Stanford Research Systems CG635 Synthesized Clock Generator
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Stanford Research Systems CG635 generates extremely stable square wave clocks from 1 µHz to 2.05 GHz with 16-digit frequency resolution, 80 ps rise times, and multiple output formats for precision ...
Product details
| Model | CG635 |
| Manufacturer | Stanford Research Systems |
| Category | RF & Microwave Signal Generators |
| Availability | Made to order |
Description
Overview
The Stanford Research Systems CG635 is a high-performance synthesized clock generator producing extremely stable square waves between 1 µHz and 2.05 GHz. With 16-digit frequency resolution and ultra-low jitter, the CG635 is ideal for applications requiring clean, precise clocks—from high-speed ADC/DAC testing to RF component characterization. The instrument's flexible output levels and modulation capabilities make it essential for validating digital system performance with ideal clock sources.
Key Features
- Frequency range: 1 µHz to 2.05 GHz with 16-digit resolution
- Rise and fall times: 80 ps
- Multiple output formats: CMOS, PECL, ECL, LVDS, RS-485
- Phase control with up to one nano-degree resolution
- Time modulation: ±5 ns via rear-panel input
- Optional PRBS for eye-pattern testing
- Optional OCXO (oven-controlled crystal) and rubidium timebases for improved stability
- 10 MHz phase-lock input for synchronization with external references
- Low-frequency phase noise minimization with optional timebases
Applications
- High-speed ADC and DAC testing and characterization
- Clock jitter and modulation susceptibility measurements
- RF mixer and signal processing component development
- Digital system and network testing and validation
- Precision timing for laboratory and test environments
- Clock synchronization in multi-instrument systems
Specifications
| Output Drivers | The CG635 has several clock outputs. The front-panel Q and -Q outputs provide complementary square waves at standard logic levels (ECL, PECL, LVDS or +7 dBm). The square wave amplitude may also be set from 0.2 V to 1.0 V, with an offset between -2 V and +5 V. These outputs operate from DC to 2.05 GHz, have transition times of 80 ps, a source impedance of 50 Ω, and are intended to drive 50 Ω loads. Output levels double when these outputs are unterminated. The front-panel CMOS output provides square waves at standard logic levels. The output may also be set to any amplitude from 0.5 V to 6.0 V. The CMOS output has transition times of less than 1 ns and operates up to 250 MHz. It has a 50 Ω source impedance and is intended to drive high impedance loads at the end of any length of 50 Ω coax cable. A rear-panel RJ-45 connector provides differential square wave clocks on twisted pairs at RS-485 levels (up to 105 MHz) and LVDS levels (up to 2.05 GHz). This output also provides ±5 VDC power for optional line receivers (CG640 to CG649). The clock outputs have 100 Ω source impedances and are intended to drive shielded CAT-6 cable with 100 Ω terminations. The differential clocks may be used directly by the target system, or with optional line receivers that provide complementary logic outputs on SMA connectors. |
| Choice of Timebases | The standard crystal timebase has a stability of better than 5 ppm. The CG635's 10 MHz timebase input allows the instrument to be phase-locked to an external 10 MHz reference. The 10 MHz output may be used to lock two CG635s together. There are two optional timebases. An oven-controlled crystal oscillator (OCXO) provides about 100 times better frequency stability than the standard crystal oscillator. A rubidium frequency source provides about 10,000 times better stability. Either optional timebase will substantially reduce the low-frequency phase noise of the synthesized output. |
| Phase and Time Modulation | The clock phase can be adjusted with high precision. The phase resolution is one degree for frequencies above 200 MHz, and increases by a factor of ten for each decade below 200 MHz, with a maximum resolution of one nano-degree. This allows clock edges to be positioned with a resolution of better than 14 ps at any frequency between 0.2 Hz and 2.05 GHz. The timing of clock edges can be modulated over ±5 ns via a rear-panel time-modulation input. The input has a sensitivity of 1 ns/V and a bandwidth from DC to over 10 kHz, allowing an analog signal to control the phase of the clock output. This feature is very useful for characterizing a system's susceptibility to clock modulation and jitter. |
| For Every Application | With its exceptionally low phase noise and high frequency resolution, the CG635 replaces RF signal generators in many applications. Front-panel outputs provide square waves up to +7 dBm—ideal for driving RF mixers. Should your application require sine waves, in-line low-pass filters are commercially available to convert the CG635's square wave outputs to low distortion sine wave outputs. The CG635 can provide a wide range of clean, precise clocks for the most critical timing requirements. The instrument is an essential tool for demonstrating a system's performance with a nearly ideal clock, and for understanding a system's susceptibility to a compromised clock. The CG635 has the frequency range, precision, stability, and jitter-free performance needed to fulfill all your clock requirements. |
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Stanford Research Systems CG635 Synthesized Clock Generator
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