Hi, I have a customer working on a VHF design using the ADRV9009 and they are seeing some fairly high LO harmonics in the 135 – 185 MHz frequency band. With the LO set to 75MHz, you can clearly see these harmonics. Here are the setup details: ADRV9009 dev kit, iioscope used to configure the ADRV9009, first profile, 100 MHz B/W 122.88 MHz sample rates for Tx, Rx, and Obs. LO set to 75 Mhz, Tx set to DDS, with DDS programmed for 1 MHz – resulting in a CW output at 76 MHz. The dev kit is NOT locked to an external reference, the 122.88 MHz clock is free running. The spectrum shows the fundamental at 76MHz, and the harmonics at 228, 380, 532 MHz. These harmonics are at an extremely high level, and not so easy to filter out at these lower operating frequencies. Are there any suggestions on how to minimize the harmonics?

ADRV9009 - LO harmonic in VHF band

MikeLowrie@Arrow

on Apr 20, 2021

Hi,

I have a customer working on a VHF design using the ADRV9009 and they are seeing some fairly high LO harmonics in the 135 – 185 MHz frequency band.

With the LO set to 75MHz, you can clearly see these harmonics. Here are the setup details:

ADRV9009 dev kit, iioscope used to configure the ADRV9009, first profile, 100 MHz B/W 122.88 MHz sample rates for Tx, Rx, and Obs.
LO set to 75 Mhz, Tx set to DDS, with DDS programmed for 1 MHz – resulting in a CW output at 76 MHz.
The dev kit is NOT locked to an external reference, the 122.88 MHz clock is free running.
The spectrum shows the fundamental at 76MHz, and the harmonics at 228, 380, 532 MHz. These harmonics are at an extremely high level, and not so easy to filter out at these lower operating frequencies.

Are there any suggestions on how to minimize the harmonics?

LO harmonics adrv9009 Wideband Transceiver IC RF Integrated Transceivers