Top 5 Clever Solutions to Common Problems of RF and Microwave PCB Designs

The following article titled "Top 5 Clever Solutions to Common Problems of RF and Microwave PCB Designs" was prepared for and submitted to RF Cafe by its author, Ken Ghadia, of TechnoTronix Electronics Manufacturing Services. He wrote asking whether he could provide an article on an aspect of PCB design relevant to RF Cafe visitors, so I suggested addressing the issue of placing digital and analog / RF signals on a common substrate. TechnoTronix has a state of the art facility here in the United States that enables clients to successfully overcome production and PCB fab challenges to produce the innovative, cutting-edge electronics products and providing PCB prototype services, PCB, PCB assembly service, PCB manufacturing service, PCB fabrication service & more in U.S. and around the world.

Top 5 Clever Solutions to Common Problems of RF and Microwave PCB Designs

With the ability of RF and Microwave PCB designs to capture higher frequencies, there importance cannot be overstated. RF & Microwave circuits are today a part of a wide variety of products, with communication devices being the most notable among them. PCB Manufacturing for RF And Microwave PCB is done in huge numbers to utilize in different devices. However, higher frequencies also come with a host of design challenges. Here are some handy solutions to mitigate some of these issues:

#1 Effective Design Hacks

Be mindful of using these design hacks to ensure that the potential for any errors can be minimized during the assembly process:

• Isolation- If you are dealing with PCBs that have analog, digital as well as RF components, the one thing that you need to keep an eye on at the design stage is to keep such parts separate.
• Ground layer- In case of multilayer PCBs, the one thumb rule to go by is to have a ground layer below any layer that has RF or microwave signal lines.
• Tackling Noise- With high frequency signals being extremely sensitive to noise, here are the many ways to tackle it:
  • Thermal Noise- This kind of noise is the result of thermal agitation. It is imperative, therefore, to minimize the effects of the temperature on the circuit by regulating the temperature through cooling systems as well as heat-dissipation features.
  • Shot Noise- Caused on account of the fluctuations in electrical current, this kind of noise can be minimized through the use of metallic resistors.
  • Phase Noise- Affecting radio frequency signals, this appears as fluctuations or phase jitters. Clean signals are the best way to reduce this noise.
  • Flicker Noise- Caused by direct current flow, this kind of noise manifests itself like phase noise. The solution to this lies in processing the signal through a specialized filter.
  • Avalanche Noise- This noise results on account of the fact that a junction diode operates close to the point of avalanche breakdown. The best solution for this is to use a capacitor based filter.

#2 Impedance Matching

With high frequency signals having low tolerance for impedance matching, here are some aspects to watch out for:

• Skin effect loss- Skin effect refers to the flow of electrons along the outer surface of the conductor, at higher frequencies. At the trace, there is a small area that is used to funnel electrons. However some electrons are also trapped here. The signal energy is converted to heat. To minimize this loss, proper impedance matching is crucial. Also plating the PCB with gold works as an antidote.
• Line Lengths- Signal loss is impacted by the line lengths. The longer the lines, the more the signal loss. It is ideal to ensure that the line is 1/20 of the wavelength. Either way it should be longer than 1/16 of the wave length, which is the critical signal length.

#3 Return Loss

Caused by signal reflection, the way to minimize the return loss is to ensure that the ground planes should be continuous from the driver to the receiver. In the absence of this, the return signal will pass through other power planes and cause signal noise.

#4 Cross Talk

Simply put, cross talk is the transfer of energy between conductors that causes a coupled signal. Typically, the incidence of crosstalk increases as the density as well as the performance of PCB increases. The other aspects that play a role include:

• Proximity of conductors
• Distance over which they run parallelly
• Edge rate of the active line

Some of the ways to reduce cross talk include:

• Ensuring the distance from center to center is kept at four times the trace width.
• Minimizing parallel lines
• Minimizing the dielectric spacing
• Inserting a ground plane between the traces
• Ending the line on its characteristic impedance

#5 Laminate Properties

The properties of the laminate impact the functionality of the RF or microwave PCB. For example, FR4 has a high dissipation factor resulting in higher insertion losses as signal frequencies increase. Also the dielectric constant of FR4 is higher than that of high frequency laminates, which has an impact on impedance. The property of the laminate impacts dielectric loss. The use of substrates with low dissipation factors is recommended to be able to avoid this loss.

Here's to solving common problems of RF & Microwave PCB designs and to improving their efficiency!

Goodluck on your RF/Microwave PCB Designing!

About TechnoTronix

One of the PCB assembly magnate, TechnoTronix adopts advanced production techniques and manufacturing practices with specialization in a varied range of PCB fabrication process, producing high quality multi-layered PCBs from tailor-made layouts.

With over 40 years of combined experience in rendering high tech PCB assembly and manufacturing services, we are not just an assembler, we can completely test at board level to box build level to provide the benefit of unparalleled technical expertise and the most progressive solutions at competitive prices.

Contact Info

Ken Ghadia

TechnoTronix Electronics Manufacturing Services

1381 N. Hundley St.

Anaheim, CA 92806, U.S.

Phone: 714-630-9200

E-mail: keng@technotronix.us

Website: www.technotronix.us

Posted August 20, 2021