What are the most important impedance matching techniques to use in high-frequency PCB design?

The first thing to do when impedance matching is not to determine if you need lumped or distributed elements. The first thing you should do is answer the following: 1) Is there already impedance matching on your component die? 2) If not, what is the bandwidth in which you require impedance matching? This will dictate whether you need to add discrete components for narrowband or wideband impedance matching, whether you can use something like a taper, or whether you need very high-Q impedance matching with transmission line sections. Also it does not really matter what frequency range you are in, distributed elements almost never offer "compact matching solutions", just compare the typical t-line section to a passive package to see this.

The choice between the two depends on the balance between frequency requirements, design complexity, and the level of precision needed in the impedance matching process.

One must bear in mind the Bode Fano criterion, which essentially means that a broader band match will *always* be worse than a narrow band case. For RFIC and MMIC design, the parameters of the transistor can be optimised to achieve a match which can be useful for reducing the real estate consumed by the passives, although feedback techniques are likely to be used with the smaller geometry. The balanced configuration is also worth a look for achieving good matches, particularly when a good noise match is required. Don't forget that common emmiter/source is not the only way to use a transistor. Last, but not least, do not forget about the effects of your matching network on stability. Include the option of adding stabilising resistance.

You can never get a perfect match with a transmission line section like a quarter wave match, it is physically and mathematically impossible because the impedance of your transmission line always has some small reactive component due to the presence of losses. Same goes for stubs.

It is important to consider also for active components the DC block and RF block. Pi-network is a good option for attenuating power as well.

Matching is very important to make sure your design will present optimal performance in the desired frequency range. In high frequency applications, the design of the PCB traces, dielectric material properties, and manufacturing tolerances such as copper roughness, trace etching and microwave glass weave are some aspects that needs to be considered to avoid unexpected surprises.

Some points of view for high freq’ pcb matching: 1. Broadband or narrow band matching ? Digital high speed or RF high freq? - different solutions. Single or differential signals? 2. Use dedicated pcb materials for high speed, low loss (like rogers and others) 3. Use special low esr/ esl passive elements. 4. Optimize pcb routing and ground using 3D simulators (hfss, cst ect) 5. Use RF spice model for the passive elements to have the most accurate simulation possible (modelitics, avx, murata ect ..) 6. Verify your pcb manufacture using test coupons. 7. Optimize and debug your board using TDR or VNA. (Pay extra care for good probing and measure).

Impedance matching is critical to circuit design, especially in high-frequency applications. Juliano is an authority in this area, and his comments come from a proper authority on the subject. I just recently began exploring the concept of SI and impedance matching. I want to target my comment regarding the width of the traces on a PCB. I understand there is much more than this, but from my recent experience, working with trace width has played a pivotal role in impedance matching. As we all know, trace width affects the characteristic impedance of the PCB transmission lines since a narrower trace increases the impedance while a wider one decreases it.