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RF Electronics Chapter 7: RF Filters Page 238 2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0. Figure 7.48 shows the frequency response of the harmonic stub circuit. It can be seen that there is some effect on the passband of the filter, so that further optimisation to the design of the hairpin filter must be carried out in order to ensure that the combination of the hairpin filter and the harmonic stubs have the required passband response. Figures 7.51 and 7.52 show the frequency response of the actual filter of figure 7.46 and compares this with the frequency response of the simulation. Figure 7.49. Circuit schematic of hairpin filter as built. The filter hardware was realised from the circuit schematic using the "MCFIL" elements as shown in figure 7.49. To compare the different ways this circuit can be simulated, The MCFIL elements can be replaced with the coupled line element "MCLIN" with "MLEF" elements compensating for the end effect of the open circuited ends of the coupled line elements, as shown in figure 7.50. An AXIEM EM simulation is carried out on the circuit of figure 7.49, as described in the EM Simulation section later in this chapter. Finally the MTEE$, MCROSS$ and MLEF elements in 7.49 are replaced with the EM based elements MTEEX$, MCROSSX$ and MLEFX. Figure 7.50. Circuit schematic of hairpin filter using MCLIN elements. The value of E r = 3.38 was specified by the manufacturer and is used for the simulation and optimisation of this filter prior to its manufacture. Figures 7.51 and 7.52 show a comparison between the simulated and measured performance. The EM simulation, using AXIEM and EM EXTRACTION, gives a better agreement for the passband centre frequency and bandwidth, than the circuit simulations. Using EM based elements MTEEX$, MCROSSX$ and MLEFX makes no noticeable difference below 2 GHz. Figure 7.52 shows the stopband performance of the filter for both the measured performance and the computer simulation. The most significant difference is the reduction in attenuation in the stopband. This is due to EM coupling between parts of the RF Electronics: Design and Simulation 238 www.cadence.com/go/awr