GENERAL INFORMATION
1-4
Modulation
Comprehensive amplitude, frequency (plus wide bandwidth FM), phase and optional pulse
modulation are combined with an analog IQ (vector) capability. A digital mode of operation uses
internal digital signal processing to convert digital data into the complex modulation formats used
on modern digital communication systems. An internal modulation oscillator is provided, having a
frequency range of 0.1 Hz to 500 kHz, with a resolution of 0.1 Hz. A second modulation oscillator
can be included as an option. Two independent BNC inputs on the front panel allow external
modulation signals to be mixed with the internal signal(s). Therefore, a maximum of four
modulation sources may be available at one time. These sources may be combined to give the
single, dual, composite, dual composite and vector and digital modes.
The wide frequency modulation range capability provides a 1 dB bandwidth of 1 MHz and
provides FM deviation up to a maximum of 1 MHz for frequencies up to 21 MHz, 1% of carrier
frequency elsewhere. Phase modulation is also available with a 10 kHz bandwidth up to a
maximum of 10 radians.
Both AC and DC coupled FM is available. In the DC coupled FM mode a patented offset
correction system eliminates the large carrier frequency offsets that occur with normal signal
generators. As a result the 2050T series signal generators can be used confidently for testing tone
and message paging equipment.
Wideband frequency modulation with a 3 dB bandwidth of 10 MHz is provided via a rear panel
BNC socket for tests on equipment using frequency shift keying for high speed digital
transmission.
Amplitude modulation with a bandwidth of typically greater than 50 kHz and with modulation
depths of up to 99.9% is available with a resolution of 0.1%. Pulse modulation is available as an
option with typical rise and fall times of 5 ns and 70 dB on/off ratio.
An automatic level control facility is provided for both of the external modulation inputs and
provides correctly calibrated modulation for input levels varying from 0.7 to 1.4 V RMS. HI and
LO indications show when the input level is outside the range of the ALC system.
The signalling facility allows testing of radio equipment with sequential and sub-audible tone
capability. The sequential calling tone system is accessible from the utility menu for all four
modulation modes. Sub-audible calling tones are specified within the modulation source select
display.
Vector modulation
In vector modulation the generator provides IQ modulation at frequencies from 10 MHz to
1.35 GHz (2050T) or to 2.7 GHz (2051T and 2052T) by frequency conversion of one of four IFs
to the required output frequency. Analog I and Q inputs are provided with a typical bandwidth of
10 MHz.
The wide IQ bandwidth allows the generation of direct sequence spread spectrum signals as well
as OFDM and QAM signals for new broadcasting formats.
Precision radar chirp signals can be simulated to test radar receivers using a dual arbitrary
waveform generator to provide the required I and Q signals.
A linear envelope input allows for external voltage control of the RF output level to simulate the
RF burst signals used on Time Domain Duplex (TDD) and Time Domain Multiple Access
(TDMA) systems.
A switchable input impedance of 50
Ω
or 300
Ω
simplifies operation with 50
Ω
voltage sources
and interfacing with operational amplifiers or digital to analog converters.