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1
TBMDA4
Modulated Wideband Power Amplifier
1 Introduction
The TBMDA4 modulated wideband power amplifier is designed in order to create an inexpensive signal source
for immunity testing of electronic building blocks and products. It is designed to be driven by the tracking
generator output of spectrum analyzers. With an input power range of -5 dBm…0 dBm, it can boost the output
power of a tracking generator up to 5W. With a frequency range from 100 kHz to 50 MHz, it is an ideal
complement to the TBMDA3, which covers 10 MHz to 1 GHz. The TBMDA4 is ideal to drive Tekbox near field
probes in order to find the sensitive spot of an electronic circuit or to create electric fields up to 550V/m when
driving the Tekbox TEM Cell TBTC0, 300V/m when driving the TBTC1, 150V/m when driving the TBTC2 or
100V/m when driving the TBTC3. Test signals for immunity testing can be CW, AM or PM modulated.
Consequently, the TBMDA4 provides built in modulation capability to generate 1 kHz AM or PM signals. In PM
mode, the TBMDA4 can also generate a 217 Hz Signal with 12.5% duty cycle in order to simulate mobile phone
TDMA noise.
Picture 1 – TBMDA4 modulated wideband driver amplifier, front view
Picture 2 – TBMDA4 modulated wideband driver amplifier, rear view
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TBMDA4
Modulated Wideband Power Amplifier
Application:
General-purpose power amplifier
Signal source for immunity testing, driving near field probes
Signal source for immunity testing, driving TEM Cells
Features:
CW amplifier (modulation off)
1 kHz, 80% AM modulation
1 kHz, 50% duty cycle pulse modulation
217 Hz, 12.5% duty cycle pulse modulation
2 Electrical Specifications
Technical Data:
Input / Output: 50 Ohm, N female
Supply Voltage range: 110 V…240 V
Supply power consumption: 20 W
Operating temperature range: -20°C to 50°C
Frequency range: 100 kHz – 50 MHz
1dB output compression point @ 1 MHz: +35.5 dBm typ.
1dB output compression point @ 10 MHz: +36 dBm typ.
1dB output compression point @ 50 MHz: +36.5 dBm typ.
2nd harmonic, 20 MHz, Pout=36dBm: < - 15 dBc typ.
2nd harmonic, 25 MHz, Pout=30dBm: < - 20 dBc typ.
3rd harmonic, 25 MHz, Pout=36dBm: < - 25 dBc typ.
3rd harmonic, 25 MHz, Pout=30dBm: < - 30 dBc typ.
Total harmonic distortion:
6.7% @25MHz, Pout=27dBm typ.
8.5% @25 MHz, Pout=30 dBm typ.
12% @25 MHz, Pout=33 dBm typ.
15% @25 MHz, Pout=36 dBm typ.
Third order intercept point:
+53dBm, @25 MHz, ∆ f = 200kHz typ.
Noise figure: 9 dB
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3
50 kHz
100 kHz
500 kHz
1 MHz
5 MHz
10 MHz
25 MHz
50 MHz
70 MHz
39.3 dB
44.9 dB
47.1 dB
47.2 dB
47.3 dB
47.5 dB
48.6 dB
49.9 dB
44.5 dB
50 kHz
100 kHz
500 kHz
1 MHz
5 MHz
10 MHz
25 MHz
50 MHz
70 MHz
32.8 dBm
@Pin=
-6 dBm
33.9 dBm
@Pin=
-10 dBm
34.4 dBm
@Pin=
-12 dBm
35.3 dBm
@Pin=
-11 dBm
35.5 dBm
@Pin=
-11 dBm
35.7 dBm
@Pin=
-11 dBm
35.8dBm
@Pin=
-12 dBm
35.8 dBm
@Pin=
-13 dBm
33.2 dBm
@Pin=
-10 dBm
50 kHz
100 kHz
500 kHz
1 MHz
5 MHz
10 MHz
25 MHz
50 MHz
70 MHz
34.1 dBm
@Pin=
-3 dBm
34.9 dBm
@Pin=
-5 dBm
35.3 dBm
@Pin=
-7 dBm
36.3 dBm
@Pin=
-7 dBm
37.3 dBm
@Pin=
-7 dBm
37.4 dBm
@Pin=
-7 dBm
37.5dBm
@Pin=
-7 dBm
37.6 dBm
@Pin=
-7 dBm
36.6 dBm
@Pin=
-3 dBm
TBMDA4
Modulated Wideband Power Amplifier
Internal modulation frequency AM: 1 kHz ±20%
Internal modulation frequencies PM: 1 kHz ±10%, 217 Hz ±20%
Duty cycle, PM: 50% ±10% @ 1 kHz; 12.5% ±20% @ 217 Hz
Maximum ratings:
Maximum input power: 0 dBm
The output of the TBMDA4 is quite tolerant to output mismatch, however open or shorted load is not recommended,
potentially can cause damage.
Small Signal Gain (measured with Pin = - 20 dBm):
Linear output power:
Table 2 – TBMDA4, linear output power versus frequency, 50 kHz – 70 MHz
Saturated output power:
Table 1 – TBMDA4 gain
Table 3 – TBMDA4, saturated output power versus frequency, 50 kHz – 70 MHz
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TBMDA4
Modulated Wideband Power Amplifier
Figure 1 – 1 kHz, 80 % AM envelope, 25 MHz
Figure 2 – 1 kHz, 50 % PM envelope, 25 MHz
Figure 3 – 217 Hz, 12.5 % PM envelope, 25 MHz
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TBMDA4
Modulated Wideband Power Amplifier
3 Applications
Immunity testing using a TEM cell
Figure 4 – immunity testing set up
Immunity testing using near field probes
Figure 5 – immunity testing set up
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Frequency [MHz]
Input power
[dBm]
Output power
[dBm]
Field strength
TBTC0 [V/m]
Field strength
TBTC1 [V/m]
Field strength
TBTC2 [V/m]
Field strength
TBTC3 [V/m]
0.05
-3
34.1
405
227
113
76
0.1
-5
34.9
444
249
124
83
0.5
-7
35.3
465
260
130
87 1 -7
36.3
522
292
146
97
5
-7
37.3
585
328
164
109
10
-7
37.4
592
332
166
111
25
-7
37.5
599
335
168
112
50
-7
37.6
606
339
170
113
70
-3
36.6
540
302
151
101
TBMDA4
Modulated Wideband Power Amplifier
4 TEM Cell field strength
A typical pre compliance set up for immunity testing is typically not sophisticated enough to measure the real field
strength inside the TEM cell. However, the field strength can be approximated mathematically.
The E-field (V/m) between septum and lower (upper) wall of a TEM cell is E = V/d where V is the RMS voltage of
the applied signal and d is the distance between septum and lower (upper) wall. This is based on the simplified
assumption that the E field would be perfectly homogenous/evenly distributed. A more practical formula is E =
V*Cor/d where Cor is a correction factor for the average field strength over the volume of the DUT derived from
the analysis of the field distribution over the cross section of the cell.
Assuming the DUT is placed in the center of the cell and in the middle between bottom wall and septum, we can
however use the simplified formula with sufficient accuracy.
TBTC0: d = 2.8 cm -> E
TBTC1: d = 5 cm -> E
TBTC2: d = 10 cm -> E
TBTC3: d = 15 cm -> E
The power P in the formulas above hast to be entered in [Watt]
P
= 0.001*(10^ (P
[W]
[dBm]
= (√(P*50Ω))*35.7
[V/m]
= (√(P*50Ω))*20
[V/m]
= (√(P*50Ω))*10
[V/m]
= (√(P*50Ω))*6.66
[V/m]
/10))
Table 3 – calculated field strength for TBMDA4 driving Tekbox TEM cells
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TBMDA4
Modulated Wideband Power Amplifier
5 PC Software for immunity testing
The Tekbox EMCview SW is regularly updated and now supports immunity testing with a feature for automated
tracking generator control. This significantly simplifies immunity testing, especially in case of repeated testing
during validation of DUT modifications/improvements.
Tekbox EMCview currently supports Rigol, Siglent, R&S FPC and FPH series spectrum analyzers.
Figure 8 – screenshot of the tracking generator control feature of EMCview
WARNING:
Never connect the output of the TBMDA4 directly to the input of a
spectrum analyzer. Check the maximum input ratings of the
spectrum analyzer and protect it with an appropriate attenuator.
Open or shorted load is not recommended, potentially can cause
damage of the RF output stage.
Example:
Rigol DSA815 – maximum input power rating: +20dBm
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Part Number
Description
TBMDA4-EU
modulated power amplifier, 2 pcs 75cm N-male to N-male cables, 1 pc 30dB / 10W
attenuator with N-connectors, C13 Schuko power cord
TBMDA4-US
modulated power amplifier, 2 pcs 75cm N-male to N-male cables, 1 pc 30dB / 10W
attenuator with N-connectors, C13 US power cord
TBMDA4-UK
modulated power amplifier, 2 pcs 75cm N-male to N-male cables, 1 pc 30dB / 10W
attenuator with N-connectors, C13 English power cord
TBMDA4-AU
modulated power amplifier, 2 pcs 75cm N-male to N-male cables, 1 pc 30dB / 10W
attenuator with N-connectors, C13 Australian power cord
Version
Date
Author
Changes
V1.0
6.9.2018
Mayerhofer
Creation of the document
V1.1
30.3.2021
Mayerhofer
Updated chaper 6
V1.2
9.4.2021
Mayerhofer
Corrected table 3
TBMDA4
Modulated Wideband Power Amplifier
6 Ordering Information
Table 5 – Ordering Information
7 History
Table 6 – History
www.tekbox.com
TekBox Digital Solutions Vietnam Pte. Ltd.
Factory 4, F5, Lot I-3B-1, Saigon Hi-Tech Park, Tan Phu Ward, District 9, Ho Chi Minh City, Vietnam
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