On the receive end of the chain, the Keithley 2820 vector signal analyzer (VSA) handles receipt and recovery of signals. It uses the company’s MIMO Signal Analysis software for signal recovery, measurement, and display. As many as four VSGs and VSAs may be used together. In addition, any MIMO configuration up to 4x4 (e.g., 2x3, 4x3, 2x1) can be accommodated.
Keithley’s 2920 VSG can generate signals from 10 MHz to 6 GHz. An optional arbitrary waveform generator (AWG) lets users produce modulating signals for GSM, EDGE, WCDMA, cdma2000, single-input/single-output (SISO) wireless local-area network (WLAN), the very demanding 40-MHz wide 802.11n Wi-Fi signal, and WiMAX. The 2920 is also available as a standalone test unit.
Meanwhile, the 2820 VSA receives signals up to 6 GHz. Bandwidth is 40 MHz. It can receive, analyze, and display most popular wireless standards such as those mentioned for the 2920, both SISO and MIMO.
To use these instruments in a MIMO test system, you need the 2895 MIMO Synchronization Unit, which synchronizes all of the VSGs and VSAs. It provides a common local-oscillator (LO) output to all units, as well as a 100-MHz digital clock and trigger signals to sync all of the units for the selected MIMO configuration. The PC-based MIMO Signal Analysis software lets you test and measure all standards with configurations to 4x4 MIMO.
Pricing begins at $17,500 for the 2920 VSG and at $22,500 for the 2820 VSA. The 2895 MIMO Synchronization Unit costs $9900. MIMO signal analysis software is $9500.
Rohde & Schwarz offers several new LTE, WiMAX, and MIMO products, too. One complete 2x2 MIMO test setup that works with 3GPP LTE, WiMAX, 802.11 Wi-FI, and HSPA+ consists of the SMU200A RF signal generator and the AMU200A baseband generator along with a fading simulator in one instrument (Fig. 6). The instrument permits real-time fading measurement on all four propagation paths.
A typical MIMO system employs the 2x2 format with two transmitters and two receivers. The test setup requires two signal generators and one fading simulator. R&S offers an option that allows measurements on 2x2 MIMO receivers using a single instrument. The generator can be equipped with an internal fading simulator as well as two RF sources and two baseband sources. When equipped with this option, the instrument can simulate the four fading channels required.
R&S offers optional firmware for the SMU200A/AMU200A combo. It adds channel coding and MIMO pre-coding for up to four transmit antennas for 3GPP LTE. With it, users no longer need external fading hardware or control software for testing 3GPP LTE mobile devices.
Since the signal generators provide 3GPP TS 36.211 standardcompliant signals, the full scope of RF performance can be tested. It requires additional instruments or an external PC for signal calculation. Another option for the R&S SMU200A and some other R&S generator models, the SMx-K55 software, offers downlink and uplink testing functionalities.
R&S’s CMW500 LTE protocol tester makes testing basestations and handsets easy despite the complexity of the LTE protocol (Fig. 7). It has a frequency range up to 6 GHz with a bandwidth of 40 MHz, and it greatly facilitates conformance, performance, and interoperability tests. A full suite of tested software tools and test sequences greatly reduces LTE development efforts.
As for a WiMAX test solution, R&S’s CMW270 communications tester emulates a basestation. It’s a great testing solution for chip sets and mobile stations, combining signal generation and signal analysis in one box. It supports the 802.16e mobile WiMAX standard and covers from 100 MHz to 6 GHz. The instrument also supports all RF profiles defined by the WiMAX Forum.
Tektronix Communications recently announced some LTE and WiMAX test platforms. For instance, its G35 comprehensive network management and diagnostics solution covers all protocol layers and physical interfaces, including air and fixed line interfaces (Fig. 8). It includes the G35-LTE functional and load test platform and the NSALTE scalable platform for monitoring, troubleshooting, and optimization.
Tektronix also has a WiMAX version of the G35. The WiMAX Forum recently selected this version as the test solution to verify the interoperability of WiMAX network nodes in mobile WiMAX certified test labs around the world.
Although not an LTE or WiMAX test product, the Tektronix H600 RFHawk handheld digital RF signal hunter is designed for the surveillance and security market (Fig. 9). Its receiver contains a high-performance spectrum analyzer with an intuitive set of user controls, allowing for the quick and simple classification and location of both analog and digital RF transmissions.
Finding and physically locating RF emitters that are misusing the radio spectrum can be a challenge, especially when risk mitigation and time to response are critical. Many covert signals are designed to avoid detection by hiding among legitimate transmissions. The RFHawk was developed based on customer needs to quickly spot and locate illegitimate analog and digital RF transmission sources
Its spectrogram mode lets customers see the true signal shape through FFT-based spectrum analysis. The RFHawk uses a DSP technique called spectral correlation analysis to look at internal frequencies within the signal to discover a digital signal’s symbol rate and other repetitive internal rates to identify valid signals.
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