The importance of capturing higher frequencies through microwave and RF PCB high-frequency board design is self-evident. Microwave and RF circuits have now become a part of various products, with the most notable being communication devices. Used for manufacturing microwave and RF high-frequency circuit boards in large quantities for different devices. However, higher frequencies also pose many design challenges for high-frequency circuit boards. Here are some convenient solutions that can alleviate some of these issues:
1. Effective design techniques for microwave RF PCB circuit boards
Please note the use of these microwave circuit board/RF PCB design techniques to ensure that the possibility of any errors is minimized during the assembly process:
Isolation - If you are dealing with high-frequency PCBs with analog, digital, and RF components, one thing to note during the design phase is to separate these components. Ground plane - In the case of multi-layer PCBs (RF PCB/microwave circuit board/high-frequency circuit board), a rule of thumb is that there is a ground plane below any layer with RF or microwave signal lines.
Resolving noise - Due to the extreme sensitivity of high-frequency signals to noise, there are multiple solutions here:
Shot noise - This noise caused by current fluctuations can be minimized by using metal resistors.
Phase noise - affects radio frequency signals, manifested as fluctuations or phase jitter. A clean signal is the best way to reduce this noise.
Blinking noise - caused by direct current, which manifests as phase noise. The solution lies in processing the signal through specialized filters.
Thermal noise - This noise is the result of thermal agitation. Therefore, it is necessary to adjust the temperature through the cooling system and heat dissipation function to minimize the impact of temperature on the circuit.
Avalanche noise - This noise is generated by the fact that the junction diode is operating near the avalanche breakdown point. The best solution to this is to use a capacitor based filter.
2. Return loss
The method of minimizing return loss caused by signal reflection is to ensure that the ground plane from the driver to the receiver should be continuous. If this is not present, the return signal will pass through other power planes and cause signal noise.
3. Impedance matching of RF PCB/microwave circuit board/high-frequency circuit board
Due to the low tolerance of high-frequency signals for impedance matching, it is necessary to pay attention to the following aspects:
Skin effect loss - Skin effect refers to the flow of electrons along the surface of the conductor at higher frequencies. On the trace, there is a small region for funnel electrons. However, some electrons are also trapped here. The signal energy is converted into heat. In order to minimize this loss to the greatest extent, appropriate impedance matching is crucial. In addition, gold plated PCBs can also be used as an antidote.
Line length - Signal loss is affected by the length of the line. The longer the line, the greater the signal loss. It is best to ensure that the line is 1/20 of the wavelength. Either way, it should be longer than 1/16 of the wavelength, which is the critical signal length.
4. Intermodulation distortion
In short, crosstalk is the transfer of energy between conductors that cause coupled signals. Usually, the incidence of crosstalk increases with increasing PCB density and performance. Other aspects that play a role include:
Proximity of conductors
The distance they run in parallel
Edge rate of activity line
Some methods to reduce crosstalk include:
Ensure that the distance from the center to the center is maintained at four times the width of the wiring.
Minimize parallel lines
Minimize dielectric spacing
Insert ground plane between wiring routes
Terminate the line on its characteristic impedance
5. Microwave RF Laminate Performance
The characteristics of laminates can affect the functionality of RF or microwave PCB/RF circuit boards. For example, FR4 fiberglass board has a high dissipation factor, which leads to higher insertion loss as the signal frequency increases. In addition, the dielectric constant of FR4 is higher than that of high-frequency laminates, which has an impact on impedance. The characteristics of laminates can affect dielectric loss. It is recommended to use substrates with low loss factors to avoid such losses.
This is a method to solve common problems in microwave RF PCB/microwave circuit board/high-frequency circuit board design and improve its efficiency!