RF Electronics Chapter 7: RF Filters Page 250
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
symmetrical from the input and output. This asymmetry is expected from k and q filter
table for the1.5 dB insertion loss that this filter has, as shown in table 7.4.
Figure 7.63. Frequency response of the filter of figure 7.62, as calculated.
The filter of figures 7.62 and 63 was optimised to give a 70 MHz bandwidth at a 1 GHz
centre frequency, as shown in figure 7.64.
Figure 7.64. Frequency response of the filter of figure 7.62, after optimisation.
When the prototype filter was produced, it was found to be 20 MHz (2%) low in centre
frequency, have a passband amplitude response that is slightly sloping and a bandwidth
that was too small. To compensate the centre frequency of the designed filter, was shifted
to 1.02 GHz and the bandwidth was increased. By optimising for a low return loss in the
passband one can ensure that the insertion loss is minimised. The passband attenuation
slope is thus due to the changing transmission line losses of the resonators with frequency.
RF Electronics: Design and Simulation
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