lt5511 Linear Technology Corporation, lt5511 Datasheet - Page 12

• Manufacturer Part Number: lt5511
• Description: High Signal Level Upconverting Mixer
• Manufacturer: Linear Technology Corporation

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 50 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
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
12
(4a) Top Layer Silkscreen
+
U
and RF
U
–
, are internally connected to
W
Figure 4. Evaluation Board Layout.
U
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
(200 ) 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 2f
critical, a less expensive and smaller balun can be used.
The amplitude and phase balances of the balun will affect
the LO suppression.
LO
(4b) Top Layer Metal
spur. If the level of that spur is not
+
and RF
–
to the high impedance
5511f