adl5363 Analog Devices, Inc., adl5363 Datasheet - Page 8

• Manufacturer Part Number: adl5363
• Description: 2300 Mhz To 2900 Mhz Balanced Mixer, Lo Buffer And Rf Balun Preliminary Technical Datasheet Adl5363
• Manufacturer: Analog Devices, Inc.

ADL5363
CIRCUIT DESCRIPTION
The ADL5363 consists of two primary components: the radio
frequency (RF) subsystem and the local oscillator (LO) subsystem.
The 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.
The RF subsystem consists of an integrated, low loss RF balun,
passive MOSFET mixer, and a sum termination network.
The LO subsystem consists of an SPDT-terminated FET switch
and a three-stage limiting LO amplifier. The purpose of the LO
subsystem is to provide a large, fixed amplitude, balanced signal
to drive the mixer independent of the level of the LO input.
A block diagram of the device is shown in Figure 8.
RF SUBSYSTEM
The single-ended, 50 Ω RF input is internally transformed to a
balanced signal using a low loss (<1 dB) unbalanced-to-balanced
(balun) transformer. This transformer is made possible by an
extremely low loss metal stack, which provides both excellent
balance and dc isolation for the RF port. Although the port can be
dc connected, it is recommended that a blocking capacitor be
used to avoid running excessive dc current through the part.
The RF balun can easily support an RF input frequency range
of 2300 MHz to 2900 MHz.
NC = NO CONNECT
COMM
COMM
VPMX
RFCT
RFIN
1
2
3
4
5
VLO3
VCMI
20
6
Figure 8. Simplified Schematic
LGM3
IFOP
19
GENERATOR
7
BIAS
VLO2
IFON
18
8
PWDN
LOSW
ADL5363
17
9
COMM
NC
16
10
15
14
13
12
11
LOI2
VPSW
VGS1
VGS0
LOI1
Rev. PrA | Page 8 of 15
The resulting balanced RF signal is applied to a passive mixer
that commutates the RF input with the output of the LO subsystem.
The passive mixer is essentially a balanced, low loss switch that
adds minimum noise to the frequency translation. The only
noise contribution from the mixer is due to the resistive loss
of the switches, which is in the order of a few ohms.
As the mixer is inherently broadband and bidirectional, it
is necessary to properly terminate all the idler (M × N product)
frequencies generated by the mixing process. Terminating the
mixer avoids the generation of unwanted intermodulation
products and reduces the level of unwanted signals at the IF
output. This termination is accomplished by the addition of a
sum network between the IF output and the mixer.
The IP3 performance can be optimized by adjusting the supply
current with an external resistor. Additionally, dc current can be
saved by increasing the resistor. It is permissible to reduce the
dc supply voltage to as low as 3.3 V, further reducing the
dissipated power of the part. (Note that no performance
enhancement is obtained by reducing the value of these
resistors and excessive dc power dissipation may result.)
LO SUBSYSTEM
The LO amplifier is designed to provide a large signal level to
the mixer to obtain optimum intermodulation performance.
The resulting amplifier provides extremely high performance
centered on an operating frequency of 2700 MHz.
The ADL5363 has two LO inputs permitting multiple synthesizers
to be rapidly switched with extremely short switching times
(<40 ns) for frequency agile applications. The two inputs are
applied to a high isolation SPDT switch that provides a constant
input impedance, regardless of whether the port is selected, to
avoid pulling the LO sources. This multiple section switch also
ensures high isolation to the off input, minimizing any leakage
from the unwanted LO input that may result in undesired IF
responses.
The single-ended LO input is converted to a fixed amplitude
differential signal using a multistage, limiting LO amplifier.
This results in consistent performance over a range of LO input
power. Optimum performance is achieved from −6 dBm to
+10 dBm, but the circuit continues to function at considerably
lower levels of LO input power.
The performance of this amplifier is critical in achieving a
high intercept passive mixer without degrading the noise floor
of the system. This is a critical requirement in an interferer rich
environment, such as cellular infrastructure, where blocking
interferers can limit mixer performance. The bandwidth of the
intermodulation performance is somewhat influenced by the
current in the LO amplifier chain. For dc current sensitive
applications, it is permissible to reduce the current in the
Preliminary Technical Datasheet