ANT-403-USP
Data Sheet
Product Description
The µSplatch™ uses a grounded-line technique
to achieve outstanding performance from a tiny
surface-mount element. This unique antenna is
designed for hand or reflow-mounting directly to a
product’s circuit board. Its low cost makes it ideal
for volume applications. Unlike many compact
antennas, the µSplatch™ exhibits good proximity
performance, making it an appropriate choice for
handheld applications such as remote controls,
pagers and alert devices.
12.70 mm
(0.5")
by
9.14 mm
(0.36")
2.62 mm
(0.103")
5.1 mm
(0.20")
1.27 mm
(0.05")
Features
•
•
•
•
•
•
•
Very low cost
Ultra-compact package
Direct PCB attachment
Ideal for concealed / internal mounting
Perfect for compact portable devices
Suitable for hand- or reflow-assembly
Resistant to proximity effects
Recommended Footprint
5.1 mm
(0.20")
2.54 mm
(0.10")
2.03 mm
(0.08")
Electrical Specifications
Center Frequency:
Recom. Freq. Range:
Bandwidth:
Wavelength:
VSWR:
Peak Gain:
Impedance:
Connection:
Oper. Temp. Range:
403MHz
400 – 406MHz
6MHz
¼-wave
≤
2.0 typical at center
–8.7dBi
50-ohms
Surface-mount
–40°C to +130°C
Recommended Mounting
40.37 mm
(1.59”)
7.11 mm
(0.28”)
10.54 mm
(0.42”)
No ground plane or traces
under the antenna
PCB pads for the
µSplatch
Vias to ground plane
Ground plane on bottom
layer for counterpoise
50-ohm microstrip line
(0.21” minimum)
Electrical specifications and plots measured on 3.88 cm x 8.00
cm (1.53” x 3.15”) reference ground plane.
91.82 mm 79.88 mm
(3.62”)
(3.15”)
Ordering Information
ANT-403-USP (supplied in tubes of 63 pieces)
ANT-403-USP-T (Tape and reel of 1,000 pieces)
7.62 mm
(0.03”)
38.86 mm
(1.53”)
7.62 mm
(0.03”)
Please see AN-00502 for more details on PCB layout.
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Revised 1/3/2017
Counterpoise
Quarter-wave or monopole antennas require an associated ground plane counterpoise for proper operation.
The size and location of the ground plane relative to the antenna will affect the overall performance of the
antenna in the final design. When used in conjunction with a ground plane smaller than that used to tune the
antenna, the center frequency typically will shift higher in frequency and the bandwidth will decrease. The
proximity of other circuit elements and packaging near the antenna will also affect the final performance. For
further discussion and guidance on the importance of the ground plane counterpoise, please refer to Linx
Application Note AN-00501: Understanding Antenna Specifications and Operation.
VSWR Graph
VSWR
3:1
1.38
Reflected Power
25%
2:1
1:1
353MHz
403MHz
0%
453MHz
What is VSWR?
The Voltage Standing Wave Ratio (VSWR) is a measurement of how well an antenna is matched to a source
impedance, typically 50-ohms. It is calculated by measuring the voltage wave that is headed toward the load
versus the voltage wave that is reflected back from the load. A perfect match has a VSWR of 1:1. The higher
the first number, the worse the match, and the more inefficient the system. Since a perfect match cannot
ever be obtained, some benchmark for performance needs to be set. In the case of antenna VSWR, this
is usually 2:1. At this point, 88.9% of the energy sent to the antenna by the transmitter is radiated into free
space and 11.1% is either reflected back into the source or lost as heat on the structure of the antenna. In
the other direction, 88.9% of the energy recovered by the antenna is transferred into the receiver. As a side
note, since the “:1” is always implied, many data sheets will remove it and just display the first number.
How to Read a VSWR Graph
VSWR is usually displayed graphically versus frequency. The lowest point on the graph is the antenna’s
operational center frequency. In most cases, this is different than the designed center frequency due to
fabrication tolerances. The VSWR at that point denotes how close to 50-ohms the antenna gets. Linx
specifies the recommended bandwidth as the range where the typical antenna VSWR is less than 2:1.
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ANT-403-USP Data Sheet
by
Gain Plots
E / Vertical Gain
H / Horizontal Gain
Total Gain
XZ-Plane Gain
YZ-Plane Gain
XY-Plane Gain
About Gain Plots
The true measure of the effectiveness of an antenna in any given application is determined by the gain
and radiation pattern measurement. For antennas gain is typically measured relative to a perfect (isotropic)
radiator having the same source power as the antenna under test, the units of gain in this case will be
decibels isotropic (dBi). The radiation pattern is a graphical representation of signal strength measured at
fixed distance from the antenna.
Gain when applied to antennas is a measure of how the antenna radiates and focuses energy into free
space. Much like a flashlight focuses light from a bulb in a specific direction, antennas focus RF energy into
specific directions. Gain in this sense refers to an increase in energy in one direction over others.
It should also be understood that gain is not “free”, gain above 0dBi in one
direction means that there must be less gain in another direction. Pictorially
this can be pictured as shown in the figures to the right. The orange pattern
represents the radiation pattern for a perfect dipole antenna, which is shaped
like a donut. The pattern for an omnidirectional antenna with gain is shown in
blue. The gain antenna is able to work with a device located further from the
center along the axis of the pattern, but not with devices closer to the
center when they are off the axis – the donut has been squished.
Gain is also related to the overall physical size of the antenna, as well as
surrounding materials. As the geometry of the antenna is reduced below the effective wavelength (considered
an electrically small antenna) the gain decreases. Also, the relative distance between an electrically small
antenna and its associated ground impacts antenna gain.
Copyright © 2017 Linx Technologies
159 Ort Lane, Merlin, OR 97532
Phone: +1 541 471 6256
Fax: +1 541 471 6251
www.linxtechnologies.com
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ANT-403-USP Data Sheet
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