In the presentation the most important proprieties of the radio wave propagation in the ionosphere are explained and its impact on the high performance radio transmissions is discussed. The principles of the orthogonal frequency division multiplexing is explained and new digital radio system based on this principle is presented. Then some experimental data registered in Cracow in Poland are sho...

In this paper we present the design and analysis of a distributed regenerative frequency divider (DRFD) based on a novel distributed single-balanced mixer. Artificial transmission lines are incorporated in the distributed single balanced mixer to absorb the parasitic capacitances. The circuit is realized in a 0.18 μm standard CMOS process. It shows a division by two for an input frequency of 40...

The phase selection technique is a good solution to design programable dividers widely used in fractional synthesizers. However, as the process parameters vary, the delays in the phase selection logic change, and they erroneously trigger the phase selection. This paper presents an improvement that consists on making the phase selection logic in a semi sequential fashion. In this way if there is...

We develop adaptive channel estimation techniques for space–time block–coded (STBC) multiple–input multiple– output (MIMO) orthogonal frequency division multiplexing (OFDM) communications. The structure of the space–time code is exploited to lower the complexity of the adaptive receiver.

The performance of uncoded orthogonal frequency division multiplexing (OFDM) over fading channels is generally improved by introducing some kind of coding. Different coding schemes for OFDM has been reported in the literature. Our aim in this paper is to compare the performance of different coded OFDM systems and compare their bandwidth-complexity tradeoffs. We consider three different coded OF...

The same information is often broadcast to many receivers over diierent frequency selective channels. Digital audio signals and digital video signals are commonly distributed by such broadcasts. A coded modulation technique for orthogonal frequency division mul-tiplexing (OFDM) is presented that provides consistent performance over a variety of frequency selective channels. The range of perform...

In this paper, we investigate different antenna diversity concepts, which can be easily applied to orthogonal frequency division multiplexing (OFDM) systems. The focus is to provide diversity schemes, which can be implemented to already existing OFDM systems without changing the standards. It is also possible to combine these techniques in a suitable manner. The introduced diversity techniques ...

In this paper, an isolation enhanced multiway power divider for wideband beamforming array is proposed. This method is based on the concept which converts the divider into multi-section stepped impedance transformer. In addition to this scheme, lumped inductors and capacitors are incorporated in isolation networks to enhance the isolation bandwidth of the divider. In/Output reflection and isola...

The above difficulty is alleviated by use ofring-shaped transistors, where the ratio of device width and drain junction capacitance is approximately four times that of a regular layout [4]. However, such a structure proves b neficial if only oneofthedrainorsourceterminalsappearsinthesignalpath. Thus, high-speed divider topologies using stacked devices or pass gates do not necessarily achieve a ...