PCB Tech - Hybrid design of RF and digital-analog circuits based on PCB board

Typically, the RF portion of the PCB board is designed by RF personnel in a stand-alone environment and then merged with the rest of the mixed-technology PCB. This process is inefficient, and the proliferation of hand-held wireless communication devices and remote control devices, often required to integrate with hybrid technologies, has driven a significant increase in the need for hybrid analog, digital, and RF designs. Handheld devices, base stations, remote controls, Bluetooth devices, computer wireless communication capabilities, numerous consumer appliances, and military/aerospace systems now require RF technology. The popularity of handheld wireless communication devices and remote control devices has driven a significant increase in the need for mixed analog, digital and RF designs. Handheld devices, base stations, remote controls, Bluetooth devices, computer wireless communication capabilities, numerous consumer appliances, and military/aerospace systems now require RF technology. For years, RF design has required designers to use specialized design and analysis tools.

For years, RF design has required designers to use specialized design and analysis tools. Typically, the RF portion of the PCB is designed by RF personnel in a stand-alone environment and then merged with the rest of the mixed-technology PCB. This process is inefficient and often requires iterative design and the use of multiple unrelated databases to integrate with hybrid technologies. In the past, design functions were performed and repeated in two design environments, connected via a dumb ASCII interface. PCB system design and RF-specific design systems in both environments have their own libraries, RF design databases, and design archives. This requires design data (schematic and layout) and libraries in both environments to be managed and synchronized through a cumbersome ASCII interface.

Under this old approach, RF designers developed RF circuits in isolation from the rest of the PCB system design. This RF circuit is then translated into the overall PCB design using the ASCII file, creating a schematic and physical implementation on the main PCB. If there is a problem with the RF circuit, the design must be corrected in a separate RF solution and then retranslated into the main PCB. The RF simulator only simulates ideal RF circuits. In actual hybrid system implementations there are many fragmentary formations, ground voids and adjacent RF circuits that make analysis very difficult, and it is well known that these additional shapes will have lasting effects on RF circuit operation. This old method has been used successfully for mixed-signal board design for many years, but as the RF circuit content in products increases, the problems of two separate design systems have begun to impact designer productivity, time-to-market, and products the quality of.

RF aware PCB design
To maintain design intent between PCB and RF design, RF design tools must understand the layer-oriented structure of the PCB layout, and the PCB system must understand the parametric planar microwave components used in the RF design environment. Another key issue is that PCB systems build the layout of RF circuits as short circuits, which prevents proper design rule checking (DRC) of the design. For today's complex RF system designs, functional RF-aware DRC is a must for the design methodology to ensure the design is correct. All of these help maintain design intent. Maintaining design intent is critical because it is the foundation for enabling multiple round trips of design data between toolsets without loss of information.

RF design is an iterative process that requires many steps to tune and optimize the design. In the past, RF design was very difficult in the context of real PCB design. When an optimized RF module is implemented on a PCB, there is still no guarantee that it will still work. As a verification, electromagnetic field analysis (EM) of the PCB implementation is required. There are several problems with this design process. First, the circuit is modeled as a simple metal layer geometry, so RF tools cannot make modifications to the metal layers, and cannot return the optimized results back to the PCB design and still have a good RF circuit. Second, the EM scheme is time-consuming. In the new flow, because the PCB tool and the RF tool have a common understanding of the design intent, circuits can be passed from one tool set to another

without losing the design intent. This means that circuit simulation and EM analysis can be repeated and the results of each circuit modification can be compared. This is all done in a real PCB environment, including ground planes, RF circuit layout, traces, vias, and other components.

RF PCB Design Bottleneck
The main bottlenecks in RF PCB design are as follows., since each RF module on a PCB board may have been designed by an independent RF design team, and each module can be independently upgraded, evolved, and reused, it becomes critical to manage the entire circuit as a whole important, but still access these modules as individual circuit elements at all times. To solve this problem, schematic and layout tools must be extended to support hierarchically grouped circuits. With this method, even if an RF circuit is already laid out on the PCB, it can still be placed together as an RF circuit with other modules and can be connected to the appropriate RF design team for analysis. The next hurdle is how to design the ground plane. In the traditional design process, RF metal is used as a black box metal block, and the spacing from ground is done by hand, because the air travel has to pass through each formation. When the RF circuit is updated, the cut-out parts must be manually modified to correspond to the new circuit. For some designs, this editing process alone can take weeks. Synthesis between RF design tools and PCB design tools has been based on bidirectional conversion of ASCII IFF format files. While the format can handle some design data, it is far from seamless iterative synthesis. Lack of library synchronization is a cause of death. This design requirement has given rise to a web-based tool-to-tool communication that provides a dynamic two-way link between RF design and system-level PCB design. To support concurrent engineering, multiple PCB engineers can use the same design database at the same time, each linking one or more analog sections. RF modules can now be designed using RF design tools and synthesized as part of a system-level schematic and PCB at the right time, rather than the elusive black-box circuit of the past. At this stage, the circuit can be upgraded and its effects simulated in either environment. View each RF circuit as a set of objects to help maintain traceability, version management, and design issues. Because the design intent is preserved, any number of design iterations can be performed with no time cost. In addition, because the RF module can be simulated in a real system-level PCB board environment, its functionality should be verified in more detail to help shorten the design cycle.