5-4
Samsung Electronics
Circuit Description
5-2 Receiver Section
LOW NOISE AMPLIFIER (LNA, Q302)
The low noise amplifier amplifies a weak signal
received from the base station to obtain the
optimum scvel (Noise figure = 1.5 dB,
Gain = 16 dB).
RADIO FREQUENCY BAND PASS FILTER
(RF BPF)
The RF BPF accepts only a specific frequency (881
°æ
12.5 MHz) from the signal received from the
base station. The band width is 25 MHz.
DOWN CONVERTER (MIXER, U302)
First local signal is applied to this down converter.
The down converter transfers the signal amplified
at the LNA into 85.38 MHz IF signal. 85.38 MHz IF
signal is made by subtracting 881
°æ
12.5 MHz RF
signal from 966
°æ
12.5 MHz first local signal.
AUTOMATIC GAIN CONTROLLER (AGC)
AMP U303)
85.38 MHz IF signal is applied to IF AGC amp, the
IF AGC output level is applied to BBA (Baseband
Analog ASIC). The IF AGC amp (U302) keeps the
signal at a constant level by controlling the gain.
Dynamic range is 90dB, up gain +45dB, and down
gain -45dB.
IF BAND PASS FILTER (FOR CDMA)
IF SAW BPF (F303) is used for CDMA system
having 1.23 MHz wideband and
°æ
630 kHz
bandwidth. The filter also attenuates the image
product generated at the mixer.
BUFFER AMP (Q385)
Buffer (Q385) amplifiers signal to be applied to the
local input of the down converter (U301) when a
phase is locked between VCO (U341) and PLL IC
(U342).
Summary of Contents for SCH-470
Page 2: ... à Samsung Electronics Co Ltd APR 1998 Printed in Korea Code No GH68 60687A ...
Page 6: ...2 2 Samsung Electronics ...
Page 12: ...NAM Programming 3 6 Samsung Electronics ...
Page 24: ...Circuit Description 5 10 Samsung Electronics ...
Page 26: ...Exploded View and its Parts List 6 2 Samsung Electronics 6 1 Fixed Phone Exploded View ...
Page 30: ...6 6 Samsung Electronics Exploded View and its Parts List ...
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Page 43: ...Samsung Electronics 8 1 8 Troubleshoot ing 8 1 Logic Section 8 1 1 No Power ...
Page 45: ...Samsung Electronics 8 3 Troubleshooting 8 1 3 Abnormal Backlight Operation ...
Page 46: ...Troubleshooting 8 4 Samsung Electronics 8 1 4 Abnormal Key Data Input ...
Page 47: ...Samsung Electronics 8 5 Troubleshooting 8 1 5 Abnormal Keytone ...
Page 48: ...Troubleshooting 8 6 Samsung Electronics 8 1 6 Abnormal Alert Tone ...
Page 49: ...Samsung Electronics 8 7 Troubleshooting 8 2 RF Section 8 2 1 RF Secton Troubleshooting ...
Page 50: ...Troubleshooting 8 8 Samsung Electronics 8 2 2 Receiver Part ...
Page 51: ...Samsung Electronics 8 9 Troubleshooting 8 2 3 Transmitter Part ...
Page 52: ...Troubleshooting 8 4 Desk Top charger 8 4 1 Check 1 8 10 Samsung Electronics ...
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