![]() ![]() ![]() Out of band (either left of ~2.1 GHz and right of ~2.25 GHz) the impedance of the two resonators is comparable – the output is roughly half the input.3), the following arguments can be made, imagining this is basically a voltage divider: Now, if we consider a setup with only a single stage (one Zs and one Zp in the top of Fig. 3), and the parallel resonance frequency of the shunt resonator aligns with the series resonance frequency of the series resonator (magenta curve is shifted to the right with respect to the blue curve). 3) has a higher frequency response than the shunt resonator (blue curve in Fig. Note that the series resonator (magenta curve in Fig. Typical ladder filter configuration and impedance response of the series (Z1) and shunt (Z2) resonators, with the overall filter operation. These are expressed in decibels (dB), and less than -3 dB for insertion loss, and at least 30 dB for rejection is considered adequate filter behavior.įig. The real devices are never perfect: insertion loss signifies the non-perfect passing of signals within band, and rejection quantifies the amount of signal passed out-of-band. What do we want to achieve?įor simplicity, in this blog post we will look at band-pass filters: these allow most of the energy content between two frequencies to go through the filter, while stopping anything outside this range (see Fig. To achieve this, filters are employed: these allow only certain frequencies to pass, and depending on the range of these, can be grouped as low-pass, high-pass, band-pass and band-stop. ![]() These need to be properly isolated from each other to avoid crosstalk and unwanted noise signals. With the increase in demand for data transfer and communication between mobile devices, and especially the required bandwidth, more and more frequency bands are utilized for mobile data (2G to 5G), WiFi and even simple phone calls. In this blog post, we answer some of the fundamental why, what, and how questions regarding filter design, mainly centered around the requirement imposed by mobile communications. ![]()
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May 2023
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