ADMV1012 Data Sheet
Rev. A | Page 14 of 19
THEORY OF OPERATION
The ADMV1012 is a compact GaAs, MMIC, double sideband
(DSB) downconverter in a RoHS compliant package optimized
for both upper sideband and lower sideband point to point
microwave radio applications operating in the 17.5 GHz to
24 GHz input frequency range. The ADMV1012 supports
LO input frequencies of 7 GHz to 13.5 GHz and IF output
frequencies of 2.5 GHz to 3.5 GHz.
The ADMV1012 uses a RF LNA followed by an I/Q double
balanced mixer, where a driver amplifier drives the LO (see
Figure 1). This combination of design, process, and packaging
technology allows the functions of these subsystems to be
integrated into a single die, using mature packaging and
interconnection technologies to provide a high performance,
low cost design with excellent electrical, mechanical, and
thermal properties. In addition, the need for external
components is minimized, optimizing cost and size.
LO DRIVER AMPLIFIER
The LO driver amplifier takes a single LO input and doubles the
frequency and amplifies it to the desired LO signal level for the
mixer to operate optimally. The LO driver amplifier is self
biased, and it requires only a single dc bias voltage (VDLO),
which draws approximately 170 mA at 3 V under the LO drive.
The LO amplitude range of −4 dBm to +4 dBm makes it
compatible with the Analog Devices, Inc., wideband synthesizer
portfolio without the need for an external LO driver amplifier.
MIXER
The mixer is an I/Q double balanced mixer, and this mixer
topology reduces the need for filtering unwanted sideband.
An external 90° hybrid is required to select the upper sideband
of operation. The ADMV1012 has been optimized to work with
the Mini-Circuits QCN-45+ RF 90° hybrid.
LNA
The LNA requires a single dc bias voltage (VDRF) and a single
dc gate bias (VGRF) to operate. Starting at −1.8 V at the gate
supply (VGRF), the LNA is biased at +3 V (VDRF). Then, the
gate bias (VGRF) is varied until the desired LNA bias current
(IDRF) is achieved. The desired LNA bias current is 68 mA at
3 V under small signal conditions.
The typical application circuit (see Figure 34) shows the
necessary external components on the bias lines to eliminate
any undesired stability problems for the RF amplifier and the
LO amplifier.
The ADMV1012 is a much smaller alternative to hybrid style
image reject converter assemblies, and it eliminates the need
for wire bonding by allowing the use of surface-mount
manufacturing assemblies.
The ADMV1012 downconverter comes in a compact, thermally
enhanced, 4.9 mm × 4.9 mm, 32-terminal ceramic leadless chip
carrier (LCC) package. The ADMV1012 operates over the
−40°C to +85°C temperature range.