gain of the onboard antenna and consequently the available effective isotropic radiated power (EIRP) over the coverage area. A 10% improvement in aperture efficiency can translate into an additional 0.5–1dB of system gain, which represents a meaningful improvement in the link budget of satellite communication system. Cross-polarization discrimination is one of the most critical parameters in satellite communication systems. The results presented in Figures 11, 12 confirm that the pyramidal horn antenna produces a pure linear polarization, with a cross-polarization discrimination of approximately 62 dB on the principal axis, significantly exceeding the 30 dB minimum threshold required for satellite communication systems using single linear polarization. This result is consistent with the physical behavior of the antenna: although the pyramidal horn was excited through a bimodal port with a 90° phase shift its rectangular geometry inherently generates a linearly polarized field rather than a circularly polarized one. For the conical horn antenna, the bimodal excitation of two orthogonal TE₁₁ modes produces a circular polarization discrimination of 57–62dB on the principal axis, as shown in Figure 11. This result demonstrates the clear superiority of the conical horn over the pyramidal configuration for the implementation of circular polarization in satellite communication systems, achieved already at the smooth-wall design stage, without the introduction of corrugations.

The approximately 5dB difference in the front-to-back ratio between the two configurations is consistent with the higher gain of the pyramidal horn antenna. Nevertheless, the front-to-back ratio of the conical horn antenna, which exceeds 23dB, confirms that this configuration also concentrates the radiated energy predominantly in the principal radiation direction, in accordance with the standard requirements for satellite feed elements.

The pyramidal horn antenna is well suited to applications requiring high directivity, pure linear polarization and precise beam control. However, for use as feed element in reflector-based satellite antenna systems, the conical horn antenna represents the more appropriate choice. Its aperture efficiency of 74% maximizes uniform reflector illumination, its circular polarization discrimination of 57–62dB ensures polarization purity, and its front-to-back ratio of 23dB limits spillover losses and the system noise temperature. On the basis of the results obtained and the cited references, it can be stated that the circular polarization performance of the smooth-wall conical horn approaches that of corrugated horn antennas used on operational satellites (Xiao et al., 2022; Olver et al., 1994), validating the choice of this geometry as the electromagnetic and geometric baseline for the subsequent design of conical corrugates horn antenna.

To compare the results obtained from the simulations performed in the Ansys HFSS and CST Studio Suite environments, Table 6 presenting the performance parameters and efficiencies of the two antennas alongside the general characteristics required of antennas used in satellite sysytems. For the aperture efficiency of reflector feed elements, the typically acceptable values are 60%–80%, with values below 50% considered inefficient for a reflector system (Moy-Li et al., 2017). For linearly polarized antennas, the cross-polarization discrimination should be better than 30dB within the −1 dB points of the main beam axis and 25 dB elsewhere (International Telecommunication Union, 1995). Both antenna configurations analysed in this study meet or exceed these reference values, supporting their suitability for satellite communication applications.

TABLE 6. Comparative radiation performance (International Telecommunication Union, 1995) (Moy-Li et al., 2017).

A comparison of the two simulation environments reveals that CST Studio Suite requires significantly lower computational resources and shorter processing times than Ansys HFSS. The makes CST particularly suitable for the functional verification of antenna geometries where the primary focus is on the overall electromagnetic behavior rather than on the detailed analysis of wave propagation mechanisms. The analysis domain in CST is the time domain, which allows broadband results to be obtained from a single simulation run. Ansys HFSS operates in the frequency domain and computes the electromagnetic field distribution in detail at each frequency point, including along curved surfaces and geometric transitions, resulting along curved surfaces and geometric transitions, resulting in higher numerical accuracy. Ansys HFSS employs an adaptive tetrahedral mesh that conforms to the actual geometry of the antennas structure, whereas CST uses a Cartesian hexahedral mesh that approximates curved boundaries through staircase discretization. This fundamental difference in meshing strategy accounts for the higher RAM consumption observed in HFSS, approximately 15 GB, compared to approximately 1.5 GB in CST Studio Suite, while also explaining the higher accuracy of the HFSS results for geometrically complex structures.

The two platforms also differ in how the frequency-domain response in obtained. In HFSS, the electromagnetic field is computed independently at each frequency point. In CST, time-domain response is first calculated and then transformed into the frequency domain using the Fast Fourier Transform. This spectral extraction introduces a limited frequency resolution, which results in an additional numerical error of approximately 1 GHz in the computed S₁₁ minimum, observed in the present study as a shift from 11.22GHz (HFSS) to 10.18 GHz (CST) for the conical horn antenna. Differences in the radiation boundary conditions between the two platforms introduce additional discrepancies in the computed gain values, ranging from 0.03 dB for the pyramidal horn to 1.63 dB for the conical horn.

In this context, Ansys HFSS is based on the Finite Element Method (FEM) in the frequency domain, which enables highly accurate solutions for complex geometries and is particularly suitable for resonant structures such as waveguide components or antennas operating within well-defined frequency ranger. In contrast, CST Studio Suite provides several numerical solvers, most commonly employing the Finite Integration Technique (FIT) in the time domain. This approach allows broadband analysis to be performed within a single simulation un and enables the investigation of transient electromagnetic phenomena (Al-Asaslih, 2016).

On the basis of the above, it can be stated that the differences observed between the two simulation environments fall within the normal and documented range of inter-platform variations for microwave structures of this type. The comparative study by Luo and Ge (2020) confirms the general agreement between HFSS and CST for similar microwave structures, reporting typical gain discrepancies below 2 dB. The gain difference of 1.63dB and S₁₁ frequency shift of approximately 1 GHz observed in the present study are consistent with these reported limits and are attributable to the inherent differences in meshing strategy and spectral resolution between the two numerical methods.

5 Conclusion

The results obtained for both antenna structures confirm excellent impedance matching within the X-band frequency range (8–12 GHz), with reflection coefficient values remaining below −10dB across the entire operational bandwidth, demonstrating efficient power transfer between the feeding waveguide and the radiating structure. The pyramidal horn antenna, fed by the WR-90 rectangular waveguide, achieves a maximum gain of 23.63 dB with a narrow half-power beamwidth of approximately 6°–10°, confirming high directivity and precise beam control. The conical horn antenna, fed by the BY89 circular waveguide, achieves a maximum gain of 16.43 dB with a half-power beamwidth of approximately 30°, consistent with the illumination requirements of parabolic reflector systems employed in satellite communication platforms.

The primary contribution of this study lies in the systematic and simultaneous comparative electromagnetic analysis of the two horn antenna configurations under identical simulation conditions, an approach that has not been comprehensively addressed in the existing literature. The results demonstrate that while the pyramidal horn antenna offers superior gain and narrower beamwidth, making it suitable for applications requiring high directivity and linear polarization, the conical horn antenna presents significant and decisive advantages for satellite communication applications. Specifically, the axial symmetry of the conical geometry naturally supports the generation of circularly polarized electromagnetic waves, as validated by the Axial Ratio measurements confirming AR < 3dB over an angular region of approximately 30°, centered at the main lobe direction. This represents a critical advantage in satellite communications, where circularly polarized signals are predominantly employed to mitigate polarization mismatch losses and ensure reliable signal reception regardless of satellite orientation.

A further and equally important contribution of this work is the rigorous validation of the conical horn antenna as the direct geometric archetype of the conical corrugated horn antenna. The electromagnetic performance demonstrated in this study, namely, stable TE₁₁ mode propagation, uniform aperture field distribution, high aperture efficiency, and confirmed circular polarization capability, establishes the essential geometric and electromagnetic foundation required for the subsequent development of a conical corrugated horn antenna for satellite applications. Corrugated horn antennas are widely recognized as the optimal feeding elements for parabolic reflector systems onboard satellites, owing to their superior radiation symmetry, minimal cross-polarization levels, and excellent polarization purity. The present study therefore constitutes a complete and self-contained comparative analysis, while also representing a necessary and validated reference step within the broader doctoral research framework, upon which the subsequent design of the conical corrugated horn antenna will be built.

The dual-platform simulation methodology employed in this study, combining Ansys HFSS, based on the Finite Element Method in the frequency domain, and CST Studio Suite, based on the Finite Integration Technique in the time domain, provides a robust cross-validation framework that minimizes numerical errors and enhances the reliability of the obtained results. The strong agreement between the two simulation environments confirms the validity of the proposed antenna designs and supports their suitability for implementation in X-band satellite communication systems.

Table 7 presents previously published X-band horn antenna designs, with the reported results compared against the two antennas analysed in the present work. The pyramidal horn antenna designed in he work achieves a gain of 23.63dB, higher than the values reported by Sunny Dayal (2015) (> 20dB) and by Mukhlif (2020) (15dB) for comparable WR-90 pyramidal horn antennas in the X-band, while maintaning a narrower -3dB beamwidth of 6°–10°. The conical horn antenna achieves a gain of 16.43dB with confirmed circular polarization (AR < 3dB), comparable to the corrugated configuration reported by Xiao et al. (2022), but obtained at the smooth-wall design stage, without the additional structural complexity of corrugations or a dielectric polarizer. Beyond the individual performance values, the principal distiction of the present study is the simultaneous comparative analysis of both the pyramidal and conical configurations under identical simulation conditions and across two independent solver platforms, which is not found in the cited works, each addressing a single configuration (Arnaud et al., 2016; Heiman and Tamas, 2022). This dual-platform, dual-geometry methodology provides a consistent basis for selecting the conical horn antenna as the geometric and electromagnetic baseline for the subsequent corrugated horn design.

TABLE 7. Comparative radiation performance.

Future research within this project will focus on the design, electromagnetic analysis, and experimental fabrication of a conical corrugated horn antenna operating in the X-band, building directly upon the geometric and electromagnetic foundation established in the present work. The subsequent work, currently in progress, builds directly on the validated smooth-wall conical horn antenna through the following steps: the introduction of corrugations into the walls of the validated conical horn, the optimization of the corrugation depth and pitch for the suppression of surface modes and the fabrication and measurement of the prototype. The corrugated structure is expected to further improve radiation symmetry, reduce cross-polarization levels, and enhance the Axial Ratio bandwidth, thereby achieving performance metrics that meet the stringent requirements of modern satellite communication systems.

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Footnotes

Edited by: Francesca Benassi, University of Bologna, Italy

Reviewed by: Sattar Hasan, Salahaddin University, Iraq

Koushick Venkatesh, Vel Tech Rangarajan Dr.Sagunthala R&D Institute of Science and Technology, India