Rohde & Schwarz SMHU58 RF Signal
Generator
• I/Q Modulator for Any Phase and Amplitude Modulation (PSK, QAM, ASK,
etc.), Modulation Bandwidth DC to 200 MHz
• Second, Coherent Carrier for Simple I/Q Demodulation
• Broadband Amplitude Modulation for TV Applications
• Broadband Frequency Modulation for Satellite Communications, Radar, and
Video Applications
• Optional Coders for Generating Modulating Signals for Digital Radio Networks
to Relevant Standards (GSM, NADC, DECT, CDMA)
• Frequency Hopping - 4800 Stored Frequency and Level Settings
• Parallel Bus Interface for External Addressing of Memories
• Setting Time <1 ms for Frequency-agile Systems
• High Spectral Purity for Out-of-channel Measurements and LO Applications
• High Output Power (+19 dBm)
• High Carrier Frequency Accuracy and Drift-free FM DC for FSK and VCO
Modes
• Fast AM DC for Generating Level Bursts
RF, AF, Level, and Memory Sweeps for Automatic Test Runs
The SMHU58 Signal Generator can generate complex test signals for modern
communications and radar systems. Its high versatility is based upon the great
variety of modulation capabilities in conjunction with high spectral purity and
frequency hopping.
The I/Q and the broadband AM/FM modulators make all digital and analog
modulation modes for directional radio and satellite communications possible.
Modern radio networks use digital modulation methods, for which the SMHU58 is
ideally suited due to the high accuracy of its I/Q modulator.
For modulation using serial data signals, coders can be integrated for the
necessary signal processing and filtering to relevant standards. The optional
coders produce filtered analog signals from a serial data stream for driving the
I/Q modulator. The accuracy of the resulting phase modulation meets all
requirements placed on a reference signal for NADC, DECT, PDC, and GSM
testing. The CDMA coder uses Qualcomm chips to generate standard channels.
Broadband FM can be used for fast FSK, analog sweeping, video modulation,
and for generating chirp signals.
Modulation
Internal and external, or both internal modulation sources, can be combined for
two-tone modulation.
Frequency Modulation: The maximum deviation depends upon the carrier
frequency. Starting from a maximum deviation of 3.2 MHz in the frequency range
2.16 to 4.320 GHz, the maximum deviation decreases with the carrier frequency.
By selecting a special function, deviations of up to 800 kHz can be set even
below 125 MHz. The FM modulation frequency range covers DC to 1 MHz. In FM
DC mode, a high carrier-frequency accuracy is ensured. The frequency offset
occurring with FM DC selected is extremely small.
Amplitude Modulation: The whole of the modulation frequency range can be used
down to carrier frequencies of less than 100 kHz. The minimal phase shift at 30
Hz (AM DC) and a flat frequency response provide the precision amplitude
modulation required for testing VOR/ILS navigation receivers.
Pulse Modulation: Rise/fall times of 20 ns (<10 ns typical for frequencies >200
MHz) and an on/off ratio of 80 dB open up a wide range of possibilities for testing
telemetry, radio link, radar, and satellite communications systems.
I/Q Modulator: The I/Q modulator is adjusted for minimum amplitude and phase
error in an automatic calibration routine. The settings can also be varied to
simulate a non-ideal behavior of the modulator. With the aid of selectable defined
modulation distortion, effects on bit error rates can be determined and
demodulator maladjustments corrected.
Coder Options: The serial data signal may be derived from an external source or
from a PRBS generator in the coder. By digital processing in the coder, the data
signal is shaped as required for the prescribed filter function and split into I and Q
signals. In addition to the standard filter functions provided, special filter functions
for various bandwidths are programmed in the coder. They are used for specific
variations of the modulation spectrum to enable investigations of non-standard
signals. The extremely high modulation accuracy meets all the requirements
placed on a reference signal for use in receiver testing. Separate coders are
required for CDMA, GSM, DECT and NADC/PDC networks, since type of
modulation, clock frequency, and baseband filtering are different in each network.
The SMHU58 can accommodate one coder module.
Broadband AM: The I/Q modulator is also used for broadband amplitude
modulation within a modulation bandwidth of 50 MHz. There are no limiting
effects up to a level of +7 dBm. Modulation range, linearity, and bandwidth make
the SMHU58 an ideal instrument for TV applications.
Broadband FM: This mode allows modulation frequencies up to 20 MHz. The
frequency deviation can be adjusted in fine steps in the range from 1 kHz to 50
MHz. Through the simultaneous use of pulse modulation and Broadband FM, the
SMHU58 can generate radar chirps with a frequency variation of 100 MHz in less
than 100 ns. Further applications are in the field of video measurements and in
satellite reception.
Frequency Modulation: FM applications range from high-quality stereo
modulation to fast FSK. The maximum deviation usually decreases with the
carrier frequency. This is different when FM is simultaneously used with I/Q or
Broadband AM. The maximum deviation then has a constant value of 3.2 MHz in
the range between 5 MHz and 1.95 GHz.
High carrier frequency accuracy is ensured in FM DC mode. When FM DC is selected,
the frequency offset remains smaller than 10 -7 x fc (fc = carrier frequency) and smaller
than 400 Hz for I/Q modulation and Broadband AM. There is practically no drift. This is
particularly useful for receivers with digital signaling.
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