TD-SCDMA uses the same control technique except
that each frame is 5ms with only 7 timeslots and an
additional 75us downlink pilot and a 125us uplink pilot.
Each of the 7 slots is 675uS. For the ACPM-7886, the
Vctrl pin is used instead of Vapc. As in GSM, there is a
time mask specification that must be met, but
conformance to this spec is dictated by the Vapc ramp.
spectrum analyzer and TSM Signal Studio, all
performance tests become much simpler although,
ACLR, Gain, PAE, Idd and Spurious emission, etc. can
be measured with any spectrum analyzer.
Figure 7 shows the basic setup used to test ACPM-
7886 for TD-SCDMA. This includes DC power supply,
timing and RF signaling. In brief, the signal generator
triggers the pulse generator which in turn triggers the
spectrum analyzer and the ACPM-7886 and any other
multimeters used. The RF signal is created using Signal
Studio on a PC and downloaded to the signal generator
via GPIB.
In addition to time domain specs, TD-SCDMA must
meet linearity requirement. GSM/GMSK is referred to
as constant amplitude or constant envelope
modulation, and thus the PAM is allowed to operate in
saturation. As shown in Figure 6, each time slot
supports 16 different CDMA codes with QPSK
modulation; as a result this PA must meet similar ACLR
specifications as CDMA or WCDMA.
[2]
Signal Studio
facilitates the construction of the
complex RF waveform shown in Figure 8. Using this
software, one can generate uplink and downlink
Dedicated Physical Channel (DPCH) signals along with
the uplink and downlink pilot signals. All 7 traffic
timeslots are supported, with up to 16 individually
configurable code channels per timeslot, for a total of
112 resource units(RU).
Signaling Setup
To properly test a TD-SCDMA PA module as specified
in the TS25.102 standard, one must generate the RF
signal shown in Figure 6 along with the timing
described in the previous section.
Signal Studio for TSM and other standards can be found
at: www.agilent.com/find/signalstudio
While at the time of publication of this Application
note, Agilent Technologies did not have a TD-SCDMA
transceiver or a baseband reference module capable
of this signal generation, but it does have the E4438C
capable of generating a TD-SCDMA waveform. If used
in conjunction with Agilent Technologies E4440A
Figure 8 displays the main configuration window with
only 1 downlink timeslot turned on.
Trig In
Event1
RFin
RFout
20dB
DUT
ATTENUATOR
ISOLATOR
Trig In
Out
Figure 7. TD-SCDMA test setup.
11
AVAGO [ AVAGO TECHNOLOGIES LIMITED ]
