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TH71112
Receiver - 868/915MHz FSK/ASK, Double-Conversion Superhet (LQFP32)
 Download TH71112 Datasheet (PDF)
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TH71112 General Description
The TH71112 FSK/ASK double-conversion superheterodyne receiver IC is designed for applications in the European 868 MHz industrial-scientific-medical (ISM) band, according to the EN 300 220 telecommunications standard. It can also be used for any other system with carrier frequencies ranging from 750 MHz to 990 MHz (e.g. for applications according to FCC part 15).
TH71112 Features and Benefits
- Double-conversion superhet architecture for high degree of image rejection
- FSK demodulation with phase-coincidence demodulator
- Low current consumption in active mode and very low standby current
- Switchable LNA gain for improved dynamic range
- RSSI allows signal strength indication and ASK detection
- 32-pin Low profile Quad Flat Package (LQFP)
TH71112 Environmental Information
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TH71112 Frequently asked Questions
TH7108
Question
Hello guys, and thanks for the replies.
Yes, my volume is low (just a proto for now). I already have those XO's so I might as well use them if it's possible. I have the datasheets and I also got some schematics on how to connect the XO's to the RO inputs of TH7108 and TH71112. But no idea about the varactor/RO2 input...
help in developing UHF ASK receiver at 868 MHz
Question
we are designing 868 MHz ASK RECEIVER section for a reader. we choose melexis TH71112 receiver chip to design.
can you please help me to brief about using this TH71112 as a RECEIVER 868 MHz.
Question
thanks for information. i am trying to use this receiver TH71112 in RFid reader at 868 MHz. i need to receive ASK demodulated output.
can you brief me more about "ENRX" pin which enables the rx. MEANS how to enable receiver, is there any precautions in RFID reader point of design i should take in to account?
Answer
The ENRX pin just turns the receiver on or off. When it is off, the current is essentially zero. Remember that it takes about 1mS to start up after the ENRX pin goes high. This is caused by the start up time of the crystal oscillator. Also, the data slicer capacitor must charge up to the average signal voltage, so its value is a compromise between charging time and the longest data pulse.
Since you are the first to use the TH71112 for an RFID reader, it will be interesting to learn of your results.
Question
can i make "ENRX" high for a longer time? i am trying to send ASK modulated encoded data through one transmitter and want to receive using this TH71112.
what is the "ask output" signal format? analog or digital . will it in the form of I or Q demodulated data?
Question
is this TH71112 supports I and Q modulation.
i.e. dose this chip outputs demodulated data in the form of I or Q ?[ in phase or quadrature].
if not,then can you please explain me how to use this output from TH71112 as i or Q signal.
Answer
The TH71112 does not generate I and Q outputs. The RSSI is like an envelope detector and is proportional to the square root of Isquared + Qsquared. The IF output is available on pin 15 and goes to one input of the phase detector, named MIX3 one the block diagram. If you have a reference signal, you can apply it to pin 16 and get I or Q from pin 23 depending on the phase of the reference signal. You can add a second phase detector to get the other output.
Question
i test TH71112 by transmitting some data. its receiving but not perfect as per transmitted one.
i want to know what is format of output analog or digital? if ASK modulation is used.
in earlier mail to generate i and q what ref signal i need to feed.
i want to transmit 866 MHz carrier modulated dat and same should be received.
what modification i need to do for TH71112 board?
Question
is it possible for me to get a ready TH71112 receiver board from melexis tuned as per my application requirement?
my require freq is 866MHz at which i am transmitting with power of +5 dBm to +10 dBm.
minimum pulsewidth i should be get is 6.12 microsec.
it may be possible that any of my assembled component not functioning properly. so i need this help from melexis.
also can you please provide me circuit for decoder to obtained digital output.
regards -vijay
Question
thnks for information.
i tried with my board but its not giving proper results.
Can i get evaluation board for TH71112, with customised modification for 866MHz, and with changes for 6 us. from MELEXIS?
so that i can go ahead with my project.
class 1 receiver
Question
I am interested in design a class 1 receiver for ism band with th71112.
Is this possible?
I have problems in filtering the IF1 with a very narrow filter to reach the limits for receiver declared in EN 300 220.
Answer
It's nearly impossible to achieved the class 1 receiver requirements with our receivers. Even if the limits for blocking could be reached with a high Q SAW filter in front of the receiver, the limits for adjacent channel selectivity is too tough for a wideband PLL with integrated ring oscillators as used in the TH71112.
Moreover, filtering the IF1 brings no further improvement.
TH7112 maximum FSK data rate
Question
Maybe there is a typo in the part number you listed? (TH71112 is Melexis 868/915MHz receiver, not TH7112). The TH71112 max data rate is limited to 180kbps, the output stage impedance with capacitance to ground limits the response. Also, please verify 650kHz BW / 1Mbps data rate / your intended FSK frequency deviation, this is not practical for an FM detector = discriminator based FSK demodulator. The FSK deviation will also be low for matched filter (mark / space) type FSK detectors.
RFID 915 Mhz
Answer
The problem with UHF RFID readers is the requirement for a very large dynamic range of the receiver because the transmitted signal is large and is present when the receiver is operating. This usually requires a passive mixer or an active one operating at a realtively high current. If you can find a way to reduce the signal level, you might be able to use the RSSI output of our TH71111 or TH71112 receivers.
Buy TH71112
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