CN-0140 Datasheet, PDF (3/4 Pages) Analog Devices – High Performance, Dual Channel IF Sampling Receiver

Circuit Note
CN-0140
Figure 2. Measured Single-Tone Performance of the Circuit in Figure 1 for a 1950 MHz RF Input Signal. Sampling Frequency = 122.88 MSPS, IF Input = 153.6 MHz
COMMON VARIATIONS
Front-end LNAs and attenuators are not included in this circuit
but can easily be interfaced to the 50 Ω single-ended RF inputs
of the ADL5356 mixer. For a complete receiver design,
ADL5521/ADL5523 LNAs may be incorporated.
The standard configuration using the ADL5356 allows
reception of RF signals from 1.2 GHz to 2.4 GHz, but it is
possible to use the ADL5358 mixer, which covers RF input
frequencies from 500 MHz to 1700 MHz.
An Epcos (www.epcos.com) SAW filter follows the mixer and
provides the necessary channel selectivity over a bandwidth
ranging from 20 MHz to 40 MHz, depending on the chosen
filter. The circuit shown uses a 20 MHz bandwidth, 153.6 MHz
centered SAW filter (part number: B5206) but can also
accommodate other pin-compatible filters.
Some empirical optimization may be needed to help
compensate for actual PCB parasitics in SAW filter matching
and antialias filter implementation. Details of designing the
interstage filters can be found in the AN-742 and AN-827
application notes.
To ensure repeatability of band response, 1% capacitors are
recommended for the SAW filter matching components and the
antialiasing filter. In addition, Coilcraft 0603CS or similar
inductors are recommended. Other resistors, capacitors, and
inductors can be 10% values.
Excellent layout, grounding, and decoupling techniques must be
utilized in order to achieve the desired performance from the
circuits discussed in this note. As a minimum, a 4-layer PCB
should be used with one ground plane layer, one power plane
layer, and two signal layers.
All IC power pins must be decoupled to the ground plane with
low inductance multilayer ceramic capacitors (MLCC) of
0.01 μF to 0.1 μF (for simplicity, not shown in the diagrams).
Follow the recommendations on the individual data sheets and
in Tutorial MT-101.
The product evaluation boards should be consulted for
recommended layout and critical component placement. These
can be accessed through the product pages for the devices.
Even though the AD8376 and AD9258 (or other ADC) may be
powered from different supplies, sequencing is not an issue
because the input signal to the ADC is ac-coupled.
The individual data sheet for the ADC should be consulted
regarding the proper sequencing of the AVDD and the DVDD
power supplies (if separate supplies are used).
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