Keysight (formerly Agilent T&M) 3717A Modulator/Demodulator

The Keysight 3717A is a portable test modem for 70 MH IF microwave radio link systems. It is used to enable baseband to baseband (BB-BB) measurements. It can also be used in place of a radio link modulator or demodulator.

The 3717A has two BB input and two BB outputs, one each for telephony and one each for video. Variable gain lets the modulator operate with BB input levels over a 12 dB range. An AGC system lets the demodulator operate with IF input levels over a 16 dB range. Video signals can be inverted in both the modulator and demodulator sections. The 3717A has two independent IF outputs—one to supply the system under test, and the other to be used as a monitor point if required. A balanced telephony input and output with 124 Ω impedance is available as an option, as well as a selection of pre-/de-emphasis networks. Up to five pre-/de-emphasis networks can be fitted into the 3717A at one time. They are selected by front panel keys or optionally, via HP-IB.

• Up to five pre-/de-emphasis networks
• Video and telephony inputs and outputs
• Service channel
• Built-in 15 dB open-ended attenuator
• Optional HP-IB
• Optional balanced BB input and output

3717A specifications:

• Back-to-Back (Telephony)
  • BB frequency response: 10 kHz to 10 MHz is ≤±0.2 dB, 50 Hz to 20 MHz is typically ≤±3 dB
  • Noise loading: At manual loading for all slots, 70 to 7600 kHz (1800 channels with emphasis) is ≤25 pWOp (57 dB NPR); With thermal, mod/demod is thermally dominated and will typically tolerate a 6 dB overload with no degradation
  • Spurious: 300 kHz to 10 MHz is typically ≤-72 dBm0
• Back-to-Back (Video)
  • BB frequency response: 50 Hz to 10 MHz is ≤±0.2 dB
  • Square wave tilt (50 Hz): <1.0%
  • Differential gain (4.43 MHz): ≤0.7%
  • Differential phase (4.43 MHz): ≤0.7°
• Modulator
  • BB input (Telephony 10 kHz to 10 MHz): Impedance is 75 Ω, Return loss is ≥30 dB
  • BB input (Video 50 Hz to 10 MHz): Impedance is 75 Ω, Return loss is ≥28 dB (10 kHz to 10 MHz)
  • IF outputs: Frequency is 70 MHz ±10 kHz, Output level is +5 dBm ±1 dB, Return loss is ≥30 dB
  • BB-IF swept response (telephony or video 70 ±10 MHz): Flatness is ≤±0.2 dB, Linearity is ≤2.2%, Differential gain is ≤2%, Group delay is ≤1.0 ns, Differential phase is ≤1.5°
• Demodulator
  • IF input (60 to 80 MHz centered on 70 MHz ±100 kHz): Level range is -10 to +6 dBm, Impedance is 75 Ω, Return loss is ≥30 dB, Spurious (100 kHz to 10 MHz) is ≤-72 dBm0
  • BB output (Telephony 10 kHz to 10 MHz): Level is -28 dBm ±1 dB for 141 kHz rms deviation, Impedance is 75 Ω, Return loss is ≥30 dB
  • BB outputs (Video 50 Hz to 10 MHz): Level is 1 Vp-p ±0.1 V for 8 MHz p-p deviation, Impedance is 75 Ω, Return loss is ≥30 dB (10 kHz to 10 MHz)
  • IF-BB swept response (telephony or video 70 ±10 MHz): Linearity is ≤2%, Differential gain is ≤2%, Group delay is ≤1.5 ns, Differential phase is ≤1.5°
• Attenuator
  • Frequency range: 50 Hz o 10 MHz and 60 to 80 MHz
  • Attenuation: 15 dB in 1 dB steps
  • Flatness: ≤±0.2 dB
  • Impedance: 75 Ω
  • Input/output return loss: ≥30 dB
• Service channel nominal frequency range: 0.3 to 3 kHz with 10 kHz signal tone