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
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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.
