SA3601 Datasheet, PDF (5/14 Pages) NXP Semiconductors – Low voltage dual-band RF front-end

Philips Semiconductors
Low voltage dual-band RF front-end
Preliminary specification
SA3601
OPERATION
The SA3601 is a highly integrated dual-band radio frequency (RF)
front-end integrated circuit (IC) targeted for TDMA applications. This
IC is split into separate low-band (LB) and high-band (HB) receivers.
The LB receiver contains a low noise amplifier (LNA) and mixer that
are designed to operate in the cellular frequency range
(869–894MHz). The HB receiver contains an LNA and mixer that
are designed to operate in the PCS frequency range
(1930–1990 MHz). The SA3601 also contains a frequency doubler
that can drive the HB mixer local oscillator (LO) port, allowing a
single-band voltage controlled oscillator (VCO) to be used to drive
both mixers. Modes for bypassing the doubler are also provided, in
the case where a dual-band VCO is used.
The SA3601 has eight modes of operation that control the LNAs,
mixers, LO buffers and doubler. The select pins (PD1,2,3) are used
to change modes of operation. The internal select logic powers the
device down (0,0,0), turns on the LB LO buffer for use in transmit
mode (0,0,1), enables cellular receive mode for high and low gain
(0,1,X), enables PCS receive mode for high and low gain both
without doubler (1,1,X) and with doubler (1,0,X).
Low-Band Receive Section
The LB circuit contains a LNA followed by a wide dynamic range
active mixer. In a typical application circuit, the LNA output uses an
external pull-up inductor to VCC and is AC coupled. The mixer IF
outputs are differential and are combined with the high-band IF
mixer outputs thereby eliminating the need for extra output pins.
External inductors and capacitors can be used to convert the
differential mixer outputs to single-ended. Furthermore, the LNA
provides two gain settings: high gain (17dB) and low gain (–15 dB).
The desired gain state can be selected by setting the logic pins
(PD1,PD2,PD3) appropriately.
High-Band Receive Section
The HB circuit contains a LNA followed by a Gilbert cell mixer with
differential inputs. The LNA output uses an internal pull-up inductor
to VCC , which eliminates the need for an external pull-up. The
mixer IF outputs are differential and are combined with the low-band
IF mixer outputs thereby eliminating the need for extra output pins.
Similar to the LB LNA, the HB LNA has two gain settings: high gain
(16 dB) and low gain (–15 dB).
Control Logic Section
Pins PD1, PD2, and PD3, control the logic functions of the SA3601.
The PD1 selects between LB and HB operations. In LB receive
mode, the LB LNA is in high gain mode (or on) when PD1,2,3 are
(0,1,1). In all other modes, the LB LNA is off. The LB mixer is on
when PD1,2,3 are (0,1,X). In all other modes, the LB mixer is off.
During transmit mode when PD1,2,3 are (0,0,1), the LB LO buffer is
on, enabling use of the LO signal for the transmitter.
In HB receive mode, the HB LNA is in high gain mode (or on) when
PD1,2,3 are (1,X,1). In all other modes, the HB LNA is off. The HB
mixer is on when PD1,2,3 are (1,X,X), and is off in all other modes.
The on-chip frequency doubler (X2) is on in (1,0,X) modes. When
the frequency doubler is on, the input signal from the LB LO buffer is
doubled in frequency, which can then be used to drive the HB mixer
LO port. The frequency doubler can also be bypassed in modes
(1,1,X), in which case the HB mixer is driven directly by an external
2 GHz LO signal.
1999 Nov 09
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