Analyzers Test New 3G Wireless Formats

Jan. 26, 1998
This series of spectrum analyzers can now fully characterize components and systems for TD-SCDMA and 1xEV-DV applications.

Third-generation (3G) cellular technologies are slowly but surely gaining ground on the promise of delivering the high data rates required for Internet access and multimedia at acceptable speeds. To ensure that designers of these systems have the right measurement tools, Agilent Technologies (Santa Rosa, CA) has added enhancements to their Performance Spectrum Analyzer (PSA) Series spectrum analyzers that allow them to characterize two of the most promising entrants: time-division synchronous code-division multiple access (TD-SCDMA) and 1x evolution, data and voice (1xEV-DV) technology. The analyzers have also been upgraded to work with external harmonic mixers at measurement frequencies as high as 325 GHz.

The PSA instruments include models with standard frequency ranges as wide as 3 Hz to 50 GHz. These are the company's highest-performance spectrum analyzers, with digital resolution-bandwidth filters as narrow as 1 Hz and as wide as 8 MHz. They feature outstanding stability, accuracy, and low noise (noise sidebands of −151 dBc/Hz at 6 MHz from the carrier).

TD-SCDMA is virtually assured of being one of the primary access methods employed in the 3G wireless systems in China. Developed by the Chinese Wireless Telecommunications Standards group, TD-SCDMA is a unique access method that can increase the capacity of the network by using a single frequency band for both uplink and downlink transmission paths. It also dynamically allocates base-station resources for either uplink or downlink as dictated by traffic conditions. It was conceived to fully exploit the benefits of smart-antenna technology, and can simultaneously detect multiple parallel signals. The result is higher network capacity and greater overall throughput.

In order to give the PSA Series instruments the ability to characterize the transmit performance of TD-SCDMA components and systems, Agilent has created a TD-SCDMA measurement personality, available as Option 211. The enhancement provides the user with a dedicated interface that simplifies the measurement process, and allows the instruments to make power measurements on both uplink and downlink signals, including power versus time, transmit power, adjacent-channel power, multichannel power on up to 12 channels, spurious emissions, and spectrum emissions masks.

Within each of these categories, the user has various options for configuring the test routine. For example, when measuring transmit power, the display can include minimum, maximum, and mean values of a single burst or complete 10-ms frame, and root-mean-square (RMS) or log averaging are available. Spectrum emission masks that confine spurious emissions tests to within user-specified frequency bands display both spectrum and tabular results simultaneously. Other variables include average or peak detection, offset frequency, reference bandwidth, and limit values.

To complement the power-measurement-analysis capabilities of Option 211, Agilent has added TD-SCDMA modulation-analysis capability to its 89601A vector-signal-analysis software. This comprehensive analysis tool, which also supports a wide array of other access methods, allows designers to troubleshoot any modulation problems with a high level of detail.

1xEV-DV is the latest revision to the cdma2000 3G access method, following in the footsteps of 1xEV-DO (1x evolution, data only), and promises to increase network capacity and maximum attainable data rates by allowing more complex modulation schemes to be allocated on demand. Unlike 1xEV-DO, 1xEV-DV supports both voice and data traffic.

To allow the PSA Series analyzers to measure the performance of components in 1xEV-DV systems, Agilent has created new composite rho and code-domain tests that support the code-domain 8PSK and 16QAM modulation techniques used by the access method. The 1xEV-DV measurement personality is available as Option 214 over Option B78 cdma2000 measurement personality for the PSA Series and for Agilent's E4406A vector signal analyzer as well.

The number of applications for extremely high-frequency (EHF) systems has been limited mostly to military and scientific applications. However, there is an increasing need to make measurements at these frequencies to support these military and scientific systems as well as some commercial applications such as adaptive cruise control, and the fourth-generation (4G) wireless access methods currently in development. The PSA Series instruments' maximum measurement frequency of 50 GHz has been greatly expand with Agilent's introduction of Option AYZ, which features software that allows the instruments to employ external mixers from Agilent (to 110 GHz) and third parties (to 325 GHz).

Agilent's two mixer families include the 110 GHz 11970 Series harmonic mixers and the 75 GHz 11974 Series preselected mixers (Fig. 1). To support the 11970 Series harmonic mixers or unpreselected third-party mixers, the analyzers can perform signal identification either with the image-shift or image-suppression techniques. The image-shift method moves the signals by a factor of the intermediate frequency (IF) divided by a user-specified harmonic number, and only the desired signal is shifted by the correct amount. The image-suppression technique automatically suppresses all images that are not the desired signal, leaving it as the only signal on the screen. The 11974 Series preselected mixers eliminate this signal-identification process, which significantly reduces measurement time.

Most third-party mixers require the bias voltage sent to the IF port of the analyzer to be adjusted for optimum performance. Option AYZ allows bias adjustment either locally or via IEEE-488 bus or LAN (Fig. 2). Harmonic number can be set automatically by the analyzer or manually by the user to match the requirements of the mixer being used, and amplitude correction provides compensation for conversion loss. Option AYZ is available for the E4440A, E4446A, and E4448A PSA Series high-performance spectrum analyzers, and upgrade kits are also available for PSA Series analyzers already in service. Agilent Technologies, Test and Measurement Organization, 5301 Stevens Creek Blvd., MS 54LAK, Santa Clara, Calif. 95052; Internet:

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