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This research review article provides a detailed examination of SMA (SubMiniature version A) connectors, which are integral components in high-frequency electronic systems. Through extensive S-parameter and time-domain reflectometry (TDR) measurements conducted on various SMA connector constructions, this study aims to evaluate the performance and impact of SMA connectors on signal integrity. Results reveal insights into the comparative performance of different SMA connector types mounted on PCB land pads, highlighting their strengths and limitations. Additionally, this paper explores the application of reference plane cut-outs for discontinuity impedance compensation, aiming to enhance the frequency response of SMA connectors. By linking measured performance parameters with relative market prices, this study offers valuable insights into the economic viability of different SMA connector types. The best and worst performing SMA connector measurements reveal an S11 < −10 dB bandwidth of more than 8 GHz and 1.5 GHz and a transition impedance of 46.5 Ω and 21 Ω, respectively. Overall, this research contributes to advancing the understanding and selection of SMA connectors for RF applications in telecommunications, aerospace, medical devices, and beyond. [ABSTRACT FROM AUTHOR]

High-speed and high-frequency PCB interconnect solutions with the slightest discontinuities in the physical geometry along the microstrip transmission line can significantly degrade the integrity of the signal being transferred. This paper presents an analysis of SMT component pads and their impact on the successive transmission line impedance. During 0805, 1206 and 2512 package size SMT component pad discontinuity evaluations it was spotted, that the increasing deviation from target impedance affects the microstrip impedance segment following the discontinuity. A 25 Ω impedance offset at the SMT pad reduces the line impedance afterwards by up to 7 Ω. A 37 Ω impedance offset results in a microstrip impedance reduction by up to 15 Ω, whereas a 45 Ω impedance change leads to a reduction of successive segment impedance by up to 30 Ω. This effect is also present in multiple evenly-spaced discontinuities. But a single reference plane cut-out, which is twice as wide as the SMT component discontinuity, substantially improves the overall impedance of the transmission line, including the successive line segment impedance drop. [ABSTRACT FROM AUTHOR]

The modern era of technology contains a myriad of high-speed standards and proprietary serial digital protocols, which evolve alongside the microwave and RF realm. The increasing data rate push the requirements for hardware design, including modern printed circuit boards (PCB). One of these requirements for modern high-speed PCB interfaces are a homogenous track impedance all the way from the source to the load. Even though some high-speed interfaces don't require any external components embedded into the interconnects, there are others which require either passive or active components—or both. Usually, component package land-pads are of fixed size, thus, if not addressed, they create discontinuities and degrade the transmitted signal. To solve this problem, impedance compensation techniques such as reference plane cut-out are employed for multiple case studies covering this topic. This paper presents an original method of finding the optimal cut-out size for the maximum characteristic impedance compensation in high-density multilayer PCB designs, which has been verified via theoretical estimation, computer simulation, and practical measurement results. Track-to-discontinuity ratios of 1:1.75, 1:2.5, and 1:5.0 were selected in order to resemble most practical design scenarios on a 6-layer standard thickness PCB. The measurements and simulations revealed that the compensated impedance saturation occurs at (150–250%) cut-out widths for a 50 Ω microstrip. [ABSTRACT FROM AUTHOR]

To process high-frequency signals on a printed circuit board (PCB), it is often necessary to carefully analyze and select the pad widths of the chip packages and components to match their impedance to the standard Z0. Modern PCBs are complex multilayer designs, utilizing either only high-end laminates, low-end laminates, or a combination of both. The on-board component footprints usually have larger pads that become discontinuities and corrupt the impedance of critical traces. One way to address this issue is to include reference plane cutouts as a measure of compensation. This paper aims to find out how an asymmetric dielectric stack-up affects the microstrip discontinuity impedance compensation using reference plane cutouts. The selected board layer stack-up imitates several different practical design scenarios, including costly PCBs that strictly comprise high-end dielectric materials, as well as trying to lower PCB cost by introducing low-cost materials without major performance sacrifice. S-parameter measurements are performed and confirmed by time domain reflectometry (TDR) measurements. [ABSTRACT FROM AUTHOR]

In the era of technology and communication, printed circuit boards (PCBs) can be found in a myriad of devices—from ordinary household items, to state of the art custom metrology equipment. Different types of component for wireless communications are available and come in various packages, supplied by multiple manufacturers. The signal landpads for some high-frequency connectors and components, encapsulated in larger packages, are usually wider than the controlled impedance trace, thereby introducing unwanted impedance mismatch and resulting in signal reflections. The component land pad and microstrip width a discrepancy issue can be found in both complex high-density industrial devices and system-level academic research papers. This paper addresses the topic of compensating discontinuities, introduced by signal pads, which are wider than the target impedance microstrip, characterizes the difference between the compensated and uncompensated microstrip with discontinuity, and proposes a generalized guideline on compensating for the introduced impedance change in multilayer PCBs. The compensation method is based upon carefully designing the stackup of the PCB allowing for a reference plane cutout under the discontinuity to even out the impedance mismatch. A 6-layer PCB with IT180A dielectric material containing three structures has been manufactured and characterized using an Agilent E8363B vector network analyzer (VNA). A 4–12 dB improvement in S11 response in the whole frequency range up to 10 GHz, compared to that when no compensation has been applied, was observed. [ABSTRACT FROM AUTHOR]