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TH71102
Receiver - 315/433MHz FSK/ASK, Double-Conversion Superhet (LQFP32)
 Download TH71102 Datasheet (PDF)
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TH71102 General Description
The TH71102 FSK/ASK double-conversion superheterodyne receiver IC is designed for applications in the European 433 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 260 MHz to 510 MHz (e.g. for applications according to FCC part 15 and ARIB STD-T67).
TH71102 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)
TH71102 Environmental Information
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TH71102 Frequently asked Questions
TH71101 Sensitivity
Answer
The LNA is just a cascode bipolar amplifier with very low feedback capacitance. The gain is set by the load impedance and the LNA current. I have never seen any instability in the application circuits, so I am not sure how high you can make it. It will be limited by the largest inductance you can tune with the approximately 2pF output capacitance of the LNA stage plus and capacitance coupling to the mixer. You will not get much improvement by making the gain much higher because the overall receiver noise figure is determined by the standard cascade noise figure equation. The current receiver overall NF is about 8dB. The single conversion receivers have virtually no image rejecton without a SAW filter on the input. If you use the TH71102 dual conversion receiver, it has about 5dB image rejection and slightly better sensitivity. The inage rejection can be increased to about 30dB by adding a double tuned circuit between the LNA and mixer
Frequency Deviation
Answer
A narrower IF filter will give some improvement. Since your data rate is low, you could go to a narrow band FM system, but this either requires a more expensive crystal IF filter or a dual conversion down to 455 or 450kHz so narrow band ceramic filters can be used. For instance, you could use 5kHz peak deviation and filters designed for 25kHz channel spacing. I have used 10.7MHz crystal filters with the TH71102 receivers and gotten -114dBm sensitivity. If you want a schematic, let me know.
TH71102
Question
I need a TH71102 circuit schematic for 415MHz and some propsal for FM.
can someone please send them to me?
in addition:
I want to use TH71102 as FM receiver
Question
you can find all info to setup the TH71102 for 415MHz in the data sheet. Page 5 shows details on frequency planning. It's esentially just another crystal - compared to the standard 433.92MHz circuit for example. Some LC matching components can also be modified slightly.
The FM circuit is shown on page 14.
Question
I'm looking at using the TH71102 as the receiver for a packet radio setup in the ~440 MHz vacinity. I would use it as an FM receiver and decode the two low frequency audio tones somewhere else. Does the TH71102 have enough selectivity for essentially very narrow bandwidth FSK, i.e. 1200 Hz frequency separation.
TH711xx family
Answer
the lowest input frequency is 260MHz if the double conversion receiver (TH71102) is used. This is because the range of the internal VCO. The TH7122x contains an VCO having an external tank circuit which can easily achieve an input frequency of 216MHz.
RoHS listing
Question
The part I am interested in is TH71102ENE, is this one RoHS compliant?
Answer
Yes, the TH71102ENE is ROHS-compliant.
TH71102 at 27MHz
Question
I was wondering if you could recommend a design guide besides the application note AN71102-Low RF to help me design using the TH71102 at 27MHz.
I am trying to understand the sizing of components at 27MHz the app note indicates it is designed for 40.68MHz
My design must be able to recieve at 300 yards using FSK
Answer
thanks for considering the TH71102 for your 27MHz application. OK, the xtal freq. can be calculated by REF = (RF+IF)/2 = (27+10.7)/2 = 18.85MHz. Other passive components that should be tuned from 40MHz to 27MHz are L2, C4, L3, C6, C7, C8, L4 and L5. You can use the well-known equation for a parallel resonant circuit for the single tank combinations of L2/C4 and L3/C6. This is f0 = 1/(2pi*sqrt(L*C)). The same eq. applies for the combination of L4/C8/L5 but you use just 1/2 of the C-value as there are two Ls in the circuit. C7 defines the coupling between the two LC tanks. I would try something between 27 and 33pF. You may use the same 100nH inductors and just tune the capacitors a bit up to resonate at 27MHz. That's it.
TH71102 Xtal cannot oscillate
Question
My evaluation board evb71102 , TH71102 was
faulty , after change the IC ,measure the XTAL RO pin26 ,no oscillation , check ENRX pin is high ,total supply current is 8mA @5V,use ASK
circuit , OUT_OA have some noise pulse , the RO pin26
is 4.8V @ supply 5V
,check Xtal OK ,PIN27 5v ,PIN25 0v
it ssem like RO voltage have problem ?please advise
Help with TH71221
Answer
you may use the TH71221 (or TH7122) but it requires a 10.7MHz crystal IF filter if a 18kHz BW is needed. The smallest BW 10.7MHz ceramic filters have about 30kHz (e.g. Murata). So this could make the circuit a bit expensive. Make sure the PA is well isolated from the IC (small S12). Otherwise the 2W booster can load pull the VCO and kick off its frequency.
The receiver TH71102 could be used at 455kHz IF where you can use a cheaper narrow-band ceramic filter. But with this IC you would have to switch the reference xtals to achieve your two RFs. The same for the transmitter, of course.
Answer
you may use the TH71221 (or TH7122) but it requires a 10.7MHz crystal IF filter if a 18kHz BW is needed. The smallest BW 10.7MHz ceramic filters have about 30kHz (e.g. Murata). So this could make the circuit a bit expensive. Make sure the PA is well isolated from the IC (small S12). Otherwise the 2W booster can load pull the VCO and kick off its frequency.
The receiver TH71102 could be used at 455kHz IF where you can use a cheaper narrow-band ceramic filter. But with this IC you would have to switch the reference xtals to achieve your two RFs. The same for the transmitter, of course.
Karl[/QUOTE]
Thanks for info, Karl. Intention would be to use 2 chips in the Controller (TX + RX) and switch TX/RX at nodes.
Just printed data to study.
TH71102 for ARIB STD67
Question
I'm currently working on receiver for japanesse standard. I chose a frequency to have 10mW (429.2MHz) power. Unfortunatly the receiver does not meet the ACP power 40dB limit (i'm near 35dB).
Can somebody confirm me if there is an issue to reach or surpass the 40dB or if as i think the max value i obtain is inherent of the TH71102.
Sorry for my mistake. It's on the transmiter TH72011 that the ACP for 12.5kHz BW doesn't complies the -40dB level needed for ARIB STD67. The receiver TH71102 work fine at the chosen fréquency.
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