695 MHz to 2700 MHz, Quadrature Demodulator
with Integrated Fractional-N PLL and VCO
I/Q demodulator with integrated fractional-N PLL
RF input frequency range: 695 MHz to 2700 MHz
Internal LO frequency range: 356.25 MHz to 2850 MHz
Input P1dB: 14.5 dBm at 1900 MHz RF
Input IP3: 37 dBm at 1900 MHz RF
Programmable HD3/IP3 trim
Single pole, double throw (SPDT) RF input switch
RF digital step attenuation range: 0 dB to 15 dB
Integrated RF tunable balun for single-ended 50 Ω input
Multicore integrated VCO
Demodulated 1 dB bandwidth: 600 MHz
4 selectable baseband gain and bandwidth modes
Digital programmable LO phase offset and dc nulling
Programmable via 3-wire serial port interface (SPI)
40-lead, 6 mm × 6 mm LFCSP
Digital predistortion (DPD) receivers
Microwave point-to-point radios
FUNCTIONAL BLOCK DIAGRAM
15 14 13
2 3 8 9 23 25 26 28 38
PLL 39 REFIN
1 19 30 36 31
27 33 40 10
The ADRF6820 is a highly integrated demodulator and synthesizer
ideally suited for next generation communication systems. The
feature rich device consists of a high linearity broadband I/Q
demodulator, an integrated fractional-N phase-locked loop (PLL),
and a low phase noise multicore, voltage controlled oscillator
(VCO). The ADRF6820 also integrates a 2:1 RF switch, an on-chip
tunable RF balun, a programmable RF attenuator, and two low
dropout (LDO) regulators. This highly integrated device fits
within a small 6 mm × 6 mm footprint.
The high isolation 2:1 RF switch and on-chip tunable RF balun
enable the ADRF6820 to support two single-ended, 50 Ω
terminated RF inputs. A programmable attenuator ensures
an optimal differential RF input level to the high linearity
demodulator core. The integrated attenuator offers an
attenuation range of 0 dB to 15 dB with a step size of 1 dB.
The ADRF6820 offers two alternatives for generating the
differential local oscillator (LO) input signal: externally via a
high frequency, low phase noise LO signal or internally via the
on-chip fractional-N synthesizer. The integrated synthesizer
enables continuous LO coverage from 356.25 MHz to 2850 MHz.
The PLL reference input can support a wide frequency range
because the divide or multiplication blocks can increase or
decrease the reference frequency to the desired value before it
is passed to the phase frequency detector (PFD).
When selected, the output of the internal fractional-N synthesizer
is applied to a divide-by-2 quadrature phase splitter. From the
external LO path, a 1× LO signal can be applied to the built-in
polyphase filter, or a 2× LO signal can be used with the divide-
by-2 quadrature phase splitter to generate the quadrature LO
inputs to the mixers.
The ADRF6820 is fabricated using an advanced silicon-germanium
BiCMOS process. It is available in a 40-lead, RoHS-compliant,
6 mm × 6 mm LFCSP package with an exposed paddle.
Performance is specified over the −40°C to +85°C temperature
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