With the development of communication technology , use of hand-held radio frequency circuit technology more widely , such as: radio pager , mobile phone , a wireless PDA, wherein the RF circuit performance directly affects the quality of the product . A most important feature of these products is smaller handheld , meaning the density miniaturized components is large, which makes the components ( including SMD, SMC, die , etc. ) interfere with each other very prominent . Electromagnetic interference signal if handled improperly , could cause the entire electrical system does not work, therefore , how to prevent and suppress electromagnetic interference, improve electromagnetic compatibility, has become a very important when designing RF pcb issue . The same circuit , different PCB design structure , its performance will vary greatly.
Here I will introduce to Protel99 SE RF PCB design process . To ensure the performance of the circuit , during RF PCB design should consider the electromagnetic compatibility , which focuses on the principles of cabling components to achieve electromagnetic compatibility purposes .
First, select the PCB plate
Select the PCB board of the PCB to produce a high performance is an important factor , the substrate comprises a printed circuit board with inorganic organic two categories . The most important properties of the substrate is a dielectric constant εr, the dissipation factor (or dielectric loss ) tanδ, and the thermal expansion coefficient of moisture absorption cet . Where εr affect the circuit impedance and signal transmission rate. For high-frequency circuits , the dielectric constant of tolerance is more crucial primary consideration should be chosen substrate dielectric constant tolerances .
Second , PCB design flow
Since protel99se software and other software to use with protel98 different, so , first briefly discuss the use of protel99se software pcb design process .
① As protel99se uses a project (project) database schema management , in windows99 is implicit , it should first establish a key database file for managing the design of the circuit schematic and pcb layout .
② schematic design . To be able to achieve a network connection between the conducting principles of design, the components used in the component library must exist , and shall make the necessary components coexist in schlib the storage file . Then , simply call the desired components from the component library, and connect to a circuit diagram of the design.
