| The
KTX2 is a miniature PCB mounting code-hopping UHF radio
transmitter suitable for use in secure remote keyless
control applications at distances up to 75 metres in-building
or 300 metres open ground. |
Figure 1: KTX2-433 |
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Features
- Designed for compliance with
EN 300 220-3 and EN 301 489-3
- Each transmitter module is pre-programmed
and unique
- No additional circuitry required
to use the module
- 32-bit encryption - more than
4 billion combinations
- Usable range up to 300m
- Available at 433.92MHz
- Fully screened module
- Suitable for use with a Radiometrix
KRX receiver-decoder
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| The module combines
full screening with extensive internal filtering for EMC -
minimising spurious radiations and susceptibilities. The KTX2
module will suit wireless control links in applications including
car and building security and secure unidirectional remote
process control. Because of the small size and low power requirement
the module is ideal for use in portable, battery-powered devices
such as hand-held remote controls requiring data integrity
and high security. |
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Technical Summary
- Crystal-locked
PLL
- FM data with Manchester encoding
- Operation from 3V to 6V
- +3dBm output on 433.92MHz
- <1uA standby, 8mA Tx current
- Supply status included in transmission
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Applications
- RF interface for Security and Alarm systems
- Status reporting and monitoring secure systems
- Industrial controls
- HVAC controls
- Wireless door entry systems
- Simple On/Off switching
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Functional and operational description
The KTX2 transmitter module is a crystal
based PLL controlled FM code-hopping transmitter with a
pre-programmed Electronic Serial Number (ESN), operating
between 3V and 6V supply, at 433.92MHz. KTX2 is designed
to meet or exceed EN 300 220-3 standards for European use
and delivers nominally +3dBm at 8mA (for 5V supply). The
module measures 36.2 x 15.2 x 4.5 mm.
The module is very easy to use: there
are no modulation input or transmitter-enable pins. The
activation of any combination of the four function lines
(S0 - S3) causes a data transmission, part of which is the
status of S0 - S3, i.e. the function code. In this way,
up to 15 different control combinations can be sent from
one module. Simple pushbuttons can be connected directly
between S0 - S3 and Vcc if desired. The module will transmit
repeatedly whilst any of the function lines is held high
for up to 30 seconds (approx.), when a power-saving time-out
feature is activated.
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 Fig.
2: KTX2 block diagram |
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User interface
Fig
3: KTX2 physical dimensions
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| Pin description |
| TX1H pin |
Name |
Function |
| 1 |
RF out |
50W
RF output to the antenna. Internally DC-isolated.
See antenna section of apps notes for details
of suitable antennas. |
| 2 |
RF GND |
RF ground, internally
connected to the module screen and pin 3 (0V).
This pin should be directly connected to the RF
return path - e.g. coax braid, main PCB ground
plane etc. |
| 3 |
0V |
DC
supply ground. Internally connected to pin 2 and
module screen. |
| 4 |
Vcc |
+3V to +6V DC
supply. Max ripple content 0.1VP-P. Decoupling
is not generally required. |
| 5 |
S0 |
Input
(0) - activate high (>0.55Vcc - Vcc) to cause
a transmission. |
| 6 |
S1 |
Input (1) - activate
high (>0.55Vcc - Vcc) to cause a transmission. |
| 7 |
S2 |
Input (2) - activate
high (>0.55Vcc - Vcc) to cause a transmission. |
| 8 |
S3 |
Input (3) - activate
high (>0.55Vcc - Vcc) to cause a transmission. |
| 9 |
Internal use |
Modulation (Data).
This pin is connected to the modulation input
of the Transmitter, therefore do not connect anything
to this pin during operation of the module. |
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Notes on the KTX2
- The Module will transmit if any of the function
lines (S0 - S3) is activated (high).
- Single message time is typically 150ms.
- Whilst S0 - S3 are all deactivated (low) standby
current consumption is <1uA.
- The Module will transmit the same message (with
the same hop-code) repeatedly whilst any of the
function lines are held active high, until power-saving
time-out occurs after approx. 30s.
- When the power-saving timeout occurs, current
consumption will be <350uA, until all function
line(s) are released again.
- Whilst a function line is held high, if another
function line is taken high then the function code
in the message changes to reflect the new state
of the function lines and the hop-code is also changed
- as if the user had released all function lines
and activated the new combination.
- Releasing individual function lines (whilst at
least one function line remains high) has no effect
on the transmitted message.
- The supply monitoring status bit is set when module
supply drops below 3.8V (approx.) and resets when
supply falls even further - below 2.2V (approx.)
- but note that this is less than the minimum supply
recommended for use with KTX2.
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| Description of
the KTX/KRX code hopping system
Every time a function code is activated
causing KTX to transmit, a hop-code is generated.
The hop-code is an encryption based upon a Manufacturer
code and the module ESN (unique to each module). An
encryption algorithm uses these two variables to generate
the hop-code, which will change for every new transmission.
Note that the data itself (i.e. the function code)
is not encrypted, as it is the identity and status
of the sender that is used to safeguard operation
of the system.
At the KRX receiver-decoder, the
hop-code can only be decrypted with the correct key.
The key is derived from the manufacturer code and
the KTX serial number. The manufacturer code is not
transmitted: it is pre-programmed into the decoder.
Because the hop-code is changed for every new transmission
the receiver decoder must be synchronised to the transmitter
encoder. This is achieved by "learning"
the transmitter to the receiver during which the serial
number and synchronisation data is stored in the receiver-decoder.
Transmissions received from all KTX modules are decoded,
but not acted upon unless the serial number has been
learned first and the decoder is synchronised to the
encoder.
If the Radiometrix KRX decoder
loses synchronisation with the transmitter (e.g. repeated
transmitter activation whilst out of range) then the
KTX module must be activated twice before the decoder
will allow the control to be processed, but only if
the KTX module is within a forward window of +32768
activations. This mechanism prevents "code-grabbers"
from breaking the security of the system by recording
and re-broadcasting old codes. Additionally, in the
KRX decoder a window exists allowing up to 14 transmissions
to occur whilst the transmitter is out of range before
two valid sequential transmissions are required to
use the system. In practice a user may not notice
the latter, since human reaction to an unsuccessful
attempt is simply to "press the button again".
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Absolute maximum ratings
Survival Maximums:
Exceeding the
values given below may cause permanent damage to the
module.
Operating temperature: -20°C
to +70°C
Storage temperature: -40°C to +100°C
Vcc (pin 4): -0.3V to +6.9V
Function input (pins 5-8): Vcc +/-0.3V
RF out (pin 1): ±50V DC 10dBm RF
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| Performance
specifications
(Figures apply at +20°C, 5.0V
supply unless otherwise stated)
| General |
pin |
min. |
typ. |
max. |
units |
notes |
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| DC supply
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| Supply
voltage |
3, 4
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3.0
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4.5
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6
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V
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3
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| TX Supply current
@ Vcc = 5V |
3, 4
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6
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8
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10
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mA
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| Standby current |
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-
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1
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-
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uA
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| RF |
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| RF power output
@ Vcc = 3 - 6V |
1
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+1
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+3
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+5
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dBm
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1
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| harmonics <1GHz |
2
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-
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-46
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-
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dBc
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1
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| harmonics >1GHz |
2
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-
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-46
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-
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dBc
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1
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| RF
centre frequency |
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433.92
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MHz
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| Initial Frequency
accuracy |
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- 15
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±10
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+15
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kHz
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| Overall Frequency
accuracy |
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- 25
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±10
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+25
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kHz
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2
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| FM deviation (peak) |
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±20
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±27
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±35
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kHz
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| Antenna pin impedance |
1
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-
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50
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-
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W
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| Number of channels |
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1
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-
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Notes:
1. Measured into a 50W load.
2. -20 to +70°C @ Vcc = 5V
3. Operational at 2.8V but with reduced deviation (typ.
+/-15kHz) |
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Power supply requirement
The KTX2 module incorporates a
built-in regulator which delivers a constant 2.8V
supply to the RF circuitry when the external supply
voltage is 2.85V or greater, with 40dB or more of
supply ripple rejection. This ensures constant performance
up to the maximum permitted supply 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).
Note, however, that for supply
voltages lower than 2.85V the regulator is effectively
inoperative and supply ripple rejection is considerably
reduced. Under these conditions the ripple/noise on
the supply rail should be below 10mVp-p to avoid problems.
If the quality of the supply is in doubt, it is recommended
that a 10mF low-ESR tantalum or similar capacitor
be added between the module supply pin (Vcc) and ground,
together with a 10W series feed resistor between the
Vcc pin and the supply rail.
The module current in standby mode
(Vcc applied, S0, S1, S2, S3 all at 0V) is less than
1mA.
The KTX2 incorporates a low voltage shutoff circuit,
which prevents any possibility of erratic operation
by disabling the RF output if the supply voltage drops
below 2.2V (±5%). This feature is self-resetting,
i.e. restoring the supply to greater than 2.2V will
immediately restore RF output from the module.
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| Module mounting
considerations
The module may be mounted vertically
or bent horizontal to the motherboard. Good RF layout
practice should be observed - in particular, any ground
return required by the antenna or feed should be connected
directly to the RF GND pin at the antenna end of the
module, and not to the OV pin which is intended as
a DC ground only. All connecting tracks should be
kept as short as possible to avoid any problems with
stray RF pickup.
If the connection between module
and antenna does not form part of the antenna itself,
it should be made using 50W
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.
The module may be potted if required
in a viscous compound which cannot enter the screen
can.
Warning:
DO NOT wash the module. It is not hermetically sealed.
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Figure 4: Module mounting options
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Antenna requirements
Three types of integral antenna are recommended and
approved for use with the module:
A) Helical:
Wire coil, connected directly to pin 2, open circuit
at other end. This antenna is very efficient given
it's small size (20mm x 4mm dia.). The helical is
a high Q antenna, trim the wire length or expand the
coil for optimum results. The helical de-tunes badly
with proximity to other conductive objects.
B) Loop: A loop of
PCB track tuned by a fixed or variable capacitor to
ground at the 'hot' end and fed from pin 2 at a point
20% from the ground end. Loops have high immunity
to proximity de-tuning.
C) Whip: This is a
wire, rod ,PCB track or combination connected directly
to pin 2 of the module. Optimum total length is 17cm
(1/4 wave @ 418MHz) Keep the open circuit (hot) end
well away from metal components to prevent serious
de-tuning. Whips are ground plane sensitive and will
benefit from internal 1/4 wave earthed radial(s) if
the product is small and plastic cased.
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| The antenna choice and position
directly controls the system range. Keep it clear of
other metal in the system, particularly the 'hot' end.
The best position by far, is sticking out the top of
the product. This is often not desirable for practical/ergonomic
reasons thus a compromise may need to be reached. If
an internal antenna must be used try to keep it away
from other metal components, particularly large ones
like transformers, batteries and PCB tracks/earth plane.
The space around the antenna is as important as the
antenna itself. |
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Figure
5: integral antenna configurations
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Integral antenna
summary:
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whip
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helical
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loop
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| Ultimate performance |
***
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| Ease of design
set-up |
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| Size |
*
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***
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| Immunity to proximity
effects |
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*
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***
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Range
open ground
(for KTX2-433-40-5 & RX2A-433-10) |
300
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200
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100
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| Variants and ordering
information
The KTX2 is available as a standard
version:
KTX2-433
The standard frequency is 433.92MHz,
for other frequency variants, please contact sales
department.
To make a complete code-hopping
system:
Suitable Receiver module to use
with KTX2:
RX2A-433-10
Suitable Decoder IC for use with
RX2A:
KRX416-000-DIL
Or use a complete relay output
board (includes RX2A module) for use with KTX2 modules
(mapping the four KTX2 function lines to four change-over
relays)
KDEC-433-000
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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 wireless
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:
Licensing
policy manual
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