This is an overall guide to the very best clinic printed circuit board (PCB) design rules for a high frequency or radio frequency (RF) circuit. Following these rules can help one to avoid some of the very frequent drawbacks in RF design. Poor PCB layout is one of the very frequent reasons for inadequate transmit or receive performance and EMC failures as a result of spurious emissions. Ideally an engineer undertaking a PCB design needs to be familiar with the IPC standards since these provide a rich supply of information and best practice on the general principles of PCB design and style.
When intending to layout an RF PCB fabrication , the very first place to start is to contact your favorite board manufacturer and get a set of their guidelines and manufacturing capacities. This will include the minimum difference and track widths, drill sizes and other key parameters. The board manufacturer should also have the ability to supply you with their standard layer heap and substance data, this can incorporate the copper weights, dielectric constant, and the thickness of core and pre-preg layers in multi-layer planks. Unless the circuit is extremely simple I suggest a 4 layer board is used this ensures that a continuous earth plane. When working with a dual sided board it is quite tricky to be certain that the bottom plane is un broken. Use a micro-strip calculator to determine the necessary track width for the design impedance and ensure that it is within the produces capabilities, if not you could have to go over the layer-stack with the manufacturer and select a non standard build. Yet another point to notice is that within my own experience wanting to keep separate ground nets for different signal area’s usually causes problems instead of any benefit and can be essentially a throw back to the days prior to multilayer boards, even a single non impedance ground plane is the safest path.
It’s quite okay to make use of FR-4 for boards up to 2.4GHz unless the highest amount of operation is required. In a few circumstances it is worth specifying the board controlled impedance to supply consistent RF functionality.
Having determined that the track and board geometries that the next step is to tackle the component placement. Make sure that the RF components are presented so that the whole RF monitors can be continued the top surface with minimum span and changes in management. Start with lower signal level are as at the antenna or RF input signal and work backward towards the baseband or digital area. Keep power and digital supply are as from the analogue RF circuitry and retain all of the RF components on one side of this plank.
Where your RF monitors can’t be run at a straight line, utilize mitered bends in case a CAD system supports themuse right angled bends over RF signal lines. In case mitered bends are not supported use a collection of 45 degree bends or arcs, this reduces impedance mismatches that would increase losses and spurious emissions.
On RF layouts it is not uncommon to supply a floor flood on top layer and also to”stitch” this on the bottom plane using multiple . If you would like to do this, be sure that the aluminum is kept a suitable distance from the RF monitors and components otherwise the impedance will be lowered and cause more harm than good.
Tracks to earth in RF components should be considered as short as possible and use 2 or 3 in parallel via to minimize the impedance.