Ferroelectric tunable filters have been envisioned, but never
commercially developed. nGimat's nanolayered BST dielectric
coatings will enable frequency-agile filters for consumer wireless
products. Existing filters operate at fixed frequencies, determined
by the physical dimensions of the filter. nGimat's tunable filters
are being developed that will allow wireless products to be tuned to
multiple frequency bands using a DC control voltage. For cellular
applications, the use of frequency-agile filters will result in 30 -
40% lower transmitter power, longer battery life, reduced handset
size, weight and cost as well as the ability to operate in multiple
frequency bands with a single device.
Tunable Filters Brochure
A duplexer (a transmit and receive filter combined into one device) allows CDMA cellular phones to transmit and receive signals simultaneously. Current duplexers operate at a fixed frequency and vary in size depending on center frequency, bandwidth and insertion loss. Cellular phones designed to operate at multiple frequencies require multiple filters of varying sizes. nGimat's tunable duplexer allows the filter center frequency to be changed simply by applying a DC control voltage, eliminating the need for multiple filters and enabling smaller filters which reduce handset weight and battery usage.
nGimat will offer a CDMA duplexer that will be at least 4 times smaller, weigh less and will replace fixed frequency duplexers currently used in cell phones. The smaller size, lower insertion loss (<2dB) and electronic tuning capability of nGimat's tunable filter will result in up to 40% less battery consumption than existing alternatives. This lower battery consumption will enable increased talk time or allow handset manufacturers to further shrink the size of the battery while maintaining the same talk time.
nGimat's initial duplexer product operates in the U.S. PCS cellular band at 1.9GHz. CDMA handsets in the U.S. must be dual band, operating in the 800MHz band in addition to 1.9GHz. nGimat also plans a tunable duplexer for the cellular band at 800MHz that will be competitive in size and will have superior insertion loss when compared to SAW (Surface Acoustic Wave) filters.
GSM Multiband Filters
nGimat will also offer frequency-agile multiband filters for use in GSM handsets. Existing GSM handsets operate on up to three different frequency bands, with a fourth band (US cellular at 800MHz) being desired:
- 800MHz U.S.
- 900MHz Europe
- 1800MHz Europe
- 1900MHz U.S.
Each of these frequency bands requires a SAW filter and a dedicated receiver. This results in a very complex handset architecture with a high parts count and high cost.
nGimat's tunable filter technology will permit a single filter to operate in both the 800MHz and 900MHz bands, with the handset dynamically tuning the filter to the correct frequency. A second tunable filter will handle the 1800 and 1900MHz bands. This allows a quad band handset to be constructed with the same complexity as today's dual band handset.
For cellular handset manufacturers, this will be a significant improvement. A single hardware platform will work anywhere in the world, independent of frequency allocations. A universal quad band handset would remove the geographic restriction without adding cost to the handset.