
11
RFin
RFout
DUT
ISOLATOR
ATTENUATOR
20dB
Vctrl
Vdd2
Vdd3
Vdd1
10MHz
Out
10MHz
In
Event1
Trig In
Out
Trig In
GPIB
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 speci-
cation that must be met, but conformance to this spec is
dictated by the Vapc ramp.
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 dier-
ent CDMA codes with QPSK modulation; as a result this
PA must meet similar ACLR specications as CDMA or
WCDMA.
Signaling Setup
To properly test a TD-SCDMA PA module as specied in
the TS25.102 standard, one must generate the RF signal
shown in Figure 6 along with the timing described in the
previous section.
While at the time of publication of this Application note,
Agilent Technologies did not have a TD-SCDMA trans-
ceiver 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 conjunc-
tion with Agilent Technologies E4440A spectrum analyzer
and TSM Signal Studio, all performance tests become
much simpler although, ACLR, Gain, PAE, Idd and Spuri-
ous 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.
Signal Studio [2] facilitates the construction of the
complex RF waveform shown in Figure 8. Using this
software, one can generate uplink and downlink Dedi-
cated Physical Channel (DPCH) signals along with the
uplink and downlink pilot signals. All 7 trac timeslots
are supported, with up to 16 individually congurable
code channels per timeslot, for a total of 112 resource
units(RU).
Signal Studio for TSM and other standards can be found
at: www.agilent.com/nd/signalstudio
Figure 8 displays the main conguration window with
only 1 downlink timeslot turned on.
Figure 7. TD-SCDMA test setup.