OMB EM 1000 HE DIG PLUS COMPACT - COMPLIANCE AND LEGAL NOTICES; Declaration of Conformity

FMTRANSMITTER
TREM1000HEDIGPLUSCOMPACT
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TechnicalManual1v2November2019  78
3.11.1STEREOGENERATORBOARD(OPTIONAL)
Thephasecontrolloop(PLL)circuitiscontainedentirelyintheintegratedcircuitIC2,whose
referencefrequencyisgeneratedinaTCXOcalledTCXO1inthediagram.Thesignalgenerated
bythisoscillatorhas afrequencyof12.8MHz.Tooperatecorrectlyinthechosenreference
frequency, the synthesizer circuit IC2 must be programmed serially by the Microcontroller
withcomplexinformation,ataskcarriedoutthroughthreecontrollines.
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The integrated circuit IC1, through its two sections, filters the output of the frequency
comparator, both towards the modulating varicap diodes and towards the phasehook
detectioncircuit.
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It may be noted that the gate bias voltage is removed from the output MOSFETs through
transistorsTR4and TR3to suspendthe RF outputof theunit whilethe phase controlloop
(PLL)isnotcorrectlyengagedinphaseattheselectedfrequency.Thecontrolloophasbeen
designed to ensure that the crosstalk added to the stereo multiplexed baseband signal is
below55dBat30Hz,beingvirtuallynegligibleathigherfrequencieswithinthebaseband.The
followingfigureshowsthechanneloscillatorcircuitandPLL.
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Figure:Stereogeneratorboard
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