CN-0248 Datasheet, PDF (1/6 Pages) Analog Devices – An IQ Demodulator-Based IF-to-Baseband Receiver with IF and Baseband Variable Gain and Programmable Baseband Filtering

Circuit Note
CN-0248
Circuits from the Lab™ reference circuits are engineered and
tested for quick and easy system integration to help solve today’s
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information and/or support, visit www.analog.com/CN0248.
Devices Connected/Referenced
ADRF6510
30 MHz Dual Programmable Filters and
Variable Gain Amplifiers
ADL5387
50 MHz to 2 GHz Quadrature
Demodulator
ADL5336
LF to 1 GHz VGA with 48 dB Gain Control
Range and Programmable RMS Detectors
An IQ Demodulator-Based IF-to-Baseband Receiver with IF and Baseband Variable
Gain and Programmable Baseband Filtering
EVALUATION AND DESIGN SUPPORT
Circuit Evaluation Boards
ADRF6510 Evaluation Board (ADRF6510-EVALZ)
ADL5387 Evaluation Board (ADL5387-EVALZ)
ADL5336 Evaluation Board (ADL5336-EVALZ)
AD8130 Evaluation Board (AD8130-EBZ) two required
Design and Integration Files
Schematics, Layout Files, Bill of Materials
CIRCUIT FUNCTION AND BENEFITS
This circuit is a flexible, frequency agile IF-to-baseband receiver.
Variable gain at both IF and baseband is used to adjust the signal
level. The ADRF6510 baseband ADC driver also includes a
programmable low-pass filter that eliminates out-of-channel
blockers and noise.
ADL5387
The bandwidth of this filter can be dynamically adjusted as the
bandwidth of the input signal changes. This ensures that the available
dynamic range of the ADC that this circuit drives is fully used.
The core of the circuit is an IQ demodulator. The 2×LO based
phase-splitting architecture of the ADL5387 allows for operation
over a wide frequency range. Precise quadrature balance and
low output dc offsets ensure that there is minimal degradation
of the error vector magnitude (EVM).
The interfaces between all of the components in this circuit are
fully differential. Where dc coupling is required between stages,
the bias levels of the adjacent stages are compatible with each other.
ADRF6510
AD9248
ADL5336
RF
0°
DIV BY 2
90°
I
2xLO
Q
BITS
BITS
VCO
CORE
ADF4350
Figure 1. Direct Conversion Receiver Simplified Schematic (All Connections and Decoupling Not Shown)
Rev. 0
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