Tektronix, Inc.

Tektronix International Sales Gmbh

Yoneo Akita

Koichi Yoshihara

Koichi Sega

Hideaki Ogata

Kenichi Miyake

The present invention is directed to a display for easily understanding time changes of communication conditions of channels using a plurality of sub-carriers. Layers corresponding to the plurality of channels are displayed along the time base in such a manner that width of each layer is determined in accordance with the number of sub-carriers used for each channel at any given time. Additionally, colors or patterns of each layer may be modified in accordance with modulation types or power levels of the corresponding layer. The relationship between colors or patterns of the layer and modulation types or power levels is displayed.

Measurement apparatus, displays and methods for indicating channel status

Constellation display allows a user to evaluate the quality of a signal under test with the constellation display even if the signal is a digital modulation signal that has many possible ideal phases. A signal analyzeracquires time domain data of the signal under test that has N ideal phases. The signal analyzerdemodulates the signal under test to measure the phases &#x3b8;m and amplitudes Am of the symbols of the signal. Phase differences d&#x3b8; between the ideal and measured phases of the measured symbols are calculated. K group phases &#x3b8;gi are assigned to N of the ideal phases. The signal analyzer displays a constellation using phases &#x3b8;gi+d&#x3b8; and the measured amplitudes Am. That is, points are plotted at locations of X=Am*cos(&#x3b8;gi+d&#x3b8;)+jAm*sin(&#x3b8;gi+d&#x3b8;) on a complex plane.

Signal analyzer and methods for displaying constellations

A measurement indicator, 'transfer efficiency,' is provided for evaluating conditions of propagation paths of wireless communication systems having a plurality of transmitting and receiving antennas. Transfer functions of signal paths are calculated from data of received signals that are obtained with receiving antennas by receiving OFDM signals transmitted by transmitting antennas. A demodulation matrix is calculated for demodulating a transmitting vector from a receiving vector concerning a desired subcarrier of the received signals. A noise amplification factor is calculated as a square root of a sum of second powers of components of the demodulation matrix of the receiving antennas concerning the desired transmitting antenna. The noise amplification factor or the inverse is displayed as a value or as a graph that has an axis concerning the subcarrier and an axis concerning the noise amplification factor or the inverse.

Apparatus and method for evaluating propagation path conditions

A method of despreading modulated signals with low noise to demodulate a sum of spread signals from a base station of a mobile phone system provides the sum of spread signals to several paths. A despreading circuit in each path despreads the sum of spread signals by respective spreading codes. The despread signals are separated into channels and symbols for each channel are estimated on each path. The symbols are modulated by applicable Walsh codes corresponding to the respective channels, added and spread to produce an estimated spread signal corresponding to the spreading code for each path. Then the sum of spread signals is despread again on each path after the estimated spread signals of other paths are subtracted from the sum of spread signals so that the noise due to interference between the spreading codes is reduced.

Despreading of modulated signals with low noise

A first test signal from a test signal source is provided to a spectrum analyzer to produce first measurement data. The test signal source is expressed by a first transfer function G(w) and the spectrum analyzer is expressed by second transfer function F(w). A second test signal is provided to the spectrum analyzer to produce second measurement data where the second test signal is derived from the first test signal by shifting the frequency by a known increment. From the first and second measurement data, the components are the same on G(w) but different on F(w). The G(w) components are cancelled by calculation using the first and second measurement data and then the second transfer function F(w) is evaluated independently of G(w).

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Tokyo, Japan

Yoneo Akita