RF2722_1 Datasheet, PDF (18/26 Pages) RF Micro Devices – GSM/GPRS/EDGE RECEIVER

RF2722
Proposed
near DC. In addition, the RF6001/3 will notch out 100kHz converted DC components for channel bandwidths less than or
equal to 85kHz. The RF6003 will also notch out 120kHz converted DC components for channel bandwidth of 90kHz. This is
only useful in VLIF mode.
In DCR mode there may be significant spectral content near DC during the final adapt of the RF6001/3. This may result in a
significant DC component that will track the input desired signal level. It is assumed that the baseband DSP will be able to
remove any such static DC error. In addition, if the DC adapt of the RF6001/3 is performed during the guard times then the
spectral content of the input signal should be a tone in the region of 50kHz to 70kHz and should not interfere with the DC
adapt process.
If DC_TIME2 is extended to encompass the fine DC adapt time of the RF6001/3 then the input signal will not interfere with the
adapt process as the LNAs will be muted. However, if there is any residual LO leakage into the LNA input then this error will
remain after the DC correction process. This may be a smaller residual error than that due to the input signals.
A diagram depicting the composite DC correction and RX startup of the RF2722 and RF6001/3 is presented below.
System
Warm-Up
t=-140usec
t=-120usec
Activate RF2722/ RF2722 DCOCl
RF6001/3
completed
t=-90usec
Initial Cal
completed
RX_EN,
EN_SE
RF2722
Turn on
Initial
Calibration
PLL
Lockup
RF2722
RXI, Q
DCOC
RF6001/3
RXI,Q
DCOC
DC_TIME1
<20mV DC
DC_TIME2
Valid
Data
t=-20usec
RF6001/3
PLL lock
completed
t=0usec
RF6001/3 DCOC
completed
BURST STARTS
t=42
RF6001/3 filter
data flushed
receive valid
data
<80uV DC
42 usec latency
GPO Control
The RF2722 allows the GPOs to switch to an alternate setting defined by TRDC during RX DC offset correction when TRD is pro-
grammed high. This is triggered by the rising edge of RX_EN pin and terminated by the expiration of DC_TIME2 in the RF2722.
This mode of operation is used to turn off the LNAs or redirect the T/R switch to TX mode during the DCOC time interval so that
the signal present from the previous time slot or LO leakage will not cause an error in the DCOC.
18 of 26
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at ([phone] or [e-mail].
Rev A4 DS050919