ADL5367-EVALZ AD [Analog Devices], ADL5367-EVALZ Datasheet - Page 17

• Manufacturer Part Number: ADL5367-EVALZ
• Description: 500 MHz to 1700 MHz Balanced Mixer, LO Buffer and RF Balun
• Manufacturer: AD [Analog Devices]

CIRCUIT DESCRIPTION
The ADL5367 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, sum termination network, and IF
amplifier.
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 49.
COMM
COMM
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 500 MHz to 1700 MHz.
NC = NO CONNECT
VPMX
RFCT
RFIN
1
2
3
4
5
VCMI
VLO3
20
6
Figure 49. Simplified Schematic
LGM3
IFOP
19
GENERATOR
7
BIAS
VLO2
IFON
18
8
PWDN
LOSW
ADL5367
17
9
COMM
NC
16
10
15
14
13
12
11
LOI2
VPSW
VGS1
VGS0
LOI1
Rev. 0 | Page 17 of 24
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.
Because 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. Figure 37 and Figure 39
illustrate how various bias resistors affect the performance with a
5 V supply. 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 1100 MHz. The best
operation is achieved with either high-side LO injection for RF
signals in the 500 MHz to 1200 MHz range or low-side injection
for RF signals in the 900 MHz to 1700 MHz range. Operation
outside these ranges is permissible, and conversion loss is
extremely wideband, easily spanning 500 MHz to 1700 MHz,
but intermodulation is optimal over the aforementioned ranges.
The ADL5367 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.
ADL5367