## 4 Discussion and Conclusions  
In terms of electrical perspectives, a PCB physical channel is characterized by frequency-dependent material losses, reflections from discontinuities as connector board interfaces and interferences from neighboring data paths. Attenuated and dispersed signal leads to ISI. Reflections are addressed in modern links with via back drilling, T-coil matching networks or optimized connector interfaces as presented in [10; 17]. Conventional approaches to EQ design are based on time domain simulations along with experimental validation of results in an iterative way until specifications are met [10]. For a given frequency range, an EQ should fit the following rules: approximately flat transfer function, matched input and output, and low residual losses. An example of amplitude EQ is presented in [16] with resistor loaded, a resonant unit and the link represented through a transmission line.  
In the previous sections, we described the use of EQ in the signaling systems with in depth analyses on the passive EQ. The performance of the system is limited by ISI due to frequency-dependent IL of the line. The scope of EQ is to flatten the frequency response of the transmission system to increase the bandwidth of the line and to be able to increase the data rates. EQs may be included in the transmitter or receiver or split between the two.  
Using the filters' synthesis approach, we started the analysis from the IL expressed in dB of the given microstrip single ended line. The K coefficient was resolved and a series of EQ were synthesized as follows: derivative RC, series RL, combined of the first two variants for RLC EQ, bridged T RLC, and RL variants with open stub inserted to overcome the frequency-dependent behavior of the interconnect which were implemented in MWO. The EQ has to compensate for high frequency attenuation. Clearly, the EQ compensated for lossy line's frequency behavior, making IL flatter across frequency domain. However, the flatness implies an overall attenuated amplitude of the signal. A practical EQ trade off the IL for flatness response.  
The time domain simulation results show clear improvement on the data eye metrics. Before integration in the circuit of the EQ, overshoot and undershoot were observed in the waveform at the output of the interconnect due to fast rise and fall time of the simulated source and because the IL has no flat characteristic in frequency domain. In practice, a real driver is typically slower and the signal path's loss is slightly higher so a small overshoot in simulation can be accepted. The new microstrip resonator structure proposed was evaluated by simulation means in time domain and evidentiated similar results with the existing model in [15], but with the advantage of positioning in front of the link. Future evaluation of the proposed EQ might show some limitations of the structure.  
Passive EQs offer the advantage of improved performance with no additional power consumption. Moreover, we need to mention that this type of EQ fits easier integration into the silicon. However, they demand tighter control of the components values for typical digital applications. In addition, variation of the frequency response for passive EQ implies active circuitry that will tend to degrade the power benefit.  
Further investigation is based on the last variant of distributed elements EQ implemented at the schematic level in previous section.  
The work has been funded by the Operational Programme Human Capital of the Ministry of European Funds through the Financial Agreement 51675/09.07.2019, SMIS code 125125.  
The data presented in this study are available on request from the author.  
Special thanks to AWR Company for supporting the author with the necessary simulation software tools for the work done in the article.  
The author declares no conflict of interest.