PRODUCT SUMMARY
CX74061: Rx ASIC for CDMA, AMPS, PCS, and GPS Mobile
Handset Applications
APPLICATIONS
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Tri-band, quad-mode handsets
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PCS and GPS phones
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CDMA and GPS phones
After RF LNA signal amplification and filtering from the
antenna, the received signal is mixed down from RF to the IF.
There are separate mixers for AMPS, CDMA-cellular, CDMA-
PCS, and GPS modes. The CDMA and PCS mixers have
balanced outputs for the IF SAW filters, while the AMPS
differential output can be combined externally to mate to a
single-ended SAW filter. The GPS mixers have a differential
output for an external L-C bandpass filter. After IF filtering, the
IF signal is amplified by a Variable Gain Amplifier (VGA) and fed
to an I/Q demodulator, resulting in baseband I/Q signals at the
output.
The CX74061 is also designed with two Local Oscillator (LO)
input ports, one for the AMPS/CDMA/PCS mixer and one for the
GPS mixer. These mixers operate at different RF frequency
inputs, but have the same IF frequency output. This usually
refers to a single IF (SIF) plan at 183.6 MHz.
The PCS/CELL_LO signal (pin 36) provides an LO port for the
CDMA-cellular and CDMA-PCS mixers. The PCS band is
selected by default as an input LO frequency to the PCS mixer.
In the cellular band, the frequency is divided by two by an
internal divider, which provides the LO input to the cellular
mixer. Only one external VCO is required for the UHF PLL.
Additionally, the mixer LO signal is coupled and amplified
internally, which provides another RF signal to drive the
transmtiter upconverter LO port.
The VGA has a minimum dynamic range of 90 dB with a
control voltage range of 0.3 to 2.5 V, which is common to all
modes. A VHF oscillator operates with external tank circuits to
provide LO frequencies for the I/Q demodulator in the cellular,
PCS, and GPS modes.
The noise figure, gain, and third order Input Intercept Point
(IIP3) of each stage in the receiver chip are optimized to meet
the system requirements for AMPS and CDMA modes
according to TIA/EIA-98-C. The ASIC design employs BiCMOS
technology for low cost, high performance, and a high level of
integration.
A block diagram of the CX74061 is shown in Figure 1.
FEATURES
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Two-step gain control PCS LNA
Three-step gain control cellular LNA
GPS LNA
External resistor to adjust LNA bias current
Independent AMPS, CDMA, PCS, and GPS mixers
Single LO input for CDMA and PCS mixer
Buffered LO signal for transmit upconverter
Single external UHF VCO for PLL circuitry
90 dB dynamic range VGA
200 to 600 MHz VHF oscillator
VCO_ON control for current optimization
Battery cell operation (2.7 V < Vcc < 3.3 V)
7 x 7 mm 48-pin RFLGA™ package with down-set paddle
DESCRIPTION
The CX74061 Application-Specific Integrated Circuit (ASIC) is a
single Intermediate Frequency (IF), multi-mode, tri-band
receiver intended for use in Code Division Multiple Access
(CDMA) phones in Personal Communications System (PCS),
cellular CDMA, Advanced Mobile Phone System (AMPS), and
Global Positioning System (GPS) modes.
The CX74061 is a highly integrated super-heterodyne receiver.
Except for the Surface Acoustic Wave (SAW) filters and
matching components, the device incorporates all the
components required to implement the receiver chain, from
the Low-Noise Amplifier (LNA) to the In-Phase and Quadrature
(I/Q) demodulator stages. Three LNAs are in the front-end
receiver: a three-step gain stage cellular LNA (high, mid, and
bypass), a two-step gain stage PCS LNA (high, bypass), and a
high gain stage GPS LNA.
Skyworks Solutions, Inc. Proprietary and Confidential
103083A
[781] 376-3000 I FAX [781] 376-3100 I SALES@SKYWORKSINC.COM I WWW.SKYWORKSINC.COM
1
FEBRUARY 5, 2003
SKYWORKS [ SKYWORKS SOLUTIONS INC. ]
