1. Printed circuit boards made from conventional composite materials primarily use glass fiber as the filler in the dielectric layer.
2. However, the unique woven structure of glass fiber alters the local dielectric constant of the PCB board.
3. This effect is particularly pronounced at millimeter wave frequencies, where the glass weaving in thinner laminates becomes more significant.
4. The resulting local non-uniformity in Dk leads to substantial variations in the performance of radio frequency circuits and antennas.
5. We investigated the influence of PCB structure on transmission line performance using a 100 μm thick glass woven PTFE laminate, examining various glass woven structures, and found that the dielectric constant of the PCB board ranges from 0.01 to 0.22, fluctuating within this range.
6. To explore how different glass braided structures affect antenna performance, we constructed a series-fed microstrip patch array antenna on Rogers commercial laminates RO4835 and RO4830.
7. Experimental results show that the antenna processed with RO4830 laminate exhibits electrical performance that aligns more closely with calculated values, with smaller deviations and improved reflectivity and boresight gain.
Here is the revised version of the article, maintaining the same line count and numbering:
Self-driving cars are currently being developed to enhance safety for both drivers and pedestrians. To achieve this, high reliability is crucial, as these vehicles must prevent fatal accidents effectively. Therefore, the circuits in these systems must be highly reliable. Millimeter wave radar, with its compact design and high environmental detection sensitivity, offers a dependable target detection solution for autonomous driving. Commercial millimeter-wave radar systems operating in the 76 to 81 GHz frequency range use cross-fed microstrip antennas, which are designed to be simple, compact, mass-producible, and cost-effective.
(1). Higher frequencies correspond to shorter wavelengths, necessitating smaller transmission lines and antennas for millimeter-wave applications compared to lower frequencies. To ensure optimal performance of automotive radar, it is essential to study how PCBs impact transmission lines and microstrip antennas, particularly for circuits operating under varying external conditions (temperature and humidity) over extended periods.
(2). When selecting PCB circuit laminates, the consistency of material performance indicators is crucial. Materials like copper foil, glass fiber, ceramic fillers, and others significantly affect performance consistency at high frequencies. Therefore, the reliability of these component circuits must be assured. Laminates are typically composed of glass fiber cloth and polymer resin, forming a dielectric layer covered with copper foil on both sides. The dielectric constant (Dk) of glass cloth is relatively high, around 6.1, whereas low-loss polymer resin has a Dk of 2.1-3.0, leading to noticeable differences in Dk over small areas. Figure 1 illustrates the microscopic top view and cross-section of the glass fiber weave in the laminate. The “knuckle bundle” areas show higher Dk due to more glass fiber content, while the “bundle” areas exhibit higher Dk due to increased resin content. Factors such as glass fabric thickness, spacing between fabrics, fabric flattening methods, and glass content in different directions can impact performance.
The test employs a microchip transmission line with a 1 mm terminal connector. Initially, the connector connects to a 50 ohm ground coplanar wave (GCPW) and is converted to a high-impedance microcircuit transmission line through an impedance converter. The microstrip transmission line measures 2 inches in length. This setup allows the experimental protocol to evaluate the effects of different glass weave structures. The solution includes a copper layer, glass cloth, and a thin polytetrafluoroethylene (PTFE) layer. To compare different glass weave structures, we created transmission line diagrams using three PCB laminate types: 1080 glass fiber PTFE fabric, 1078 glass fiber PTFE ceramic-filled PTFE laminate, and 1080 glass fiber fabric. The processed circuits were examined to find suitable transmission lines for testing, measuring amplitude and phase angle characteristics. Parameters such as phase angle (the phase value after opening), group delay (based on phase angle changes with frequency), and propagation delay (calculated from the phase angle) determine the laminate’s dielectric constant.
In summary, the laminate structure impacts the performance of transmission lines and antennas. Variations in glass fiber cloth construction affect the dielectric constant along the line, potentially reducing product performance and quality. Compared to RO4835 laminates, antennas made from RO4830 laminates exhibit better performance compatibility. The improvements in antenna performance and production processes are largely due to the use of composite materials: flat glass fiber fabric with low glass content (reducing conductor-glass fiber proximity), and thick coatings. The antenna efficiency is influenced by the electrical properties of materials like RO4830 laminates, which have low dielectric constants and loss tangents. Thus, antennas made from Rogers RO4830 laminates offer superior performance and compatibility for low-wavelength millimeter frequency radar compared to those made from RO4835 laminates.
2. However, the unique woven structure of glass fiber alters the local dielectric constant of the PCB board.
3. This effect is particularly pronounced at millimeter wave frequencies, where the glass weaving in thinner laminates becomes more significant.
4. The resulting local non-uniformity in Dk leads to substantial variations in the performance of radio frequency circuits and antennas.
5. We investigated the influence of PCB structure on transmission line performance using a 100 μm thick glass woven PTFE laminate, examining various glass woven structures, and found that the dielectric constant of the PCB board ranges from 0.01 to 0.22, fluctuating within this range.
6. To explore how different glass braided structures affect antenna performance, we constructed a series-fed microstrip patch array antenna on Rogers commercial laminates RO4835 and RO4830.
7. Experimental results show that the antenna processed with RO4830 laminate exhibits electrical performance that aligns more closely with calculated values, with smaller deviations and improved reflectivity and boresight gain.
Here is the revised version of the article, maintaining the same line count and numbering:
Self-driving cars are currently being developed to enhance safety for both drivers and pedestrians. To achieve this, high reliability is crucial, as these vehicles must prevent fatal accidents effectively. Therefore, the circuits in these systems must be highly reliable. Millimeter wave radar, with its compact design and high environmental detection sensitivity, offers a dependable target detection solution for autonomous driving. Commercial millimeter-wave radar systems operating in the 76 to 81 GHz frequency range use cross-fed microstrip antennas, which are designed to be simple, compact, mass-producible, and cost-effective.
(1). Higher frequencies correspond to shorter wavelengths, necessitating smaller transmission lines and antennas for millimeter-wave applications compared to lower frequencies. To ensure optimal performance of automotive radar, it is essential to study how PCBs impact transmission lines and microstrip antennas, particularly for circuits operating under varying external conditions (temperature and humidity) over extended periods.
(2). When selecting PCB circuit laminates, the consistency of material performance indicators is crucial. Materials like copper foil, glass fiber, ceramic fillers, and others significantly affect performance consistency at high frequencies. Therefore, the reliability of these component circuits must be assured. Laminates are typically composed of glass fiber cloth and polymer resin, forming a dielectric layer covered with copper foil on both sides. The dielectric constant (Dk) of glass cloth is relatively high, around 6.1, whereas low-loss polymer resin has a Dk of 2.1-3.0, leading to noticeable differences in Dk over small areas. Figure 1 illustrates the microscopic top view and cross-section of the glass fiber weave in the laminate. The “knuckle bundle” areas show higher Dk due to more glass fiber content, while the “bundle” areas exhibit higher Dk due to increased resin content. Factors such as glass fabric thickness, spacing between fabrics, fabric flattening methods, and glass content in different directions can impact performance.
The test employs a microchip transmission line with a 1 mm terminal connector. Initially, the connector connects to a 50 ohm ground coplanar wave (GCPW) and is converted to a high-impedance microcircuit transmission line through an impedance converter. The microstrip transmission line measures 2 inches in length. This setup allows the experimental protocol to evaluate the effects of different glass weave structures. The solution includes a copper layer, glass cloth, and a thin polytetrafluoroethylene (PTFE) layer. To compare different glass weave structures, we created transmission line diagrams using three PCB laminate types: 1080 glass fiber PTFE fabric, 1078 glass fiber PTFE ceramic-filled PTFE laminate, and 1080 glass fiber fabric. The processed circuits were examined to find suitable transmission lines for testing, measuring amplitude and phase angle characteristics. Parameters such as phase angle (the phase value after opening), group delay (based on phase angle changes with frequency), and propagation delay (calculated from the phase angle) determine the laminate’s dielectric constant.
In summary, the laminate structure impacts the performance of transmission lines and antennas. Variations in glass fiber cloth construction affect the dielectric constant along the line, potentially reducing product performance and quality. Compared to RO4835 laminates, antennas made from RO4830 laminates exhibit better performance compatibility. The improvements in antenna performance and production processes are largely due to the use of composite materials: flat glass fiber fabric with low glass content (reducing conductor-glass fiber proximity), and thick coatings. The antenna efficiency is influenced by the electrical properties of materials like RO4830 laminates, which have low dielectric constants and loss tangents. Thus, antennas made from Rogers RO4830 laminates offer superior performance and compatibility for low-wavelength millimeter frequency radar compared to those made from RO4835 laminates.
