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The Agilent 8644B, 8664A, and 8665B are high performance RF signal generators positioned as the spectral-purity and frequency-coverage flagships of the Agilent synthesized signal generator line. The 8644B covers 252 kHz to 1030 MHz (extendable to 2060 MHz with Option 002) and is specified for lowest SSB phase noise, lowest spurious, highest output power, and lowest residual FM in the family. The 8664A extends coverage to 3000 MHz, and the 8665B extends coverage to 6000 MHz, with both higher-frequency models offering AM, wideband FM, and optional high-performance pulse modulation.
The datasheet identifies specific applications across the three instruments. For RF communications, the 8644B is positioned for out-of-channel receiver testing on receivers with ≥ 90 dB selectivity and spurious immunity of ≥ 85 dB, while the 8664A serves the same application class with Option 004 and the 8665B extends that performance to 6 GHz. For component test, the 8644B is identified for mixer testing where highest output power is needed, the 8664A for clock-source applications driving high-speed digital components, and the 8665B for response testing requiring output level accuracy to 6 GHz. For radar and EW test, all three models provide full functionality, with the 8664A and 8665B offering optional pulse modulation with internal delay and width adjust.
Hewlett-Packard's test and measurement business was spun out as Agilent Technologies in 1999, and the electronic measurement division was further separated as Keysight Technologies in 2014. Instruments originally branded HP and later Agilent — including the 8644B, 8664A, and 8665B signal generators — trace their direct support and calibration lineage through Keysight today.
The 8644B, 8664A, and 8665B form Agilent's high performance RF signal generator family, sharing the same synthesized architecture, the same internal modulation source design, the same GPIB programming interface, and the same surface-mount construction with three-year recommended calibration interval. They differ primarily in upper frequency coverage and in the specific spectral-purity and modulation tradeoffs optimized for different application classes.
The 8644B is the spectral-purity flagship, covering 252 kHz to 1030 MHz (or 2060 MHz with Option 002) and specified for the lowest SSB phase noise, lowest spurious, highest output power, and lowest residual FM in the family. The 8664A extends coverage to 3000 MHz with wideband FM rates suitable for many digital systems, and the 8665B extends the same architecture to 6000 MHz for applications requiring coverage of the upper microwave bands.
Each pre-owned model in this family is listed on its own dedicated product page with condition-matched pricing and inventory. Selecting the model below opens that page so you can review the specific configuration, options installed, and current availability.
Frequency range is the primary differentiator: 0.252 to 1030 MHz on the 8644B (extendable to 2060 MHz with Option 002), 0.1 to 3000 MHz on the 8664A, and 0.1 to 6000 MHz on the 8665B. SSB phase noise specifications also differ — at a 1 GHz carrier and 20 kHz offset, the 8644B is specified at –136 dBc/Hz (typical –142 dBc/Hz), the 8664A and 8665B at –117 dBc/Hz standard or –134 dBc/Hz with Option 004 in the 515 to 1030 MHz band. The 8644B also offers a built-in 2 GHz frequency counter (Option 011) and specified VOR/ILS signal simulation (Option 009) not available on the 8664A or 8665B.
Output level range is +16 to –137 dBm on the 8644B and +13 to –139.9 dBm on the 8664A and 8665B. Pulse modulation is standard on the 8644B with > 35 dB on/off ratio and < 100 ns rise/fall time, while on the 8664A and 8665B it is offered as Option 008 with > 80 dB on/off ratio, < 5 ns rise/fall time, and a built-in pulse generator with variable delay and width from 50 ns to 999 ms. The comparison table below summarizes the headline specifications side by side.
| Model | Frequency Range | Max Output Power | SSB Phase Noise @ 1 GHz, 20 kHz Offset |
|---|---|---|---|
| 8664A | 0.1 MHz to 3000 MHz | +13 dBm (+9 dBm with Option 008) | -117 dBc/Hz standard, -134 dBc/Hz with Option 004 (515 to 1030 MHz) |
| 8644B | 0.252 MHz to 1030 MHz (to 2060 MHz with Option 002) | +16 dBm (+13 dBm with Option 002/005) | -136 dBc/Hz (515 to 1030 MHz); -142 typical |
| 8665B | 0.1 MHz to 6000 MHz | +13 dBm (+9 dBm with Option 008) | -117 dBc/Hz standard, -134 dBc/Hz with Option 004 (515 to 1030 MHz) |
Additional differences in specifications beyond the few shown above are not listed here — see each model's full specifications below.
| Specification | 8644B | 8664A, 8665B |
|---|---|---|
| Frequency | ||
| Range | 0.252 to 1030 MHz; 0.252 to 2060 MHz with Option 8644B-002 | 0.1 to 3000 MHz (8664A); 0.1 to 6000 MHz (8665B) |
| Resolution | 0.01 Hz | 0.01 Hz |
| Accuracy (std. timebase, < 1 year of calibration) | 0.375 x 10-6 times carrier in Hz | 0.375 x 10-6 times carrier in Hz |
| Switching speed (typical, within 100 Hz) | < 350 ms | < 50 ms (within 0.33 ppm); < 100 ms with Option 8664A-004 or 8665B-004 |
| Spectral Purity — SSB Phase Noise (dBc/Hz at 20 kHz offset) | ||
| 4120 to 6000 MHz | N/A | Standard: -105; Option 004: -116 |
| 3000 to 4120 MHz | N/A | Standard: -105; Option 004: -122 |
| 2060 to 3000 MHz | N/A | Standard: -111; Option 004: -122 |
| 1030 to 2060 MHz | -130 (Option 8644B-002) | Standard: -111; Option 004: -128 |
| 515 to 1030 MHz | -136 (-142 typical) | Standard: -117; Option 004: -134 |
| 257.5 to 515 MHz | -142 | Standard: -122; Option 004: -139 |
| 128.5 to 257.5 MHz | -145 | N/A |
| 0.25 to 128.5 MHz | -145 | N/A |
| 187.5 to 257.5 MHz (8664A, 8665B) | N/A | Standard: -128; Option 004: -144 |
| 0.1 to 187.5 MHz (8664A, 8665B) | N/A | Standard: -117; Option 004: -131 |
| Nonharmonics | < -105 dBc, > 10 kHz offset, 0.252 to 1030 MHz; < -100 dBc, > 10 kHz offset, 1030 to 2060 MHz | < -100 dBc, > 10 kHz offset, 187.5 to 2060 MHz; < -90 dBc, > 10 kHz offset, 2060 to 6000 MHz, 0.1 to 187.5 MHz |
| Harmonics | < -25 dBc, output ≤ +10 dBm | < -30 dBc, output ≤ +10 dBm |
| Subharmonics | None, 0.252 to 515 MHz; < -52 dBc, 515 to 1030 MHz; < -40 dBc, 1030 to 2060 MHz | < -75 dBc, 0.1 to 1500 MHz; < -40 dBc, 1500 to 3000 MHz; < -50 dBc, 3000 to 6000 MHz |
| Residual AM (0.3 to 3 kHz post det. BW) | < 0.01% AM rms | < 0.04% AM rms |
| SSB AM noise floor (offsets > 100 kHz) | < -157 dBc/Hz, 10 dBm, < 1030 MHz; < -150 dBc/Hz, 10 dBm, < 2060 MHz | < -137 dBc/Hz, 13 dBm, < 187.5 MHz; < -150 dBc/Hz, 13 dBm, > 187.5 MHz |
| Internal Reference Oscillator | ||
| Stability type | Standard high stability | Option 001 high stability with EFC |
| Aging | +1.5 x 10-8/day after 10 days | ±3 x 10-10/day after 10 days |
| Temperature | +7 x 10-10, 0 to 55 °C | ±6 x 10-10, to 55 °C |
| Line voltage | ±2 x 10-10, (+5%, -10%) | ±1 x 10-10, ±10% |
| Reference output | 10 MHz, > 0.15 Vrms into 50 Ω | 10 MHz, > 1 Vrms into 50 Ω |
| External reference input | Accepts 10 MHz ±5 ppm and a level range of 0.5 V to 2 Vrms into 50 Ω | |
| Output Level | ||
| Range | +16 to -137 dBm; +13 dBm with Option 8644B-002/005 | +13 to -139.9 dBm; +9 dBm with Option 8664A-008 or 8665B-008 |
| Resolution | 0.01 dB | 0.01 dB |
| Absolute accuracy | ±1 dB, output ≥ -127 dBm; ±3 dB, output < -127 dBm | ±1 dB, output ≥ -119.9 dBm, 1 to 1000 MHz; ±1.5 dB, 1000 to 3000 MHz; ±2 dB, 3000 to 6000 MHz, < 1 MHz; ±3 dB, output ≥ -129.9 dBm |
| Reverse power protection | 50 watts | 25 watts (1 watt on 8665B), 0.1 to 2060 MHz; 1 watt, > 2060 MHz |
| Third order intermod (frequencies < 1300 MHz, two signals at +8 dBm, 25 kHz apart) | < -50 dBc | < -47 dBc |
| Overrange | Typically 2 dB | Typically 2 dB |
| Switching speed (typical) | < 50 ms | < 50 ms |
| SWR (≥ 0 dBm) | < 2.2:1 | < 1.75:1 (< 3000 MHz); < 2.0:1 (≥ 3000 MHz) |
| SWR (< 0 dBm) | < 1.5:1 | < 1.5:1 (< 3000 MHz); < 1.75:1 (≥ 3000 MHz) |
| Output impedance | 50 Ω | 50 Ω |
| Amplitude Modulation | ||
| Depth | 0 to 100%, output ≤ +7 dBm | 0 to 100%, output ≤ +7 dBm |
| Resolution | 0.1% | 0.1% |
| Bandwidth (3 dB) | dc to > 100 kHz, > 128 MHz | dc to > 10 kHz for > 10 MHz |
| Accuracy at 1 kHz rate | ±(7% of setting +1%) up to 80% depth | ±(6% of setting +1%) up to 90% depth |
| Distortion (30% depth, 1 kHz rate) | < 3%; < 4% (8644B-002) | < 4% |
| Incidental phase modulation (at 30% depth, 1 kHz rate) | < 0.2 radians peak | < 0.2 radians peak, ≤ 2000 MHz; < 0.2 radians peak, > 2000 MHz |
| Frequency Modulation | ||
| Maximum peak deviation | 20 MHz/200 kHz, > 1030 MHz; 10 MHz/100 kHz, > 515 MHz; 5 MHz/50 kHz, > 257.5 MHz; 2.5 MHz/25 kHz, > 128.5 MHz; 1.25 MHz/12.5 kHz, > 64 MHz; 62.5 kHz/6.25 kHz, > 32 MHz | 20 MHz, 3000 to 6000 MHz; 10 MHz, 1500 to 3000 MHz; 5 MHz, 750 to 1500 MHz; 2.5 MHz, 375 to 750 MHz; 1.25 MHz, 187.5 to 375 MHz; 5 MHz, < 187.5 MHz |
| Resolution | 2.5% of setting | 2.5% of setting |
| Bandwidth (3 dB) | dc to 100 kHz | dc to 800 kHz |
| Carrier accuracy in FM | ±0.5% of setting | ±0.6% of setting |
| External input impedance | 600 Ω | 600 Ω |
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
3 GHz
1
High Stability Time Base
2
2 GHz Doubled Output
3
Rear-Panel Input/Output
4
Low-noise Enhancement
5
Electronic Attenuator (N/A with Option 002)
7
Synthesized Audio Oscillator
8
Pulse Modulation
9
Specified VOR/ILS
10
Reduced-Leakage Configuration
11
2 GHz Internal Frequency Counter
H10
DECT Modulation
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