Texas Instruments TRF1500 - Manual (Page 37)

SWRA004A
38 TRF1500 Integrated Dual-Band RF Receiver User’s Guide
High-Band IF Output
Figure 15 details the high-band mixer IF output configuration. The
high-band mixer has a differential IF output with a 1k
Ω
differential
output impedance. For evaluation purposes, a 16:1 transformer
balun, with an insertion loss of 1.8 dB, is used to transform the
1k
Ω
differential output to a single-ended output which is then
matched to 50
Ω
. In the actual application, the IF output is usually
connected to a narrow band channel select filter with a differential
input and the transformer balun is not required.
The supply voltage (VCC) is applied to the IF terminals with pull-
up inductors (L21, L22). A low-pass filter network is provided prior
to the balun. The filter also acts as part of the impedance
matching network. The IF response is shaped by the shunt-L
(L52) after the transformer balun. L52 is also used to block
unwanted noise that could be reflected back to the mixer. The
series capacitor (C51) near the HB_IF_OUT port is used as a dc
block for evaluation purposes and does not have to be
implemented in the end-users system.
Figure 15. High-Band IF Output Configuration