June 15, 2005
6815854H01-A
3-18
Theory of Operation:
Receiver Front-End
3.10.1.5 Mixer (D3258)
The received signal is down-converted by a double-balanced mixer to an Intermediate Frequency
(IF) of 109.65 MHz. The mixer is designed to provide low conversion loss and high intermodulation
performance. The injection buffer provides a 20 dBm LO signal to the mixer. High-side injection is
used.
3.10.2 UHF Range 1 (380–470 MHz) Band
The receiver circuits primary duties are to detect, filter, amplify, and demodulate RF signals in the
presence of strong interfering noise and unintended signals. The receiver (see
) is
broken down into the following blocks:
• Front-end, which includes:
- High pass fIlter and first low-noise amplifier (LNA)
- Preselector filter
- Switchable 15 dB attenuator
- Second LNA
- Image Filter
- First mixer
• Back-end, which includes:
- Intermediate Frequency (IF)
- ABACUS III IC
Figure 3-15. Receiver Front-End and Back-End (UHF Range 1)
Ant. SW.
Harm. FLT
Pre-Amp
Switch
Pre-Amp
Switch
Pre-Amp
Switch
Pre-Amp
Switch
Mixer
Preselector 15 dB
Att.
Low Pass
Filter
RF Input
Crystal
24dBm
1st LO
Backend A/D Converter
SSI
Dec.
Filter
CLK
Synth.
LO
Synth.
2nd
LO
18MHz
CLK
IF Amp
Crystal
109.65MHz
A
10 dB
Att.
380-470MHz
LNA
High Pass
Filter
LNA
ADC
ABACUS III IC
A
Содержание XTL 1500
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