Data Sheet
ADMV4540
K Band Quadrature Demodulator with Integrated Fractional-N PLL and VCO
FEATURES
FUNCTIONAL BLOCK DIAGRAM
► Fractional-N synthesizer with low phase noise VCO
► K band quadrature demodulator
► Programmable via 4-wire SPI
► RF operating frequency range: 17 GHz to 22 GHz
► LO internal frequency range: 17 GHz to 21.5 GHz
► Double sideband noise figure: 5 dB at maximum conversion gain
► Output integrated phase noise, 1 kHz to 10 MHz: <1°
► Maximum conversion gain of >50 dB
► Conversion gain control range of >50 dB
► IM3 of −54 dBc at −30 dBm composite input level, ΔfRF = 1 MHz
Figure 1.
► 3 baseband, SPI-selectable LPFs with corner frequencies of:
125 MHz, 250 MHz, and 500 MHz on each baseband path
APPLICATIONS
► Satellite communications
GENERAL DESCRIPTION
The ADMV4540 is a highly integrated quadrature demodulator with
integrated synthesizer ideally suited for next generation K band
satellite communication.
The high dynamic range baseband output amplifiers of the
ADMV4540 provide an overall nominal conversion gain of
57 dB. The three baseband voltage variable attenuator (VVA) pins
(VCTRL_BBVVAx) of the ADMV4540 can be used for automatic
gain control (AGC), giving the ADMV4540 a wide RF input dynamic
range.
The RF front end of the ADMV4540 consists of two low noise
amplifier (LNA) paths, each with an optimal cascaded, 5 dB, double
sideband noise figure at maximum gain, while minimizing external
components. The dual paths allow support for antenna polarization.
Selection of the LNA path can be done through the SPI.
This feature rich device contains an integrated fractional-N phase-
locked loop (PLL) and a low phase noise voltage controlled oscil-
lator (VCO) that generates the necessary on-chip local oscillator
(LO) signal for the two double balanced I/Q mixers, eliminating
the need for external frequency synthesis. The VCO utilizes an
internal automatic calibration routine that allows the PLL to select
the necessary settings and lock.
The LNA output is then downconverted to baseband using an
inphase and quadrature (I/Q) mixer. The I/Q mixer output is then
fed into fully differential low noise and low distortion programmable
filters and variable gain amplifiers (VGAs). Each channel is capable
of rejecting large, out of band interferers while reliably boosting
the wanted signal, thus reducing the bandwidth and resolution
requirements on the analog-to-digital converters (ADCs) of the
system. The excellent matching between channels and their high
spurious-free dynamic range (SFDR) over all gain and bandwidth
settings make the ADMV4540 ideal for satellite communication
systems with dense constellations, multiple carriers, and nearby
interferers.
The reference input (REFIN) to the PLL of the ADMV4540 employs
a differentially excited crystal oscillator at 50 MHz. Alternatively,
the REFIN can be driven by an external single-ended frequency
reference up to 100 MHz. The phase frequency detector (PFD)
comparison frequency operates up to 100 MHz, which allows for
continuous LO coverage from 17 GHz to 21.5 GHz in extremely fine
steps.
The three filter corners of 125 MHz, 250 MHz, and 500 MHz are all
programmable via a serial peripheral interface (SPI). The filters
provide a sixth-order Butterworth response with −3 dB corner fre-
quencies of 141 MHz, 282 MHz, and 565 MHz. For operation be-
yond 565 MHz, the filter can be disabled and completely bypassed,
thereby extending the −3 dB bandwidth up to 900 MHz.
The ADMV4540 operates on a 3.3 V supply with less than 3.2 W
of total power dissipation. It is available in a 48-terminal, RoHS
compliant, 7 mm × 7 mm LGA package with an exposed paddle.
The ADMV4540 can operate over the −40℃ to +85℃ temperature
range on a + 3.3 V power supply.
Rev. 0
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