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Duet CDMA Channel Sounder SystemThe Duet Channel Sounder™, a two part transmitter and receiver system providing comprehensive analysis including BER, Multipath, Eb/No and RSSI. The Duet is a sequential correlating channel sounder which is an improved version of the "sliding correlator sounder". The Duet Channel Sounder provides insight into propagation analysis in the presence of fades, noise and multipaths for the PCS band assisting engineers in the planning and deployment of PCS Systems.
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PROPAGATION
ANALYSIS OF DIGITALLY MODULATED SIGNALS
Digitally modulated signals at PCS frequencies have unique characteristics when reflected. These reflections may cause unphased additions of data symbols resulting in bit errors of the received data. Signal strength measurements alone, using narrow bandwidth signals, such as CW, are deceptive, as such signals might appear strong, but nevertheless could exhibit a poor BER (bit error rate) performance. The cause is often multipath reflections, better known as time dispersions of the RF carrier. Time dispersion or delay spreading results in multipath reception caused by reflections and scattering off objects in the propagation environment. These signal distortions must be understood, and eliminated or at least minimized in the planning stage, before full deployment of PCS system. Today's designers and RF engineers need greater knowledge in analyzing the propagation of digitally modulated RF signals, the actual measurements of which provide data to calculate time dispersion effects and path loss. Time dispersion can be characterized by excess delay, mean excess delay, and RMS delay spread. The path loss exponent n and standard deviation o can characterize path loss with a simple statistical model in the log normal shadowing environment. THE DUET CHANNEL SOUNDER A two part transmitter and receiver system providing comprehensive analysis including BER, Multipath, Eb/No and RSSI. The Duet is a sequential correlating channel sounder which is an improved version of the "sliding correlator sounder". The codes between the transmitter and receiver do not "slide" by each other (have different frequencies). Instead, they step from one phase alignment to another. This technique produces considerably less noise, since the codes are not getting misaligned during correlations. This synchronous technique is used in The Duet, and avoids a "smearing" of correlated data over long symbol analysis. The Duet Channel Sounder provides insight into propagation analysis in the presence of fades, noise and multipaths for the PCS band. The Duet allows the user to transmit a digital ly-sp read signal and to examine the spectrum, received multipaths, signal strengths, and bit error rates at the receiver similar to the way the system will operate when deployed. The Duet system comprises a 10 watt stimulus transmitter and companion correlating receiver, equipped with an 8-channel, differential GPS receiver for geographical positioning and time coordination. The system can be remotely accessed and controlled to allow forward or reverse link propagation studies. The receiver has data logging capabilities to track a selectable number of paths and provide information on the magnitude and delay of each path, BER for any path, RSSI, position and time. This tool is specifically designed to meet the requirements for practical propagation analysis of TDMA, FDMA or CDMA formats in the PCS band.
The color LCD displays real time graphs of multipath components. The absolute power (dBm) of the 3 main peaks is displayed numerically. The graph is scalable in both the x and y directions and may be scrolled to view peaks that may be delayed in time more than the current scale. BER can be measured at any multipath signal (peak) using the cursor. Current GPS position, time and altitude are displayed. Real time of measurement and the remaining capacity of PCMCIA card are also shown. The following data is saved to both the PCMCIA card and serial output port (up to 4 measurements/sec):
Using a fixed PN sequence, the strongest 13 peaks are sampled and saved 100 times per second. Displayed on the screen are the GPS positions, time and altitude coordinates as well as the remaining PCMCIA card storage capacity. The following data is saved to both the PCMCIA card and PC serial output port (up to 100 measurements/sec):
RF SPECTRUM ANALYSIS (Optional) A maximum of 24 MHz is swept and the resulting measurement (dBm) displayed in spectrum analyzer fashion. The cursor is used to select any frequency for numerical display in dBm. The following data is saved to both a PCMCIA card and serial output port (4 measurements/sec):
POST PROCESSING Data from Duet measurements are saved to a 2 Mbyte PCMCIA battery backed-up card and to an RS-232 serial port for direct storage to a PC (up to 38K baud, selectable). The PCMCIA card data can be down-loaded to a PC using the supplied PC software. Serial output may be binary (compressed) for later conversion or in an ASCII comma delimited format. The Duet data can be imported directly into third-party software including spread sheets, such as EXCEL or propagation analysis software such as TEC's WIZARD. |
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The Duet Channel Sounder System Features:
Transmitter Features:
Receiver Features:
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The drive study was generated using a stationary Duet transmitter and a mobile Duet receiver plotted by Map Info. The color attributes indicate mean delay spread or multipaths of the digitally modulated signal. Data from The Duet measurements are saved to a 2 Mbyte PCMCIA battery backed-up card and to an RS-232 serial port for direct storage to a PC (up to 38K baud, selectable). The PCMCIA card data can be down-loaded to a PC using the supplied PC software. Serial output may be binary (compressed) for later conversion or in an ASCII comma delimited format. The data can be imported directly into third-party software including spread sheets, such as EXCEL or propagation analysis software such as TEC's WIZARD.
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Can the Duet system be sold separately as a stand-alone transmitter or receiver? We have sold components of the Duet system to customers in the past but BVS highly recommends the use of all Duet components for the fullest functionality that serious propagation studies demand. Does the Duet require or include a laptop PC? The Duet receiver fully integrates and contains a 486 PC complete with LCD screen, memory storage system and RS-232 and modem ports. |
® 2009 Berkeley Varitronics Systems
