Community Research and Development Information Service - CORDIS

Better cordless connections

The Digital Enhanced Cordless Telecommunication (DECT) standard was originally conceived for low-cost cordless telephone applications. As such, relatively high carrier frequency and modulation index deviations are permitted. Also, the radio frequency (RF) transceiver is typically based on a limiter-discriminator architecture, which is low cost but has high non-linearity, so produces distortion. Signal equalization thus has a strong influence on the design of the RF section, with a significant impact on overall costs. Designed specifically to comply with DECT systems, the RadioSECOND radio equalizer module uses new signal equalization techniques to increase system tolerance to multipath radio propagation. Only one module is required in the whole system, resulting in significant cost savings.

Based on a decision feedback equalizer (DFE), the RadioSECOND circuit effectively pre-distorts the signal, essentially applying inverse filtering of the channel to the transmitted signal. This signal then feeds a voltage-controlled oscillator performing Gaussian Filtered Shift Keying (GFSK) modulation, or an in-phase and quadrature (I-Q) generator for upconversion. When the pre-distorter is used in conjunction with the equalizer, it significantly reduces the total Bit Error Rate (BER) of the system, increasing both subjective quality in voice transmissions and accuracy in data transmissions. The circuit can be used in any DECT-based application, such ad Cordless Terminal Mobility (CTM) and Wireless Local Loop (WLL), with no impact on either terminals or network terminations.


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