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| radiometrix ltd., nim1b transceiver data sheet page 1 features ?? conforms to en 300 220-3 and en 301 489-3 (10mw version only) ?? compliant with fcc part 90 and part 95 (murs) ?? standard frequency 154.570mhz or 154.600mhz (re-programmable) ?? other frequencies from 120mhz to 175mhz ?? data rates up to 5kbps for standard module ?? usable range over 1km ?? fully screened ?? low power requirements ?? 25khz channel spacing ?? feature-rich interface (true analogue and/or digital baseband) the nim1b is a half duplex radio transceiver modul e for use in long range bi-directional data transfer applications at ranges up to 1kilometres. the modul e operates on the us 154mhz murs band allocation. nim1b is also available as separate nim1bt transmi tter and nim1br receiver, which can be, used as dual- in-line equivalents of tx1 transmitter and rx1/nrx1 receiver respectively. applications ?? multi-use radio service (murs) ?? industrial telemetry and telecommand ?? high-end security systems ?? vehicle data up/download ?? rov/machinery controls technical summary ?? fully integrated sigma-delta pll synthesizer based design ?? high stability tcxo reference ?? data bit rate: 5kbps max. ?? transmit power: +13dbm (20mw) ?? image rejection: >70db ?? receiver sensitivity: -120dbm (for 12db sinad) ?? rssi output with >50dbm range ?? supply: 3.3v - 15v @ 30ma transmit, 18ma receive ?? dimensions: 33 x 23 x 11mm (fully screened) evaluation platforms : nbek + bim / smx carrier the narrow band nim1b transceiver offers a low power, reliable data link in a radiometrix transceiver standard pin ou t and footprint. the nim1b is a frequenc y p rogrammable, narrowband design, suitable for licensed and unlicensed vh f allocations, fcc part 90 and part 9 5 (murs) operations. frequency programmable 25khz nbfm vhf transceiver hartcran house, 231 kenton lane, harrow, middlesex, ha3 8rp, england tel: +44 (0) 20 8909 9595, fax: +44 (0) 20 8909 2233, www.radiometrix.com issue 2, 09 february 2018 nim1b figure 1: nim1b (murs)
radiometrix ltd., nim1b transceiver data sheet page 2 figure 2: nim1b schematic s radiometrix ltd., nim1b transceiver data sheet page 3 functional description the transmit section of the nim1b consists of a highl y integrated sigma delta (f ractional n) synthesizer based single chip rf device, configured over an spi se rial bus by an on-board microcontroller. the primary frequency reference for the transmitter is a 30mhz vc-tcxo. modulation is applied directly to this reference via an af baseband filter (rather than using the chip's internal modulator) to permit a wider range of baseband data rates and waveforms. operation is controll ed by the n_txe line, the transmitter achieving full rf output typically within 5ms of this line being pull ed low. the rf output is filtered to ensure compliance with the appropriate radio regulations and fed to the 50 ? antenna pin. the receiver section of the nim1b consists of a hi ghly integrated sigma delta (f ractional n) synthesizer based local oscillator (lo), configured over an spi se rial bus by an on-board microcontroller. the primary frequency reference for the lo is a 26mhz tcxo. the remainder of the receiver is a conventional dual conversion super-heterodyne, using a wide dynamic range dual gate mosfet mi xer and crystal / ceramic filter elements for optimum performance. the rf input is filtered using a multi- stage lc filter in the front end to provide image rejection and enhanced blocking perform ance. this reduces the user programmable frequency range to the filter passband, but can easily be re-banded (in the factory) to other frequencies. user interface 18 17 16 15 14 13 12 11 10 0 volt vcc n_txe txd af rxd rssi 0 volt 1 2 3 4 5 6 7 8 9 rf gnd antenna rf gnd rf in (rx)* rf out (tx)* no pin 33 mm 30.48 mm 23 mm 11 mm side view (through can) top view (without can) side view (with can) recommended pcb hole size: 1.2 mm module footprint size: 25 x 32 mm pin pitch: 2.54 mm pins 4, 5, 6, 7, 8 & 9 are not fitted figure 3: nim1b pin-out and dimension nim1b pin name function 1, 3, 10, 18 0v ground 17 vcc 3.3 ? 15v dc power supply 16 n_rxe / rx pgm pull low to enable receiver / receive programming in put 15 n_txe / tx pgm pull low to enable tr ansmitter / transmit programming in put 14 txd dc coupled input for 3v cmos logic. r in = 100k ? 13 af 500mv pk-pk audio. dc coupled, approx 1.5v bias 12 rxd open collector output, with a 10k ? pullup to vcc. suitable for biphase codes 11 rssi dc level between 0.5v and 2v. 50db dynamic range notes : 1. n_rxe and n_txe have (10k approx.) pullups to +vin 2. unit is programmable (in much the same way as an ntx2b or nrx2b) using the n_rxe or n_txe pins reprogramming requires a 0v to +vin logic level non-inverted rs232 data-stream to pin 3 or 4 alternatively. an rs232 port can be directly connect ed to the enable pin for programming, without risk 3. avoid n_rxe and n_txe both low: undefined module operation may occur (but damage will not result) 4. pinout is as bim1. on rf connector end only pins 1,2,3 are present (*except for nim1b with separate rx and tx ports which has 4 pins. see ordering info ( p12) for further details on this special build). 5. switching time as controlled by n_txe or n_rxe pi ns is <5ms, but when power is first applied to the unit there is a 20ms long ?calibration? peri od before the transmitter becomes active. if the rail is switched (as opposed to the en pins ) then this should be considered as a 25ms device radiometrix ltd., nim1b transceiver data sheet page 4 absolute maximum ratings exceeding the values given below may cause permanent damage to the module. operating temperature -20 ? c to +70 ? c storage temperature -30 ? c to +85 ? c rf in (pin 1) ? 50v @ <10mhz, +13dbm @ >10mhz all other pins -0.3v to +15.0v performance specifications : (vcc = 5v / temperature = 20 ? c unless stated) general pin min. typ. max. units notes dc supply supply voltage 17 3.3 - 15 v tx supply current (20mw) 17 30 ma rx supply current 17 18 ma antenna pin impedance 2 50 ? rf centre frequency 154.570 / mhz 1 154.600 mhz channel spacing 25 khz number of channels 1 1 transmitter rf rf power output 2 +12 +13 +14 dbm 2 spurious emissions 2 -50 dbm 3 adjacent channel tx power -37 dbm frequency accuracy ? 1.5 (5ppm) khz 4 fm deviation (peak) ? 2.5 ? 3.0 ? 3.5 khz 5 baseband modulation bandwidth @ -3db 0 3.5 khz dc coupled txd input level (logic low) 14 0 v 6 txd input level (logic high) 14 3.0 v 6 dynamic timing tx select to full rf 5 ms receiver rf/if rf sensitivity @ 12db sinad 2, 13 -120 dbm rf sensitivity @ 1ppm ber 2, 12 -112 dbm rssi range 2, 11 50 50 db 7 blocking 2 84 db image rejection 2 70 db adjacent channel rejection 2 63 db 3 spurious response rejection 2 70 db lo leakage, radiated -70 dbm 4 baseband baseband bandwidth @ -3db 13 5 khz af level 13 500 mv p-p 8 dc offset on af out 13 1.5 v distortion on recovered af 12 5 % radiometrix ltd., nim1b transceiver data sheet page 5 general pin min. typ. max. units notes dynamic timing rx enable with signal present n_rxe active (low) to stable af output 16, 13 10 n_rxd active (low) to stable rxd output 16, 12 25 ms signal applied with receiver enabled signal to valid af 2, 11 10 ms signal to stable data 2, 12 25 ms notes: 1. programs to any 154mhz murs 25khz bandwidth frequencies 2. measured into 50 ? resistive loads. 3. exceeds en/emc requirements at all frequencies. 4. 5ppm tcxo. total over full supply and temperature range. 5. with 0v ? 3.0v modulation input. 6. to achieve specified fm deviation. 7. see applications information for further details. 8. for received signal with ? 3khz fm deviation. channel programming at the heart of the device is a fractional n synthesiz er locked to a high stability vcxo. the minimum step size of this pll is (approximately) 4.8hz the data required by the pll consists of two coefficient s: the integer (inte) and t he fraction (frac). output frequency relates to these values thus: nim1b uses 30mhz vctcxo and the output divider (outdiv) value for 140mhz - 175mhz band is 24 (corresponding to a programmed ?band? value of 0x0d. see page 7) for correct operation, the component (frac / 2 19 ) must have a value between 1 and 2 in interface terms, these coefficients are expressed as a 32-bit binary word (eight hexadecimal digits) where the most significant byte comprises the integer val ue, and the remaining three bytes (24 bits) make up the "fraction" inte = 61-1 = 60 (0x3c) frac = (0.828 +1) ? 524288 = 958398 (0x0e9fbe) frac2 = 0x0e frac1 = 0x9f frac0 = 0xbe radiometrix ltd., nim1b transceiver data sheet page 6 however, the frequency programmed into the receiver section is the local oscillator (lo) frequency, not the actual channel frequency, and the reference frequenc y is 26mhz rather than 30mhz, so some of the calculations are also different (for example, the minimum step size is approximately 4.1hz) for unit operating on a channel frequency of 163mhz or hi gher, the local oscillator is 21.4mhz below the carrier (so subtract 21.4mhz). af output w ill be inverted on higher receive frequency units. for units operating on frequencies below 156mhz, the local oscillator is 21.4mhz above the channel. receivers operating between 156 and 163mhz (and trans mitters below 142mhz) are a special case. these are fitted with a different lo chip (an si 4464 instead of an si4060), which has a coverage of 119 to 159mhz, allowing conventional low side injection to be maintained inte = 70-1 = 69 (0x45) frac = (0.388 +1) ? 524288 = 727712 (0x0b1aa0) frac2 = 0x0b frac1 = 0x1a frac0 = 0xa0 when programming the nim1b, keep in mind that the uni t maintains in sram the current values of all programmable values (frequency, band of operation, rf power and frequency offset adjustments values) and that toggling the pgm pin does not erase or corrupt them. these values are only loaded from eeprom at cold st art power-up (but not when the relevant n_txe or n_rxe pins are cycled) there is one "write all values to eeprom" command. it is usually necessary to load the relevant current operating ram value(s) and then issue a suitabl e command to write the ram value to eeprom. the nim1b stores frequency coefficients (for trans mit and receive), frequency offsets, band select and tx rf power level constants in internal eproms. always remember that the transmit and receive sections of the nim1b are independant, and are progra mmed entirely separately . no command sent to the transmitter will have any effect on the receiver, and vice-versa. for the nim1b rx section, power level should always be set to 3 programming a value or coefficient over the serial bus over-writes the previous value and implements this change on the pll immediately, but does not change the eeprom contents until a relevant "program eeprom" command is issued in general, the most recent stimulus receiv ed by the unit will decide the operating frequency. whenever a frequency coefficient is programmed into the unit, the frequenc y will change immediately to this new value regardless of other modes or operation. this is the simplest and most flexible means of controlling the unit. radiometrix ltd., nim1b transceiver data sheet page 7 serial interface commands nim1b is programmable (in the same way as an ntx2b or nrx2b, or a nim2b) using the n_rxe or n_txe pins. reprogramming requires a 0v to +vin logic le vel non-inverted rs232 data-stream to pin 3 (rx pgm) or 4 (tx pgm). an rs232 port can be directly connected to the enable pin for programming. the serial data should be in the following format: 9600bps, 8 data bits, no parity, 1 stop every command string starts with the phrase "@ prg_" and terminated with carriage return radiometrix ltd., nim1b transceiver data sheet page 8 applications information power supply requirements the nim1b have built-in regulators, which deliver a const ant 3.3v to the transmitter and the receiver circuitry when the external supply voltage exceeds 3.3v. this ensures constant perfo rmance up to the maximum permitted rail, and removes the need for external supply dec oupling, except in cases where the supply rail is extremely poor (ripple/noise content >0.1vp-p). the unit will continue to function with a 3v supply, but power output will fall 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 mu st be added in series with the txd input to limit the modulating input voltage to a maximum of ar ound 3v on pin 14. txd input resistance is 100k ? to ground, giving typical required resistor values as follows: vcc series resistor ? 3v 3.3v 5v 9v - 10 k ? 68k ? 220k ? rx received signal strength indicator (rssi) the nim1b wide range rssi which measures the str ength of an incoming signal over a range of 50db or more. this allows assessment of link quality and avail able margin and is useful when performing range tests. the output on pin 11 of the module has a standing dc bias of up to 0.5v (approx.) with no signal, rising to around 2.0v at maximum indication. (vmin-vmax) is typically 1v and is largely independent of standing bias variations. output impedance is 56k ? . pin 11 can drive a 100 ? a meter directly, for simple monitoring. please note that the actual rssi voltage at any giv en rf input level varies somewhat between units. the rssi facility is intended as a relative indicator only - it is not designed to be, or suitable as, an accurate and repeatable measure of absolute signal le vel or transmitter-receiver distance. typical rssi characterist ic is as shown below: figure 4: rssi level with respect to received rf level at nim1b antenna pin radiometrix ltd., nim1b transceiver data sheet page 9 expected range predicting the range obtainable in any gi ven situation is notoriously difficu lt 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 reflecti ons from nearby conductive objects ?? data rate and degree of filtering employed the following are typical examples ? but range test s should always be performed before assuming that a particular range can be achiev ed in a given situation: data rate tx antenna rx antenna environment range 5kbps half-wave half-wave rural/open 3-4km 5kbps helical half-wave urban/obstructed 500m-1km 5kbps helical helical in-building 100-200m the nim1b txd input is normally driven directly by l ogic signals, but will also accept analogue drive (e.g. 2- tone signalling). in this case the txd pin can either be directly dc driven with a 3v pp waveform with a 1.5v centre point, or a 3v pp signal can be ac coupled (when t he input circuits will self-bias to 1.5v). do not exceed 3v pp, or the baseband waveform will begin to c lip. the vc-tcxo in the nim1b is highly linear, and tx distortion figures well under 5% should be seen. at the other end of the link the nim1b af output (or the rxd pin) may be used to drive an external dec oder or other signal processing circuitry. although the modulation bandwidth of the nim1b ext ends down to dc it is not advisable to use data containing a dc component. this is because frequenc y errors and drifts between the transmitter and receiver occur in normal operation, resulting in dc offset errors on the nim1b audio output. the nim1b in standard form incorporates a low pass filt er with a 3.5khz nominal bandwidth. this is suitable for transmission of data at raw bit rates up to 5kbps. in applications such as long range fixed links where data speed is not of prime concern, a considerable increase in range can be obtained by using the slowest po ssible data rate together with filtering to reduce the receiver bandwidth to the minimum necessary. antennas the choice and positioning of transmitter and receiver ant ennas 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 t he larger externally-mounted types and hence tend to be effective only over limited ranges. they do however re sult in physically compact equipment and for this reason are often preferred for portable applications. part icular 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 ant enna 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 ant enna 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 t he antenna is as important as the antenna itself. 2. microprocessors and microcontrollers tend to radi ate significant amounts of radio frequency hash which can cause desensitisation of the re ceiver 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 tra cking. in extreme cases system range may be reduced by a factor of 5 or more. to minimise any adver se effects situate antenna and module as far as possible radiometrix ltd., nim1b transceiver data sheet page 10 from any such circuitry and keep pcb track lengt hs to the minimum possible. a ground plane can be highly effective in cutting radiated interf erence and its use is strongly recommended. a simple test for interference is to monitor the re ceiver rssi output voltage, which should be the same regardless of whether the microcontroller or ot her logic circuitry is running or in reset. 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 effect ive antenna formed from a coil of wire. it is very efficient for its size, but because of its high q it su ffers badly from detuning caused by proximity to nearby conductive objects and needs to be care fully 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 5cm 2 ), tuned and matched with 2 capacitors. loops are re latively 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: whip helical loop ultimate performance *** ** * ease of design set-up *** ** * size * *** ** immunity to proximity effects ** * *** helical antenna rf loop antenna rf gnd rf c tune c match capacitors may be variable or fixed (values depend on loop dimensions) track width = 1mm min. area 500mm 2 whip antenna 463mm @ 154mhz rf wire, rod, pcb track or a combination of these length(mm) = 71250 / freq(mhz) trim wire length or expand coil for best results 35-40 turns wire spring length 120mm, dia 10mm figure 5: integral antenna configurations external antennas these have several advantages if portability is not an i ssue, 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 t he integral type mentioned above, commercially- available helical antennas normally have the coil elem ent protected by a plas tic moulding or sleeve and incorporate a coax connector at one end (usually a st raight or right-angle bnc type). these are compact radiometrix ltd., nim1b transceiver data sheet page 11 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 elem ent usually consists of a stainless steel rod or a wire contained within a semi-flexible moulded pl astic jacket. various mounting options are available, from a simple bnc connector to wall brackets, th rough-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 bas e of the whip out to a radius of 300mm or more (under these conditions performance appr oaches that of a half-wave dipole) but even relatively small metal areas will produce a worthwhile improvement over t he whip alone. the ground plane should be electrically connected to the coax outer at the bas e of the whip. magnetic mounts are sli ghtly different in that they rely on capacitance between the mount and the metal surface to achieve the same result. 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 50 ? coax feed can be achieved if the elements are angled downwards at approximately 30-40 ? to the horizontal. fig.6: 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 wh ips mounted in line vertically and fed in the centre with coaxial cable. the bottom whip takes the pl ace of the ground plane described previously. a variant is available using a helical instead of a whip fo r the lower element, giving similar performance with reduced overall length. this antenna is suitable for m ounting on walls etc. but for best results should be kept well clear of surrounding conductive objec ts and structures (ideally >1m separation). 2. the end-fed half wave is the same length as the dipol e but consists of a single rod or whip fed at the bottom via a matching network. mounting options ar e 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 m ount in the clear and above surrounding obstructions. yagi. this antenna consists of two or more elements m ounted 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. please note: using a yagi or other gain antenna with the nim1b will exceed the maximum radiated power permitted by uk type approval regulations. it can be us ed in the uk only in conjunction with the nim1br receiver. for best range, in fixed link applications use a half- wave antenna on nim1bt transmitter and a half-wave or yagi on nim1br receiver, both mounted as high as possible and clear of obstructions. 50 ?? coax feed metal ground plane 50 ?? coax feed 3 0 - 4 0 d e g . ( 3 - 4 , e qu a l ly sp aced) 1/ 4-w a ve rad ial e l e men ts 1/4-wave whip (463mm long @ 154mhz) 1/4-wave whip radiometrix ltd., nim1b transceiver data sheet page 12 good rf layout practice should be observed. if the connection between module and antenna is more than about 20mm long use 50 ? 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. module mounting considerations good rf layout practice should be observed. if the connection between module and antenna is more than about 20mm long use 50 ? 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 nim1bt transmitters, nim1br receivers and nim1 b transceivers are manufactured in the following variants as standard: at 154.570 mhz : nim1b-154.570-5 transceiver nim1bt-154.570-5 transmitter nim1br-154.570-5 receiver at 154.600 mhz : nim1b-154.600-5 transceiver nim1bt-154.600-5 transmitter nim1br-154.600-5 receiver (depending on the built state, nim1b can be reprogr ammed on any frequencies with in the 120 - 175mhz band) nim1b with separate tx and rx rf ports: nim1b-154.570-5-tr the nim1b can be factory built with separate rx and tx ports. this special built will have 4 pins on the rf connector instead of three (refer to figure 3) pin 1 rf gnd 2 rf out (tx) 3 rf gnd 4 rf in (rx) the rf in (rx) port must be externally ac coupled, as it has a bias voltage on it this is useful if an application requires using an exte rnal tx power amp, rx pr e-amp, or separate antennas tx and rx. radiometrix ltd hartcran house 231 kenton lane harrow, middlesex ha3 8rp england tel: +44 (0) 20 8909 9595 fax: +44 (0) 20 8909 2233 sales@radiometrix.com www.radiometrix.com copyright notice this product data sheet is the orig inal work and copyrighted property of radiometrix ltd. reproduction in whole or in part must give clear a cknowledgement to the copyright owner. limitation of liability the information furnished by radiometrix ltd is be lieved 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 lt d does not assume any liability arising from the application or use of any product or circuit described herein, nor for any infri ngements of patents or other rights of third parties which may result from the us e 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 fini shed product on the market under the provisions of the r&tte directive. equipment within the scope of the r&tte di rective 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/ information requests ofcom riverside house 2a southwark bridge road london se1 9ha tel: +44 (0)300 123 3333 or 020 7981 3040 fax: +44 (0)20 7981 3333 information.requests@ofcom.org.uk european communications office (eco) peblingehus nansensgade 19 dk 1366 copenhagen tel. +45 33896300 fax +45 33896330 ero@ero.dk www.ero.dk |
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