RXM-315-LR RXM-418-LR RXM-433-LR WIRELESS MADE SIMPLE LR SERIES RECEIVER MODULE DATA GUIDE DESCRIPTION The LR Receiver is ideal for the wireless transfer of serial data, control, or command n. information in the favorable 260-470MHz band. The receiver’s advanced synthesized superhet 0.630 in. architecture achieves an outstanding typical sensitivity of -112dBm, which provides a 5-10 times improvement in range over previous Figure 1: Physical Dimensions solutions. When paired with a compatible Linx transmitter, a reliable wireless link is formed, capable of transferring data at rates of up to 10,000bps at distances in excess of 3,000 feet. Applications operating at short distances, or lower data rates will also benefit from increased link reliability and superior noise immunity. Housed in a tiny reflow compatible SMD package, the LR Receiver module is footprint compatible with the popular LC-S Receiver, allowing existing users an instant path to improved range and lower cost. No external components are required (except an antenna), allowing for easy integration, even by engineers without previous RF experience. FEATURES „ Long-Range „ Low Power Consumption „ Low-Cost „ Wide Supply Range (2.7 - 5.2VDC) „ PLL Synthesized Architecture „ Compact Surface-mount Package „ Direct Serial Interface „ Wide Temperature Range „ Data Rates to 10,000 bps „ RSSI and Power-Down Functions „ Qualified Data Output „ No Production Tuning „ No External Components Needed APPLICATIONS INCLUDE ORDERING INFORMATION „ Remote Control PART # DESCRIPTION „ Keyless Entry EVAL-***-LR Basic Evaluation Kit „ Garage / Gate Openers MDEV-***-LR Master Development Kit „ Lighting Control TXM-315-LR Transmitter 315 MHz „ Medical Monitoring / Call Systems TXM-418-LR Transmitter 418 MHz „ Remote Industrial Monitoring TXM-433-LR Transmitter 433 MHz „ Periodic Data Transfer RXM-315-LR Receiver 315 MHz „ Home / Industrial Automation RXM-418-LR Receiver 418 MHz „ Fire / Security Alarms RXM-433-LR Receiver 433 MHz „ Remote Status / Position Sensing *** Insert Frequency „ Long-Range RFID Receivers are supplied in tubes of 40 pcs. „ Wire Elimination Revised 11/26/03 PRELIMINARY RECEIVER SPECIFICATIONS PERFORMANCE DATA These performance parameters are based on module operation at 25°C 5VDC from a 3.0VDC supply unless 1 NC ANT 16 330 Parameter Designation Min. Typical Max. Units Notes otherwise noted. Figure 2 at the right 3VDC 2 NC GND 15 External 3 NC NC 14 POWER SUPPLY Resistor illustrates the connections 4 GND NC 13 Operating Voltage V – 2.7 3.0 3.6 V CC necessary for testing and operation. DC 5 VCC NC 12 6 PDN NC 11 With Dropping Resistor 4.3 5.0 5.2 VDC 1,5 It is recommended all ground pins 7 RSSI NC 10 Supply Current I – be connected to the groundplane. 4.0 5.2 7.0 mA CC 8 DATA NC 9 Power-down Current I 5 The pins marked NC have no 20 28 35 µA PDN electrical connection. RECEIVER SECTION Figure 2: Test/Basic Application Circuit Receive Frequency Range F C ABSOLUTE MAXIMUM RATINGS – – – RXM-315-LR 315 MHz – – – RXM-418-LR 418 MHz Supply voltage V -0.3 to +3.6 VDC – 433.92 – – RXM-433-LR MHz CC Supply voltage V , using resistor -0.3 to +5.2 VDC – – – Center Frequency Accuracy -50 +50 kHz CC Operating temperature -30°C to +70°C –– – dBm 2,5 LO Feedthrough -80 Storage temperature -45°C to +85°C –– – 5 IF 10.7 MHz Soldering temperature +225°C for 10 seconds N – – – Noise Bandwidth 280 kHz 3DB RF input, Pin 16 0 dBm – – – Data Rate 100 10,000 bps Any input or output Pin -0.3 to +3.6 VDC Data Output *NOTE* Exceeding any of the limits of this section may lead to permanent –– – 3 Logic Low 0.0 VDC damage to the device. Furthermore, extended operation at these maximum ratings may reduce the life of this device. Logic High –– – 3 3.0 VDC – 4 Receiver Sensitivity -106 -112 -118 dBm RSSI / Analog: TYPICAL PERFORMANCE GRAPHS –– – 5 Dynamic Range 80 dB – 50 – 5000 5 Analog Bandwidth Hz –– – 5 Gain 16 mV/dB –– – 5 PDN Voltage/No Carrier 1.5 V Supply ANTENNA PORT R – – 5 RF Input Impedance 50 Ω IN RX DATA RX Data TIMING Receiver Turn-On Time: – 3.0 10.0 5, 6 Via V 7 mSec CC – 0.04 0.5 5, 6 Via PDN 0.25 mSec –– – 5 Max Time Between Transitions 10 mSec ENVIRONMENTAL Figure 4: Turn-On Time From PDN Figure 3: Turn-On Time From V ° CC Operating Temperature Range – -40 – +70 C 5 5.40 Table 1: LR Series Receiver Specifications 5.35 Notes RFIN >-35dBm 1. The LR can utilize a 4.3 - 5.2VDC supply provided a 330 ohm resistor is placed in series with V . 5.30 CC 2. Into a 50 ohm load. 3. When operating from a 5 volt source it is important to consider that the output will swing to well less 5.25 With Dropping NO RFIN than 5 volts as a result of the required dropping resistor. Please verify that the minimum voltage will Resistor 5.20 meet the high threshold requirement of the device to which data is being sent. -5 4. For BER of 10 at 1200bps. 5.15 5. Characterized, but not tested. 6. Time to valid data output. 5.10 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 Supply Voltage (VDC) Figure 6: RSSI Response Time Figure 5: Consumption VS Supply Page 2 Page 3 PRELIMINARY Supply Current (mA) PHYSICAL PACKAGING RECEIVER DESCRIPTION The receiver is packaged as a hybrid SMD module with sixteen pins spaced The LR receiver is a low-cost, high-performance synthesized AM/OOK receiver, 0.100" on center. capable of receiving serial data at up to 10,000 bits/second. Its exceptional sensitivity results in outstanding range performance. The LR’s compact surface- mount package is friendly to automated or hand production. LR Series modules 0.812" are capable of meeting the regulatory requirements of many domestic and international applications. 50Ω RF IN (Antenna) 0.630" 0.125" Band Select 10.7MHz Data Slicer 0˚ Filter IF Filter - Data Out LNA Limiter + ∑ 90˚ RSSI/Analog Figure 7: LR Series Receiver Package Dimensions PLL VCO PIN DESCRIPTIONS XTAL Figure 9: LR Series Receiver Block Diagram 1 NC ANT 16 2 NC GND 15 THEORY OF OPERATION 3 NC NC 14 The LRreceiver is designed to recover 4 GND NC 13 data sent by an AMor Carrier-Present 5 VCC NC 12 Carrier-Absent (CPCA) transmitter also Data 6 PDN NC 11 referred to as CW or On-Off Keying 7 RSSI NC 10 (OOK). This type of modulation represents Carrier a logic low ‘0’ by the absence of a carrier 8 DATA NC 9 and a logic high ‘1’ by the presence of a Figure 8: LR Series Receiver Pinout (Top View) carrier. This modulation method affords Figure 10: CPCA (AM) Modulation numerous benefits. The two most important are: 1) cost-effectiveness due to design simplicity and 2) higher allowable output power and thus greater range in countries (such as the US) that average output power measurements over time. Please refer to Linx application Pin Number Name Description note #00130 for a further discussion of modulation techniques. 1 - 3 N/C No Connection The LR receiver utilizes an advanced single-conversion superheterodyne architecture. Transmitted signals enter the module through a 50-ohm RF port 4 GND Analog Ground intended for single ended connection to an external antenna. RFsignals V 5 Supply Voltage entering the antenna are bandpass filtered and then amplified by an NMOS CC cascode Low Noise Amplifier (LNA). The filtered, amplified signal is then down- 6 PDN Power Down converted to a 10.7MHz Intermediate Frequency (IF) by mixing it with a low-side 7 RSSI Received Signal Strength Indicator Local Oscillator (LO). The LO frequency is generated by a Voltage Controlled Oscillator (VCO) locked by a Phase-Locked Loop (PLL) frequency synthesizer 8 DATA Digital Data Output that utilizes a precision crystal reference. The mixer stage incorporates a pair of 9 - 14 N/C No Connection double balanced mixers and a unique image rejection circuit. This circuit, along with the high IFfrequency and ceramic IF filters, reduces susceptibility to 15 GND Analog Ground interference. The IF frequency is further amplified, filtered, and demodulated to 16 RF IN 50-ohm RF Input recover the baseband signal originally transmitted. The baseband signal is squared by a data slicer and output to the data pin. The architecture and quality of the components utilized in the LR module enable it to outperform many far more expensive receiver products. Page 4 Page 5 PRODUCTION GUIDELINES AUTOMATED ASSEMBLY The LR modules are packaged in a hybrid SMD package that supports hand or For high-volume assembly most users will want to auto-place the modules. The automated assembly techniques. Since LR modules contain discrete modules have been designed to maintain compatibility with reflow processing components internally, the assembly procedures are critical to ensuring the techniques, however, due to the their hybrid nature certain aspects of the reliable function of the LR product. The following procedures should be reviewed assembly process are far more critical than for other component types. with and practiced by all assembly personnel. Following are brief discussions of the three primary areas where caution must be observed. PAD LAYOUT The following pad layout diagram is designed to facilitate both hand and automated assembly . Reflow Temperature Profile The single most critical stage in the automated assembly process is the reflow 0.065" process. The reflow profile below should be closely followed since excessive temperatures or transport times during reflow will irreparably damage the modules. Assembly personnel will need to pay careful attention to the oven's profile to 0.610" ensure that it meets the requirements necessary to successfully reflow all components while still meeting the limits mandated by the modules themselves. 0.070" Forced Air Reflow Profile 300 Ideal Curve 0.100" C Limit Curve 250 Figure 11: LR-RX Pad Layout 220 C 210 C 200 180 C RECEIVER HAND ASSEMBLY Temperature 150 The LR receiver’s primary mounting Reflow Zone 125 C Soldering Iron surface is sixteen pads located on the 20-40 Sec. Soak Zone Tip 100 bottom of the module. Since these pads 2 Minutes Max. are inaccessible during mounting, Preheat Zone 50 2-2.3 Minutes Ramp-up Cooling castellations that run up the side of the 1-1.5 Minutes module have been provided to facilitate 0 Solder 0 30 60 90 120 150 180 210 240 270 300 330 360 solder wicking to the module’s underside. PCB Pads Time (Seconds) This allows for very quick hand soldering Figure 12: LR-RX Soldering Technique for prototyping and small volume Figure 13: Required Reflow Profile production. Shock During Reflow Transport If the recommended pad guidelines have been followed, the pads will protrude slightly past the edge of the module. Use a fine soldering tip to heat the board pad Since some internal module components may reflow along with the components and the castellation, then introduce solder to the pad at the module’s edge. The placed on the board being assembled, it is imperative that the modules not be solder will wick underneath the module providing reliable attachment. Tack one subjected to shock or vibration during the time solder is liquid. module corner first and then work around the device taking care not to exceed the times listed below. Washability The modules are wash resistant, but are not hermetically sealed. Linx Absolute Maximum Solder Times recommends wash-free manufacturing, however, the modules can be subjected to a wash cycle provided that a drying time is allowed prior to applying electrical Hand-Solder Temp. TX +225°C for 10 Seconds power to the modules. The drying time should be sufficient to allow any moisture that may have migrated into the module to evaporate, thus eliminating the Hand-Solder Temp. RX +225°C for 10 Seconds potential for shorting damage during power-up or testing. If the wash contains Recommended Solder Melting Point +180°C contaminants, the receiver performance may be adversely affected, even after Reflow Oven: +220°C Max. (See adjoining diagram) drying. Page 6 Page 7 POWER SUPPLY REQUIREMENTS THE DATA OUTPUT The LR receiver module does not have an internal A CMOS-compatible data output is available on Pin 8. This output is normally used voltage regulator, therefore it requires a clean, well- to directly drive a digital decoder IC or a microprocessor that is performing the data regulated power source. While it is preferable to power decoding. The receiver’s output is internally qualified, meaning that it will only the unit from a battery, the unit can also be operated transition when valid data is present. In instances where no carrier is present the 10R from a power supply as long as noise and ‘hash’ are output will remain low. Likewise, when the carrier is detected the output will go high. less than 20mV. Power supply noise will manifest itself The data output line can be directly connected to a digital IC or microprocessor that as AM and FM noise and can significantly affect the will register the data and perform some function. In addition, the module can be receiver sensitivity, therefore, providing a clean power connected to an RS232 level converter chip, like the MAX232, or to a Linx USB Figure 14: Supply Filter supply for the module should be a high design priority. module for interfacing with a PC. The LR Series modules can also be used with standard UARTs. Since a UART utilizes high marking to indicate the absence of A 10Ω resistor in series with the supply followed by a 10µF tantalum capacitor data, a designer using a UART may wish to insert a logic inverter between the data from V to ground will help in cases where the quality of supply power is poor. CC output of the LR receiver and the UART. Note that operation from 4.3 to 5.2 volts requires the use of an external 330Ω resistor placed in-line with the supply to prevent V from exceeding 3.6 volts. RECEIVING DATA CC USING THE PDN PIN Once a reliable RF link has been established, the challenge becomes how to effectively transfer data across it. While a properly designed RF link provides The receiver's Power Down (PDN) pin can be used to power the receiver down reliable data transfer under most conditions, there are still distinct differences without the need for an external switch. The PDN pin has an internal pull-up, so from a wired link that must be addressed. Since the LR modules do not when the PDN pin is held high or simply left floating the module will be active. incorporate internal coding/decoding, a user has tremendous flexibility in how When the PDN pin is pulled to ground the receiver will enter into a low-current data is handled. (<40µA) power-down mode. During this time the receiver is off and cannot It is always important to separate what type of transmissions are technically perform any function. It may be useful to note that the startup time coming out of possible from those that are legally allowable in the country of intended power-down will be slightly less than when applying Vcc. operation. You may wish to review application notes #00125 and #00140 along The PDN pin allows easy control of the receiver state from external components with Part 15 Section 231 for further details on acceptable transmission content. such as a microcontroller. By periodically activating the receiver, checking for If you want to transfer simple control or status signals such as button presses or data, then powering down, the receiver’s average current consumption can be switch closures, and your product does not have a microprocessor on board or greatly reduced, saving power in battery operated applications. you wish to avoid protocol development, consider using an encoder and decoder N No otte e:: The voltage on the PDN pin should not exceed 3.6V. When using with a higher IC set. These chips are available from a wide range of manufacturers including voltage control source, such as a 5V microcontroller, an open collector line should be used Linx, Microchip, Holtek, and Motorola. These chips take care of all encoding and if available. As an alternative, a diode may be placed in series with the control line. Either decoding functions and generally provide a number of data pins to which of these methods will prevent damage to the module by preventing 5V from being placed switches can be directly connected. In addition, address bits are usually provided on the PDN pin while still allowing the line to be pulled to ground. for security and to allow the addressing of multiple receivers independently. USING THE RSSI PIN These ICs are an excellent way to bring basic remote control/status products quickly and inexpensively to market. Additionally, it is a simple task to interface The receiver's Received Signal Strength Indicator (RSSI) pin serves a variety of with inexpensive microprocessors such as the Microchip PIC or one of many IR, uses. This pin has a dynamic range of 80dB (typical) and outputs a voltage remote control, DTMF, and modem IC’s. proportional to the incoming signal strength. A graph of the RSSI pin's characteristics appears on Page 4 of this manual. It should be realized that the While the LR is ideally suited to the long range transfer of control and command RSSI levels and dynamic range will vary slightly from part to part. It is also information it can also be used with great success for the transfer of true variable important to remember that RSSI output indicates the strength of any in-band RF data such as temperature, pressure, or sensor data. However, the 260 - 470MHz energy and not necessarily just that from the intended transmitter, therefore, it band in which the receiver operates is tightly regulated by Part 15 Section 231. should be used only to qualify the level and presence of a signal. Many types of transmissions, especially those involving automatic transmissions or variable data are required to be periodic. A careful review of these The RSSI output can be utilized during testing or even as a product feature to requirements should be made prior to development. Application Note #00125 assess interference and channel quality by looking at the RSSI level with all discusses these requirements in more detail. intended transmitters shut off. The RSSI output can also be used in direction- finding applications although there are many potential perils to consider in such Another area of consideration is that of data structure or protocol. If you are not systems. Finally, the RSSI pin can be used to save system power by "waking up" familiar with the considerations for sending serial data in a wireless environment external circuitry when a transmission is received or crosses a certain threshold. you will want to review Linx application note #00232. The RSSI output feature adds tremendous versatility for the creative designer. Page 8 Page 9 TYPICAL APPLICATIONS PROTOCOL GUIDELINES Figure 15 shows a circuit using the Linx LICAL-DEC-LS001 decoder chip. This chip While many RF solutions impose data formatting and balancing requirements, works with the LICAL-ENC-LS001 encoder chip to provide simple remote control the LR Series does not encode or packetize the signal content in any manner. capabilities. The decoder will detect the transmission from the encoder, check for Naturally the received signal will be affected by such factors as noise, edge jitter, errors, and if everything is correct, the encoder’s inputs will be replicated on the and interference but it is not purposefully manipulated or altered by the modules. decoder’s outputs. This makes registering keypresses very simple. This gives the designer tremendous flexibility for protocol design and interface. Despite this transparency and ease of use it must be recognized that there are RELAY OUT distinct differences between a wired and a wireless environment. Issues such as RXM-XXX-LR-S interference and contention must be understood and allowed for in the design 1 16 NC ANT 15 process. To learn more about protocol considerations for the LR series we suggest GND 14 NC VCC you read Linx application note #00232. 13 VCC NC 12 C NC Errors from interference or changing signal conditions can cause corruption of PDN NC RELAY-SPDT 7 RSSI NC the data packet, so it is generally wise to structure the data being sent into small DATA NC 1N4148 packets. This allows errors to be managed without affecting large amounts of data. A simple checksum or CRC could be used for basic error detection Once GND 2N2222 1 an error is detected the protocol designer may wish to simply discard the corrupt VCC VCC GND 2.2K 10K data or implement a more sophisticated scheme to correct it. 3 6 D3 D1 GND GND 4 5 VCC SEL_BAUD D2 INTERFERENCE CONSIDERATIONS BUZZER Figure 15: LR Receiver and LS Decoder The RF spectrum is crowded and the potential for conflict with other unwanted sources of RF is very real. While all RF products are at risk from interference its Figure 16 shows a typical RS232 circuit using the LR receiver and a Maxim effects can be minimized by better understanding its characteristics. MAX232 chip. The LR will output a serial data stream and the MAX232 will convert Interference may come from internal or external sources. The designer’s first that to RS232 compliant signals. responsibility is to eliminate interference from sources under their control. This VCC VCC means paying careful attention to layout, grounding, filtering and bypassing in C1 + C2 4.7uF 4.7uF order to eliminate all radiated and conducted interference paths. For many DB-9 MAX232 RXM-XXX-LR-S products this is straightforward, however, products containing components such 1 16 + 1 16 GND 6 NC ANT C3 C1+ VCC 2 15 2 15 2 as switching power supplies, motors, crystals, and other potential sources of 4.7uF NC GND V+ GND 14 C1- NC 4 3 C2+ 13 noise must be approached with care. Comparing your own design with a Linx VCC 5 8 NC 12 + C4 C NC V- 7 9 evaluation board can help to determine if and at what level design-specific 11 4.7uF T2OUT NC 8 5 R2IN 10 RSSI NC interference is present. 8 9 DATA NC GND C5 GND External interference can manifest itself in a variety of ways. Low-level 4.7uF GND interference will produce noise and hashing on the output and reduce the link’s GND overall range. Figure 16: LR Receiver and MAX232 IC High-level interference is caused by products sharing the same frequency in Figure 17 shows an example of using the LR receiver with a Linx SDM-USB-QS-S proximity or from near-band high-power devices. It can even come from your USB module. The LR will output a serial data stream and the USB module will own products if more than one transmitter is active in proximity. It is always convert that to low speed USB compliant signals. important to remember that only one transmitter at a time can occupy a frequency regardless of the coding of the transmitted signal. In most instances, this type of interference is less common than those mentioned previously, but in USB-B 4 SDM-USB-QS-S RXM-XXX-LR-S GND 1 16 1 16 severe cases it can prevent all useful function of the affected device. DAT+ USBDP RI NC ANT 2 15 2 DAT - 15 USBDM GND 5V GND 3 14 Although technically it is not interference, multipath is also a factor to be GND NC 4 13 VCC VCC NC understood. Multipath is a term used to refer to the signal cancellation effects 5 12 GND GND SUSP_IND C NC 6 11 that occur when RF waves arrive at the receiver in different phase relationships. RX_IND NC 7 10 TX_IND NC This effect is a particularly significant factor in interior environments where 8 9 485_TX DTR DATA NC objects provide many different signal reflection paths. Multipath cancellation results in lowered signal levels at the receiver and, thus, shorter useful distances GND for the link. Figure 17: LR Receiver and Linx USB Module Page 10 Page 11 6 GSHD 5 GSHD 1 2 + + BOARD LAYOUT CONSIDERATIONS MICROSTRIP DETAILS If you are at all familiar with RF devices you may be concerned about specialized A transmission line is a medium whereby RF energy is transferred from one board layout requirements. Fortunately, because of the care taken by Linx in place to another with minimal loss. This is a critical factor, especially in high- designing the LRseries, integrating an LR receiver is very straightforward. frequency products like the LR, because the trace leading to the module’s Despite this ease of application it is still necessary to maintain respect for the RF antenna can effectively contribute to the length of the antenna, changing its stage and exercise appropriate care in layout and application in order to resonant bandwidth. In order to minimize loss and detuning, some form of maximize performance and ensure reliable operation. The antenna can also be transmission line between the antenna and the module should be used, unless influenced by layout choices. Please review this manual in its entirety prior to the antenna connection can be made very close proximity, <1/8in. from the beginning your design. By adhering to good layout principles and observing module. One common form of transmission line is a coax cable, another is the some basic design rules you well along on the path to RF success. Microstrip. This term refers to a PCB trace running over a groundplane that is designed to serve as a transmission line between the module and the antenna. Figure 18 shows the suggested PCB GROUNDPLANE G GROUNDPLANE ROUNDPLANE The width is based on the desired characteristic impedance of the line, the footprint for the LR Series receiver. The ON LOWER LAYER O ON LOWER LAYER N LOWER LAYER thickness of the PCB, and the dielectric constant of the board material. For actual pad dimensions are shown on page standard 0.062in thick FR-4 board material, the trace width would be 111 mils. 6. A groundplane (as large as possible) The correct trace width can be calculated for other widths and materials using should be placed on a lower layer of your the information below. Handy software for calculating microstrip lines is also PC board opposite the LR receiver. This available on the Linx website (www.linxtechnologies.com). groundplane can also be critical to the performance of your antenna, which will be discussed later in the manual. During prototyping, the module should be Figure 18: Suggested PCB Layout soldered to a properly laid-out circuit board. The use of prototyping or "perf" boards is strongly discouraged. No conductive items should be placed within 0.15in. of the module’s top or sides. Do not route PCB traces directly under the module. The underside of the module has numerous signal-bearing traces and vias which could short or couple to traces on the product's circuit board. AM/OOK receivers are particularly subject to noise. The LR receiver module should, as much as reasonably possible, be isolated from other components on your PCB, especially high-frequency circuitry such as crystal oscillators, switching power supplies and high-speed bus lines. Make sure internal wiring is routed away from the module and antenna, and is secured to prevent displacement. The power-supply filter components should be placed close to the module's Vcc line. The trace from the module to the antenna should be kept as short as possible. A simple trace is suitable for runs up to 1/8 inch for antennas with wide bandwidth characteristics. For longer runs or to avoid detuning narrow bandwidth antennas, such as a helical, use a 50-ohm coax or 50-ohm microstrip transmission line as described in the following section.  In some instances, a designer may wish to encapsulate or "pot" the product. Figure 19: Microstrip Formulas (Er = dielectric constant of PC board material) Many Linx customers have done this successfully; however, there are a wide variety of potting compounds with varying dielectric properties. Since such Effective Dielectric Characteristic Dielectric Constant Width/Height (W/d) compounds can considerably impact RF performance it is the responsibility of Constant Impedance the designer to carefully evaluate and qualify the impact and suitability of such 4.8 1.8 3.59 50.0 materials. 4 2 3.07 51.0 2.55 3 2.12 48.0 Page 12 Page 13 RECEIVER ANTENNA CONSIDERATIONS GENERAL ANTENNA RULES The choice of antennas is a critical and The following general rules should help in maximizing antenna performance: often overlooked design consideration. 1. Proximity to objects such as a user’s hand or body, or metal objects will cause The range, performance, and legality of an antenna to detune. For this reason the antenna shaft and tip should be an RF link is vitally dependent upon the positioned as far away from such objects as possible. antenna. While adequate antenna 2. Optimum performance will be obtained performance can often be obtained by from a 1/4- or 1/2-wave straight whip trial and error methods, antenna design mounted at a right angle to the and matching is a complex task. A groundplane. In many cases this isn’t professionally designed antenna, such OPTIMUM NOT RECOMMENDED desirable for practical or ergonomic USEABLE as those offered by Linx, will help Figure 23: Linx Antennas reasons, thus, an alternative antenna ensure maximum performance and Part Figure 20: Groundplane Orientation style such as a helical, loop, patch, or 15 compliance. base-loaded whip may be utilized and the corresponding sacrifice in A receiver antenna should be optimized for the frequency or band in which the performance accepted. receiver operates and minimize the reception of off-frequency signals. The 3. If an internal antenna is to be used, keep it away from other metal components, efficiency of the receiver’s antenna is critical to maximizing range-performance. particularly large items like transformers, batteries, and PCB tracks and Unlike the transmitter antenna, where legal operation may mandate attenuation groundplanes. In many cases, the space around the antenna is as important as or a reduction in antenna efficiency, the receiver’s antenna should be optimized the antenna itself. Objects in close proximity to the antenna can cause direct as much as is practical. detuning, while those farther away will alter the antenna’s symmetry. It is usually best to utilize a basic quarter-wave whip until your prototype product VERTICAL λ/4 GROUNDED 4. In many antenna designs, particularly 1/4-wave is operating satisfactorily. Then other antennas can be evaluated based on the ANTENNA (MARCONI) whips, the groundplane acts as a counterpoise, E DIPOLE the cost, size and cosmetic requirements of the product. You may also wish to ELEMENT forming, in essence, a 1/2-wave dipole. For this review application note #00500 “Antennas: Design, Application, Performance". λ/4 reason adequate groundplane area is essential. I ANTENNA SHARING The groundplane can be a metal case or ground- fill areas on a circuit board. Ideally, it should have In cases where a transmitter and receiver GROUND PLANE a surface area > the overall length of the 1/4-wave VIRTUAL λ/4 λ/4 module are combined to form a transceiver DIPOLE V DD radiating element. This is often not practical due to it is often advantageous to share a single 0.1µF 0.1µF Transmitter size and configuration constraints. In these Module antenna. To accomplish this an antenna 0.1µF Figure 21: Dipole Antenna GND instances a designer must make the best use of switch must be used to provide isolation Antenna the area available to create as much groundplane in proximity to the base of the between the modules so that the full GND 0.1µF antenna as possible. When the antenna is remotely located or the antenna is transmitter output power is not put on the Receiver Module not in close proximity to a circuit board plane or grounded metal case or a small 0.1µF sensitive front end of the receiver. There is Select metal plate may be fabricated to maximize antenna performance. a wide variety of antenna switches available which are cost-effective and 5. Remove the antenna as far as possible from potential interference sources. Any straight-forward to use. Among the most frequency of sufficient amplitude to enter the receiver’s front end will reduce Figure 24: Typical Antenna Switch popular are switches from Alpha and NEC. system range and can even prevent reception entirely. Switching power Look for an antenna switch that has high isolation and low loss at the desired supplies, oscillators, even relays can also be significant sources of potential frequency of operation. Generally, the TX or RX status of a switch will be interference. The single best weapon against such problems is attention to controlled by a product's microprocessor, but selection may also be made placement and layout. Filter the module’s power supply with a high-frequency manually by the user. In some cases where the characteristics of the TX and RX bypass capacitor. Place adequate groundplane under potential sources of antennas need to be different or switch losses are unacceptable it may be more noise. Shield noisy board areas whenever practical. appropriate to utilize two discrete antennas. 6. In some applications it is advantageous to place the module and its antenna away from CONNECTOR OPTIONS CASE the main equipment. This avoids The FCC requires that antennas designed for use on Part 15 products be either interference problems and allows the GROUNDPLANE NUT permanently attached or utilize a unique and proprietary connector not available (MAY BE NEEDED) antenna to be oriented for optimum RF to the general public. In cases where the antenna needs to be removable, Linx performance. Always use 50Ω coax, such offers a full line of connectors designed to comply with these requirements. Figure 22: Remote Groundplane as RG-174, for the remote feed. Page 14 Page 15 COMMON ANTENNA STYLES ON-LINE RESOURCES There are literally hundreds of antenna styles and variations that can be employed with the LR receiver. Following is a brief discussion of the styles most commonly utilized. Additional antenna information can be found in Linx application notes #00500, #00100, #00125 and #00140. Linx also offers a broad line of antennas and connectors which offer outstanding performance and cost-effectiveness. www.linxtechnologies.com A whip-style antenna provides outstanding overall performance  Latest News Whip Style and stability. A low-cost whip is can be easily fabricated from a wire or rod, but most designers opt for the consistent  Data Guides performance and cosmetic appeal of a professionally made model. To meet this need, Linx offers a wide variety of straight  Application Notes and reduced height whip-style antennas in permanent and connectorized mounting styles.  Knowledge Base The wavelength of the operational frequency determines an antenna’s overall length. Since a full wavelength is often quite  Software Updates long, a partial 1/2- or 1/4-wave antenna is normally employed. If you have questions regarding any Linx product and have Internet access, Its size and natural radiation resistance make it well matched to Linx modules. The proper length for a straight 1/4-wave can be make www.linxtechnologies.com your first stop. Our website is organized in an 1/4-wave wire lengths easily determined using the formula below. It is also possible to for LC frequencies: intuitive format to give you the answers you need in record time. Day or night, reduce the overall height of the antenna by using a helical 315Mhz=8.9" the Linx website gives you instant access to the latest information regarding the winding. This reduces the antenna’s bandwidth, but is a great 418Mhz=6.7" products and services of Linx. It's all here: manual and software updates, way to minimize the antenna’s physical size for compact 433Mhz=6.5" application notes, a comprehensive knowledge base, FCC information and much applications. This also means that the physical appearance is not always an indicator of the antenna's frequency. more. Be sure to visit often! 234 Where: L = L=length in feet of quarter-wave length F MHz F=operating frequency in megahertz Specialty Styles Linx offers a wide variety of specialized antenna styles and www.antennafactor.com variations. Many of these styles utilize helical elements to reduce the overall antenna size while maintaining reasonable The Antenna Factor division of Linx offers performance. A helical antenna's bandwidth is often quite a diverse array of antenna styles, many of narrow and the antenna can detune in proximity to other which are optimized for use with our RF objects, so care must be exercised in layout and placement. modules. From innovative embeddable antennas to low-cost whips, domes to yagi's, and even GPS, Antenna Factor Loop Style A loop- or trace-style antenna is normally printed directly on a likely offers or can design an antenna to product's PCB. This makes it the most cost-effective of antenna meet your requirements. styles. The element can be made self-resonant or externally resonated with discrete components but its actual layout is usually product specific. Despite its cost advantages, PCB antenna styles are generally inefficient and useful only for short-range applications. Loop-style antennas are also very sensitive to changes in layout or substrate dielectric which can introduce www.connectorcity.com consistency issues into the production process. In addition, printed styles initially are difficult to engineer, requiring the use of Through its Connector City division, Linx offers a wide expensive equipment including a network analyzer. An improperly selection of high-quality RF connectors, including FCC- designed loop will have a high SWR at the desired frequency which compliant types such as RP-SMAs that are an ideal can introduce instability in the RF stages. match for our modules and antennas. Connector City focuses on high-volume OEM requirements, which Linx offers low-cost planar and chip antennas which mount directly allows standard and custom RF connectors to be offered to a product's PCB. These tiny antennas do not require testing and provide excellent performance in light of their compact size. They at a remarkably low cost. offer a preferable alternative to the often problematic "printed" antenna. Page 16 Page 17 ACHIEVING A SUCCESSFUL RF IMPLEMENTATION LEGAL CONSIDERATIONS Adding an RF stage brings an exciting new DECISION TO UTILIZE RF IS MADE dimension to any product. It also means that NOTE: LR Series modules are designed as component devices which RESEARCH RF OPTIONS additional effort and commitment will be needed to require external components to function. The modules are intended to allow ORDER EVALUATION KIT(S) for full Part 15 compliance, however, they are not approved by the FCC or bring the product successfully to market. By utilizing any other agency worldwide. The purchaser understands that approvals premade RF modules, such as the LR series, the TEST MODULE(S) WITH BASIC HOOKUP may be required prior to the sale or operation of the device, and agrees to design and approval process will be greatly utilize the component in keeping with all laws governing its use in the LINX MODULE IS CHOSEN simplified. It is still important, however, to have an country of operation. objective view of the steps necessary to ensure a INTERFACE TO CHOSEN CIRCUIT AND DEBUG successful RF integration. Since the capabilities of When working with RF, a clear distinction must be made between what is technically each customer vary widely it is difficult to recommend CONSULT LINX REGARDING ANTENNA OPTIONS AND DESIGN possible and what is legally acceptable in the country where operation is intended. one particular design path, but most projects follow Many manufacturers have avoided incorporating RF into their products as a result of LAY OUT BOARD steps similar to those shown at the right. uncertainty and even fear of the approval and certification process. Here at Linx our SEND PRODUCTION-READY In reviewing this sample design path you may notice desire is not only to expedite the design process, but also to assist you in achieving PROTOTYPE TO LINX FOR EMC PRESCREENING a clear idea of what is involved in obtaining the necessary approvals to legally market that Linx offers a variety of services, such as antenna OPTIMIZE USING RF SUMMARY your completed product. design and FCC prequalification, that are unusual for GENERATED BY LINX a high-volume component manufacturer. These In the United States the approval process is actually quite straightforward. The SEND TO PART 15 services, along with an exceptional level of technical TEST FACILITY regulations governing RF devices and the enforcement of them are the responsibility of the Federal Communications Commission. The regulations are contained in the support, are offered because we recognize that RF is RECEIVE FCC ID # Code of Federal Regulations (CFR), Title 47. Title 47 is made up of numerous a complex science requiring the highest caliber of COMMENCE SELLING PRODUCT volumes, however, all regulations applicable to this module are contained in volume products and support. “Wireless Made Simple” is 0-19. It is strongly recommended that a copy be obtained from the Government more than just a motto, it’s our commitment. By TYPICAL STEPS FOR Printing Office in Washington, or from your local government book store. Excerpts of choosing Linx as your RF partner and taking IMPLEMENTING RF applicable sections are included with Linx evaluation kits or may be obtained from advantage of the resources we offer, you will not only the Linx Technologies web site (www.linxtechnologies.com). In brief, these rules survive implementing RF, you may even find the process enjoyable. require that any device which intentionally radiates RF energy be approved, that is, tested, for compliance and issued a unique identification number. This is a relatively HELPFUL APPLICATION NOTES FROM LINX painless process. Linx offers full EMC pre-compliance testing in our HP/Emco- equipped test center. Final compliance testing is then performed by one of the many It is not the intention of this manual to address in depth many of the issues that independent testing laboratories across the country. Many labs can also provide should be considered to ensure that the modules function correctly and deliver other certifications the product may require at the same time, such as UL, CLASS the maximum possible performance. As you proceed with your design you may A/B, etc. Once your completed product has passed, you will be issued an ID number wish to obtain one or more of the following application notes, which address in which is then clearly placed on each product manufactured. depth key areas of RFdesign and application of Linx products.These Questions regarding interpretations of the Part 2 and Part 15 rules or measurement applications notes are available on-line at www.linxtechnologies.com or by procedures used to test intentional radiators, such as the LR modules, for contacting the Linx literature department. compliance with the Part 15 technical standards, should be addressed to: Federal Communications Commission Equipment Authorization Division NOTE # LINX APPLICATION NOTE TITLE Customer Service Branch, MS 1300F2 7435 Oakland Mills Road 00100 RF 101: Information For The RF Challenged Columbia, MD 21046 Tel: (301) 725-1585 / Fax: (301) 344-2050 E-Mail: labinfo@fcc.gov 00125 Considerations For Operation In The 260MHz to 470MHz Band International approvals are slightly more complex, although many modules are designed to allow all international standards to be met. If you are considering the 00130 Modulation Techniques For Low-Cost RF Data Links export of your product abroad, you should contact Linx Technologies to determine the specific suitability of the module to your application. 00140 The FCC Road: Part 15 From Concept To Approval All Linx modules are designed with the approval process in mind and thus much of 00150 Use And Design Of T-Attenuation Pads the frustration that is typically experienced with a discrete design is eliminated. Approval is still dependent on many factors such as the choice of antennas, correct 00232 General Considerations For Sending Data With The LC Series use of the frequency selected, and physical packaging. While some extra cost and design effort are required to address these issues, the additional usefulness and 00500 Antennas: Design, Application, And Performance profitability added to a product by RF makes the effort more than worthwhile. Page 18 Page 19 WIRELESS MADE SIMPLE U.S. CORPORATE HEADQUARTERS: LINX TECHNOLOGIES, INC. 575 S.E. ASHLEY PLACE GRANTS PASS, OR 97526 Phone: (541) 471-6256 FAX: (541) 471-6251 http://www.linxtechnologies.com Disclaimer Linx Technologies is continually striving to improve the quality and function of its products. For this reason, we reserve the right to make changes without notice. The information contained in this Data Sheet is believed to be accurate as of the time of publication. Specifications are based on representative lot samples. Values may vary from lot to lot and are not guaranteed. Linx Technologies makes no guarantee, warranty, or representation regarding the suitability of any product for use in a specific application. None of these devices is intended for use in applications of a critical nature where the safety of life or property is at risk. The user assumes full liability for the use of product in such applications. Under no conditions will Linx Technologies be responsible for losses arising from the use or failure of the device in any application, other than the repair, replacement, or refund limited to the original product purchase price. Some devices described in this publication are patented. Under no circumstances shall any user be conveyed any license or right to the use or ownership of these patents. © 2003 by Linx Technologies, Inc. The stylized Linx logo, Linx, and “Wireless Made Simple” are the trademarks of Linx Technologies, Inc. Printed in U.S.A. Page 20