Phase Noise Measurement - Analog Devices EVAL-ADF4152HVEB1Z User Manual

EVAL-ADF4152HVEB1Z User Guide
Prescaler for Microwave VCO
The board contains the ADF5001, an 18 GHz divide by 4
prescaler, to interface a high frequency microwave VCO to the
ADF4152HV. For example, when interfacing to the 12 GHz
external VCO, use the VTUNE SMA as described in the External
VCO Option section, but, in this case, connect the VCO output
to the PRE_IN SMA connector. The prescaler must be enabled
by moving Jumper LK1 into Position B. The
be programmed to accept a 12 GHz ÷ 4 frequency, or 3 GHz.
Isolate the VCO tracks from the output of the prescaler by
removing C37. It is recommended to interface the prescaler
differentially for best performance; therefore, swap C38 (100 pF)
into the space provided for C35. R33 can be removed as shown in
Figure 3. Note that the loop filter must be redesigned when
changing the VCO and/or reference frequencies.
ADF4152HV
Figure 3. Configuration of the Board for External Microwave VCO Using the

PHASE NOISE MEASUREMENT

With the default settings, in-band phase noise of close to
−101 dBc/Hz can be measured. This measurement translates
to a normalized phase noise floor of −211 dBc/Hz. To measure
the ADF4152HV
−213 dBc/Hz, increase the loop bandwidth to 50 kHz or greater
by changing the R
must
resistor increases the charge pump current from 384 µA to
594 µA with a corresponding increase in loop bandwidth. With
the wider loop bandwidth, a phase noise (PN) of −103 dBc/Hz
can be measured.
PN = −213 + 10 log(25 MHz) + 20 log(1500/25) =
−103 dBc/Hz
The variation of phase noise vs. PLL loop bandwidth can be
modeled in ADIsimPLL.
Rev. 0 | Page 5 of 20
normalized phase noise specification of
resistor (R4) to 3.3 kΩ. This 3.3 kΩ R4
SET
ADF5001 Prescaler
UG-963