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Linx HP SERIES-II, Design Manual

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Linx HP SERIES-II Design Manual Download Page 19

Page 19

ANTENNA SHARING

Many times when a transmitter
and receiver module are
combined to form a
transceiver the designer will
find it advantageous for the
modules to share a single
antenna. To accomplish this an
antenna switch must be used
to provide isolation between
each of the modules. There
are a wide variety of antenna
switches available which are
cost-effective and straight-
forward to use. Among the most
popular are switches from Alpha, Motorola, Philips, TriQuint, and NEC. Look for
an antenna switch that has high isolation and low loss at the desired frequency
of operation. Generally, the TX or RX status of a switch will be controlled by a
product’s microprocessor, but selection may also be made manually by the user.
In some cases where the characteristics of the TX and RX antennas need to be
different or switch losses are unacceptable the designer may find it more
practical to utilize two discrete antennas.

LINX ANTENNA OPTIONS

Linx offers a full line of antennas which
are optimized for the frequencies at
which our modules operate.

The

antennas are cost-effectively priced in
volume and designed to maximize the
performance of your product. For
complete details,visit the Linx website at
www.linxtechnologies.com, or contact
the Linx literature department at
(800)736-6677.

Antenna

Transmitter

Module

Receiver

Module

0.1

µ

F

0.1

µ

F

0.1

µ

F

0.1

µ

F

0.1

µ

F

GND

GND

VDD

Select

Figure 20: Typical Antenna Switch 

;;;

;;;

;;;

yyy

yyy

yyy

;;;

;;

;

;;;

yyy

yy

y

yyy

;;;;;;;;;;

;;;;;;;;; ;

;

;;;;;;;; ;

;;;;;;;;;;

yyyyyyyyyy

y

yyyyyyyy y

y

yyyyyyyy y

yyyyyyyyyy

Part 15-Compliant Connectors

LINX CONNECTOR OPTIONS

The FCC requires that antennas designed for use on Part 15 products be either
permanently attached, or utilize a unique and proprietary connector not available
to the general public. Linx offers a full line of connectors designed to comply with
these requirements. To insure the continued compliance of these connectors,
details are not available on our website. However, complete connector
specifications may be obtained by contacting the Linx literature department at
(800)736-6677.

Summary of Contents for HP SERIES-II

Page 1: ...eiver module is designed for the cost effective high performance wireless transfer of analog or digital data in the popular 902 928MHz band The receiver offers eight selectable channels and when paired with an HP Series II transmitter is capable of receiving analog and digital information for distances up to 1000 feet under optimum conditions The receiver employs an advanced microprocessor control...

Page 2: ...2 Noise Bandwidth N3DB 280 KHz Data Bandwidth 300 50 000 Bps Audio Bandwidth 50 25 000 Hz Sensitivity 92 95 100 dBm 3 DC Modulation Sensitivity 88 dBm 4 RSSI Dynamic Range 60 70 80 dB Gain GRSSI 24 mV dB Voltage No Carrier 1 6 mV Spurious Emmissions 45 dBm Interference Rejection Half FC Spurious 60 dB FC 1MHz 20 dB SPECIFICATIONS 1 Over full operating voltage 2 Depends on CS0 CS2 voltage levels 3 ...

Page 3: ...ents are grouped on the front Pin 1 is on the far left of the board when viewed from the front PRODUCTION CONSIDERATIONS The SIP module may be installed using hand or wave solder techniques The module should not be subjected to reflow If the module is subject to production wash cycles adequate drying time should be allowed prior to power up If the wash cycle introduces contaminants the module s pe...

Page 4: ...transmitter is high This time is shown in figure 8A as T1 In short T1 is the maximum time required for the data output of the receiver to be valid once the transmitter s CTS pin goes high This assumes that the receiver is already powered up T2 The minimum baud rate of the HP II receiver is 300 baud assuming that the serial data is 10 bits including a start and stop bit each of opposite polarity Th...

Page 5: ...lect 1 CS1 CS1 Channel Select 2 Received Signal Strength Indicator Digital Ground Voltage Input 2 7 16V 1V p p Analog Output Digital Data Output Power down Active Low CS2 CS2 PDN RSSI RSSI Gnd VCC Analog Out Data Out N C 1 2 8 9 10 11 12 13 14 15 16 17 18 50Ω 4 7K VIN PDN 470K VIN 10K 10K 10K PIN DESCRIPTIONS Figure 9 Pin functions and equivalent circuits ...

Page 6: ...stortion at the receiver s analog output pin The user supplied antenna is connected at pin 1 see Figure 1 The HP II RXM RF port is matched to 50 ohms to support interface to commonly available antennas such as those manufactured by Linx The RF signal coming in from the antenna is filtered by a SAW surface acoustic wave filter The purpose of the SAW BPF is to attenuate unwanted RF energy i e not in...

Page 7: ...lbert multiplier The output of the IF strip is a demodulated waveform that after filtering very closely resembles the original waveform used to modulate the transmitter A high performance active low pass filter cleans up the audio signal removing all of the unwanted noise from the FM demodulation process The output of this filter is provided to the audio output pin and to the BitPERFECT bit slicer...

Page 8: ...laid over so that the side with the crystal is closest to the PC board and the RF side is facing away from the PC board The trace from the receiver to the antenna should be kept as short as possible A simple trace is suitable for runs up to 1 4 inch for antennas with wide bandwidth characteristics For longer runs or to avoid detuning a high Q narrow bandwidth antenna such as a helical use a 50 ohm...

Page 9: ...rocessor reads the external channel selection lines and sets the frequency synthesizer to the appropriate channel Once the frequency synthesizer has locked on to the selected channel s frequency the receiver is ready to accept data Figure 4 on Pg 3 shows the typical turn on response time for an HP Series II receiver The response time was measured by connecting the module s RF input to a signal gen...

Page 10: ...f reducing receiver power consumption is to turn the receiver off via the PDN pin for some time interval and wake the receiver periodically to check for the presence of a transmitted signal In order to implement this method with an HP II receiver successfully there are some timing requirements the user must observe when powering up the receiver to check for channel activity At power up the receive...

Page 11: ...eive data When the RF signal input level is below the DC modulation sensitivity but above the data sensitivity the receiver s output will contain valid data when the incoming carrier is modulated However in this condition the receiver may not hold a continuous high level on the data output when the carrier is not being modulated This feature is unique to the HP Series II and is designed to support...

Page 12: ...tter or receiver is active at any time When combined with certain high gain antennas the HP II transmitter can in close proximity exceed 10dBm power into the receiver Since the receiver does not incorporate an AGC this can result in poor performance or complete shutdown of the receiver This effect occurs when both the transmitter and receiver have the high gain antennas connected and are in close ...

Page 13: ...ntaneous increase in output power If the carrier is AM modulated or OOK modulated in the case of data the RSSI pin can be used for demodulation If your application requires that you accurately measure the incoming signal strength distance measurement for example then you must calibrate the RSSI circuit on a receiver by receiver basis The calibration process is simple Using a signal generator injec...

Page 14: ...plication For instance high rate data communications would require a BER of 1 5 where a low rate data application with redundant data transmission may only require a BER of 1 2 Based on the sensitivity characterization of the HP II receiver and the output power of the transmitter as legally allowed by the FCC a path loss model can be used to show that the open field range of an HP II link can exce...

Page 15: ... antenna in order to achieve full legal power while meeting size cost or cosmetic objectives For this reason a transmitter s antenna can generally be less efficient than the antenna used on the receiver THE RECEIVER ANTENNA A receiving antenna should give its optimum performance at the frequency or in the band for which a receiver was designed and capture as little as possible of other off frequen...

Page 16: ...to enter the receiver s front end will reduce system range cause increased bit errors and can even prevent reception entirely There are many possible sources of internally generated interference Switching power supplies oscillators even relays can also be significant sources of potential interference Here again the single best weapon against such problems is attention to placement and layout Filte...

Page 17: ... frequency to be received or transmitted determines an antenna s length Since an antenna has a dielectric constant greater than that of free space the velocity of a wave on the antenna is slower This fact along with several other factors has led antenna designers to accept the formula below as an accurate starting point for determining the physical length of a half wave antenna The resultant lengt...

Page 18: ... want to have a loop professionally designed and optimized PARAMETER LOOP HELICAL WHIP Ultimate performance Ease of design setup Size Immunity to proximity effects HP II Range open ground to similar antenna 400 ft 600 ft 1 000 ft FAIR GOOD EXCELLENT HP Antenna Selection Chart Helical Style A helical is a wire coil usually wound from steel copper or brass This antenna is very efficient given its sm...

Page 19: ...rete antennas LINX ANTENNA OPTIONS Linx offers a full line of antennas which are optimized for the frequencies at which our modules operate The antennas are cost effectively priced in volume and designed to maximize the performance of your product For complete details visit the Linx website at www linxtechnologies com or contact the Linx literature department at 800 736 6677 Antenna Transmitter Mo...

Page 20: ... other certifications the product may require at the same time such as UL CLASS A B etc Once your completed product has passed you will be issued an ID number which is then clearly placed on each product manufactured Questions regarding interpretations of the Part 2 and Part 15 rules or measurement procedures used to test intentional radiators such as the HP II modules for compliance with the Part...

Page 21: ...vive implementing RF but you may even find the process enjoyable DECISION TO UTILIZE RF IS MADE RESEARCH RF OPTIONS LINX MODULE IS CHOSEN ORDER EVALUATION KIT S TEST MODULE S WITH BASIC HOOKUP INTERFACE TO CHOSEN CIRCUIT AND DEBUG CONSULT LINX REGARDING ANTENNA OPTIONS AND DESIGN LAY OUT BOARD SEND PRODUCTION READY PROTOTYPE TO LINX FOR EMC PRESCREENING OPTIMIZE USING RF SUMMARY GENERATED BY LINX ...

Page 22: ...561 7 794 3 1588 7 9 7 943 56 0 630 2 891 3 1782 5 10 10 000 57 0 707 1 1000 0 2000 0 11 12 589 58 0 793 4 1122 0 2244 0 12 15 849 59 0 890 2 1258 9 2517 9 13 19 953 60 0 998 8 1412 5 2825 1 14 25 119 61 0 1120 7 1584 9 3169 8 15 31 623 62 0 1257 4 1778 3 3556 6 16 39 811 63 0 1410 9 1995 3 3990 5 17 50 119 64 0 1583 0 2238 7 4477 4 18 63 096 65 0 1776 2 2511 9 5023 8 19 79 433 66 0 1992 9 2818 4 ...

Page 23: ... 50 12 5 030 2 57 55 33 44 67 4 419 2 20 60 19 39 81 3 946 1 90 64 52 35 48 3 570 1 65 68 38 31 62 3 010 1 26 74 88 25 12 2 615 0 97 80 05 19 95 2 323 0 75 84 15 15 85 2 100 0 58 87 41 12 59 1 925 0 46 90 00 10 00 1 433 0 14 96 84 3 16 1 222 0 04 99 00 1 00 1 119 0 01 99 68 0 32 1 065 0 00 99 90 0 10 1 034 0 00 99 97 0 03 1 020 0 00 99 99 0 01 MISMATCH CONVERSION TABLE NOTES ...

Page 24: ...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 applicatio...

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