Texas Instruments TRF1500 - Manual (Page 23)

SWRA004A
24 TRF1500 Integrated Dual-Band RF Receiver User’s Guide
Figure 9. Low-Band IF Output Configuration
Low-Band LO Buffer Amplifier Output
Figure 10 details the low-band LO buffer amplifier configuration.
The low-band LO buffer amplifier can be used in either single-
ended or differential mode for a phase lock loop (PLL)
configuration. The buffer is digitally controlled and requires a
operating drive level ranging from -3 to -7 dBm. For evaluation
purposes, a 1:1 transformer balun, with an insertion loss of 2.7 dB,
is used to convert the differential output to a single-ended output.
The series capacitors at the buffer output are used for dc blocking.
The transmission line on the output of the buffer amplifier are used
to convert the 100
Ω
differential to 50
Ω
differential.
The transmission lines on the output of the buffer amplifier can be
modeled as microstrip lines. The values used for the calculations
depend on the PCB substrate, the board stackup and the required
impedance. The physical dimensions of the microstrip lines can
be calculated using standard microstrip transmission line
equations using the following values:
Frequency = 990 MHz
ER = 4.400 (FR4), Height = 12.0000 mils , Thickness = 1.5000
mils (Copper)
Electrical Parameters:
ZO = 35.350 Ohms, E_EFF = 90.000
Physical Parameters:
Width = 37.777 mils , Length = 1613.305 mils