Rohde & Schwarz demos coherent-source, nonstandard-OFDM, and group-delay measurements; touts AWR link
R&S's new techniques apply to aerospace and other applications; the AWR link supports cross-domain simulations.
By Rick Nelson, Editor-in-Chief -- Test & Measurement World, 6/14/2009 3:33:00 PM
Rohde & Schwarz (www.rohde-schwarz.com), in addition to
demonstrating 60-GHz noise-figure measurements
in conjunction with Noisecom at IMS 2009, also demonstrated the use of coherent sources to make balanced device measurements. In addition, it demonstrated capabilities for nonstandard OFDM modulation schemes and a group-delay measurement technique that doesn’t require local-oscillator access. In related news, AWR (www.awrcorp.com) introduced its AWR Connected for Rohde & Schwarz.
Coherent sources for differential measurements
The new capability for evaluating differential (balanced) devices supports applications in the aerospace and defense and other industries. It enables, for example, the characterization of phased-array antennas and the measurement of the nonlinear behavior of differential amplifiers.
To exploit the capability, users employ the R&S ZVA and R&S ZVT series of vector network analyzers (VNAs) equipped with the R&S ZVA-K6 true differential option. The VNAs are based on a true multiport architecture, with independent sources per port pair. The four coherent sources in the R&S ZVT8 VNA, for example, can be used to stimulate four antennas of a phased antenna array with defined phase or magnitude offsets. The 16 receivers of the R&S ZVT8 can be used to measure the magnitude and phase relationships between the output signals of up to 16 antennas in real time. Users can take advantage of the coherent signal sources to adjust them to a selected phase or amplitude offset.
The R&S ZVA-K6 option also supports characterization of balanced devices under large-signal conditions, thereby assisting designers who have to measure active differential devices operating close to or in compression. To get reliable results in the DUT’s nonlinear region, R&S ZVA or R&S ZVT stimulates it with true differential signals, for which both sources have a phase offset of exactly 180° in the measurement plane. The R&S ZVA-K6 targets designers and manufacturers of power transistors, amplifiers, MMICs, RFICs, and other active differential devices.
Testing user-defined OFDM
Rohde & Schwarz demonstrated a complete system for generating and analyzing user-defined and standard-independent orthogonal frequency division multiplex (OFDM) signals. The system consists of R&S signal generators and a signal analyzer using OFDM specific measurement software and covers microwave frequencies up to 40 GHz with a signal bandwidth up to 100 MHz.
A company spokesman noted that although the OFDM modulation scheme finds use in standards-based applications like LTE, WiMax, and DVB-T or DVB-T2, it is also finding use in proprietary aerospace and defense applications. To address the requirements of such applications, Rohde & Schwarz developed its R&S FSQ-K96 generic OFDM measurement software, which analyzes any kind of OFDM or OFDMA signal with any PSK or QAM modulation scheme. In addition to center frequency and level, general OFDM parameters such as guard interval and FFT length are adjustable. The structure of the preamble, the position and value of the pilots, and the position and modulation type of the data carriers can all be user-defined.
In addition to aerospace applications, the software can work with signals for systems being proposed by the Multimedia over Coax Alliance (MoCA), which also uses non-standard OFDM signals and is developing specifications for home networking over coaxial cable. The alliance’s goal is to allow home networking on existing coaxial cable in the 1-GHz microwave band at 100 Mbps using OFDM modulation, without the need for new connections.
The demonstration at IMS 2009 featured a complete system for generating and analyzing non-standard OFDM based MoCA signals. An R&S SMBV100A vector signal generator generated the MoCA signal, and an external mixer with LO input provided by an R&S SMF100A microwave signal generator upconverted the signal to microwave frequencies. An R&S FSQ signal analyzer downconverted and analyzed the signal using the R&S FSQ-K96 software.
Group-delay measurement
Rohde & Schwarz also demonstrated a new technique for measuring the group delay of frequency-converting devices. The technique does not require access to the local oscillator (LO) of the device under test, making it a useful technique in applications such as satellite communication links and highly-integrated devices in which the LO cannot be accessed. The technique is available as an option for all four-port R&S ZVA and R&S ZVT Series of vector network analyzers.
AWR introduced AWR Connected for Rohde & Schwarz
AWR (www.awrcorp.com) introduced its AWR Connected for Rohde & Schwarz, which integrates the capabilities of R&S WinIQSIM2 simulation software within AWR’s Visual System Simulator (VSS) system analysis software. The integration of R&S WinIQSIM2 gives VSS access to the range of digitally-modulated signals (including those for 3GPP LTE, 3GPP FDD/HSPA/HSPA+, and WiMAX) generated by R&S WinIQSIM2, thereby ensuring that engineers are simulating their designs with the same signal as a device will encounter in service.
For cross-domain simulations, hardware components can be integrated into any simulation. The signals generated by a Rohde & Schwarz (www.rohde-schwarz.com) instrument are sent back into VSS so the device under test can be optimized in VSS to meet the performance goals of specific wireless network standards. The cross-domain simulation capability works works with the Rohde & Schwarz vector signal generators such as the R&S SMU200A, which offers RF and base-band performance and also provide signal processing capabilities such as real-time fading required for multiple input multiple output (MIMO) measurements.
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