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Service Manual
8. VHF (136-174 MHz) Information
233
8.1.2 Low-Pass Filter Circuit
The low-pass filter is a high
–order Chebyshev filter composed of lumped-parameter inductors
and capacitors. Via this filter, the spurious signal within the stop band can be attenuated as
much as possible while the in-band ripple is within the required range.
8.1.3 Auto Power Control Circuit
In the auto power control and temperature detection circuit, the drain current from the driver
amplifier and final-stage amplifier is converted to voltage via the sampling resistor and
subtraction circuit (composed of the first operational amplifier). This voltage is compared with
the APC control voltage (output by DAC) at the second operational amplifier. Then the error
voltage, which is output by the second operational amplifier, controls TX power by controlling
the bias voltage at the gates of the amplifiers (including the driver amplifier and the final-stage
amplifier). The temperature sensor detects the surface temperature of the final-stage
amplifier, and then converts it to DC voltage. Then the DC voltage is compared with the
voltage corresponding to the protection temperature (generally 80% of the extreme
temperature) of the amplifier. If the surface temperature is too high, the bias voltage of the
amplifier will be reduced until the surface temperature falls below the protection temperature.
Summary of Contents for RDR9000
Page 1: ...RDR9000U V Service Manual ...
Page 45: ...Service Manual 6 UHF1 400 470 MHz Information 35 6 4 PCB View PCB View Main Board Top Layer ...
Page 46: ...Service Manual 6 UHF1 400 470 MHz Information 36 PCB View Main Board Bottom Layer ...
Page 48: ...Service Manual 6 UHF1 400 470 MHz Information 38 PCB View Rear Board Top Layer ...
Page 146: ...Service Manual 7 UHF3 350 400 MHz Information 136 7 4 PCB View PCB View Main Board Top Layer ...
Page 147: ...Service Manual 7 UHF3 350 400 MHz Information 137 PCB View Main Board Bottom Layer ...
Page 149: ...Service Manual 7 UHF3 350 400 MHz Information 139 PCB View Rear Board Top Layer ...
Page 248: ...Service Manual 8 VHF 136 174 MHz Information 238 8 4 PCB View PCB View Main Board Top Layer ...
Page 249: ...Service Manual 8 VHF 136 174 MHz Information 239 PCB View Main Board Bottom Layer ...
Page 251: ...Service Manual 8 VHF 136 174 MHz Information 241 PCB View Rear Board Top Layer ...
Page 346: ...Service Manual 11 Packing Guide 336 11 Packing Guide Figure 11 1Packing Guide ...
Page 352: ...342 ...