G2 Analog Signal Generator Phase Coherence
应用文章
This application note describes the achievable channel-to-channel phase coherence of Keysight’s G2 Multi-Channel Analog Signal Generator (AP5012A).
Early frequency synthesizers were not necessarily controlled by a single crystal standard. Adequate frequency stability was obtained using several internal crystal oscillators that contributed to the overall frequency stability of the output. These devices were considered non-coherent. As applied to frequency synthesizers, phase coherence describes the relation of the frequency standard to the output frequency. If the output frequency accurately reproduces the relative frequency stability of the standard, the device is considered coherent.
Despite this definition, the assumption that all contemporary systems that use a single standard (external or internal) are coherent is incorrect. Many systems that utilize fractional-N or binary DDS fine-resolution synthesizers are not truly phase coherent; rather they have specified small but finite reference-to-output errors.
What is of particular interest is the phase stability observed over a long period of time between two independent signal sources that are phase locked to the same external (usually 10 MHz) reference. This application note shows the phase coherence capability of the G2 multi-output signal sources that can be phase synchronized to each other and to an external reference.
The G2 multi-channel synthesized signal generator products are now available up to 20 GHz, enabling tight stability, phase coherency, and extremely fast tuning speeds. Each channel can be programmed independently in frequency, phase, amplitude, and modulation.