Using Ku-Band Filter to improve selectivity and performance

There are four general types of filters, based on their functions. The band pass filter allows only the desired band of frequencies to pass through. The band stop filter rejects undesired frequencies. The low pass filter lets only frequencies below a certain frequency pass through. Last, but not the least, the high pass filter allows only frequencies above a certain frequency.

So what, then, are the other filters such as lumped element LC filters and cavity filters? Such technologies – a Ku-band cavity filter, for instance – are typically used to enhance the selectivity of a receiver, or to otherwise boost performance.

Definition and Application of the Ku-band

The Institute of Electrical and Electronics Engineers (IEEE) defines the Ku-band as the range of frequencies between 12 to 18 gigahertz (GHz).

Primarily, these frequencies are used in both fixed and broadcast applications in satellite communications. In some parts of Europe, law enforcement makes use of certain frequencies in this range for vehicle speed detection.

Besides that, it is used in specific applications like NASA’s (National Aeronotics Space Administration’s) communications with the International Space Station (ISS). This band of frequencies is also useful for satellite communications from remote locations.

Advantages and Disadvantages

The Ku-band isn’t as restricted, in terms of power, when compared with the C-band that falls on the 4 to 8 GHz band of frequencies. That’s because it rarely interferes with Earth-based microwave (MW) systems.

This higher power means that receiving dishes designed for this frequency band can be made smaller without sacrificing quality. It also makes finding a dish site easier, due to increased flexibility. One trade-off of this is the need for a satellite operator to be more accurate in positioning, due to the narrow beam width of a Ku-band signal.

There are other disadvantages to be expected when operating in the Ku-band. One of these is the rain fade associated with signals in frequencies higher than 10 GHz – in places with heavy rainfall, that is. If the weather responsible for the degradation of the signal is snow, instead of rain, this phenomenon is called ‘snow fade’.

Whichever phenomenon is at work, this degradation means that Ku-band receivers will need to be more sensitive, or at least more selective in order to receive the signals properly.

Importance of a Ku-band Cavity Filter

As mentioned earlier, some filters are designed to improve a component’s performance, and one way to do this is through boosting said component’s selectivity. This is a way to measure a radio receiver’s ability to pick up only signals it is tuned to, as well as to reject signals close to the frequency it’s supposed to pick up.

There are physical and practical barriers to increasing receiver selectivity, including the difficulty of constructing large-value tuning capacitors. Large inductances are another aspect limiting the increase, since these need considerably large coils or else thinner wire, which decreases internal resistance.

Since a cavity filter is typically built to have high selectivity, using one or several in a receiver would boost its selectivity while eliminating most – if not all – of these inherent difficulties.

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Designed to offer higher performance and quality factor, a well-manufactured Ku-band cavity filter, whether off-the-shelf or customized by a supplier like AWG Tech, will help to make such a communications application function as it was intended.