Theory of Operation
68P02963C70-O
2 - 3
The Receiver Path implements an Automatic Gain Control (AGC). It is required
to maintain a good receiver linearity over a wide range of incoming signals and
prevents clipping of high level signals.
The first Intermediate frequency (IF) circuit consists of the Mixer, IF Filter, and
WPIC. The second IF consists of an analog IF and a digital mixer that converts to
base band. They are located in the WPIC. The WPIC performs the following func-
tions:
•
Carries out amplification and quadrature down conversion of the signal into
the second IF.
•
Performs IF AGC.
•
Converts the second IF analog signal into digital I & Q formats.
•
Synthesizes the second VCO frequency.
•
Synthesizes the Sigma-Delta clock.
•
Synthesizes the receive and data transmit data clock.
•
Transmits the received data to the DSP.
Transmitter Section
The transmitter circuitry includes a linear class AB Power Amplifier (PA) for the
linear modulation of the MTH500. It also includes a novel cartesian feedback loop
to enhance its transmitter linearity and reduced splattering power into adjacent
channels.
The transmitter path consists of a novel cartesian feedback loop that contains the
forward and feedback paths. The forward path includes the low noise ODCT (Off-
set Direct Conversion Transmitter), Balun, Attenuator, and Power Amplifier. The
loop feedback path includes the directional coupler, attenuator, and LNODCT
(Low Noise Offset Direct Conversion Transmitter) ASIC.
The cartesian Feedback output power passes to the antenna through the Isolator,
Antenna Switch, and Harmonic Filter.
Digital Section
This section includes the REDCAP2, which controls the transmit, receive, and
synthesize operations of the integrated circuits located in the RF section. Within
the REDCAP2 is the DSP and the serial communication interface.
The digital section contains the following:
•
REDCAP2
•
Power On/Off circuitry
•
Serial peripheral interface (SPI)
•
Host memories (flash and SRAM)
•
Bottom connector signal MUX
•
Keypad block and connector
•
LCD (liquid-crystal display) circuit and connector
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 ...
Страница 50: ...Theory of Operation 2 32 68P02963C70 O THIS PAGE INTENTIONALLY LEFT BLANK ...
Страница 76: ...Troubleshooting 3 26 68P02963C70 O Offset VCO Test ...
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Страница 82: ...Programming the Radio 4 4 68P02963C70 O This page left blank intentionally ...
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 ...
Страница 104: ...MTH500 Detailed Service Manual COMPONENT BOARD LAYOUTS 6 2 68P02963C70 O This page intentionally left blank ...
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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