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] 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