Interference, Multipath, and Scintillation - Understanding GPS: Principles and Applications - page 250

AGC
gain

Digital
comp

Digital-to-
analog converter

Digital
integrator

1/N Sum N

J/N Meter

T%

OR gate

DQ
Flip
flop

+ Magnitude

Comp

V B

Vi

Analog IF

G

A

DQ

Sign

Comp

0

Flip
flop

AGC amplifier

V β

− V B

Ge
A

= α

i

DQ − Magnitude

Comp

Flip
flop

DQ

Comp

0.8V B

Flip
flop

Exclusive
OR

− 0.8V B

DQ

Comp

Flip
flop

LPF

DQ

CW flag

Comp

V CW

Flip
flop

Figure 6.1 AGC amplifier followed by a nonuniform ADC, CW detector, and digital J / N meter.

extremely high-level output to the nearby extremely low-level input signals).
Self-jamming has the same detrimental effect as continuous gain compression (or
saturation) of the receiver front end, except that no external RF interference is
required.
If a 1-bit ADC is used, no AGC is required because the ADC is simply a limiter.
However, 1-bit ADCs are extremely vulnerable to being captured by very low levels of
CW interference (see the following section). AGC is always used with multibit ADCs.

6.2.2.3 A/D Conversion Effects
A/D conversion consists of two distinct processes: signal sampling and signal
quantization. If the quantization process is instantaneous and continuous, as in a