# Multifunction RF Systems for Naval Platforms
## 1 Introduction
A second receive beam in the direction of a ship target is being used by the ES function. The radar is utilizing another receive beam to capture signal returns from the helicopter target that it is simultaneously illuminating. Note that the beamforming task is not explicitly broken out as a separate block in this figure because it is generally performed by a combination of the assets shown, depending upon the particular system implementation. Also, communications modems are not separately depicted, as their modulation and demodulation functions can conceptually be included in the waveform generator and receiver blocks. Figure 1: Conceptual diagram for MFRF system. MFRF systems can potentially provide the following benefits:  
* Reduction of the ship RCS: By reducing the number of topside antennas, the aggregate contribution of the antenna apertures to the ship's RCS is mitigated. * Performance optimization of RF functions: In general, the overall performance of the suite of RF functions controlled by a central RAM is improved as a result of more tightly integrated scheduling of RF tasks. Of particular note, coordination of frequency usage between RF functions as part of waveform generation control by the RAM results in lower risk of mutual electromagnetic interference, as compared to the situation with separate RF subsystems where frequency management through less centralized control is generally suboptimal. * Lower integration and life-cycle costs: The decrease in both the number of topside antennas and the amount of associated hardware can lead to less hardware integration effort and cost at the installation stage. Furthermore, the use of common hardware for the RF functions in a MFRF system can substantially reduce life-cycle costs as a result of requiring less unique spare parts, less maintenance training, and fewer personnel to operate and maintain equipment, relative to the situation with multiple single-purpose RF subsystems. While MFRF systems may yield important benefits, it is also worthwhile to note a potential risk: the consolidation of RF functions within a fewer number of antenna apertures may increase vulnerability to a single point of failure. For example, if the topside antenna of a MFRF system is destroyed in battle, overall ship RF functionality may be more severely degraded than would be the case if the antenna supported only a single RF function. This risk would be considered in the cost/benefit analysis conducted to inform a decision on a MFRF system deployment. This paper highlights a number of factors and challenges to be considered in the design and implementation of a naval MFRF system, and identifies MFRF resource management as a key topic for future research in this area. The next section reviews the requirements for naval radar, EA, ES and communications functions that have specific impact on MFRF system design. In Section 3, MFRF system design considerations and trade-offs are summarized. Specific MFRF system prototype development programs that have been previously conducted are described in Section 4. Section 5 provides a description of MFRF resource management, and conclusions are contained in Section 6. It is assumed throughout the paper that the reader is somewhat familiar with the underlying AESA theory and terminology. If not, one of a number of references can be consulted, such as [2; 3; 4; 5].