GENERAL INFORMATION
1-12
Predefined modulation types
The following can be selected:
Modulation type
System
π
/4 DQPSK
NADC (DAMPS), PDC (JDC),
TETRA, APCO25, TFTS
GMSK
GSM, Mobitex, CDPD, MC9,
DSRR, MD24-192N/W, Modacom
FSK POCSAG,
CITYRUF
4FSK ERMES,
APCO25
OQPSK Inmarsat
'M'
8DPSK VDR
(VDL)
Modulation accuracy
At the decision points with the envelope input at 1 V or disabled, and
filter above 0.25 for raised cosine filters and 0.3 for root raised cosine
filters:
PSK and QAM
<1.5% RMS vector error;
NADC and PDC
<1% RMS vector error (EIA, RCR 27A method);
GSM and CDPD
<3
°
RMS phase error (typical).
FSK/GMSK
Frequency deviation can be set with 1 Hz resolution across the range
100 Hz to 20 kHz.
Accuracy:
<1% of set deviation.
Modulation errors
Modulation errors can be added to simulate:
IQ skew from 0 to
±
20
°
in 0.1
°
steps,
IQ imbalance from 0 to
±
10 dB in 0.1 dB steps,
Carrier leak from 0 to 10% in 0.1% steps.
Range of errors allowed is limited by the peak envelope power.
Modulation errors are not available in GSM or OQPSK modes.
IQ outputs
Baseband IQ output signals available on the front panel at a level of
0.5 V PD nominal into 50
Ω
. Levels are reduced by 12 dB in
advanced digital mode.
Burst control
Available on the rear panel D-type connector. A logical '1' on the
burst control turns the RF on over a time interval corresponding to
three data symbols. Propagation delay is matched to the data path
delay. Can be used at the same time as the ENVELOPE input.
ON/OFF ratio
Greater than 80 dB.
Advanced digital modulation
In advanced digital mode the instrument produces TETRA
modulation,
π
/4 DQPSK at 18 ksymbols/s through a root raised
cosine filter with
α
of 0.35.
Adjacent channel power
Adjacent channel power across RF frequency range 100 to 490 MHz
and temperature range +25
°
C
±
5
°
C with IQ errors and fading
disabled: <70 dBc at +25 kHz offset.
Carrier leak
Better than
−
35 dBc (typically
−
38 dBc).
Vector modulation
Provides for IQ modulation of the carrier output from an external
source for carrier frequencies of 10 MHz to 1.35/2.7 GHz.
Carrier leakage and
SSB suppression
Following self-calibration, the RF carrier leakage and SB image
rejection are typically 50 dB.
Vector inputs
IQ inputs on the front panel. The RF level requested is obtained with
0.5 V DC applied to one of the inputs.
Input impedance is selectable between 50
Ω
and 300
Ω
.
DC vector accuracy
For carrier frequencies up to 2 GHz:
±
1% amplitude of full scale;
±
1
°
at full scale.
For carrier frequencies above 2 GHz:
±
1.5% amplitude of full scale;
±
1.5
°
at full scale.
Vector bandwidth
±
0.5 dB wrt DC for modulation frequencies up to 3 MHz.
±
1 dB wrt DC for modulation frequencies up to 10 MHz and carrier
frequencies up to 2 GHz.
.
±
1.3 dB wrt DC for carrier frequencies up to 2.7 GHz