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PDF TA0022 Data sheet ( Hoja de datos )
| Número de pieza | TA0022 | |
| Descripción | Low Cost HBT Upconverters | |
| Fabricantes | RF Micro Devices | |
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TA0022
TA0022
RF9938: Low-Cost HBT Upconverters for CDMA Transmitter ICs
To support the increasing demand for Code Division
Multiple Access (CDMA), the latest digital communica-
tion technology in cellular industry, RF Micro Devices
(RFMD) developed CDMA chip sets for both receiver
and transmit chain. The CDMA chip sets were
designed and manufactured on an advanced GaAs
Heterojunction Bipolar Transistor (HBT) process from
TRW. The HBT process offers several advantages
over other processes such as high Ft, low noise tran-
sistors, and process consistency. The CDMA program
is two-fold. The first chip set, which was designed for
cellular band, consists of a receive and a transmit IF
AGC amps (RF9907 and RF9909), a receive LNA/
mixer (RF9906), and a transmit upconverter (RF9908).
The second chip set, designed for PCS band, consists
of a receive LNA/mixer (RF9936) and a transmit
upconverter (RF9938). This article describes the two
transmit upconverters for this CDMA program.
Design architecture is the same for both cellular and
PCS designs. The PCS upconverter, RF9938, is a
modified RF9908 with performance optimized for the
PCS band. Both ICs operate at 3.6VDC with 0dB con-
version gain.
With -10dBm input at the IC, typical Adjacent Channel
Power Rejection (ACPR) for the RF9908 is -37dB for
the 880kHz offset and -58dB for the 1.98MHz offset.
The typical ACPR for the RF9938 is -43dB. The nom-
inal power supply current for the RF9908 is 18mA and
25mA for the RF9938. The overall performance is
affected by less than +1dB over temperature, fre-
quency, and the LO drive level. Both ICs are pin com-
patible and are packaged in a standard 8-lead plastic
SOIC package.
Figure 1 is a simplified circuit topology of the mixer. As
shown in the figure, the mixer is a Gilbert Cell based
multiplier with an IF amplifier at the bottom and the LO
switching transistors at the top. Double balanced mix-
ers such as this offers the best port to port isolation
and low LO feed-through at the output. Minimum port
to port isolation is 30dB for both upconverters and the
minimum spurious signal in a 60MHz bandwidth is
50 dBc.
Input ports for the IF and LO are configured for differ-
ential operation. However, the LO can be driven single
ended if one of the input port is AC grounded. Input
impedance for the IF amplifier is 265Ω, set by the inter-
VCC
MIXER OUT
MIXER B OUT
LOA
LOB
IFA
IFB
Figure 1. Simplified Circuit Topology
Title
Size
A
Date:
RF MICRO DEVICES, INC.
GREENSBORO, NC
PCS UPCONVERTER - MIXER
Document Number
April 1, 1996
Sheet
REV
of
Copyright 1997-2000 RF Micro Devices, Inc.
13
13-103
1 page | ||
| Páginas | Total 4 Páginas | |
| PDF Descargar | [ Datasheet TA0022.PDF ] | |
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