6-1
Chapter 6
BRIEF TECHNICAL DESCRIPTION
Introduction
The 2026Q CDMA Interferer MultiSource generator consists of two synthesized RF signal sources
with both independent and combined RF outputs. The combined RF output provides a path to and
from the radio under test and an appropriate CDMA test set. Each source is a fully functional RF
signal generator with AM, FM,
Φ
M and pulse modulation capability. Each source covers the
frequency range of 10 kHz to 2.4 GHz while the combined output covers the range 800 MHz to
2 GHz. Output levels range from
−
137 dBm to +24 dBm. A block schematic for the instrument is
shown in Fig. 6-1.
The block diagram shows the internal circuits of one of the sources, the A source, in detail. The B
source has the same configuration. Data from the AUXILIARY PORT and the instrument
frequency standard are fed to both sources. RF output from each source is switched either directly
to its individual RF OUTPUT socket or to the combiner then out to the CONNECTION TO
RADIO connector. A third input to the combiner is provided by the INPUT FROM RADIO TEST
SET socket on the rear panel. This input may also be used by an external signal generator.
Modulation
The carrier frequency of each signal source can be frequency, phase or amplitude modulated from
internal or external modulation sources. The internal modulation source can be the sum of two
signals and used in combination with an external modulation source connected to the front-panel
EXT MOD INPUT connector. In addition to analogue FM, 2-level and 4-level FSK signals are
generated from external logic inputs to the AUXILIARY PORT connector.
Frequency generation
A voltage controlled oscillator (VCO) in each signal source covering the frequency range 400 to
533 MHz is phase locked to a 10 MHz oven controlled crystal oscillator (OCXO) using a
fractional-N synthesizer system. Additional frequency coverage is achieved by means of frequency
division or multiplication. Low frequencies are generated by a beat frequency oscillator (BFO)
system.
Display
The display is a high-definition dot-matrix liquid crystal panel with backlighting to cater for
variations in ambient light conditions. The display contrast can be adjusted.
Control
The 2026Q is a menu-driven instrument. Main menus are displayed by the use of hard keys, and
parameters are changed by means of soft keys which change as the menu changes. Internal control
of the instrument is achieved by a microprocessor which receives data from the various controls
and sends instructions via an internal 8-bit data bus to the signal processing circuits.
The instrument can also be controlled by either the built-in General Purpose Interface Bus (GPIB)
or the RS-232 interface. The interfaces enable the instrument to be used both as a
manually-operated bench-mounted instrument and as part of a fully automated test system. The
RS-232 interface can also be used to reprogram the internal flash memory.
