# Multifunction RF Systems for Naval Platforms
## 2 Requirements for Naval RF Functions  
The particular requirements for naval RF functions that most impact MFRF system design relate to transmit and/or receive specifications, since these are the requirements that can pose the greatest challenge to sharing a common set of electronics and antenna apertures between multiple RF functions. Table 1 provides a comparison of key transmit/receive requirements that are representative of naval radar, ES, EA and communications functions, with further explanation following the table. A description of the terminology in Table 1 is provided below. * _Frequencies of operation_: This refers to the range of frequencies over which the RF function is required to operate. For the radar function entries in the table, IEEE frequency band designations are used to characterize the frequencies of operation, as is a common practice in the radar field. These designations are defined in Annex A for convenience. * _Signal bandwidth_: Signal bandwidth refers to the maximum instantaneous bandwidth of the signals that must be accommodated by the RF function. This requirement impacts design of the MFRF system receiver channels, in that the receiver analog bandwidth, as well as the sampling rate of the _a_nalog-to-_d_igital converter (ADC) needed to digitize the signal, must be at least equal to the instantaneous signal bandwidth. It is notable that one disadvantage to increasing the receiver bandwidth is that it leads to a larger system noise bandwidth, which may make noise-limited detection of signals more challenging. Another system design area that may be affected by this requirement is the array beam steering. If the instantaneous signal bandwidth is large enough, TTD beam steering may be necessary, as opposed to a simpler implementation with phase shifters. * _Dynamic range_: This refers to the instantaneous dynamic range of the receiver, which is a metric that reflects the ability of a receiver to accommodate a range of input power levels from the antenna. It is calculated as the ratio of the strongest to weakest input power levels that can be properly measured by the receiver. * _EIRP_: The Effective Isotropically Radiated Power (EIRP) is a standard measure of transmitted power that is calculated as \(EIRP=PG_{t}\), where \(P\) is the peak transmitter power and \(G_{t}\) is the antenna boresight gain upon transmit. For an AESA antenna, the peak transmitter power is determined by the sum of the peak power outputs from all of the HPAs utilized. As the HPA is often the most costly component in an AESA design, the EIRP requirement represents one of the most significant AESA cost drivers. * _One-way beamwidth_: The one-way beamwidth requirement listed in Table 1 refers to the width of the beam formed upon transmit or receive, as measured between the \(-3\) dB points of the beam mainlobe pattern. For naval radar and communications functions which employ both Tx and Rx beams, the transmit and receive beamwidths may be different if differently sized subarrays on the antenna aperture are used to form the transmit and receive beams, or separate Tx and Rx arrays of different sizes are employed. However, they are often the same in practice, and are assumed to