LT5511 Просмотр технического описания (PDF) - Linear Technology

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LT5511

High Signal Level Upconverting Mixer

Linear Technology 

LT5511

APPLICATIO S I FOR ATIO

On the evaluation board (Figure 4), 1nF DC-blocking

capacitors are used on the IF input pins. A 220pF capacitor

on the 50Ω source side of the input balun is used to tune

out the excess inductance to improve the match at 50MHz.

To shift the match higher in frequency, this capacitor value

should be reduced.

RF Output Port

The RF outputs, RF+ and RF–, are internally connected to

the collectors of the mixer switching transistors. These

differential output signals should be combined externally

through an RF balun transformer or 180° hybrid to achieve

optimum performance. These pins are biased at the

supply voltage, which can be applied through the center

tap of the output transformer. (The center tap should be RF

bypassed for best performance). A pair of series inductors

can be used to match RF+ and RF– to the high impedance

(200Ω) side of a 4:1 balun.

The output balun has a significant impact on the perfor-

mance of the mixer. A broadband balun provides better

rejection of the 2fLO spur. If the level of that spur is not

critical, a less expensive and smaller balun can be used.

The amplitude and phase balances of the balun will affect

the LO suppression.

(4a) Top Layer Silkscreen

Figure 4. Evaluation Board Layout.

(4b) Top Layer Metal

5511f

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