The Stanford Research Systems CG635 is a synthesized clock generator capable of producing extremely low-jitter clock signals across a broad frequency range from 1 µHz to 2.05 GHz. With sub-picosecond jitter performance, flexible output levels, and highly stable optional internal timebases, it is a premier reference source for telecom, semiconductor testing, and precision timing applications.
Specifications
General
| Parameter | Value |
|---|---|
| Interfaces | GPIB, RS-232 |
| Display | 16-character alphanumeric LED display |
Physical
| Parameter | Value |
|---|---|
| Power Supply | 90 to 264 VAC, 47 to 63 Hz, <50 W |
| Operating Temperature | 0 °C to 40 °C |
| Dimensions (W×H×D) | 216 mm × 89 mm × 330 mm |
| Weight | 4.1 kg |
Frequency Characteristics
| Parameter | Value |
|---|---|
| Frequency Range (Q & -Q) | 1 µHz to 2.05 GHz |
| Frequency Range (CMOS) | 1 µHz to 250 MHz |
| Frequency Resolution | 1 µHz |
| Standard Timebase Stability | ±5 ppm (0 °C to 40 °C) |
| Standard Timebase Aging | <5 ppm/year |
Q & -Q Outputs
| Parameter | Value |
|---|---|
| Q & -Q Output Logic Levels | PECL, LVPECL, ECL, LVDS, +7 dBm RF, or Custom (Variable) |
| Q & -Q Rise/Fall Time | <100 ps (20% to 80%) |
| Q & -Q RMS Jitter | <1 ps rms (any frequency), typically <250 fs rms above 100 MHz |
| Q & -Q Random Jitter | <80 fs rms (typical at 622.08 MHz, 12 kHz to 20 MHz band) |
| Q & -Q Output Connector Type | SMA (female) |
Custom Q & -Q Levels
| Parameter | Value |
|---|---|
| Custom Q & -Q Amplitude Range | 0.2 V to 1.0 V into 50 Ω |
| Custom Q & -Q Offset Range | -2.00 V to +3.00 V |
| Custom Q & -Q Resolution | 10 mV |
CMOS Output
| Parameter | Value |
|---|---|
| CMOS Amplitude Range | 0.25 V to 3.0 V into 50 Ω (0.5 V to 6.0 V into high impedance) |
| CMOS Rise/Fall Time | <1 ns (typically 300 ps, 20% to 80%) |
| CMOS Output Impedance | 50 Ω |
| CMOS Output Connector | BNC (female) |
Phase Control
| Parameter | Value |
|---|---|
| Phase Range | -360.00° to +360.00° |
| Phase Resolution | 0.01° |
| Phase Delay Range | -100 ns to +100 ns |
| Phase Delay Resolution | 1 ps |
Timebase Options
| Parameter | Value |
|---|---|
| Option 01 OCXO Temperature Stability | 0.005 ppm (0 °C to 40 °C) |
| Option 01 OCXO Aging Rate | <0.2 ppm/year |
| Option 02 Rubidium Temperature Stability | 0.0001 ppm (0 °C to 40 °C) |
| Option 02 Rubidium Aging Rate | <0.05 ppb/month (<0.5 ppb/year) |
Reference Clock Input/Output
| Parameter | Value |
|---|---|
| External Reference Input Frequency | 10 MHz (accepts ±10 ppm) |
| External Reference Input Level | 0.1 Vpp to 5 Vpp |
| External Reference Input Impedance | 50 Ω |
| Reference Output Frequency | 10 MHz |
| Reference Output Level | 1.0 Vpp into 50 Ω |
Spectral Purity
| Parameter | Value |
|---|---|
| Spurious Noise (Non-Harmonic) | <-70 dBc |
| Harmonics | <-40 dBc |
Expansion & Options
| Parameter | Value |
|---|---|
| Rear Panel Expansion Slots | Two slots for optional CG640–CG649 series output translators |
Performance
| Parameter | Value |
|---|---|
| SSB Phase Noise (10 MHz, 100 Hz offset) | -130 dBc/Hz (typical) |
| SSB Phase Noise (10 MHz, 10 kHz offset) | -143 dBc/Hz (typical) |
| SSB Phase Noise (100 MHz, 100 Hz offset) | -110 dBc/Hz (typical) |
| SSB Phase Noise (100 MHz, 10 kHz offset) | -135 dBc/Hz (typical) |
| SSB Phase Noise (622.08 MHz, 100 Hz offset) | -95 dBc/Hz (typical) |
| SSB Phase Noise (622.08 MHz, 10 kHz offset) | -118 dBc/Hz (typical) |
| SSB Phase Noise (2.025 GHz, 100 Hz offset) | -85 dBc/Hz (typical) |
| SSB Phase Noise (2.025 GHz, 10 kHz offset) | -108 dBc/Hz (typical) |
| Sub-harmonics | None (≤ 1.025 GHz), <-40 dBc (> 1.025 GHz) |
Outputs
| Parameter | Value |
|---|---|
| Q & -Q Output Impedance | 50 Ω |
| Reference Output Impedance | 50 Ω |
Features
| Parameter | Value |
|---|---|
| PRBS Generator (Option 03) | PRBS7, PRBS10, PRBS15, PRBS23, PRBS31 |
| Instrument State Storage | 9 setup locations |
Option 04 Rear-Panel CMOS Outputs
| Parameter | Value |
|---|---|
| Option 04 Output Channels | 4 |
| Option 04 Frequency Range | 1 µHz to 250 MHz |
| Option 04 Amplitude Range (Hi-Z) | 0.5 V to 4.0 V |
| Option 04 Amplitude Range (50 Ω) | 0.25 V to 2.0 V |
| Option 04 Amplitude Resolution | 10 mV |
| Option 04 Rise/Fall Time | < 1.5 ns |
| Option 04 Source Impedance | 50 Ω |
| Option 04 Connector Type | BNC |
Option 03 PRBS Generator
| Parameter | Value |
|---|---|
| PRBS Polynomial Patterns | 2^7-1, 2^10-1, 2^15-1, 2^23-1, 2^31-1 |
| PRBS Data Format | NRZ |
Clock Outputs (Q & -Q)
| Parameter | Value |
|---|---|
| LVDS Differential Swing | 350 mV |
| LVDS Common-Mode Voltage | 1.25 V |
| CML Output Swing | 400 mV (0 V to -0.4 V) |
Reference Input
| Parameter | Value |
|---|---|
| External Reference Lock Range | ±10 ppm |
Technology
Synthesized Clock Generator
Applications
Precision Timing, Telecom Clocking, Phase Noise Measurement, Semiconductor Testing
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