Temperature Effect on a Lumped Element Balanced Dual-Band Band-Stop Filter

In this manuscript, the thermal effect on a lumped element balanced (differential) dualband band-stop filter (BSF) has been discussed in detail for the first time. The response of a novel filter should maintain consistency over a wide range of temperature. Although any microwave filter in general is designed for room temperature condition, the filter is employed for applications where the operating temperature constantly changes. Therefore, it is necessary to check the reliability of the filter response within a specific temperature range based on its application. Modern simulation software helps to make an initial assumption about the filter performance at different thermal conditions before its lab testing or actual application. Here, a quantitative analysis has been provided to show how change in temperature contributes to the change in each component value of a lumped element filter. This analysis is followed by a simulation to show that a balanced lumped element filter exhibits lower loss than its single-ended counterpart. Also, as the temperature varies, the balanced design demonstrates less deviation in the loss value than a two-port design. Next, a balanced dual-band BSF prototype with center frequencies 1.151 GHz and 1.366 GHz (25 degrees C) is characterized with a 4-port network analyzer under different temperature conditions. The experimental results exhibit a good match with the simulation results. For a variation of 80 degrees C in temperature, the maximum deviation obtained for the filter center frequency, absolute bandwidth (ABW), and insertion loss (Sdd21) are 5MHz, 2.8MHz and 2 dB, respectively.