RCT-433-AS [ETC]
Low-Cost SAW-stabilized surface mountOOK RF transmitter; 低成本SAW稳定的表面mountOOK射频发射器
| 型号： | RCT-433-AS |
| 厂家： | 
ETC |
| 描述： | Low-Cost SAW-stabilized surface mountOOK RF transmitter |
| 文件： | 总6页 (文件大小：306K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Low-Cost SAW-stabilized surface mount
Embedding the wireless future..
OOK RF transmitter
Features
Typical Applications
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315/418/433.92 MHz versions
Low Cost
.5-12V operation
5mA current consumption at 3V
Small size: .30” x .4”
0dBm output power at 3V
4800 baud operation
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Remote Keyless Entry (RKE)
Remote Lighting Controls
On-Site Paging
Asset Tracking
Wireless Alarm and Security Systems
Long Range RFID
Automated Resource Management
Description
The RCT-433-AS is ideal for remote control
applications where low cost and longer range are
required. The transmitter operates from a 1.5-12V
supply, making it ideal for battery-powered
applications. The transmitter employs a SAW-
stabilized oscillator, ensuring accurate frequency
control for best range performance. Output power
and harmonic emissions are easy to control,
making FCC and ETSI compliance easy. The
manufacturing-friendly SMT style package and low-
cost make the RCT-433-AS suitable for high
volume applications.
(shown actual size)
Ordering Information
Frequency
315 MHz
418 MHz
Part Number
RCT-315-AS
RCT-418-AS
433.92 MHz RCT-433-AS
Domestic and international orders:
Canadian orders:
Mouser Electronics 1-800-346-6873 (http://www.mouser.com)
Haltronics Ltd. 1-800-387-7969 (http://www.haltronicsltd.com/)
For a Radiotronix Representative in your area please visit www.radiotronix.com and visit our corporate
information page.
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Document Control
Created By
Steve Montgomery
Tom Marks
05/21/02
8/21/03
8/21/03
8/21/03
8/21/03
Engineering Review
Marketing Review
Approved - Engineering
Approved - Marketing
Bryan Montgomery
Tom Marks
Bryan Montgomery
Revision History
Revision Author Date
Description
1.1.0
1.2.0
1.3.0
SJM
BFA
SJM
05/21/02
07/30/03
8/21/03
Document Created
Revision
Revision. Added troubleshooting and design
tips.
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RCT-XXX-AS Low-Cost SAW-stabilized surface mount OOK RF transmitter
© 2001,2002,2003 All Rights Reserved
Pin Out Diagram
Pin Description
Pin No.
Pin Name
Description
50 ohm antenna output. The antenna port impedance affects output
power and harmonic emissions. An L-C low-pass filter may be
needed to sufficiently filter harmonic emissions.
1
ANT
2
3
GND
Transmitter ground. Connect to ground plane.
Digital data input. This input is CMOS compatible and should be
DATA
driven with CMOS level inputs.
Pin 4 provides operating voltage for the transmitter. VCC should be
bypassed with a .01uF ceramic capacitor and filtered with a 4.7uF
tantalum capacitor. Noise on the power supply will degrade
transmitter noise performance.
4
VCC
Mechanical Drawing
0.30”
Figure 1: Mechanical Drawing of RCT-XXX-AS
Figure 2: Suggested Pad Layout
Absolute Maximum Ratings
Parameter
Min
Max
Units
Power Supply and All Input
Pins
-0.3
+15
VDC
Storage Temperature
Soldering Temperature
(10sec)1
-50
NA
100
350
°C
°C
NOTES 1) Hand Solder Only. The Transmitter is not suitable for IR reflow or hot air soldering.
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8/21/2003
RCT-XXX-AS Low-Cost SAW-stabilized surface mount OOK RF transmitter
© 2001,2002,2003 All Rights Reserved
Detailed Electrical Specifications
Parameter (General)
Symbol
Vcc
Min
1.5
---
Typ.
3.0
Max Units
Notes
Operating Voltage
12
---
Volts DC
Operating Current
Icc
4.5
mA
uA
@3V
@3V
@3V
DATA=VCC
Operating Current
DATA=GND
---
100
0
---
Icc
Frequency Accuracy
Center Frequency
TOLfc
Fc
-75
---
+75 Khz
315.0
418.0
433.92
0
---
MHz
RCT-315-AS
RCT-418-AS
RCT-433-AS
@3V
Output Power
---
dBm
Baud Rate – NRZ
DC
---
4800 BPS
Theory of Operation
OOK Modulation
OOK modulation is a binary form of amplitude modulation. When a logical 0 (data line low) is
being sent, the transmitter is off, fully suppressing the carrier. In this state, the transmitter current
is very low, less than 1mA.
When a logical 1 is being sent, the carrier is fully on. In this state, the module current
consumption is at its highest, about 4.5mA with a 3V power supply.
OOK is the modulation method of choice for remote control applications where power
consumption and cost are the primary factors. Because OOK transmitters draw no power when
they transmit a 0, they exhibit significantly better power consumption than FSK transmitters.
OOK data rate is limited by the start-up time of the oscillator. High-Q oscillators which have very
stable center frequencies take longer to start-up than low-Q oscillators. The start-up time of the
oscillator determines the maximum data rate that the transmitter can send.
DESIGN HINT “Using the RCT-XXX-AS with a microcontroller UART”: Data should be
inverted when using the transmitter with a UART. The normal marking state of a UART is a logic
1, which will cause constant transmission. By inverting the data, the transmitter will be off in a
marking state and on in a spacing state (logical 0), ensuring that the transmitter is on only when
data is being sent. The output of the receiver would also need to be inverted to properly recover
data.
SAW stabilized oscillator
The transmitter is basically a negative resistance LC oscillator whose center frequency is tightly
controlled by a SAW resonator. SAW (Surface Acoustic Wave) resonators are fundamental
frequency devices that resonate at frequencies much higher than crystals.
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8/21/2003
RCT-XXX-AS Low-Cost SAW-stabilized surface mount OOK RF transmitter
© 2001,2002,2003 All Rights Reserved
The output of the oscillator is derived directly from the collector of the oscillator transistor. It is,
therefore, very sensitive to VSWR. The module is designed to work with a 50 ohm load, which
exhibits a VSWR of 1. The designer must ensure that the antenna exhibits no more than a
VSWR of 2 to guarantee operation. This is particularly true for PCB trace antennas. If the
module does not appear to have any output at the antenna port, it is likely that the antenna does
not meet this requirement.
TROUBLESHOOTING HINT:
If the module appears to have no output at the antenna port, try the following: disconnect the
antenna and put a 1000pF cap in series with a 51 ohm resistor to ground. This will ensure that
the transmitter is properly loaded. Then look at the output with a scope and you should see the
oscillator working. If it is working, the antenna is not properly tuned and that is the reason that
the module is not working properly. If not, then check the power supply and data input for proper
voltage levels.
Data Rate
The oscillator start-up time is on the order of 40uSec, which limits the maximum data rate to 4.8
kbit/sec.
TROUBLESHOOTING HINT:
If the module appears to have a good output, but your data rate is corrupted, that could be a sign
that the start-up time of the oscillator is too long. The load on the antenna affects oscillator start-
up time. To determine the start-up time of the oscillator, use a 2 channel digital storage
oscilloscope. Attach channel 1 to the data input and channel 2 to the antenna output (don’t
worry, it won’t affect the antenna VSWR). Trigger the scope on a rising edge on channel 1. Now,
toggle the data pin from low to high and capture the resulting waveform. You should see a
square edge on channel 1 and the oscillator ring-up on channel 2. Measure the time between the
rising edge on channel 1 and when the oscillator waveform is at its full voltage swing, and you
have the start-up time. To determine if the antenna is the problem, remove it and place a 1000pF
cap in series with a 51-ohm resistor to ground and repeat the test. If the start-up time is correct
with the test load, the problem is the antenna.
Power Supply
The RCT-433-AS is designed to operate from a 1.5 -12V power supply. It is crucial that this
power supply be very quiet. The power supply should be bypassed using a 0.01uF low-ESR
ceramic capacitor and a 4.7uF ceramic capacitor. These capacitors should be placed as close to
the power pins as possible.
Antenna Output
Pin 1 is a 50 ohm antenna output. It will support most antenna types, including printed antennas
integrated directly onto the PCB. The performance of the different antennas varies. There are
many good application notes available that describe external and PCB trace antennas. We
maintain a list in the technical support section of our website.
DESIGN HINT “Antenna traces”:
Any time a trace is longer than 1/8th the wavelength of the frequency it is carrying, it should be a
50 ohm micro strip. This ensures that a proper match is maintained between the transmitter
output and the antenna.
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8/21/2003
RCT-XXX-AS Low-Cost SAW-stabilized surface mount OOK RF transmitter
© 2001,2002,2003 All Rights Reserved
DESIGN HINT “Harmonic Filter”:
The impedance at the antenna power affects the VSWR, power output, and harmonic output of
the transmitter. In most cases, the output of the transmitter may need a low-pass LC filter to
reduce harmonic emissions. A good calculator is available on line at http://www-
users.cs.york.ac.uk/~fisher/lcfilter/. Calculate the filter for a 3dB cut-off of the module’s center
frequency plus 10%. For example, the cut-off for a 433.92 MHz module would be about 470
MHz.
Contact Information
Address:
207 Industrial Blvd
Moore, Oklahoma 73160
Phone:
Fax:
405-794-7730
405-794-7477
www:
support:
sales:
www.radiotronix.com
support@radiotronix.com
sales@radiotronix.com
Technical Support Policy
Radiotronix is committed to providing our customers with world-class technical support.
We offer several tools to support you during development. Our RApid Development (or
RAD) kits are designed to make evaluation of our products simple and fast. They also
serve as a known-good reference when debugging your designs. The knowledge base on
our website answers the most commonly asked questions regarding our products.
If you need to communicate with one of our technical support people, the best way is to
post a message in the support forum. Our technical support staff monitor the forum
continuously. By using the forum, you will get the fastest response to your technical
support questions, and other customers will benefit from the information. Also, you may
find that another customer has an answer for your question.
You can also e-mail your question to support@radiotronix.com. The forum is given a
higher priority than e-mail, but we realize that sometimes you just need direct contact
with a support engineer.
We also offer telephone technical support at no charge. Generally, the forum is checked
more often and you are likely to get a faster response, but we do realize that sometimes
nothing replaces a person-to-person conversation. When you call for phone support, your
contact information will be recorded and the next available support engineer will call you
back. This can take 24-48 hours, depending on the volume of support requests.
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8/21/2003
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