## 4 Results and Discussion  
Figure 8 shows the frequency responses of the proposed microstrip diplexer. At 1.66 GHz for the first channel (Tx), the proposed diplexer design displays an insertion loss (IL) of 3.2 dB and a return loss (RL) of 16 dB. The first frequency band's transmission channel (Tx) has a fractional bandwidth (\(\Delta F\)) of 4.94% and extends from 1.626 GHz to 1.708 GHz. The reception channel (Rx) for the second frequency band spans the range of 2.469 GHz to 2.598 GHz, with a central frequency of 2.52 GHz and \(\Delta F\) of 5.12%. Furthermore, the insertion loss and return loss for this channel are detected to be 2.88 dB and 21 dB, respectively. Based on the results of the simulation, it has been determined that the configuration that has been proposed can maintain an isolation of 31 dB between the two filters. There are some operational characteristics of the diplexer that are depicted in Figure 9. A few examples of these features are the scattering parameters' group delays (S11, S21, S31, and S32). A visual representation of these qualities can be found in the figure and Table 2. It is necessary to make use of the group delay (GD) measurement to acquire an understanding of the average filter delay over a variety of frequencies. A negative group delay indicates that the diplexer can forecast the position of the pulse at a later time by making use of the current location of the pulse rather than the position of the pulse at the time of prediction. It is possible to conclude that a negative group delay is a signal delay and is an essential property that must be taken into consideration when developing a diplexer. This conclusion can be reached following the aforementioned information. In the realm of radio frequency microwave systems, it has garnered a significant amount of attention in recent years. Below, you can find a detailed table that describes each value contributing to the group delay. Operation of a microstrip diplexer with a negative group delay requires the use of the phase of some special components like meander line resonators as a source of the requiredphase shift. Additionally, it clocks signals and performs such functions as signal processing, filtering, and equalization to eventually improve performance of high-tech communication systems through the reduction of latency and the gaining of greater transmission rates. A good design and appropriate tuning should be achieved in order to meet the negative group delay needs for special application function. Figure 8: The simulated S-parameters by AWR simulator. Figure 9: The Simulation GD for the designed microstrip diplexer. One of the most fundamental capabilities that may be found in a variety of devices, such as diplexers, amplifiers, and filters, is the capacity to convert an input signal into an output signal. Furthermore, it is essential to acknowledge the significant influence that the phase of the input signal has on the phase of the output signal for optimal results. This discovery highlights the relevance of the phase shift on the signal that is produced as a result, providing valuable insight into the working of the diplexer. Figure 10 illustrates the phase response for the projected diplexer, which provides an understanding of the structural design for the modeled device. Based on Figure 10, the phase response explains the connection that exists between the phase of an input sinusoidal signal and the phase of the output signal. It is possible to see the relationship between the two phases of the diplexer by looking at this figure that illustrates frequency jumps. The scattering parameters, also known as S-parameters, exhibit a significant correlation, which is an indication of the high-quality consistency of the design.