Modern RF and microwave communication systems require compact, high power filtering solutions to suppress unwanted harmonic signals generated by power amplifiers. Harmonics can degrade signal quality, interfere with adjacent channels, and reduce overall system efficiency. To address this challenge, Tri-TeQ has developed a miniaturised broadband tuneable harmonic switched filter bank (THSFB) designed to provide effective harmonic suppression, while significantly reducing system size and complexity.
The basis of the harmonic switched filter bank is a lowpass filter. The lowpass filter passes the fundamental frequency and rejects all the harmonic signals at a frequency of an octave and higher. If the PA operates over a multi-octave frequency range, then multiple lowpass filters will be required. The filters switch between each band corresponding to the frequency at which the PA is functioning.
Traditional harmonic switched filter banks rely on multiple fixed low pass filters connected through single pole multi throw (SPnT) switches. Each filter is designed for a specific frequency band, and the system switches between filters depending on the operating frequency of the power amplifier. While effective, this approach results in large, bulky assemblies because many filters and switches are required to cover a wide frequency range.
The THSFB architecture improves on this design by incorporating tuneable filters. By allowing each filter to operate across multiple frequency bands, the system reduces the total number of filters and switches needed. For example, three tuneable filters can be configured to generate ten operating bands, compared with six fixed filters typically required in conventional designs. This simplified topology reduces insertion loss, lowers power dissipation, and minimises thermal management requirements.
Tri-TeQ’s flagship TH-112 filter bank demonstrates the benefits of this approach. The device supports continuous wave power handling up to 100 W and integrates ten harmonic filter bands in a compact package measuring approximately
Table 1. Key TH-112 performance parameters.
Beyond size reduction, the tuneable architecture also simplifies system integration. Fewer components lead to reduced control complexity, shorter build times, and improved reliability. Lower component counts also reduce manufacturing costs and lead times. These advantages make tuneable harmonic filter banks well suited for demanding applications such as broadband, multi octave military frequency hopping radios and other high power RF communication systems.
By combining tunability with high power capability, the THSFB represents a significant advancement in RF filtering technology, enabling compact, efficient harmonic suppression in modern wideband communication platforms.
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