Introduction To High Frequency Circuit PCB Design Techniques Part 1

The design of a high-frequency circuit board is a complicated process, and many factors may directly affect the performance of the high-frequency circuit. The design and wiring of high-frequency circuits are very important to the entire design. Today, the professional and technical personnel of Taike Electronics specially recommend the following high-frequency circuit PCB design techniques to you, let's take a look!

High frequency circuit PCB design

Multilayer board wiring

High-frequency circuits usually have high integration and high wiring density. The use of multi-layer boards is not only necessary for wiring, but also an effective means to reduce interference. In the PCB layout stage, a reasonable selection of the printed board size with a certain number of layers can make full use of the intermediate layer to set up the shield, better realize the nearest grounding, effectively reduce the parasitic inductance, shorten the signal transmission length, and greatly reduce the signal cross-interference. These methods are conducive to improving the reliability of high-frequency circuits. The data shows that when the same material is used, the noise of the four-layer board is 20dB lower than that of the double-sided board. However, there is also a problem. The more the number of half-layers of the PCB, the more complicated the manufacturing process and the higher the unit cost. This requires us not only to select the appropriate number of PCB layers, but also to plan a reasonable component layout and use the correct wiring rules to complete the design.

The less the lead bends between the pins of high-speed electronic devices, the better

The lead of the high-frequency circuit wiring is preferably a full straight line that needs to be rotated. It can be rotated by 45 degree polyline or arc. This requirement is only used to improve the fixing strength of the copper foil in the low-frequency circuit, and in the high-frequency circuit, meeting this requirement can reduce the external emission and mutual coupling of high-frequency signals.

The shorter the lead between the pins of the high-frequency circuit device, the better

The radiation intensity of the signal is proportional to the wiring length of the signal line. The longer the high-frequency signal lead, the easier it is to couple with nearby components. Therefore, for high-frequency signal lines, such as signal clocks, crystal oscillators, DDR data, LVDS lines, USB lines and HDMI lines, the traces must be as short as possible.

Alternation of lead layers between pins of high-frequency circuit devices is as small as possible

The so-called "the less the inter-layer alternation of the leads, the better" means that the fewer vias (Via) used in the component connection process, the better. According to the side, one via can bring about 0.5pF distributed capacitance, and reducing the number of vias can significantly increase the speed and reduce the possibility of data errors.

High frequency circuit PCB design

Pay attention to the "crosstalk" introduced by the signal lines in parallel with close distances

High-frequency circuit wiring should pay attention to the "crosstalk" introduced by the close parallel routing of signal lines. Crosstalk refers to the coupling phenomenon between signal lines that are not directly connected. Because high-frequency signals are transmitted in the form of electromagnetic waves along the transmission line, the signal line will act as an antenna, and the energy of the electromagnetic field will be emitted around the transmission line. Undesired noise signals are generated due to the mutual coupling of electromagnetic fields between the signals. Called crosstalk (Crosstalk). The parameters of the PCB layer, the spacing of the signal lines, the electrical characteristics of the driving end and the receiving end, and the signal line termination method all have a certain impact on the crosstalk.

The above temporarily introduces five high-frequency circuit PCB design techniques, and I hope to provide you with some reference!