How do I integrate an RF subsystem with a digital baseband processor on a single PCB?

Integrating an RF subsystem with a digital baseband processor on a single PCB combines the analog RF front end (LNA, mixer, filter, PA) with the digital signal processing (ADC, DAC, FPGA or DSP) on one board, reducing the system size, weight, cost, and interconnect complexity. The key design challenges are: partitioning (physically divide the PCB into an RF zone and a digital zone; the RF zone contains: the LNA, filters, mixers, and analog signal conditioning; the digital zone contains: the ADC/DAC, FPGA/DSP, memory, and digital interfaces; place the ADC/DAC at the boundary between the two zones (it serves as the analog-to-digital transition point)), layer stackup (use a multilayer PCB (8-16 layers or more) with: dedicated RF signal layers (typically 1-2 outer layers for microstrip), dedicated digital signal layers (inner layers for stripline routing), continuous ground planes separating the RF and digital layers (at least 2 ground planes: one under the RF layers and one under the digital layers), and separate power planes for RF and digital supplies), clock and data converter placement (the ADC/DAC and its clock source are the most critical components for the RF-digital interface; place the ADC/DAC between the RF and digital zones with: the analog input/output traces routed in the RF zone on RF signal layers, the digital output/input traces routed in the digital zone on digital signal layers, and the sampling clock routed on an inner layer with continuous ground reference and away from both RF and digital signals), and ground plane strategy (use a common ground plane for the entire board (splitting the ground creates more problems than it solves by forcing return currents to take long paths); however: do not allow digital traces to cross under RF traces on the same ground reference layer (this couples the digital return current into the RF circuit); route digital and RF traces with orthogonal orientation on adjacent layers to minimize coupling).