Meet Demanding Requirements for Modern Vector Signal Sources
Today, digital modulation schemes are widely used in communication systems, and the increasing need for data bandwidth has pushed the signal purity and modulation bandwidth requirements for modern vector signal sources. Other applications with similar performance requirements include radio surveillance, interference analysis, radar signal analysis, and electronic warfare.
Addressing these demanding requirements, the Keysight G3 Vector Signal Generator provides frequency coverage to 40 GHz and is available as a single-output desktop unit or a rackmount instrument with multiple phase-coherent outputs. The G3 offers a cost-effective and flexible tool for generating high-quality, complex, wideband, digitally modulated signals. Each output channel has:
- Internal waveform memory up to 512 MS, at 32 bits per sample, for storage of several thousands of I/Q data segments
- Internal dual-channel arbitrary waveform generator with integrated asynchronous re-sampler that outputs 16-bit samples to 500 MSPS
- Proprietary mixed digital / analog self-calibrated I/Q modulator with flat frequency response over the ±200 MHz instantaneous modulation bandwidth (see Figure 1) and good image rejection and local oscillator suppression
- Pulse modulator with a minimum pulse width of 10 ns, 2 ns rise / fall times, and > 80 dB on/off ratio
- Single sideband phase noise of -150 dBc / Hz at 100 kHz offset from a 1 GHz carrier (see Figure 2)
- Excellent harmonic and spurious rejection
- Sub-μs switching speed
- Options for relative phase stability and phase-coherent switching for beamforming and quantum computing applications
Figure 1. Digital modulation flatness across the modulation bandwidth at several carrier frequencies
Figure 2. Single sideband phase noise with I/Q on
The instrument has a modular and scalable architecture, controlled from a Linux kernel that runs the device firmware. Multiple instruments, each with up to four channels, can be operated in a high-performance clocking system, providing outstanding phase coherence among dozens of channels. The instruments can be operated in various modes to support different applications (see Figure 3).
Figure 3. G3 Vector Signal Generator block diagram
I/Q data playback
User-defined I/Q data files in different formats can be uploaded into the instrument’s internal memory using the supplied graphical software (see Figure 4). The internal data format supports up to four markers for signal synchronization using TTL outputs. In addition to a proprietary data format, the graphical interface supports other file formats to maximize flexibility, including CSV, Matlab, and I/Q formats from third-party suppliers. Preloaded waveforms can be played back in a user-defined sequence and at a sampling rate set by the user.
The graphical interface can also be used to program waveforms such as multi-tone, user-defined chirps, or broadband noise; it also enables control of the internal analog modulators, including the function generators for pulse trains, and the optional real-time coders.
Figure 4. Screenshot of the G3 Vector Signal Generator graphical interface
Options
The G3 Vector Signal Generator can be ordered with several options:
Fast control port (option FCP): The G3 can be controlled with the fast control port (FCP), a reconfigurable parallel port with LVDS signal inputs. Depending on the requirement, the FCP has four use cases:
- Frequency hopping or sweeping. Using the frequency, amplitude and phase words applied to the FCP interface, the user can implement very fast frequency hopping — above 1 MHz — over the entire frequency range with real-time input.
- Low latency playback control. Pre-stored waveforms can be addressed as memory segments and triggered for immediate play with low latency, typically 200 ns.
- Digital I/Q streaming. Digital I/Q data can be directly applied to the internal modulator at up to 250 MSPS.
- Real-time data streaming. User data can be read in real-time and coded on one of the built-in modulation schemes, like QAM or QPSK.
Built-in Analog Modulation (option MOD): The G3 uses the internal function generator to generate high-quality amplitude, frequency, and pulse modulation. Wideband, high rate, multi-tone FM, PM, or AM can be combined with precise, phase-synchronous pulse modulation, with pulse widths down to 10 ns and on-off ratios > 80 dB.
Analog I and Q Data Inputs (option AIQ): External analog inputs for I and Q data are supported with more than 100 MHz signal bandwidth.
Internal I/Q Generator (option IVM): Using a novel architecture for I/Q modulation, the G3 provides quick, “user-friendly” waveform generation (see Figure 3). The baseband generator supports the playback of pure digital data, mapping digital symbols into a selected I/Q constellation at symbol rates to 10 MHz in real-time, passing the result through the selected pulse-shaping filter to generate the final waveform, updated in real-time at the full sampling rate, to drive the 16-bit DACs. This baseband signal is then modulated onto an RF carrier using the internal I/Q vector modulator. The symbols can be a fixed pattern, PRBS data from an internal source, a downloaded user list, or streamed real-time from the FCP data port. The constellation mapping can be user-defined and the digital filters include user-defined FIR.
Summary
The G3 vector signal generator is ultra-agile, with wide modulation bandwidth and flexible operating modes. It is available in a single- (desktop) or multi-channel (rackmount) form, well-suited for applications such as quantum computing, radar, wireless communication, electronic warfare, beamforming, and other applications where high-quality signals are needed.
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