External Lo Port Impedance Matching Network - Analog Devices ADRV9001 User Manual

Reference Manual ADRV9001
RF PORT INTERFACE INFORMATION
Figure 240. Tx1/Tx2 Return Loss
Figure 241. Tx1/Tx2 Insertion Loss, Simulated

EXTERNAL LO PORT IMPEDANCE MATCHING NETWORK

The external LO1 and LO2 PORT are used to inject LO signals with very high spectral purity for internal receivers and transmitters. Implement
the RF matching network for these ports on single-ended and differential sides of the balun to reduce insertion loss due to reflections at the
desired LO frequency. The method of obtaining a matching network is similar to the receiver and transmitter port matching. Depending on the
selected divide ratio of the ADRV9001 external LO input frequency divider SPI register setting, a band of frequency must operate in the external
LO matching networks, and the chosen division ratio must derive these correctly.
External LO Inputs
Unlike the internal synthesizers that always operate from 6 GHz to 12 GHz regardless of the RF-tuned frequency, when using external LO pins,
apply a frequency that is a multiple of two times (i.e., 2x, 4x, 8x, and so on) of the desired RF signal channel frequency. The LO input signal
is internally divided by a series of dividers to generate the required LO quadrature relationship at the desired RF frequency of upconversion or
downconversion for internal transmitters and receivers. Table 110 describes the specifications for the external LO input pins when the input pins
are driven by a differential signal using a balun.
Alternatively, use a single-ended external LO signal source for the positive side of the external LO pin, with the negative side of the input pin
terminated with a capacitor to provide AC ground. Set the frequency of the external LO source to 4x of the desired receiver or transmitter
frequency, with the external LO divider configured to the division of four for the best in-phase and quadrature generation of the LO necessary
for internal receivers and transmitters. Table 111 describes the specifications for the single-ended external LO input source.
In general, the higher power level of the applied external LO signal gives better phase noise to some extent. Use the minimum input power level
that satisfies the receiver/transmitter phase noise requirements with some margin. See Table 111 for power level recommendations.
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