What is the difference between high speed PCB and high frequency PCB?

                                     What is the difference between high speed PCB and high frequency PCB ?

    In the PCB industry, when it comes to the terms high-speed PCB and high-frequency PCB, people often think that they are the same, but in fact, the meaning of the two is completely different. High speed usually refers to digital technology that transmits data at a very high rate, which is related to the time domain; high frequency is usually related to the radio frequency (RF) of the analog signal at high frequency moving energy, which is how electromagnetic waves respond in a specific frequency or range of frequencies, related to frequency.

    However, there is also a fundamental relationship between high-speed digital signals (HSD) and high-frequency (RF) techniques. For example, pulses for digital information transmission are generated by RF waveforms. Basically, a sine wave can be thought of as an RF waveform. When several sine waves of different frequencies are combined, they can form a square wave, and a square wave can generate a pulse of a digital signal. As a simple example, the 2GB/s digital pulse speed (clock speed) is formed by RF signals at frequencies of about 1 GHz, 3 GHz, 5 GHz, 7 GHz, etc., sorted by a given frequency, respectively, at the fundamental frequency (1 GHz), The fundamental frequency three times harmonic (3GHz), five times harmonic (5GHz) and seven times harmonic (7GHz) frequencies.

    When designing a PCB at millimeter-wave frequencies, the wavelengths associated with PCB design characteristics are important, and wavelength segments can affect circuit performance. A stripline PCB with a material Dk of 3 is used, which has a wavelength of about 0.100" (2.54 mm) at 70 GHz. When the circuit characteristics are about 1/2 of the wavelength, the waveform performance is significantly affected, even at 1/4 of the wavelength, there is also an effect; the negative effect of this feature on the waveform performance can be avoided when it is less than 1/8 wavelength. For example, the physical dimension of the strip line associated with 1/8 wavelength at 70 GHz is 12.5 mil (0.32 mm). Basically, any signal greater than 1/8 of the wavelength will affect the performance of the 70 GHz waveform, and simply getting energy from the connector can be a problem.

    Wavelengths at millimeter wave frequencies can affect circuit performance, while material properties can affect the RF performance of the circuit. Most materials used in high frequency PCBs have a woven glass reinforcement to increase the mechanical stability of the material.

    Commonly used high frequency materials are ROGERS series high frequency PCB material, TACONIC series microwave PCB, ARLON series microwave radio frequency PCB, for more detail about the high frequency PCB material please click the links: high frequency PCB material list . Commonly used high speed materials are TU875, TU872SLK, N4000-13, R5725(M4), S7439, FR408HR, R5775(M6), IT150DA, EM370D and so on.