High Frequency (HF) Printed Circuit Board (PCB)

High Frequency PCBs are used to transmit electromagnetic waves in the frequency of GHz with minimal loses in the variety of applications, including mobile, microwave, radio frequency (RF) and high-speed design applications. Hence, printed circuit board with some specific characteristics are used to transmit these electromagnetic waves. Several parameters are taken into consideration while designing a PCB for high frequency applications. A high frequency PCB can meet your needs when incorporating a special signal requirement into your electronic devices and products. These higher transmission frequencies are capable of supporting the faster signal flow rates that are a necessity in today’s increasingly complex electronic switches and other components.

  

Applications of High Frequency PCB

  • High frequency PCB’s are always used in the following applications

  • Automotive Radar Systems

  • Global Positioning Satellite Antennas

  • Cellular Telecommunications Systems – Power Amplifiers and Antennas

  • Direct Broadcast Satellites

  • E-band Point to Point Microwave Links

  • RF Identification (FRID) Tags

  • Airborne and Ground Based Radar Systems

  • Millimeter Wave Applications

  • Missile Guidance Systems

  • Space Satellite Transceivers

The demand for high frequency PCB is on the rise in the various industrial vectors. They meet the requirements which traditional PCB fail to deliver efficiently. If you are still skeptical about incorporating high frequency PCBs in your electronic PCBs, you can always approach an industry expert in MADPCB. The company has provided standard, as well as customized high frequency PCBs to various industries. Want to know the cost of your high frequency PCB? Ask a quick quote now.

 

How to Select PCB Materials for High Frequency Applications?

The PCB laminate materials you select for your PCB building can be critically important to the overall functionality and lifespan of your final product. When operating frequencies go into the Microwave or even Radio Frequency (RF) regions, your PCB laminate material selection will have a significant impact on the overall loss of the finished PCB after PCB assembly and final assembly. Electrical, thermal, and mechanical properties must all be considered carefully when determining the best suitable material for your high frequency PCB manufacturing.

In high frequency designs, you may find that FR4 sometimes just doesn’t to do the job at some higher frequencies. It’s obvious you select a wrong PCB material. The main concern with FR4 at high frequencies is its relatively high dielectric constant (/permittivity), which is typically considered to be approximately 4.2. While, FR4 can still act as a suitable laminate material for high frequency PCBs when it comes to a hybrid construction, in which the fabrication is combined with high frequency laminate. At MADPCB, we carry a selection of materials specifically designed to maintain signal integrity in Radio Frequency and Microwave regions.

 

High Frequency PCB Materials from Rogers

The most popular high-frequency-specific laminate materials were developed by Rogers Corporation, and referred to with either “RO” or “RT/duroid” prefix, including RO3003, RO3006, RO4003C, RO4350B, RT/duroid 5870, RT/duroid 5880. These high-end materials exhibit approximately a 20-30% reduction in dielectric constant when compared to FR4; they also have rather impressive thermal characteristics, with Tg values above 280oC. The chart below shows the Rogers materials always be used for high frequency PCB manufacturing.

Vendor

Part Number

Type

Tg (oC)

Td(oC)

DK
@1GHz

Loss
Tangent
(@1GHz)

ROGERS

RO3003

Ceramic-filled PTFE

-

500

3.00 ± 0.04
@ 10 GHz/23°C

0.0010 @10 GHz/23°C

RO3006

Ceramic-filled PTFE

-

500

3.50 ± 0.05
@ 10 GHz/23°C

0.0015 @10 GHz/23°C

RO4003C

Reinforced Hydrocarbon/Ceramic

>280

425

3.38 ± 0.05
@ 10 GHz/23°C

0.0027 @10 GHz/23°C
0.0031 @2.5 GHz/23°C

RO4350B

Reinforced Hydrocarbon/Ceramic

>280

390

3.48 ± 0.05
@ 10 GHz/23°C

0.0037 @10 GHz/23°C
0.0031 @2.5 GHz/23°C

RT/duroid 5870

Reinforced PTFE

-

500

2.33 ± 0.02
@ 10 GHz/23°C

0.0005 @1 MHz/23°C
0.0012 @10 GHz/23°C

RT/duroid 5880

Reinforced PTFE

-

500

2.20 ± 0.02
@ 10 GHz/23°C

0.0004 @1 MHz/23°C
0.0009 @10 GHz/23°C


At MADPCB, we normally keep stock of RO4350B and RO4003C, since these are the most commonly requested of the Rogers PCB materials, but it is always a good idea to contact us in advance so that we can make sure we have the specific Rogers material required in your new project. Once the high frequency materials are worked out, you can look into some of the other valuable services we offer for your high frequency PCB project, like components sourcing and PCB assembly.

 

Controlled Impedance Transmission Lines Applied into High Frequency PCBs

The design of controlled impedance transmission lines is very important in high frequency PCBs, which is for the purpose of avoiding any signal loss, and there are two common approaches to set controlled impedance transmission lines known as Microstrip and Stripline.

  • Microstrip is the existence of the trace on the outer layers that come with a ground plane below. The impedance calculation of a microstrip is a little bit tricky and complex though and depends on various factors including relative permittivity of the high frequency PCB base material, thickness and width of the trace and its height above the plane. In order to achieve better result, ground plane must be closer to the outer layers.

  • Stripline is another addition to control impedance which is quite identical to microstrip with one exception, which comes with an extra ground plane on the top of the trace. In this impedance calculation mode, trace must be placed between the layers of two planes. Stripline is better as compared to microstrip because it has an ability to contain EMI radiation within the two planes.

For protecting against losses in your PCBs, we offer professional Impedance Controlled PCB services, including TDR coupons for verification. The coupons and measuring results can be shipped out together with the high frequency PCBs to you.