Transcript
SMIQ as Fading Simulator for External Signals
Application Note 1MA07_0E Subject to change Roland Minihold 98-3
Products:
Signal Generator SMIQ Signal Generator SMT/SME
Contents
2.
1. Overview 2. Problem Definition 3. Principle of SMIQ Signal Processing with Vector Modulation 4. Suggested Measurement Procedures
Multipath reception (fading) causes problems in the receiver sections of both analog and digital radiocommunication systems. To test receiver sensitivity with regard to fading, very expensive fading simulators have been required so far. SMIQ fitted with option SMIQ -B14 offers versatile fading capabilities for the integrated digital modulation functions at a favourable price. In the following, various ways are described of how to expand the fading capabilities of SMIQ as required for a given application using additional equipment. Thus, signals of any source and with any type of modulation can be faded, for example analog FM- or PM-modulated mobile radio signals, FM stereo sound broadcast signals, VOR/ILS signals, digitally modulated pager signals to POCSAG, ERMES, FLEX or REFLEX standard.
4.1. Signal Supplied by Signal Generator 4.2. Suppression of Unwanted Sideband with 90° Power Splitter 4.3. Use of Additional Mixer and 90° Phase Shifter 4.4. Use of External IQ Demodulator
5. Summary of Pros and Cons 6. References 7. Ordering Information
1.
Problem Definition
Overview
3. Principle of SMIQ Signal Processing with Vector Modulation
Signal Generator SMIQ has versatile analog and digital internal modulation capabilities. Optional Fading Simulator SMIQ-B14 adds a variety of fading functions to the integrated digital modulation capabilities of SMIQ at a highly attractive price as compared with similar products. This application note describes how to apply fading to signals of any source and with any type of modulation (analog and digital) in a very convenient way.
Fig. 1 is a basic diagram showing the location of the fading simulator in SMIQ. The fading simulator operates in the baseband and can be used both with signals generated by the modulation coder and with external IQ signals. It has a 3 dB bandwidth of 7 MHz; the roll-off is <0.5 dB up to 5 MHz.
IQ modulator
RF up/down converter
cos(ω 2t)
I ext
Baseband fading simulator
RF OUT
fIF
Q ext B-3dB = 7 MHz
Modulation coder (SMIQB10)
-sin(ω 2t)
f2= ω 2/2*π = 300 MHz
Fig. 1: Basic diagram showing signal processing with vector modulation and fading simulation in SMIQ
1MA07_0E
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Rohde & Schwarz
∑ A( t ) = A( t ) *cos(ω 2 * t + ϕ ) *cos(ω 1 * t + ψ ( t ))
The output signals of the fading simulator are taken to the IQ modulator, which operates at an IF of 300 MHz. The IF is converted to the output frequency by means of an up/downconverter.
Using the trigonometric function
cos α ∗cos β = 12 *cos(α − β ) +
External signals (I, Q) can be applied to the fading simulator basically in the following ways:
1 2
*cos(α + β )
the following is obtained:
1. The I and Q components of the signal to be faded are available in the baseband.
∑ A( t ) = 21 * A( t ) *cos(ω 2 * t + ϕ − ω 1 * t − ψ ( t )) + 21 * A( t ) *cos(ω 2 * t + ϕ + ω 1 * t + ψ ( t ))
2. A modulated carrier signal is applied to the I or Q input.
= 21 * A( t ) *cos((ω 2 − ω 1 ) * t + ϕ − ψ ( t ))
3. A modulated carrier signal is applied to the I input and simultaneously, phase-shifted by 90°, to the Q input.
+
1 2
* A( t ) *cos((ω 2 + ω 1 ) * t + ϕ + ψ ( t ))
In this way, two signals with a sum and a difference frequency (f 2+f 1, f 2-f1), each with the amplitude 1/2, are obtained at the output of the IQ modulator, formed by the applied carrier frequency and the LO frequency.
The different techniques of applying the signal: 1. I/Q signals in baseband: The I and Q signals are available in the baseband (for example from Arbitrary Waveform Generator ADS from Rohde & Schwarz). This corresponds to signal feed from the internal modulation coder.
1/2
1/2
The IF frequency of the IQ modulator is in this case equal to its LO frequency of f 2 = 300 MHz. The output frequency of SMIQ is equal to the set frequency.
suppressed LO frequency f 2
2. Modulated carrier signal to either I or Q input:
f f2-f1
A modulated carrier signal with the frequency f 1 is applied to one of inputs I or Q. The signal is converted in the IQ modulator same as in a normal mixer.
f2
f2+f1
Fig. 2: Output spectrum of IQ modulator with carrier signal f1 applied to I input
Let the signal at the I input of SMIQ be: 3. Modulated carrier signal to I input and simultaneously, phase-shifted by 90°, to Q input
A1 ( t ) = A( t ) * cos(ω 1 * t + ψ ( t )) , where
The Q signal is identical to the I signal except for a phase shift of 90°.
A(t) is the time function of the amplitude
ω 1 = 2π * f 1
In this case, single-sideband frequency conversion takes place in the IQ modulator of SMIQ. The output frequency is as follows:
and ψ ( t ) is the time function of the phase (with no signal present at Q input).
Frequency set on SMIQ + carrier frequency f 1 (or - carrier frequency f 1, depending on whether the I or the Q signal is leading in phase). The other sideband and the frequency set on SMIQ are suppressed. The degree of suppression depends on the quality of the I/Q modulator, the accuracy of the 90° phase shift and the I and Q amplitude imbalance.
The signal is multiplied with the LO signal of the IQ modulator in the upper mixer. The output signal of the IQ mixer is as follows:
1MA07_0E
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Rohde & Schwarz
The basic function can be deduced easily as follows:
1
Let the signal at the I input of the IQ modulator be:
A1 ( t ) = A( t ) * cos(ω 1 * t + ψ ( t )) The signal at the Q input is identical but shifted by +90° in phase. This corresponds to a sinewave signal, ie:
A2 ( t ) = A( t ) *sin(ω 1 * t + ψ ( t ))
Suppressed 2nd sideband
In the IQ modulator of SMIQ, A 1(t) and A2(t) are multiplied with the LO signal or the LO signal shifted 90° in phase, respectively, and added. The output signal of the IQ mixer is then as follows:
Suppressed LO frequency f 2
f f2-f1
f2
f2+f1
Fig. 3: Output spectrum of IQ modulator with carrier signal applied to I input and, with 90° phase shift, to Q input
∑ A( t ) = A( t ) *cos(ω 2 * t + ϕ ) *cos(ω 1 * t + ψ ( t )) − A( t ) *sin(ω 2 * t + ϕ ) *sin(ω 1 * t + ψ ( t ))
The output frequency of SMIQ is then as follows: frequency set on SMIQ + applied carrier frequency.
Using the trigonometric functions
cos α ∗cos β = 12 *cos(α − β ) + and
1 2
*cos(α + β )
sin α *sin β = 12 *cos(α − β ) −
1 2
*cos(α + β )
4.
To furnish signals with analog modulation, Signal Generator SMT from R&S is particularly suitable, whereas SME is an ideal source for special digitally modulated signals (and analog signals in addition). SME features as standard the ERMES protocol, for example, and the following protocols are optionally available:
the following is obtained:
∑ A( t ) = 21 * A( t ) *cos(ω 2 * t + ϕ − ω 1 * t − ψ ( t )) + 21 * A( t ) *cos(ω 2 * t + ϕ + ω 1 * t + ψ ( t )) − 12 * A( t ) *cos(ω 2 * t + ϕ − ω 1 * t − ψ ( t )) +
1 2
Suggested Measurement Procedures
FLEX protocol: SME-B41 POCSAC protocol: SME-B42 REFLEX TM protocol: SME-B43
* A( t ) *cos(ω 2 * t + ϕ + ω 1 * t + ψ ( t ))
The terms with
Setting of SMIQ fading simulator:
1 * A( t ) *cos(ω 2 * t + ϕ − ω 1 * t − ψ ( t )) 2
The setting of the SMIQ fading simulator greatly depends on requirements. Setting parameters include type of fading (eg Rayleigh fading), simulated speed, delay between fading channels, and number of fading channels.
cancel one another out to yield the following:
SMIQ output power with fading:
∑ A( t ) = A( t ) *cos(ω 2 * t + ϕ + ω 1 * t + ψ ( t )) = A( t ) *cos((ω 2 + ω 1 ) * t + ϕ + ψ ( t ))
If fading is activated, the maximum possible output level of SMIQ is reduced by 18 dB, ie the "Level overrange" warning will be output already on exceeding a set level of -5 dBm. For further information please refer to section 2.9.1 of SMIQ operating manual.
In this case, only a signal with the sum frequency (applied carrier frequency f 1 + LO frequency f 2 of IQ modulator) is obtained at the output of the IQ modulator; the modulation (time-dependent amplitude A(t) and phase ψ (t)) is maintained.
1MA07_0E
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Rohde & Schwarz
is to generate a signal with any type of modulation at around 3 MHz for f 1 by means of a signal generator (eg SMT or SME). The signal is applied to the I or Q input of Vector Signal Generator SMIQ and upconverted to the desired RF. If the I input is used, the frequency of SMIQ is to be set below the desired output frequency by the amount f 1 (if SMIQ is set above the desired output frequency by f 1, sideband inversion will result, ie an increase in frequency at the I input will lead to a decrease of frequency of the output signal). The level is to be set for 0.5 V peak voltage (+4 dBm in the case of modulation with constant signal amplitude, and correspondingly less in the case of AM, PSK or QAM).
Level at IQ inputs of SMIQ: The rated peak voltage at the IQ inputs is 0.5 V. This corresponds to a level of +7 dBm in the case of modulation with constant amplitude (eg FSK, MSK). For modulation types with varying amplitude (eg AM, PSK, QAM), the level must be reduced accordingly (eg by -6 dB with AM) since it must be ensured in these cases too that the peak voltage of 0.5 V at the IQ inputs is not exceeded. The output level of SMIQ is reduced correspondingly.
4.1.
Signal Supplied by Signal Generator
The easiest and in most cases satisfactory approach SIGNALGENERATOR
5kHz...1.5GHz
SMT02
1039.2000.02 DATA INPUT
3.000 000 0
FREQ
FREQUENCY LEVEL ANALOG MOD VECTOR MOD DIGITAL MOD DIGITAL STD LF OUTPUT SWEEP LIST MEM SEQ UTILITIES
MHz
LEVEL
7.0
FREQ
7
8
9
LEVEL
4
5
6
SAVE
1
2
3
SME/T OPERATING
RCL
Next menu
RETURN
Previous menu
VERSION:
n
0
.
M
k
-
µ
m x1
ç
Move cursor
SELECT
G
dBµV PULSE
dBm
ENTER
µV
mV EXT 1 dB(m)
EXT 2
MENU / VARIATION RETURN
SELECT LF
ï ð
1.33
RF 50
RF 1 = 3 MHz, any type of modulation
QUICK SELECT STBY
ASSIGN
MENU1
MENU2
PRESET
ERROR
STATUS
HELP
M0D 0N/0FF
LOCAL
!
RF 0N/0FF
MAX 50 W REVERSE POWER
ON
+4 dBm
MADE IN GERMANY
(Vpk = 0.5 V) SIGNALGENERATOR
SMIQ03
300kHz...3.3GHz
1084.8004.03 DATA
DATA INPUT
497.000 000 0
FREQ
FREQUENCY LEVEL ANALOG MOD VECTOR MOD DIGITAL MOD DIGITAL STD LF OUTPUT SWEEP LIST MEM SEQ UTILITIES
MHz
LEVEL
- 10.0
FREQ
7
8
9
LEVEL
4
5
6
SAVE
1
2
RCL
0
.
dBm
SMIQ OPERATING
3
-
G n M µ k
m x1
ç
ENTER
dBµV BIT CLOCK µV
SYMBOL CLOCK
mV
dB(m)
Move cursor
SELECT
Next menu
RETURN
Previous menu
VERSION:
(BB-AM) I
MENU / VARIATION RETURN
SELECT Q
ï ð
1.33
QUICK SELECT STBY
ASSIGN
MENU1
MENU2
PRESET
ERROR
STATUS
ON
HELP
LOCAL
M0D 0N/0FF
RF 0N/0FF
! MAX 50 W REVERSE POWER
MADE IN GERMANY
RFOUT: 500 MHz, any type of modulation, with fading
Fig. 4: Generation of faded signal with any type of modulation solely by means of additional signal generator
Settings for generation of faded signal with 500 MHz carrier frequency and any type of modulation: SMIQ:
SME/T:
Output spectrum (see Fig. 5): Apart from the desired output frequency •, there appear the suppressed RF ƒ (frequency set on SMIQ) and the 2nd sideband ‚ (frequency set on SMIQ - f 1). Further spectral components obtained are spurious resulting from the harmonics of the signal applied „ ….
Frequency: 497 MHz Level: any (max. -5 dBm, ie output level max. -11 dBm because power is split between the two sidebands) Vector modulation: ON Fading simulator: ON Configuration of fading simulator as required for task in hand
The level of the desired output frequency (and the level of the 2nd sideband) is 6 dB lower than the level set on SMIQ due to the signal power being split up between the two sidebands. This applies to modulation with constant envelope (eg FM, FSK) and a nominal level of +4 dBm at the I/Q inputs.
Frequency: 3 MHz Level +4 dBm 1) Modulation: any
1)
With AM, PSK or QAM modulation, the level is to be re duced so that the peak voltage at the I (or Q) input will not exceed 0.5 V. For example, with 100% AM, the level must be reduced by 6 dB, ie to -2 dBm.
1MA07_0E
5
Rohde & Schwarz
The additional spectral components should typically have no effect in testing selective receivers. If necessary, the frequency spacing can be slightly
varied by varying the frequency f 1. However, it must be ensured that f1 will not exceed 5 MHz (= 0.5 dB bandwidth of fading simulator).
2
1
4
4 5
5
3
Fig. 5: Output spectrum of SMIQ. At 6 MHz below the useful signal •, there appears the 2nd sideband ‚ at the same level. Both levels are 6 dB lower than the level set on SMIQ.
Evaluation:
J
Simplest test setup
L
The 2nd sideband is not suppressed, the max. output level is reduced by 6 dB as compared with other solutions, and the frequency of the test signal is fixed (approx. 2 to 5 MHz).
4.2. Suppression of Unwanted Sideband with 90° Power Splitter
If it is necessary to suppress the second sideband, it is expedient to use a 90° power splitter that operates in the frequency range 2 to 5 MHz (eg PSCQ-2-8 from Mini Circuits). Since the Q signal is phase-shifted by 90° relative to the I signal but is otherwise equal, the second sideband is suppressed and the power fully applied to the other sideband. The output level of SMIQ is therefore equal to the set level. The test setup is as follows:
1MA07_0E
6
Rohde & Schwarz
SIGNALGENERATOR
5kHz...1.5GHz
SMT02
1039.2000.02 DATA INPUT
3.000 000 0
FREQ
MHz
LEVEL
7.0
7
8
9
LEVEL
4
5
6
M
3
k
ç
ENTER
n
dBµV PULSE
dBm
SAVE
FREQUENCY LEVEL ANALOG MOD VECTOR MOD DIGITAL MOD DIGITAL STD LF OUTPUT SWEEP LIST MEM SEQ UTILITIES
G
FREQ
SME/T
1
2
0
.
OPERATING
RCL
-
µ
m
x1
µV
mV EXT 1
dB(m)
Move cursor
SELECT
RETURN
VERSION:
EXT 2
MENU / VARIATION RETURN
Next menu
SELECT LF
Previous menu
ï ð
1.33
RF 50
RF 1 = 3 MHz, any type of modulation, Vpk = 0.7 V (+7 dBm)
QUICK SELECT STBY ASSIGN
MENU1
MENU2
PRESET
ERROR
STATUS
M0D 0N/0FF
LOCAL
HELP
ON
!
RF 0N/0FF
MAX 50 W REVERSE POWER
MADE IN GERMANY
SIGNALGENERATOR
SMIQ03
300kHz...3.3GHz
1084.8004.03 DATA
DATA INPUT FREQ
497.000 000 0
FREQ
FREQUENCY LEVEL ANALOG MOD VECTOR MOD DIGITAL MOD DIGITAL STD LF OUTPUT SWEEP LIST MEM SEQ UTILITIES
MHz
LEVEL
- 10.0
7
8
LEVEL
4
5
SAVE
1
2
9
dBm
SMIQ OPERATING
RCL
0
.
6
-
G
M
n
dBµV
µ
µV
m
mV
3
k
ç
ENTER
x1
BIT CLOCK
SYMBOL CLOCK
dB(m)
Move cursor
SELECT
Next menu
RETURN
Previous menu
VERSION:
(BB-AM) I
MENU / VARIATION RETURN
Vpk = 0.5 V
SELECT Q
ASSIGN
MENU1
MENU2
PRESET
-90°
ï ð
1.33
QUICK SELECT STBY
90° power splitter
Optional lowpass filter
ERROR
STATUS
HELP
LOCAL
ON
M0D 0N/0FF
RF 0N/0FF
! MAX 50 W REVERSE POWER
MADE IN GERMANY
RFOUT: 500 MHz, any type of modulation, with fading
Fig. 6: Generation of faded signal with any type of modulation by means of additional signal generator and 90° phase shifter
Settings for generation of faded 500 MHz signal with any type of modulation: SMIQ:
Level: any (max. -5 dBm) Frequency: 497 MHz Vector modulation: ON Fading simulator: ON Configuration of fading simulator as required for task in hand
SME/T:
Frequency: 3 MHz Level: +7 dBm 2) Modulation: any
Output spectrum (see Fig. 7, Fig. 8): The suppression achievable for the second sideband ‚ is typically 40 dB without additional adjustment (fine adjustment of amplitude and phase by additional controls), the suppression of the LO signal ƒ approx. 50 dB. The harmonics of the signal applied appear as spurious „… and can be suppressed by a lowpass filter connected ahead of the 90° power splitter (see Fig. 8).
2)
With AM, PSK or QAM modulation, the level is to be re duced so that the peak voltage at the I (or Q) input will not exceed 0.5 V. For example, with 100% AM, the level must be reduced by 6 dB, ie to +1 dBm.
1MA07_0E
7
Rohde & Schwarz
1
2 3 4
5
Fig. 7: Output spectrum with 90° power splitter
1
2 3
Fig. 8: Output spectrum same as Fig. 4, with additional lowpass filter
1MA07_0E
8
Rohde & Schwarz
Evaluation:
J
L
4.3. Use of Additional Mixer and 90° Phase Shifter
Uncomplicated test setup, suppression of second sideband
If the output frequency of the signal to be faded is in the RF range (> approx. 30 MHz), it is expedient to downconvert the signal to the 3 MHz IF by means of an external mixer. Analogously to 4.2, the 3 MHz IF is then applied to the I-Q inputs of SMIQ via a 90° power splitter.
The frequency of the test signal is fixed (range approx. 2 to 5 MHz). The max. fading bandwidth is limited to approx. 2 MHz by the 90° power splitter.
Typical application: Fading of 935.2 MHz output signal of GSM base station transmitter
High-power attenuator RF1 = 935.2 MHz
SIGNALGENERATOR
SMT02
5kHz...1.5GHz
1039.2000.02 DATA INPUT
890.000 000 0MHz
FREQ
FREQUENCY LEVEL ANALOG MOD VECTOR MOD DIGITAL MOD DI GITAL STD LF OUTPUT SWEEP LIST MEM SEQ UTILITIES
LEVEL
13.0
FREQ
7
8
9
LEVEL
4
5
6
SAVE
1
2
3
G n
dBµV PULSE
dBm
SME/T OPERATING
RCL
0
.
M µ k
-
m x1
ç
µV
mV EXT 1 dB(m)
ENTER
Move cursor
SELECT
Next menu
RETURN
Previous menu
VERSION:
EXT 2
MENU / VARIATION RETURN
SELECT
RF
LF
ï ð
1.33
LO
RF 50
QUICK SELECT STBY
ASSIGN
MENU1
MENU2
PRESET
ERROR
STATUS
HELP
M0D 0N/0FF
LOCAL
!
RF 0N/0FF
MAX 50 W REVERSE POWER
ON
MADE IN GERMANY
RF2= RF1 - IF (932.2 MHz), Level: +13 dBm, unmodulated
Frequency setting: RF3= RF2 (932.2 MHz), vector modulation ON SIGNALGENERATOR
SMIQ03
300kHz...3.3GHz
1084.8004.03 DATA
DATA INPUT FREQ
497.000 000 0 MHz
FREQ
FREQUENCY LEVEL ANALOG MOD VECTOR MOD DIGITAL MOD DI GITAL STD LF OUTPUT SWEEP LIST MEM SEQ UTILITIES
LEVEL
- 10.0
7
G
8
9
dBm
SMIQ
LEVEL
4
5
SAVE
1
2
RCL
0
.
OPERATING
6 3
-
n M
k
µ
m x1
ç
ENTER
dBµV BIT CLOCK µV
Next menu
RETURN
Previous menu
VERSION:
+ 7 dBm IF: 3 MHz
dB(m)
Move cursor
SELECT
90° power splitter
SYMBOL CLOCK
mV
(BB-AM) I
MENU / VARIATION RETURN
Vpk = 0.5 V
SELECT Q
ï ð
1.33
-90°
RF 50
QUICK SELECT STBY
ASSIGN
MENU1
MENU2
PRESET
ERROR
STATUS
HELP
ON
LOCAL
M0D 0N/0FF
RF 0N/0FF
! MAX 50 W REVERSE POWER
MADE IN GERMANY
RFOUT = RF1 (935.2 MHz) with fading
Fig. 9: Fading of RF signal with any type of modulation (example: GSM transmitter signal) by means of additional mixer and 90° power splitter
1MA07_0E
9
Rohde & Schwarz
Settings for fading of any RF signal, eg 935.20 MHz:
4.4.
Test signal: Frequency: any, eg 935.2 MHz Level: -10 dBm, Modulation: any
Maximum fading bandwidth (+-5 MHz, -1 dB), eg for special wideband CDMA signals, can be achieved by converting the signal to be faded to the baseband by means of a suitable external IQ demodulator (for example ZAMIQ-895 D from Mini Circuits, suitable for RF signals in the range 868 to 895 MHz). The output signals of the IQ demodulator are to be boosted to the level of +4 dBm required by SMIQ (peak voltage: 500 mV) by means of suitable amplifiers (block diagram of test setup shown in Fig. 10).
SME/T:
(supplies LO signal for the mixer) Frequency: frequency of test signal - IF (932.2 MHz), Level: +13 dBm, Modulation: unmodulated
SMIQ:
Output spectrum:
Level: any (max. -5 dBm) Frequency: 932.2 MHz Vector modulation: ON Fading simulator: ON Configuration of fading simulator as required for task in hand.
Use of External IQ Demodulator
The quality of a signal converted to the baseband is decisively influenced by the quality of the IQ demodulator, which will in general be markedly lower than that of the SMIQ modulator. Quality criteria include carrier suppression (DC offset), IQ imbalance, quadrature offset.
Same as 4.2, see Figs 7, 8.
Impairment of quality can be avoided (at smaller fading bandwidths) by carrying out conversion to the 3 MHz IF also with the IQ mixer. In this case, however, test setup according to 4.2 or 4.3 would be the simpler one.
Evaluation:
J
Any RF test signal can be faded.
L
Complex test setup (external mixer, amplifier, etc required); additional signal generator needed to furnish LO signal for mixer
Signal Generator 1 SIGNALGENERATOR
5kHz...1.5GHz
SMT02
1039.2000.02 DATA INPUT
890.000 000 0 MHz
FREQ
FREQUENCY LEVEL ANALOG MOD VECTOR MOD DIGITAL MOD DIGITAL STD LF OUTPUT SWEEP LIST MEM SEQ UTILITIES
LEVEL
-10.0
FREQ
7
8
9
LEVEL
4
5
6
SAVE
1
2
RCL
0
.
G n
dBµV
dBm
PULSE
SME/T OPERATING
3
M
µ
k m
-
x1
ç
µV
mV EXT 1 dB(m)
ENTER
Move cursor
SELECT
Next menu
RETURN
Previous menu
VERSION:
EXT 2
MENU / VARIATION RETURN
SELECT LF
ï ð
1.33
RF 1 any type of modulation
QUICK SELECT STBY
ASSIGN
MENU1
MENU2
PRESET
ERROR
STATUS
HELP
M0D 0N/0FF
LOCAL
!
RF 0N/0FF
External IQ demodulator
MAX 50 W REVERSE POWER
ON
MADE IN GERMANY
SIGNALGENERATOR
SMT02
5kHz...1.5GHz
Q
1039.2000.02 DATA INPUT
890.000 000 0 MHz
FREQ
LEVEL
13.0
FREQ
7
8
9
LEVEL
4
5
6
1
2
0
.
dBm
SAVE
FREQUENCY LEVEL ANALOG MOD VECTOR MOD DIGITAL MOD DIGITAL STD LF OUTPUT SWEEP LIST MEM SEQ UTILITIES
SME/T OPERATING
RCL
3
SELECT
Next menu
RETURN
Previous menu
n
k
-
dBµV PULSE
µ
m x1
ç
Move cursor
VERSION:
G
M
Vpk = 0.5 V (+4 dBm)
µV
mV EXT 1 dB(m)
ENTER
LO
EXT 2
MENU / VARIATION RETURN
90°
SELECT
0°
RF
LF
1.33
ï ð
RF 50
QUICK SELECT STBY
ASSIGN
MENU1
MENU2
PRESET
ERROR
STATUS
HELP
M0D 0N/0FF
LOCAL
ON
!
RF 0N/0FF
MAX 50 W REVERSE POWER
RF 2 unmodulated
MADE IN GERMANY
Signal Generator 2 Signal Generator 3 SIGNALGENERATOR
SMIQ03
300kHz...3.3GHz
I Vpk = 0.5 V (+4 dBm)
1084.8004.03 DATA
DATA INPUT
1.8000 000 0
FREQ
GHz
LEVEL
- 10.0
FREQ
7
8
9
LEVEL
4
5
6
1
2
0
.
dBm
SAVE
FREQUENCY LEVEL ANALOG MOD VECTOR MOD DIGITAL MOD DIGITAL STD LF OUTPUT SWEEP LIST
SMIQ OPERATING
RCL
Move cursor
SELECT
Next menu
RETURN
Previous menu
VERSION:
MEM SEQ UTILITIES
3
-
G n M
k
µ
m x1
ç
dBµV BIT CLOCK µV
mV
SYMBOL CLOCK
dB(m)
ENTER
(BB-AM) I
MENU / VARIATION RETURN
SELECT Q
1.33
ï ð
RF 50
Signal with analog/digital Modulation and fading
QUICK SELECT STBY ON
ASSIGN
MENU1
MENU2
PRESET
ERROR
STATUS
HELP
LOCAL
M0D 0N/0FF
RF 0N/0FF
! MAX 50 W REVERSE POWER
MADE IN GERMANY
Fig. 10: Test setup for fading a signal with any type of modulation by means of external IQ demodulator
1MA07_0E
10
Rohde & Schwarz
Evaluation:
J
Any RF test signal can be faded by means of a suitable IQ demodulator. Maximum bandwidth through conversion to baseband (IF = 0).
L
Highly complex test setup
5.
Summary of Pros and Cons Criteria:
Procedure to:
Complexity of test setup
Distortion of useful signal
Spurious
Possible bandwidth
4.1 with 2nd signal generator
JJ
J
LL( 0 dB)
J approx. 4 MHz
4.2 with 90° power splitter
J
J
K (approx. -40 dB)
K
approx. 2 MHz
4.3 with external mixer
L
J
K (approx. -40 dB)
K
approx. 2 MHz
4.4 with external I/Q demodulator
L
L
J <-50 dB
J J approx. 10 MHz
Table 1: Advantages and disadvantages of various procedures using SMIQ as fading simulator for external signals
7. 6.
References
1. William C. Jakes, Microwave Mobile Communications, IEEE Press 2. Operating manual for Vector Signal Generator SMIQ, section 2.9, Fading Simulation
.
Ordering Information
Vector Signal Generator
SMIQ03
Fading Simulator
SMIQ-B14 1085.4002.02
Signal Generator
SMT02
1039.2000.02
Signal Generator
SME02
1038.6002.02
.
ROHDE & SCHWARZ GmbH & Co. KG P.O.B. 80 14 69 D-81614 München . Telephone +49 89 4129 -0 · Telefax +49 89 4129 - 3777 Internet: http://www.rsd.de
1084.8004.03
