6-GHz signal generators meet design challenges in radar, military communications and consumer wireless: Page 4 of 6

May 02, 2012 //By Jean-Pierre Joosting
Agilent Technologies has announced four X-Series signal generators that claim unmatched performance in phase noise, output power, ACPR, EVM and bandwidth. With these capabilities, the latest MXG and EXG products (available in analog and vector models) support the development of components and receivers that meet the complex challenges of mitigating interference, speeding data throughput and increasing signal quality in applications such as radar, military communications and consumer wireless.
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Figure 2: The MXG and EXG support customized user I/Q (vector) to compensate for flatness and group delay at the DUT. "Reproduced with Permission, Courtesy of Agilent Technologies, Inc."

This customized vector-correction capability is especially beneficial for wide-bandwidth signals or complex connections between the signal generator and the DUT, which may include filters, amplifiers and switches.

High output power with low distortion

Large signals are needed to directly drive power amplifiers to levels that exercise their nonlinearities, thereby producing harmonics, intermodulation and compression. In a signal generator, high output power is useful only if signals can be produced with very high quality—low harmonic distortion, broadband noise, ACPR, and EVM.

External power amplifiers are sometimes used with RF signal generators but this adds complexity and expense to the test solution. It may also compromise performance by adding additional signal elements such as switching that are outside the signal generator’s calibration loop.

The X-Series signal generators combine output power of up to +27 dBm with low ACPR of up to -73 dBc (W-CDMA TM1, 64 DPCH) and low EVM to provide a one-box solution that is both powerful and pure enough for direct testing of high performance components and systems.

Using “phase noise injection” to optimize for imperfect oscillators

The extremely low phase noise of the MXG is not always a benefit—and a process called phase noise injection enables selective and precise degradation as needed. Signal generators are often used to generate complex modulated RF signals and to substitute for various oscillators or synthesizers in the design process (Figure 3).

Figure 3: Using a signal generator to substitute for an oscillator or synthesizer can help reduce development time. "Reproduced with Permission, Courtesy of Agilent Technologies, Inc."

In real-world designs, any improvement to frequency stability is expensive in terms of cost, power and space. As a result, engineers have an interest in creating assemblies with performance that is just good enough. The

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