Theory of Operation
2 - 12
68P02963C70-O
and C984), enters the Mixer at pin 3. The LO power at the LO mixer input is -
2dBm. The 2.7V DC is supplied by switch Q500 to pin.4.
The mixer conversion Loss is 7dB.
An impedance matching net is placed between the mixer and the IF filter (FL502).
It consists of L512, C525, C531, C524, L504 and C539.
IF Filter
The IF signal is routed via the IF filter (FL502), which has IL of 2.5dB and atten-
uates parasitic products of the Mixer, and via an impedance matching network that
consist of C546, C536 and L501 to the BALUN.
BALUN
The Balun transforms the single ended input RF signal to a differential double-
ended output. It consists of L519, C526, C527, L520, C530 and C534.
The differential signal is routed to the WPIC (Word Phone IC) at pin A4 and B4.
WPIC (receiver section)
The differential IF signal is amplified and transferred into the WPIC and mixed
with 2nd LO signal. The 2nd LO signal is routed to the WPIC at pin D1 and divid-
ed by 2 in to the quadrature generator block of the WPIC. The baseband signal
from the mixer passes via a Baseband filters and amplifiers arrays that gives lower
noise and better I & Q balance, to the WPIC A/D block and than to the DSP.
An internal AGC that is controlled by a control unit, establishes an appropriate at-
tenuation for unwanted signals as well as an appropriate gain for wanted signals.
The voltage at external capacitor C557 indicates the AGC attenuation level for the
different input signal levels. The voltage at the capacitor varies from 1.4V to 2.7V
as a function of the power of the received signal.
Содержание MTH500
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Страница 14: ...Foreword xiv 68P02963C70 O THIS PAGE INTENTIONALLY LEFT BLANK ...
Страница 18: ...Overview 1 4 68P02963C70 O THIS PAGE INTENTIONALLY LEFT BLANK ...
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Страница 76: ...Troubleshooting 3 26 68P02963C70 O Offset VCO Test ...
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Страница 100: ...Maintenance 5 18 68P02963C70 O Figure 23 Exploded View 1 2 3 4 5 7 6 X6 8 ...
Страница 101: ...Maintenance 68P02963C70 O 5 19 Figure 24 Exploded View of Chassis Assembly 9 12 13 10 11 14 ...
Страница 102: ...Maintenance 5 20 68P02963C70 O ...
Страница 103: ...MTH500 Detailed Service Manual COMPONENT BOARD LAYOUTS 68P02963C70 O 6 1 Component Board Layouts ...
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Страница 109: ...MTH500 Detailed Service Manual Schematic Diagrams and Parts Lists 68P02963C70 O 6 7 Schematic Diagrams and Parts Lists ...
Страница 134: ...SCHEMATIC DIAGRAMS MTH500 Flex CD 6 32 68P02963C70 O This page left blank intentionally ...
Страница 140: ...Replacement Parts and Kits 6 68P02963C70 O ...
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