1. Frequency Range: The RF/LO range of the TRF370315IRGER is 400 MHz to 4 GHz, whereas the AD8345 operates from 140 MHz to 1 GHz. The AD8345 covers VHF and lower UHF bands (e.g., below 300 MHz), which are outside the TRF370315's operational range. If the original design frequency is below 400 MHz, substitution is entirely unfeasible. 2. Linearity and Power Consumption: The TRF370315 has a P1dB of 9.5 dBm, significantly higher than the AD8345's 2.5 dBm. This indicates superior output linearity, enabling it to handle higher-power signals without distortion. However, this comes at the cost of higher power consumption. Its supply current is 235 mA (at 4.5–5.5 V), compared to just 78 mA for the AD8345 (at 2.7–5.5 V). Substitution would substantially increase system power draw (by approximately 3x), generate more heat, and necessitate more stringent power supply and thermal management design. 3. Output Power and Noise Floor: The TRF370315's specified output power is -2.3 dBm (tested at 2.14 GHz), lower than the AD8345's 2 dBm (tested at 800 MHz). This does not represent a performance degradation but rather reflects different optimized operating frequencies and internal architectures. Its superior noise floor (-162 dBm/Hz) has negligible impact on the system link budget, as the primary noise contributor in a modulator is typically local oscillator phase noise—a parameter not provided in the datasheets. 4. Power Supply and Integration: The AD8345 supports a single supply voltage from 2.7 V to 5.5 V, offering better compatibility with low-voltage digital systems. The TRF370315 requires 4.5 V to 5.5 V, providing less flexibility in power supply design. Furthermore, the TRF370315 uses a 24-pin VQFN package, likely integrating additional features (e.g., an integrated LO buffer), while the AD8345 comes in a 16-pin TSSOP package. Their peripheral circuits are inherently different, necessitating a PCB redesign.