RF2514PCBA-41X datasheet(12/18 Pages) RFMD

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RF2514

Rev A5 DS040115

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Pin 5 (MOD IN) is the data input to the modulator and must have a series resistor (RMOD_IN) between it and the raw data

source. The value of RMOD_IN and the voltage at its input determine the output power level, with maximum power obtained for

RMOD_IN=3kΩ, the minimum allowable resistance. A three-element filter structure (series R, shunt C, series R) has been found

to be effective in reducing the out-of-band spectral content by filtering the higher frequency components of the baseband data.

For this filter, RMOD_IN is the sum of the two series resistors. The filter values will vary according to the particular data rate of a

given application and are best determined experimentally. When the input to RMOD_IN is a high logic level, the carrier is trans-

mitted; when the input is a low logic level, the carrier is not transmitted. For use as a local oscillator (LO) source, simply tie the

MOD IN pin to the supply voltage through a suitable series resistor.

Pin 13 (LD FLT) is used to set the threshold of the lock detect circuit. A shunt capacitor is used to set an RC time constant with

an on-chip series 1k

Ω resistor. The time constant should be approximately 10 times the reference period.

General RF bypassing techniques must be observed to get the best performance. Choose capacitors such that they are series

resonant near the frequency of operation.

Board layout is always an area in which great care must be taken. The board material and thickness are used in calculating the

RF line widths. The use of vias allows IC and component ground pins to be connected closely to the ground plane, minimizing

ground inductance. When laying out the traces around the VCO, it is desirable to keep the parasitics equal between the two

legs. This will allow equal valued inductors to be used.

It is recommended that pre-compliance testing be performed during the design process to avoid surprises during final compli-

ance testing, helping to keep the product development and release on schedule. Pre-compliance testing can be done with a

GTEM cell, an open area test site, or at a compliance testing laboratory.

After the design has been completed and passes compliance testing, then application will need to be made to obtain final cer-

tifications with the respective regulatory bodies for the geographic region in which the product will be operated.

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