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Although direct conversion transmitters and receivers share the same structure certain differences in their behavior can be found. These differences result in diverse performance limitations. This paper derives a linear model of direct conversion transmitters and receivers. Based on this model methods to extract the frequency dependent characteristics are introduced and compensators are suggested...
In practical communication systems, frequency offsets between transmitters and receivers cannot be avoided. Both transmitter and receiver require local clocks which are usually derived from independent crystal oscillators. Typical low-cost crystals show a relative frequency tolerance of 20 ppm. Though devices with less tolerance are available, they are too expensive for most mass market devices. It...
We propose a quadrature undersampling technique that makes it possible to extract baseband inphase (I) and quadrature (Q) data from an input RF signal directly. These I and Q data are derived from three sampling points which lay in one cycle of the RF signal. A traveling-wave type of sample and hold (S/H) circuit with phase delay per-section of θ can sample an input signal at the three points with...
Orthogonal frequency division multiplexing (OFDM) is the modulation scheme of choice for digital video broadcasting-handheld (DVB-H), which is required to operate under high mobility conditions resulting in significant Inter-carrier Interference (ICI). To mitigate ICI, several cancellation schemes have been proposed but they require reliable channel information at the receiver which is quite challenging...
Correlative minimum shift keying (MSK), a second order polynomial modulation scheme known as tamed frequency modulation (TFM), is a constant envelope type of modulation with a perfect peak to average power ratio (PAPR), besides the property of low out of band power. We apply the linearized TFM to the single carrier transmission with frequency domain equalization (SC/FDE) concept. We then obtain a...
In this paper we consider the coexistence issue between OFDM-based WLANs of the 802.11a family and time-hopping ultra wideband (TH-UWB) systems. A general analytical expression is provided for the bit error rate (BER) of the OFDM transceiver operating in the presence of UWB interference and the interferences caused by the multipath propagation phenomenon on the 802.11a OFDM signal, comprising intersymbol...
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