Intersil QHx220 Hardware User's Manual
Application Note 1559
QHx220 Hardware User Guide
Table of Contents
QHx220 System Overview ................................................................................................................... 2
General Application System Block Diagram for QHx220 .......................................................................... 2
Description of QHx220 System Block Diagram....................................................................................... 2
Essential Factors to Integrating the QHx220 Device into Your System ..................................................... 3
Connecting the QHx220 Evaluation Board to a PC for Manual Control ...................................................... 4
MTV Product Application ..................................................................................................................... 5
QHx220 Board Layout ....................................................................................................................... 5
QHx220 Board Schematics (for MTV) ................................................................................................... 6
QHx220 Board Bill of Materials (for MTV).............................................................................................. 7
MTV Optimization Setup (Static Coupling Channel) ................................................................................ 7
MTV Application Setup ....................................................................................................................... 9
GPS Product Application ................................................................................................................... 10
QHx220 Board Layout...................................................................................................................... 10
QHx220 Board Schematics (for GPS) ................................................................................................. 11
QHx220 Board Bill of Materials (for GPS) ............................................................................................ 12
GPS Optimization Setup (Static Coupling Channel)............................................................................... 12
GPS Application Setup ..................................................................................................................... 14
WLAN Product Application ................................................................................................................. 15
QHx220 Board Layout...................................................................................................................... 15
QHx220 Board Schematics (for WLAN) ............................................................................................... 16
QHx220 Board Bill of Materials (for WLAN) ......................................................................................... 17
WLAN Optimization Setup (Static Coupling Channel) ............................................................................ 17
WLAN Application Setup................................................................................................................... 19
Q:ACTIVE........................................................................................................................................... 19
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CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Application Note 1559
QHx220 System Overview
General Application System Block Diagram for QHx220
NOISE SOURCE
COUPLING CHANNEL
SAMPLER
VICTIM
ANTENNA
F
C
QHx220
FIGURE 1. TYPICAL APPLICATION DIAGRAM
Description of QHx220 System Block
Diagram
The block diagram shown in Figure 1 illustrates the
typical system architecture for the implementation of the
QHx220 noise canceller. The QHx220 integrates the LNA
gain stages in the sampler path as well as the DACs
which control the I and Q (or ultimately the gain and
phase) of the device. The LNA gain stages and the I and
Q are controlled via the SPI bus interface. The GUI
software supplied with the evaluation board provides a
means to manually tune all of these parameters.
A known noise source is sampled by a variety of tapping
methods depending on the accessibility of sampling the
noise source. The sampled noise is then filtered by a
bandpass filter that has the same bandwidth as the
victim receive band. It may be possible to eliminate this
filter stage. However, this is dependent on the
characteristics of the aggressor source, the sampling
methodology and the location of the cancellation node
F
C
CANCELLATION
NODE
VICTIM
RECEIVER
SIGNAL INTEGRITY
PARAMETER FEEDBACK
VIA SPI BUS
AND
BASEBAND
within the receiver chain. The QHx220 has internal LNA
gain stages that can be set to pre-amplify the sampled
input noise if necessary. The amount of pre-amplification
required (if any) depends on coupling factors between
the noise source and the victim antenna as well as the
level of the sampled noise at the input of the QHx220.
Since the dynamic range of the QHx220 is typically 50dB,
the noise level at the input of the QHx220 should be
approximately 25dB higher than the noise level present
at the victim receiver (when using the minimum gain
setting). Higher gain settings should be used when it is
not possible to find a strong enough tapping point of the
noise source. Setting this level correctly will allow for a
maximum tuning range when using the QHx220 tuning
control. This characterization will determine the amount
of pre-amplification necessary for any given application.
It is important to remember not to exceed the -45dBm
maximum input power of the QHx220 device. The
QHx220 has a high output impedance which only
introduces, on the order of tenths of a dB, insertion loss
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Application Note 1559
to the victim receiver path. It taps the victim receive
path directly.
The QHx220 evaluation platform is an open loop system,
meaning that the optimization is performed manually.
With the addition of a microcontroller and some kind of
signal quality parameter fed back from the victim
receiver such as C/N, BER, RSSI, etc., the system can
operate closed loop. A simple algorithm can be coded to
optimize the gain and phase of the cancellation signal
based on the previous state of the quality parameter
provided by the victim receiver. Seed values can also be
used to improve the initial starting point state for the
optimization algorithm. Thus minimizing the number of
iterations required to achieve convergence. A look-up
table could also be implemented for systems operating
on multiple channel frequencies, but this may not be
necessary for extremely narrow band applications.
Essential Factors to Integrating the QHx220
Device into Your System
The purpose of this section is to provide some design
guidelines to ensure the successful integration of the
QHx220 into your system.
1. DO NOT exceed approximately -45dBm (exact limits
are specified within the datasheet depending on
frequency band) maximum input power of the
QHx220 device.
2. The sampled noise must be the same noise
(correlated with) as the noise that aggresses the
victim antenna. The amount of correlation is
proportional to the amount of cancellation that can
be achieved using the QHx220 device. It is often
necessary to try multiple tapping points and tapping
methods in order to achieve the best possible
correlation to the noise present in the victim
antenna.
3. Be sure to choose the correct level of pre-amplification
as described in the previous sections. If this is not
set correctly, it will limit the tuning range of the
QHx220 device and hence limit the amount of
cancellation that it is possible to achieve.
4. The delay from the noise source to the cancellation
node (via the coupling channel) should be matched
with the delay of noise source to the cancellation
node (via the sampler path). The main source of
mismatched delay is often due to the filter in the
receiver path. Using the same filter in the sampler
path is often a simple means of achieving sufficient
matching of the delay of both paths. One could also
move the cancellation node to precede the filter in
the receive path and eliminate the filter in the
sampler path. This could have drawbacks in some
applications depending on the out-of-band noise
characteristics and the noise sampling method
used.
5. The high impedance RF output of the QHx220
devices must be placed <5mm from the cancellation
node (the tapping point of the victim receiver),
otherwise resonances can occur that will attenuate
the cancellation signal. Figure 2 shows the effect of
varying the distance “L” between the QHx220 output
and the tapping point of the victim receiver.
1
2
3
4
1516 14 13
12
QHx
6578
11
10
9
0
-5
L = 5mm
-10
VICTIM ANTENNA
dB (S(2, 1))
-15
L
TO RADIO
FIGURE 2. DISTANCE FROM CANCELLATION NODE vs FREQUENCY
-20
-25
0 0.5 1.0 1.5 2.0 2.5 3.0
L = 25mm
L = 20mm
L = 15mm
FREQUENCY (GHz)
L = 10mm
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Connecting the QHx220 Evaluation Board to
a PC for Manual Control
The Basic I-Q Control Software User Guide (AN1563)
provides a detailed description of how to install the
software GUI program that is used to manually control
the QHx220 evaluation board. The software should be
installed prior to connecting the hardware to the PC. The
Basic I-Q Control Software User Guide (AN1563) also
provides detailed instruction on how to configure all the
software settings required to control the frequency band,
gain, and gain and phase of the device. Please note that
the evaluation boards are populated to operate in a
specific frequency band. A tank circuit and matching
components are specifically chosen for each desired band
of operation. If a different frequency band is chosen via
the software GUI, then the QHx220 board should be
reconfigured accordingly. The correct BOM for MTV, GPS,
and WLAN frequency bands can be found in the
subsequent sections of this user guide.
A USB controller board plugs into the USB port of the PC
and is used to control the SPI bus interface of the
QHx220 device. The USB controller board also has a 1.8V
regulated supply that is used to power the QHx220
device. The user may alternatively power the device with
an external power supply if so desired. A custom cable is
also provided which is keyed so that it plugs into the USB
controller board in the correct orientation. Figure 3 shows
the USB controller board and cable connection.
The opposite end of the cable plugs into the QHx220
evaluation board to provide the 1.8V power supply
voltage and SPI connection to control the device. These
connectors are not “keyed” so please be sure that they
are oriented correctly. There are markings on the socket
and plug of each connector to identify the correct
orientation. Figure 4 shows these markings and the
orientation of the cable connections.
Three Hirose to SMA cables are provided for all of the RF
connections (Noise Sampler Input and Rx Input/Output).
SPI
INTERFACE
FIGURE 3. THE QHx220 USB CONTROLLER BOARD
INPUT
NOISE SAMPLER
Rx OUTPUT
(TO RECEIVER)
FIGURE 4. QHx220 USB CONTROLLER BOARD WITH PARTS LABELED
INTERSIL
QHX220
LED
Rx INPUT
(FROM ANTENNA)
1.8V
INPUT
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MTV Product Application
The following is a general overview on how the QHx220 can be applied for use in Mobile TV product applications.
QHx220 Board Layout
NOISE
SAMPLER
INPUT
GND
1.8V INPUT
LED
Rx INPUT
(FROM ANTENNA)
Rx OUTPUT
(TO RECEIVER)
INTERSIL
QHx220
FIGURE 5. QHx220 EVALUATION BOARD LAYOUT (MTV)
5
SPI INTERFACE
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QHx220 Board Schematics (for MTV)
FIGURE 6. SCHEMATIC OF QHx220 EVALUATION BOARD (MTV)
Application Note 1559
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