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The Agilent 8648 Series Signal Generators are a four-model family of RF signal sources covering carrier frequencies from 9 kHz to 4 GHz, depending on model. The 8648A covers 100 kHz to 1 GHz; the 8648B extends to 2 GHz; the 8648C reaches 3.2 GHz; and the 8648D covers the full range to 4 GHz. All four share a common platform with 0.001 Hz settable frequency resolution, AM/FM/phase modulation, and GPIB remote programming.
A signal generator produces known, controllable RF signals used to stimulate or characterize other equipment. The 8648 series supports receiver testing, RF component characterization, transmitter alignment, and general-purpose stimulus for laboratory and production environments. With output ranges extending to –136 dBm and amplitude modulation depth from 0 to 100%, the family is configured for both high-level drive applications and low-level receiver sensitivity work.
Agilent Technologies was spun out of Hewlett-Packard in 1999 when HP separated its test and measurement, life sciences, and chemical analysis businesses from its computing business. In 2014, Agilent further divided, with the electronic measurement business becoming Keysight Technologies. Instruments originally sold under the Agilent brand, including the 8648 series, trace through this lineage and are documented across HP, Agilent, and Keysight references depending on the production date.
The Agilent 8648 series is a four-model family of RF signal generators sharing a common platform but differing in upper frequency limit. The 8648A covers 100 kHz to 1 GHz; the 8648B, 8648C, and 8648D extend the lower limit to 9 kHz and extend the upper limit to 2 GHz, 3.2 GHz, and 4 GHz respectively. Modulation capabilities, frequency resolution, and remote programming are common across all four.
Within the family, certain options are model-specific. The pager signaling option (1EP) is available only on the 8648A. The pulse modulation option (1E6) and the high output power option (1EA) are available only on the 8648B, 8648C, and 8648D. Option 1E5 (high-stability timebase) and Option 1E2 (modulation generator) are available across the full family.
Each pre-owned model below is listed as its own product page with condition-matched pricing, current inventory status, and the specific option configuration of the unit in stock. Confirm the frequency range and installed options against the requirements of the intended application before ordering.
The four 8648 models are distinguished primarily by upper frequency limit and by the lower frequency limit on the 8648A (100 kHz versus 9 kHz on the others). The output power range is also model-specific: the 8648A provides +10 to –136 dBm across its full range, while the 8648B/C/D provide +13 to –136 dBm up to 2500 MHz and +10 to –136 dBm above. With the high output power Option 1EA, the 8648B/C/D reach +20 dBm at frequencies through 1000 MHz.
Phase noise, residual FM, and modulation deviation ranges scale with frequency band. FM peak deviation, for example, increases from 200 kHz below 249 MHz to 800 kHz at frequencies up to 4000 MHz. The comparison table below summarizes the key differences across the family at a glance.
| Model | Frequency Range | Max Output Power | Phase Noise (1 GHz, 20 kHz offset) |
|---|---|---|---|
| 8648B | 9 kHz to 2000 MHz | +13 dBm (≤2500 MHz) | <-116 dBc/Hz |
| 8648A | 100 kHz to 1000 MHz | +10 dBm | <-116 dBc/Hz |
| 8648C | 9 kHz to 3200 MHz | +13 dBm (≤2500 MHz) | <-116 dBc/Hz |
| 8648D | 9 kHz to 4000 MHz | +10 dBm (≤4000 MHz) | <-116 dBc/Hz |
Additional differences in specifications beyond the few shown above are not listed here — see each model's full specifications below.
| Specification | Value |
|---|---|
| Frequency | |
| Range (8648A) | 100 kHz to 1000 MHz |
| Range (8648B) | 9 kHz to 2000 MHz |
| Range (8648C) | 9 kHz to 3200 MHz |
| Range (8648D) | 9 kHz to 4000 MHz |
| Resolution (settable) | 0.001 Hz |
| Resolution (display) | 10 Hz |
| Accuracy | Typically ±3x10⁻⁶ × carrier frequency (Hz); ±0.15x10⁻⁶ × carrier frequency for Option 1E5 |
| Switching speed (typical, <1001 MHz) | <75 ms |
| Switching speed (typical, ≥1001 MHz) | <100 ms |
| Internal Reference Oscillator | |
| Aging (standard timebase, typical) | <±2 ppm/year |
| Aging (Opt 1E5 high stability) | <±0.1 ppm/year; <±0.0005 ppm/day |
| Temperature (standard) | <±1 ppm |
| Temperature (Opt 1E5, typical) | <±0.01 ppm |
| Line Voltage (standard) | <±0.5 ppm |
| Line Voltage (Opt 1E5, typical) | <±0.1 ppm |
| Output | 10 MHz, typically >0.5 Vrms into 50 Ω |
| External reference input | 2, 5, 10 MHz ±10 ppm typical (±1 ppm typical with Opt 1E5), 0.5 to 2 Vrms into 50 Ω |
| Spectral Purity | |
| Harmonics (output ≤+4 dBm) | <-30 dBc |
| Subharmonics (<1001 MHz) | <-60 dBc |
| Subharmonics (≤3200 MHz) | <-50 dBc |
| Subharmonics (≤4000 MHz) | <-40 dBc |
| Nonharmonics (<249 MHz) | <-55 dBc |
| Nonharmonics (<1001 MHz) | <-60 dBc |
| Nonharmonics (<2001 MHz) | <-54 dBc |
| Nonharmonics (≤4000 MHz) | <-48 dBc |
| Residual FM (<249 MHz) | <7 Hz, typically <4 Hz |
| Residual FM (<501 MHz) | <4 Hz, typically <2 Hz |
| Residual FM (<1001 MHz) | <7 Hz, typically <4 Hz |
| Residual FM (<2001 MHz) | <14 Hz, typically <8 Hz |
| Residual FM (≤4000 MHz) | <28 Hz, typically <12 Hz |
| SSB phase noise at fc 500 MHz (20 kHz offset, typical) | <-120 dBc/Hz |
| SSB phase noise at fc 1000 MHz | <-116 dBc/Hz |
| SSB phase noise at fc 2000 MHz | <-110 dBc/Hz |
| SSB phase noise at fc 3000 MHz | <-106 dBc/Hz |
| SSB phase noise at fc 4000 MHz | <-104 dBc/Hz |
| Output | |
| Range (8648A) | +10 to -136 dBm |
| Range (8648B/C/D, ≤2500 MHz) | +13 to -136 dBm |
| Range (8648B/C/D, ≤4000 MHz) | +10 to -136 dBm |
| Display resolution | 0.1 dB |
| Accuracy (≤2500 MHz) | ±1.0 dB |
| Accuracy (≤3200 MHz) | ±1.5 dB |
| Accuracy (≤4000 MHz) | ±2.0 dB |
| Reverse power protection (≤2000 MHz) | 50 watts |
| Reverse power protection (≤4000 MHz) | 25 watts |
| SWR (<249 kHz, typical) | <2.5:1 |
| SWR (<2500 MHz, typical) | <1.5:1 |
| SWR (≤4000 MHz, typical) | <2.0:1 |
| Output impedance | Nominally 50 Ω |
| Maximum Leveled Power (High Power Option 1EA, 8648B/C/D only) | |
| ≤100 kHz | +17 dBm |
| ≤1000 MHz | +20 dBm |
| ≤1500 MHz | +19 dBm |
| ≤2100 MHz | +17 dBm |
| ≤2500 MHz | +15 dBm |
| ≤4000 MHz | +13 dBm |
| Amplitude Modulation (fc >1.5 MHz) | |
| Range | 0 to 100% (output ≤+4 dBm) |
| Resolution | 0.1% |
| Accuracy (1 kHz rate) | ±5% of setting ±1.5% |
| External rates (DC) | DC to 25 kHz (typical, 3 dB BW) |
| External rates (AC) | 1 Hz to 25 kHz (typical, 3 dB BW) |
| Distortion (30% AM, 1 kHz, THD+N) | <2% |
| Distortion (8648A at 90% AM) | <3% |
| Distortion (8648B/C/D at 70% AM) | <3% |
| Frequency Modulation | |
| Peak deviation (<249 MHz) | 0 to 200 kHz |
| Peak deviation (<501 MHz) | 0 to 100 kHz |
| Peak deviation (<1001 MHz) | 0 to 200 kHz |
| Peak deviation (<2001 MHz) | 0 to 400 kHz |
| Peak deviation (≤4000 MHz) | 0 to 800 kHz |
| Resolution (≤10% peak deviation, <2001 MHz) | 10 Hz |
| Resolution (≤10% peak deviation, ≥2001 MHz) | 20 Hz |
| Resolution (>10% to max, <2001 MHz) | 100 Hz |
| Resolution (>10% to max, ≥2001 MHz) | 200 Hz |
| Deviation accuracy (<1001 MHz) | ±3% of FM deviation ±30 Hz |
| Internal rates | 400 Hz or 1 kHz, or 10 Hz to 20 kHz with Opt 1E2 |
Please review the Manufacturer's Data Sheet to verify published specifications. Feedback on this webpage is always welcome — please reach out to your Test Architect at any time for questions or concerns. Thank you, we truly appreciate you being our customer.
Model No
Agilent
Condition
Used
Manufacturer
Agilent
Frequency
2 GHz
100
Modulation generator
100000
High stability time base
1000000
Pulse modulation
1EA
High output power
1EP
Pager signaling capability
H31
Power Out => 16DBM when ordered w/ option 1EA and 1E6. Pulse input conn on front panel
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