## 1 Introduction  
Acousto-Optical Tunable Filters (AOTFs) are used in many different ground- and space-based applications for different purposes [1, 2, 3, 4, 5, 6, 7]. The device can act as a filter in order to select optical wavelengths of interests at a high spatial and temporal resolution [8, 9, 10, 4, 11].  
The working principle of an AOTF is based on the interaction between soundwaves and light, having birefringence and consequently creating the filter capability. This sound-light interaction occurs in an area called the acoustic column (Figure 1). Due to the photo-elastic effect, the refractive index of the AOTF is changed. The velocity of these soundwaves, propagating through the AOTF, depends on the used material of the crystal [12, 13]. The soundwaves inside the AOTF are generated using an RF signal, which is applied to a transducer, mounted at the side of the crystal (Figure 1). The transducer, which includes a piezoelectric layer, is able to convert this RF signal into acoustic waves that propagate inside the AOTF's crystal. In order to convert the applied RF power efficiently, the transducer needs to be matched in two ways. On the one hand, the mechanical matching has to be carried out on the optical crystal, but on the other hand the electrical matching should fit on the RF side. In order to activate the filter capability of the AOTF in an efficient way, the pure sinewave RF signal has to have a specific frequency and power level. This RF signal is generated by an RF chain, consisting of an RF generator and RFamplifier (Figure 1). The RF generator generates a single-frequency RF carrier, having a certain amplitude. The level of this signal is additionally increased in amplitude by the RF amplifier.  
The generation of the RF carrier can be achieved in several ways. Nevertheless, if the RF chain-AOTF setup is used for space-based applications, the design is prone to several limitations. The latter are related to the space environment in which these devices have to function. In order for the setup to survive in space, a wide variety of environmental tests is carried out prior to launch: I.c. thermal-vacuum tests, shock, vibration, radiation, and EMC/EMI tests. Hence, the selected RF generation designs have to be in-line with this approach. The selection of components needs to take into account the limitations listed above and additionally, and the design has to be aligned with the ECSS (European Cooperation for Space Standardization) standard of ESA and comparable rules imposed by other agencies. Consequently, existing RF designs applicable in commercial applications are not one-to-one transferable into a space-grade design. This severely limits the feasibility of RF generator techniques to those who can fulfill these specific requirements and rules.  
In this paper, five space-grade RF generator techniques, based on Commercial-Off-The-Shelf (COTS) components, are addressed, both digital and analog in origin. The approach is carried out in such a way that the design uses COTS components that have an exact comparable space-grade counterpart available. Hence, each technique is one-to-one convertible into a space-grade model, having the same performance as the COTS based version. All of the proposed techniques are discussed, additionally supported by analysis and, if possible, physical tests.