R&S SMW200A: first vector signal generator with 2 GHz bandwidth

With a new option, the R&S SMW200A high-end vector signal generator implements the record modulation bandwidth of 2 GHz, at output frequencies up to 40 GHz. The only one-box solution on the market with these features, it is the perfect choice for all upcoming high-performance radio and radar applications

100 MHz bandwidth with LTE-Advanced versus 20 MHz with LTE, 160 MHz with WLAN 802.11ac versus 40 MHz with 802.11n – in recent years, many new developments in wireless communications systems have had a considerably higher bandwidth than their predecessors. This trend is continuing: WLAN IEEE 802.11ad will require a bandwidth of 1.76 GHz, and 800 MHz is under discussion for the upcoming 5G wireless standard.

The signal sources used for developing these future systems must keep pace in terms of bandwidth and frequency range, and the R&S SMW200A vector signal generator is leading the way. The newly developed R&S SMW-B9 wideband baseband generator extends the instrument’s internal modulation bandwidth to 2 GHz, making it the first fully calibrated wideband solution featuring up to 40 GHz in one box. Used together with the R&S SZU100A I/Q upconverter, at this bandwidth the R&S SMW200A even generates frequencies up to 65 GHz. Not only is the generator an ideal tool for developing 5G and other future wideband communications systems, developers of advanced radar systems also benefit from its large bandwidth and excellent signal quality.

For current and future technologies

The R&S SMW200A fulfills the bandwidth requirements for the currently favored 5G standard: up to 400 MHz below 6 GHz, and up to 800 MHz at 28 GHz and 39 GHz. Plus, its convenient software options are helpful when configuring the signals to be generated. For example, the R&S SMW-K114 5G air interface candidates option supports developers working on potential technologies for accessing 5G mobile networks. The associated signal waveforms such as FBMC, UFMC, GFDM and f-OFDM are generated directly in the instrument. And the R&S SMW200A can already generate 5G signals based on the Verizon 5G open trial specification (V5G).

Established standards have not been neglected. The generator produces LTE signals up to and including release 12, providing 4G and 5G signals from a single box. Soon, other standards such as 3GPP FDD WCDMA and GSM will also be available for the wideband version of the generator. The signals of all important digital standards can be conveniently generated using the R&S WinIQSIM2 PC software.

Outstanding modulation characteristics

A fully calibrated one-box solution, the R&S SMW200A generates wideband signals with outstanding modulation characteristics, for example 1.76 GHz WLAN 802.11ad signals (MCS 12 at an IF of 15 GHz) with a measured EVM of –34 dB. Due to the very large bandwidths of the new communications standards, frequency response effects are considerably more noticeable than is the case with narrowband systems. In order to minimise unwanted signal distortions, a vector signal generator must exhibit a modulation frequency response that is as flat as possible. The R&S SMW200A attains values of < 0.4 dB over the entire bandwidth of 2 GHz. To achieve anywhere near this kind of performance, existing multibox solutions require additional, time-consuming calibrations.

The core of the new baseband section is the R&S SMW-B9 baseband generator. It includes an arbitrary waveform generator as well as a coder for real time signal generation and can be configured with different software options to match the specific requirements. The maximum signal bandwidth is 500 MHz in the base version, and 2 GHz in the fully configured instrument. There are also two configurations for the ARB memory depth: 256 Msample and 2 Gsample. Besides the aforementioned digital standards, the new baseband generator can generate user-defined digital modulation signals in real time with symbol rates up to 600 Msymbol/s. It supports many formats, including the higher-order quadrature amplitude modulation (QAM) formats that are often needed for simple receiver tests in satellite systems.

There is room for up to two R&S SMW-B9 baseband generators in a single instrument, allowing the R&S SMW200A to generate two independent wideband signals up to 20 GHz with any desired modulation type. A setup of this kind previously required a vector signal generator and a separate wideband arbitrary waveform generator per signal source, i. e. an R&S SMW200A replaces four instruments. Now compact test setups are possible for sophisticated applications in A&D and wireless communications, for example to simulate complex radar scenarios or wanted / interfering signal configurations.

Why a flat I/Q modulation frequency response is important

To generate signal scenarios of several 100 MHz up to 2 GHz, the I/Q modulation frequency response should be as flat as possible. Otherwise signal distortions will occur that could significantly impair the measurements. Some examples:

• A flat modulation frequency response leads to a low frequency response and better image suppression in the case of multicarrier CW signals, which are often used in component tests. With measurements of this type, the signal distortions caused by the DUT are analysed, which is why the signals provided by the generator should be as ideal as possible.
• With wideband, digitally modulated signals as occur in 5G or IEEE 802.11ad, the I/Q modulation frequency response directly influences EVM performance.
• Wideband chirp signals are often used in radar tests. A flat modulation frequency response results in better linearity.

If modulated multicarrier scenarios with a large overall bandwidth are generated, a large modulation frequency response can considerably distort the relative level ratios of the carriers.

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