Rainbow-electronics MAX7034 Instrukcja Użytkownika Pobierz pdf (Strona 11)

Peak Detector

The peak-detector output (PDOUT), in conjunction with

an external RC filter, creates a DC output voltage equal

to the peak value of the data signal. The resistor pro-

vides a path for the capacitor to discharge, allowing the

peak detector to dynamically follow peak changes of

the data-filter output voltage. For faster data slicer

response, use the circuit shown in Figure 4. For more

details on hysteresis and peak-detector applications,

refer to Maxim Application Note 3671,

Data Slicing

Techniques for UHF ASK Receivers

Layout Considerations

A properly designed PCB is an essential part of any

RF/microwave circuit. On high-frequency inputs and

outputs, use controlled-impedance lines and keep them

as short as possible to minimize losses and radiation.

At high frequencies, trace lengths that are on the order

of λ/10 or longer act as antennas.

Keeping the traces short also reduces parasitic induc-

tance. Generally, 1 inch of a PCB trace adds about

20nH of parasitic inductance. The parasitic inductance

can have a dramatic effect on the effective inductance

of a passive component. For example, a 0.5 inch trace

connecting a 100nH inductor adds an extra 10nH of

inductance or 10%.

To reduce the parasitic inductance, use wider traces

and a solid ground or power plane below the signal

traces. Also, use low-inductance connections to ground

on all GND pins, and place decoupling capacitors

close to all V

connections.

MAX7034

315MHz/434MHz ASK Superheterodyne

Receiver

______________________________________________________________________________________ 11

DATA

SLICER

DATAOUT

DSN

DFO

DSP

MAX7034

DATA

SLICER

DATAOUT

*OPTIONAL

DSP

DFO

DSN

MAX7034

Figure 3. Generating Data Slicer Hysteresis

DATA

SLICER

25kΩ

DATAOUT

DSN

DFO

PDOUT

DSP

MAX7034

47nF

Figure 4. Using PDOUT for Faster Startup

Figure 2. Generating Data Slicer Threshold

1 2 ... 6 7 8 9 10 11 12 13

Receiver 1

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