RF2942PCBA Просмотр технического описания (PDF) - RF Micro Devices

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RF2942PCBA

UHF QUADRATURE MODULATOR AND TRANSMITTER

RF Micro Devices 

Theory of Operation

Modulator

The modulator is a direct conversion double balanced

quadrature mixer architecture. The local oscillator sig-

nal is buffered then split with internal phase shifters

that are optimized for twice the operating frequency.

The LO buffer provides isolation from load changes

that may occur as the power amplifier section is turned

on and off. In addition, the LO buffer may be left on

when the transmit section is turned off to prevent load

pulling of the external oscillator, by holding TX EN low

and leaving the bias on VCC1.

The baseband I and Q pins are connected to the inter-

nal mixer bias, therefore it is recommended that the

modulation signal be DC-blocked if a similar external

reference voltage cannot be provided. The baseband

drive may be either single-ended with the complemen-

tary input AC-grounded with a capacitor or driven dif-

ferentially.

Power Amplifier

The power amplifier requires matching on the output

(RF OUT) and the interstage transistor (PA VCC).

RF2942

Rev A4 040115

11-199

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