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3 Tips for RF PCB Layout

  • Jan 8
    3 Tips for RF PCB Layout



    Because the radio frequency (RF) circuit is a distributed parameter
    circuit, skin effect and coupling effect are prone to occur in the
    actual work of the circuit, so in the actual PCB design, it will be
    found that the interference radiation in the circuit is difficult to
    control, Such as: mutual interference between digital circuit and analog
    circuit, noise interference of power supply, interference caused by
    unreasonable ground wire, etc. Because of this, how to weigh the pros
    and cons in the PCB design process to find a suitable compromise, to
    reduce these interferences as much as possible, and even to avoid the
    interference of some circuits, is the key to the success or failure of
    the RF PCB design. From the perspective of PCB LAYOUT, this article
    provides some processing skills, which are of great use to improving the
    anti-interference ability of radio frequency circuits.To get more news
    about Cavity PCB, you can visit pcbmake official website.



    1.RF layout



    What we discussed here is the layout of the components of the
    multilayer board. The key to the layout of components is to fix the
    components on the RF path. By adjusting its direction, the length of the
    RF path is minimized, and the input is far away from the output, and
    the high-power circuit and the low-power circuit are separated as far as
    possible. The signal is far away from high-speed digital signals and RF
    signals.



    1.1 One-line layout



    The components of the RF main signal are arranged in a straight line
    as much as possible, as shown in Figure 1. However, due to the
    limitation of PCB board and cavity space, it cannot be laid out in a
    straight shape in many cases. At this time, L-shaped layout can be used.
    It’d be better not to use U-shaped layout (as shown in Figure 2). When
    it is unavoidable, it’d be better to increase the distance between input
    and output to at least 1.5cm.
    In addition, when using an L-shaped or U-shaped layout, the turning
    point should not turn as soon as it enters the interface, as shown on
    the left in Figure 3, but after a slight straight line, as shown on the
    right in Figure
    The feed inductance of the bias circuit is placed perpendicular to the
    RF channel, as shown in Figure 6, mainly to avoid mutual inductance
    between inductive devices.
    In order to use the space reasonably, the devices can be arranged in a
    45-degree direction to make the RF line as short as possible, as shown
    in Figure 7.
    2.RF Routing



    The overall requirements for wiring are: RF signal traces are short
    and straight, reduce line abrupt changes, drill fewer holes, and do not
    intersect with other signal lines, and add as many ground vias as
    possible around the RF signal line.