## 1 Introduction  
Wireless networks serve in a wide variety of civilian and military applications, and have become an essential part of our routine [1, 2]. Improving the performance of wireless communication is a popular research topic. Unmanned aerial vehicles (UAVs), thanks to their low cost, high flexibility, and high probability of line-of-propagation (LoP) links, have become an attractive means of improving air-ground transmission quality [3]. In general, UAVs can not only act as base stations [4] and relays [5] to transmit or forward signals, but can also be used for data collection [6] and positioning [7]. UAV transmission technology has been widely explored. For instance, the authors in [8] considered the deployment of a cellular network in which UAV-to-UAV launch--receive pairs used the same spectrum as that of the cellular ground users' uplink, and the performance of underlay and overlay spectrum sharing mechanisms was analyzed and compared. In [9], to enhance the throughput of a single-cell multi-user orthogonal frequency division multiple access network with single UAV while guaranteeing user fairness, an efficient method was proposed that outperformed the random and cellular schemes in terms of user fairness and sum rate. A UAV-enabled relay under malicious jamming was considered in [10], and the successive convex approximation (SCA) algorithm was employed to maximize the end-to-end throughput. However, UAV networks also present some challenges that impact their performance. For instance, LoP links might be blocked, and UAV forwarding signals increase the power consumption and affect the endurance of UAVs. As an effective solution to the above-mentioned problems, intelligent reflecting surfaces (IRSs) have been explored as an intelligent and reconfigurable paradigm for future wireless communications [11]. An IRS is a plane that consists of many reflective elements that could intelligently tune the phase and amplitude of the incident signal to reconfigure the wireless transmission environment, and is an energy and cost-efficient tool for enhancing the performance of a wireless network. Driven by these advantages, IRS-aided UAV networks have been widely investigated. To minimize the weighted sum bit error rate of all IRSs, the authors in [12] considered a symbiotic UAV-aided IRS radio network, and a relaxation-based scheme was proposed. In [13], two approaches were proposed to maximize the spectrum and energy effectiveness of an IRS-aided UAV network by jointly deriving a UAV trajectory, and active and passive beamforming, and the proposed methods yielded better performance compared to that of the baselines. Security has also been researched. A secure IRS-assisted UAV system was investigated in [14], and an SCA scheme was proposed to maximize the secrecy rate (SR). With the aim of maximizing the average SR of a secure IRS-aided UAV system in [15], the fractional programming and SCA methods were applied to deal with the non-convex optimization problem. Different from the above works that focused on a single user, a multi-user network that employed UAV and IRS to support terahertz communication was considered in [16], and an iteration strategy was proposed to maximize the minimal average achievable rate among all users. Directional modulation (DM), which significantly boosts the rate of wireless communication systems, has evolved into a useful strategy for fifth-generation millimeter-wave communication systems [17; 18; 19]. DM is capable of guiding standard baseband symbols to the intended direction while warping the signal constellation diagram outside that direction [20]. In [21], a signal was generated in a predetermined direction through tuning the phase of each antenna element at the forefront of the radio frequency. The authors in [22] sketched a process for determining how to convert antenna elements into sending signals only in a given direction, and the DM array could transmit signals over a narrower beam width compared to that of a traditional reconfigurable array.