Electronic communication systems widely use bandpass
filters. In conventional radio transceivers with fixed band(s) of operation,
bandpass filters operate for a predetermined center frequency and bandwidth.
Fixed RF filtration is usually realized using lumped element L-C resonators,
transmission-line and waveguide resonators, ceramic resonators, surface acoustic
wave (SAW) resonators, or film bulk acoustic resonators (FBAR). However, in
multi-standard single-platform radio applications, such as software-defined
radio (SDR) transceivers, the frequency range of interest spans nearly two
powers, from approximately 30 to 3000 MHz, which is typically divided into a
number of narrower bands. Radio frequency (RF) bandpass filters in existing SDR
transceivers are realized in the form of switchable filter banks. As the number
of bands is generally large for wideband SDR, using the filter bank approach
drastically increases the size, weight, and manufacturing cost of the SDR RF
front-end. Furthermore, the filter technology used generally differs for
different bandwidths, and integrating a large number of these filters in a
single module can prove challenging.
To address these issues, a compact programmable bandpass
filter solution that can be used for applications in the RF front-end of
multi-band transceivers has been developed. The filter is based on integration
of RF-MEMS switches within a self-scaled filter topology, providing very
wideband tuning capability and a low-complexity tuning scheme.
Potential Applications
- SDR-defined radio architectures
- Ultrawide bandwidth (UWB) applications
- Orthogonal frequency-division multiplexing
(OFDM)
Benefits and Advantages
- A Small Footprint –filter is very compact at only 1 x 2cm
- High Linearity – frequency response of the filter is
insensitive to the levels of the input RF power, up to nearly 10 watts
- Low Insertion Loss –attenuation of the signal due to the
filter is minimal, allowing for increased system performance
- High Power Handling –ability to handle low power consumer
devices and higher power requirements of SDR radio equipment
- Low Variation Due to Temperature – adaptable to various
environments
- Minimum Complexity –single filter reduces overall system
complexity and will help increase reliability
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