Data Sheet

W
E
N
Radiometrix
Hartcran House, 231 Kenton Lane, Harrow, HA3 8RP, England
Issue 1, 26 October 2004
Tel: +44 (0) 20 8909 9595, Fax: +44 (0) 20 8909 2233
TX1H
VHF Narrow Band FM High Power TX
The TX1H transmitter modules offer a
100mW RF output VHF data link in
Radiometrix SIL standard pin-out and
footprint. This makes the TX1H ideally
suited to those low power applications
where existing narrow band and
wideband
transmitters
provide
insufficient range. Together with the
matching RX1 or BiM1R receiver a oneway radio data link can be achieved
over a distance up to 10km+ with
suitable choice of data rate and
antennas.
Figure 1: TX1H-151.300-10
Features
•
•
•
•
•
•
•
Standard frequency 151.300MHz
Other frequencies from 120MHz to 180MHz
TX1H is a BiM1T in TX1 pin-out
Data rates up to 10kbps
Usable range over 10km
Fully screened
Low power requirements
The TX1H is a narrow band radio transmitter module for use in long range data transfer applications
at ranges up to 10kilometres. TX1H transmitter circuit is the BiM1T transmitter circuit in the
TX1 pin-out with slightly enlarged dimension to accommodate extra Power Amplifier circuit to
produce 100mW RF output and operates on Australian frequency of 151.300MHz
Applications
•
•
•
•
•
•
•
EPOS equipment, barcode scanners
Data loggers
Industrial telemetry and telecommand
In-building environmental monitoring and control
High-end security and fire alarms
DGPS systems
Vehicle data up/download
Technical Summary
•
•
•
•
•
•
Size: 43 x 14.5 x 5mm
Operating frequency: 151.300MHz
Supply range: 3.8V - 15V
Current consumption: 80mA transmit
Data bit rate: 10kbps max.
Transmit power: 20dBm (100mW) nominal
Radiometrix Ltd.,
TX1H high power transmitter data sheet
Page 1
Figure 2: TX1H block diagram
Radiometrix Ltd.,
TX1H high power transmitter data sheet
Page 2
Functional description
The TX1H transmitter consists of a frequency modulated Voltage Controlled Crystal Oscillator (VCXO)
feeding a frequency doubler with two stage amplifier and RF filter. Final Power Amplifier stage is
factory pre-set to appropriate band power level. Operation can be controlled by the EN (Enable) line,
the transmitter achieving full RF output typically within 5ms of this line being pulled high. The RF
output is filtered to ensure compliance with the appropriate radio regulations and fed to the 50Ω
antenna pin.
User interface
43mm
5mm
TX1H
14.5mm
pin spacing:
2.54 mm
15.24 mm
1
2
3
4
5
6
7
7 holes of 0.7 mm dia.
pin spacing 2.54 mm
1 = RF gnd
2 = RF out
3 = RF gnd
4 = En
5 = Vcc
6 = 0V
7 = TXD
Figure 3: TX1H pin-out and dimension
TX1H pin
1, 3
2
4
5
6
7
Name
RFgnd
RF out
EN
VCC
0V
TXD
Function
RF Ground
50Ω RF input from the antenna
Pull high to enable Transmitter
3.8 – 15V DC power supply
Ground
DC coupled input for 3V CMOS logic. Rin = 100kΩ
NOTES:
1. EN pin should not be left floating
2. For Vcc greater than 9V, transmit duty cycle must be limited to 25% or less
Radiometrix Ltd.,
TX1H high power transmitter data sheet
Page 3
Absolute maximum ratings
Exceeding the values given below may cause permanent damage to the module.
Operating temperature
Storage temperature
-10°C to +60°C
-30°C to +70°C
RF in (pin 1)
All other pins
±50V @ <10MHz, +13dBm @ >10MHz
-0.3V to +16.0V
Performance specifications:
(Vcc = 3.8V / temperature = 20°C unless stated)
General
DC supply
Supply voltage
TX Supply current @ 100mW
Antenna pin impedance
RF centre frequency (100mW)
Channel spacing
Number of channels
RF
RF power output
Spurious emissions
Adjacent channel TX power
Frequency accuracy
FM deviation (peak)
Baseband
Modulation bandwidth @ -3dB
TXD input level (logic low)
TXD input level (logic high)
pin
min.
typ.
max.
units
5
5
2
3.8
80mA
50
151.300
25
1
15
V
mA
Ω
MHz
kHz
2
2
+19
+20
-40
-37
0
±3.0
+21
dBm
dBm
dBm
kHz
kHz
2
3
0
3.0
kHz
V
V
4
4
5
ms
-2.5
±2.5
0
7
7
Dynamic timing
TX select to full RF
Notes:
1.
2.
3.
4.
+2.5
±3.5
5
notes
1
Measured into 50Ω resistive load.
Total over full supply and temperature range.
With 0V – 3.0V modulation input.
To achieve specified FM deviation.
Radiometrix Ltd.,
TX1H high power transmitter data sheet
Page 4
Applications information
Power supply requirements
The TX1H has a built-in regulator which delivers a constant 3.5V to the transmitter circuitry when the
external supply voltage is 3.5V or greater. This ensures constant performance up to the maximum
permitted rail, and removes the need for external supply decoupling except in cases where the supply
rail is extremely poor (ripple/noise content >0.1Vp-p).
TX modulation requirements
The module is factory-set to produce the specified FM deviation with a TXD input to pin 14 of 3V
amplitude, i.e. 0V “low”, 3V “high
If the data input level is greater than 3V, a resistor must be added in series with the TXD input to limit
the modulating input voltage to a maximum of 3V on pin 7. TXD input resistance is 100kΩ to ground,
giving typical required resistor values as follows:
Vcc
≤3V
3.3V
5V
9V
Series resistor
10 kΩ
68kΩ
220kΩ
Expected range
Predicting the range obtainable in any given situation is notoriously difficult since there are many
factors involved. The main ones to consider are as follows:
•
•
•
•
•
Type and location of antennas in use
Type of terrain and degree of obstruction of the link path
Sources of interference affecting the receiver
“Dead” spots caused by signal reflections from nearby conductive objects
Data rate and degree of filtering employed
The following are typical examples – but range tests should always be performed before assuming that
a particular range can be achieved in a given situation:
Data rate
1.2kbps
10kbps
10kbps
10kbps
Note:
Tx antenna
half-wave
half-wave
helical
helical
Rx antenna
half-wave
half-wave
half-wave
helical
Environment
rural/open
rural/open
urban/obstructed
in-building
Range
10-15km
3-4km
500m-1km
100-200m
The figure for 1.2kbps assumes that the receiver bandwidth has been suitably reduced by
utilising an outboard sallen-key active audio filter and data slicer or similar arrangement.
The TX1H’s TXD input is normally driven directly by logic levels but will also accept analogue drive
(e.g. 2-tone signalling). In this case it is recommended that TXD (pin 14) be DC-biased to 1.2V approx.
with the modulation ac-coupled and limited to a maximum of 2Vp-p to minimise distortion over the link.
The varactor modulator in the BiM1 introduces some 2nd harmonic distortion which may be reduced if
necessary by predistortion of the analogue waveform.
Although the modulation bandwidth of the TX1H extends down to DC it is not advisable to use data
containing a DC component. This is because frequency errors and drifts between the transmitter and
receiver occur in normal operation, resulting in DC offset errors on the receiver’s audio output.
Radiometrix Ltd.,
TX1H high power transmitter data sheet
Page 5
Antennas
The choice and positioning of transmitter and receiver antennas is of the utmost importance and is the
single most significant factor in determining system range. The following notes are intended to assist
the user in choosing the most effective antenna type for any given application.
Integral antennas
These are relatively inefficient compared to the larger externally-mounted types and hence tend to be
effective only over limited ranges. They do however result in physically compact equipment and for this
reason are often preferred for portable applications. Particular care is required with this type of
antenna to achieve optimum results and the following should be taken into account:
1. Nearby conducting objects such as a PCB or battery can cause detuning or screening of the antenna
which severely reduces efficiency. Ideally the antenna should stick out from the top of the product
and be entirely in the clear, however this is often not desirable for practical/ergonomic reasons and
a compromise may need to be reached. If an internal antenna must be used try to keep it away from
other metal components and pay particular attention to the “hot” end (i.e. the far end) as this is
generally the most susceptible to detuning. The space around the antenna is as important as the
antenna itself.
2. Microprocessors and microcontrollers tend to radiate significant amounts of radio frequency hash
which can cause desensitisation of the receiver if its antenna is in close proximity. The problem
becomes worse as logic speeds increase, because fast logic edges generate harmonics across the VHF
range which are then radiated effectively by the PCB tracking. In extreme cases system range may
be reduced by a factor of 5 or more. To minimise any adverse effects situate antenna and module as
far as possible from any such circuitry and keep PCB track lengths to the minimum possible. A
ground plane can be highly effective in cutting radiated interference and its use is strongly
recommended.
The following types of integral antenna are in common use:
Quarter-wave whip. This consists simply of a piece of wire or rod connected to the module at one end.
At 151MHz the total length should be 471mm from module pin to antenna tip including any
interconnecting wire or tracking. Because of the length of this antenna it is almost always external to
the product casing.
Helical. This is a more compact but slightly less effective antenna formed from a coil of wire. It is very
efficient for its size, but because of its high Q it suffers badly from detuning caused by proximity to
nearby conductive objects and needs to be carefully trimmed for best performance in a given situation.
The size shown is about the maximum commonly used at 151MHz and appropriate scaling of length,
diameter and number of turns can make individual designs much smaller.
Loop. A loop of PCB track having an inside area as large as possible (minimum about 5cm2), tuned and
matched with 2 capacitors. Loops are relatively inefficient but have good immunity to proximity
detuning, so may be preferred in shorter range applications where high component packing density is
necessary.
Integral antenna summary:
Ultimate performance
Ease of design set-up
Size
Immunity to proximity effects
Radiometrix Ltd.,
whip
***
***
*
**
helical
**
**
***
*
TX1H high power transmitter data sheet
loop
*
*
**
***
Page 6
471mm @ 151MHz
RF
Whip antenna
RF
Helical antenna
RF
Ctune
C match
wire, rod, PCB track
or a combination of these
length(mm) = 71250 / freq(MHz)
35-40 turns wire spring
length 120mm, dia 10mm
trim wire length or expand coil
for best results
track width = 1mm
2
min. area 500mm
capacitors may be variable or fixed
(values depend on loop dimensions)
RF GND
Loop antenna
Figure 4: integral antenna configurations
External antennas
These have several advantages if portability is not an issue, and are essential for long range links.
External antennas can be optimised for individual circumstances and may be mounted in relatively
good RF locations away from sources of interference, being connected to the equipment by coax feeder.
Helical. Of similar dimensions and performance to the integral type mentioned above, commerciallyavailable helical antennas normally have the coil element protected by a plastic moulding or sleeve and
incorporate a coax connector at one end (usually a straight or right-angle BNC type). These are compact
and simple to use as they come pre-tuned for a given application, but are relatively inefficient and are
best suited to shorter ranges.
Quarter-wave whip. Again similar to the integral type, the element usually consists of a stainless
steel rod or a wire contained within a semi-flexible moulded plastic jacket. Various mounting options
are available, from a simple BNC connector to wall brackets, through-panel fixings and magnetic
mounts for temporary attachment to steel surfaces.
A significant improvement in performance is obtainable if the whip is used in conjunction with a metal
ground plane. For best results this should extend all round the base of the whip out to a radius of
300mm or more (under these conditions performance approaches that of a half-wave dipole) but even
relatively small metal areas will produce a worthwhile improvement over the whip alone. The ground
plane should be electrically connected to the coax outer at the base of the whip. Magnetic mounts are
slightly different in that they rely on capacitance between the mount and the metal surface to achieve
the same result.
Radiometrix Ltd.,
TX1H high power transmitter data sheet
Page 7
Metal ground plane
1/4-wave whip
1/ (3-4
4w , eq
av u
e all
ra y
di s p
al
a
el ce
em d)
en
ts
1/4-wave
whip
(471mm long @ 151MHz)
A ground plane can also be simulated by using 3 or 4 quarter-wave radials equally spaced around the
base of the whip, connected at their inner ends to the outer of the coax feed. A better match to a 50Ω
coax feed can be achieved if the elements are angled downwards at approximately 30-40° to the
horizontal.
50 Ω coax feed
30
-40
de
g.
50 Ω coax feed
Fig.5: Quarter wave antenna / ground plane configurations
Half-wave. There are two main variants of this antenna, both of which are very effective and are
recommended where long range and all-round coverage are required:
1. The half-wave dipole consists of two quarter-wave whips mounted in line vertically and fed in the
centre with coaxial cable. The bottom whip takes the place of the ground plane described previously.
A variant is available using a helical instead of a whip for the lower element, giving similar
performance with reduced overall length. This antenna is suitable for mounting on walls etc. but for
best results should be kept well clear of surrounding conductive objects and structures (ideally >1m
separation).
2. The end-fed half wave is the same length as the dipole but consists of a single rod or whip fed at the
bottom via a matching network. Mounting options are similar to those for the quarter-wave whip. A
ground plane is sometimes used but is not essential. The end-fed arrangement is often preferred
over the centre-fed dipole because it is easier to mount in the clear and above surrounding
obstructions.
Yagi. This antenna consists of two or more elements mounted parallel to each other on a central boom.
It is directional and exhibits gain but tends to be large and unwieldy – for these reasons the yagi is the
ideal choice for links over fixed paths where maximum range is desired.
Radiometrix Ltd.,
TX1H high power transmitter data sheet
Page 8
Module mounting considerations
The modules may be mounted vertically or bent horizontal to the motherboard.
Good RF layout practice should be observed. If the connection between module and antenna is more
than about 20mm long use 50Ω microstrip line or coax or a combination of both. It is desirable (but not
essential) to fill all unused PCB area around the module with ground plane.
Variants and ordering information
The TX1H transmitter is manufactured in the following variants as standard:
For Australian general applications on 151.300MHz
TX1H-151.300-10
Other variants can be supplied to individual customer requirements at frequencies from 120MHz to 180MHz
RF output can also be factory set from +5dBm (3mW) to +20dBm (100mW) depending on minimum order quantity.
Matching Receivers:
RX1-151.300-10
BiM1R-151.300-10
Radiometrix Ltd.,
TX1H high power transmitter data sheet
Page 9
Notes
Radiometrix Ltd.,
TX1H high power transmitter data sheet
Page 10
Radiometrix Ltd
Hartcran House
231 Kenton Lane
Harrow, Middlesex
HA3 8RP
ENGLAND
Tel: +44 (0) 20 8909 9595
Fax: +44 (0) 20 8909 2233
[email protected]ometrix.com
www.radiometrix.com
Copyright notice
This product data sheet is the original work and copyrighted property of Radiometrix Ltd. Reproduction in whole or in
part must give clear acknowledgement to the copyright owner.
Limitation of liability
The information furnished by Radiometrix Ltd is believed to be accurate and reliable. Radiometrix Ltd reserves the
right to make changes or improvements in the design, specification or manufacture of its subassembly products without
notice. Radiometrix Ltd does not assume any liability arising from the application or use of any product or circuit
described herein, nor for any infringements of patents or other rights of third parties which may result from the use of
its products. This data sheet neither states nor implies warranty of any kind, including fitness for any particular
application. These radio devices may be subject to radio interference and may not function as intended if interference is
present. We do NOT recommend their use for life critical applications.
The Intrastat commodity code for all our modules is: 8542 6000
R&TTE Directive
After 7 April 2001 the manufacturer can only place finished product on the market under the provisions of the R&TTE
Directive. Equipment within the scope of the R&TTE Directive may demonstrate compliance to the essential
requirements specified in Article 3 of the Directive, as appropriate to the particular equipment.
Further details are available on The Office of Communications (Ofcom) web site:
http://www.ofcom.org.uk/radiocomms/ifi/
Information Requests
Ofcom
Riverside House
2a Southwark Bridge Road
London SE1 9HA
Tel: +44 (0)845 456 3000 or 020 7981 3040
Fax: +44 (0)20 7783 4033
[email protected]
European Radiocommunications Office (ERO)
Peblingehus
Nansensgade 19
DK 1366 Copenhagen
Tel. +45 33896300
Fax +45 33896330
[email protected]
www.ero.dk