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TRF370417 Noise Floor Related Question

TRF370417 Noise Floor Related Question. Prepared by Bill Wu. Objective. This note is to address two questions about TRF3704 noise floor plot taken from a large span setting. Two cases all showed an elevated noise floor at the lower freq side of the carrier. Summary.

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TRF370417 Noise Floor Related Question

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  1. TRF370417 Noise Floor Related Question Prepared by Bill Wu

  2. Objective • This note is to address two questions about TRF3704 noise floor plot taken from a large span setting. Two cases all showed an elevated noise floor at the lower freq side of the carrier.

  3. Summary • A signal generator like E4438C could have a noisy far-out noise floor, which leads to the elevated noise floor at TRF3704 output. • HP 8673E has a much cleaner far-out noise floor than E4438C. • A BPF filter could be used to clean the dirty LO noise floor before sent to TRF3704 as LO source.

  4. Case 1 Spectrum PlotSA noise floor, 370417 output w/ LO freq = 4, 5, and 6 GHz

  5. Case 2 Spectrum Plot

  6. LO Signal from Agilent Vector Signal Generator, from E4438C LO freq = 4 GHz LO freq = 5 GHz LO freq = 6 GHz

  7. Observation • Agilent E4438C showed a high noise floor at the lower freq range. The noise floor elevation becomes significant when the freq is large.

  8. E4438C, 5.7 GHz signal filtered by a BPF, Freq = 5.3 GHz directly sent into Spectrum analyzer passing through a BPF (BW = 280 MHz)

  9. Conclusion • The 5.3 GHz BPF (280 MHz BW) removed the far-out noise at the lower side of the spectrum.

  10. TRF3704 RF output using Agilent E44483C as LO, PLO=10 dBm, BB freq = 1 MHz LO freq = 4 GHz LO freq = 5 GHz LO freq = 6 GHz

  11. Observation • The RF output far-out noise of TRF370417 was significant at the lower side of the RF freq using Agilent E4438C as LO. • The output noise was more significant for the higher LO frequency.

  12. RF Signal from Agilent Vector Signal Generator E4438C, Freq = 5.3 GHz LO passing through a BPF (BW = 280 MHz) LO directly sent into TRF370417

  13. Conclusion • The 5.3 GHz BPF (280 MHz BW) at the LO port cleaned the LO noise floor, which leads to a clean output noise floor of the TRF3704 RF output. • High TRF3704 RF output noise was caused by the dirty LO far-out noise floor, not by the TRF3704 modulator.

  14. TRF3704 RF output with LO from HP Signal Generator 8673E, PLO=10 dBm, BB freq = 1 MHz LO freq = 4 GHz LO freq = 5 GHz LO freq = 6 GHz

  15. Observation • HP Signal Generator 8673E has much clean far-out noise floor than Agilent E4438C.

  16. RF output Signal using HP Signal Generator 8673E as the LO source, Freq = 5.3 GHz LO passing through a BPF (BW = 280 MHz) LO directly sent into TRF370417

  17. Conclusion • There is no need to use BPF to clean the LO noise floor if HP Signal Generator 8673E was used as the LO source.

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