Tekbox TBMDA2 User guide

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TBMDA2

Modulated Wideband Driver Amplifier

1 Introduction

The TBMDA2 modulated wideband driver 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 its 1dB compression point of +27dBm, it can boost the output power of a tracking generator up to 500mW. The TBMDA2 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 170V/m when driving the Tekbox TEM Cell TBTC0, 100V/m when driving the TBTC1, 50V/m when driving the TBTC2 or 30V/m when driving the TBTC3. Test signals for immunity testing can be CW, AM or PM. Consequently, the TBMDA2 provides built in modulation capability to generate 1 kHz AM or PM signals. In PM mode, the TBMDA2 can also generate a 217 Hz Signal with 12.5% duty cycle in order to simulate mobile phone TDMA noise.

Picture 1 – TBMDA2 modulated wideband driver amplifier, front view

Picture 2 – TBMDA2 modulated wideband driver amplifier, rear view

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10 MHz

25 MHz

100 MHz

200 MHz

300 MHz

400 MHz

500 MHz

600 MHz

700 MHz

44.2 dB

46.3 dB

46.7 dB

46.6 dB

45.3 dB

44.2 dB

43.8 dB

42.9 dB

41.7 dB

800 MHz

900 MHz

1 GHz

1.1 GHz

1.2 GHz

1.3 GHz

1.4 GHz

1.5 GHz

39.6 dB

40.1 dB

39.3 dB

38.5 dB

37.3 dB

36.8 dB

35.9 dB

34.8 dB

TBMDA2

Modulated Wideband Driver Amplifier

Application:

General-purpose gain block 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, SMA female Nominal supply Voltage: 5V, typ. 700mA, Mini-USB-B connector Maximum supply voltage: 5.5V Maximum input power: -8dBm continuous, 0 dBm @ 25°C for 5 minutes max. Operating temperature range: -20°C to 50°C Frequency range: 10MHz – 1.5 GHz 1dB output compression point @ 10MHz: +24 dBm typ. 1dB output compression point @ 100 MHz: +27 dBm typ. 1dB output compression point @ 1 GHz: +27 dBm typ. 1dB output compression point @ 1.5 GHz: +26.5 dBm typ. Harmonics: < - 30 dBc typ. Internal modulation frequency AM: 1 kHz ±10% Internal modulation frequencies PM: 1 kHz ±10%, 217 Hz ±20% Duty cycle, PM: 50% ±10% @ 1 kHz; 12.5% ±20% @ 217 Hz Gain:

Table 1 – TBMDA2 gain

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Frequency

[MHz]

Output power

@ -20 dBm input

power [dBm]

Output power

@ -18 dBm input

power [dBm]

Output power

@ -16 dBm input

power [dBm]

Output power

@ -14 dBm input

power [dBm]

Output power

@ -12 dBm input

power [dBm]

Output power

@ -10 dBm input

power [dBm]

Output power

@ -8 dBm input

power [dBm]

10

24.8

24.7

24.4

24.1

24.3

25

26.4

26.1

25.7

25.4

25.5

25.7

50

27.1

27.2

26.9

26.5

26.2

26.4

100

27.1

27.6

27.5

27.2

26.7

27

200

26.7

27.8

27.9

27.6

27.2

300

26.1

27.5

27.8

27.6

27.4

27.2

400

25.6

27.4

28.2

28.1

27.8

27.4

500

24.9

26.7

28

28.2

28

27.7

27.5

600

24.1

26.1

27.6

28.2

27.8

27.6

700

23

24.9

26.6

27.6

27.8

27.6

27.3

800

20.9

22.8

24.6

26.1

26.6

26.5

900

21.2

23.2

25.1

26.8

27.9

28.1

1000

20.5

22.5

24.4

26.2

27.6

28.1

1100

19.5

21.5

23.5

25.3

27

28

28.1

1200

18.1

20.2

22.2

24.1

25.9

27.4

27.9

1300

17.7

19.7

21.7

23.7

25.5

27.2

28.1

1400

16.8

18.8

20.8

22.8

24.6

26.5

27.8

1500

15.8

17.8

19.8

21.8

23.7

25.4

27.02

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600

Output power versus frequency

Output power @ -20 dBm input power [dBm]

Output power @ -18 dBm input power [dBm]

Output power @ -16 dBm input power [dBm]

Output power @ -14 dBm input power [dBm]

Output power

TBMDA2

Modulated Wideband Driver Amplifier

Figure 1 – TBMDA2, output power versus frequency, 10MHz – 1.5GHz

Table 2 – TBMDA2 power table

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Frequency [MHz]

Input power [dBm]

Output power [dBm]

gain [dB]

10

-19.92

24.3

44.22

25

-19.8

26.5

46.3

50

-19.6

27.1

46.7

100

-19.2

27.4

46.6

200

-18.4

27.6

46

300

-17.6

27.7

45.3

400

-16.8

27.4

44.2

500

-16

27.8

43.8

600

-15.2

27.7

42.9

700

-14.4

27.3

41.7

800

-13.6

26

39.6

900

-12.8

27.3

40.1

1000

-12

27.3

39.3

1100

-11.2

27.3

38.5

1200

-10.4

26.9

37.3

1300

-9.6

27.2

36.8

1400

-8.8

27.1

35.9

1500

-8

26.8

34.8

15

17

19

21

23

25

27

29

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600

Output power [dBm]

TBMDA2

Modulated Wideband Driver Amplifier

Frequency response:

The tables above show a 10dB gain variation across the frequency range 10 MHz to 1.5 GHz. When driving the TBMDA2 with the tracking generator of a spectrum analyzer, the TG level can be set to -8 …-12 dBm to get a flat output power response over the frequency range. This will drive the amplifier into compression for lower frequencies. This is acceptable when using CW or pulse modulation for immunity testing. However, when doing immunity tests with an AM modulated signal, it would clip the AM envelope, as the modulator is in front of the output stage of the TBMDA2.

Hence, when using AM modulation, the input power shall be set to levels where the TBMDA2 is in linear operation. Linear operation: You can calculate the drive levels for linear operation using following approximation formula or the table below: P

[dBm] = 0.008 *frequency [MHz]-20

input

Table 3 – input drive levels for linear operation

As tracking generator levels usually can only be adjusted in 1dB steps, apply the closest integer value.

Figure 2 – output power, applying the drive levels given in table3, 10MHz – 1.5GHz

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TBMDA2

Modulated Wideband Driver Amplifier

Figure 3 – 1 kHz, 80 % AM envelope, applying the drive levels given in table3, 500 MHz

Figure 4 – 1 kHz, 50 % PM envelope, 500 MHz

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TBMDA2

Modulated Wideband Driver Amplifier

Figure 5 – 217 Hz, 12.5 % PM envelope, 500 MHz

Figure 6 – CW, harmonics, 200 MHz

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TBMDA2

Modulated Wideband Driver Amplifier

3 Power supply

The current consumption of the TBMDA2 is 700mA and consequently exceeds the current limit of USB 2.0 ports. Supply the TBMDA2 through a USB 3.0 port or a mobile phone charger with an output current capability of 1A or higher.

Connector: Mini-USB-B

4 Applications

Immunity testing using a TEM cell

Figure 7 – immunity testing set up

Immunity testing using near field probes

Figure 8 – 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]

10

-19.92

24.3

131

73

37

24

25

-19.8

26.5

169

95

47

31

50

-19.6

27.1

181

101

51

34

100

-19.2

27.4

187

105

52

35

200

-18.4

27.6

191

107

54

36

300

-17.6

27.7

194

109

54

36

400

-16.8

27.4

187

105

52

35

500

-16

27.8

196

110

55

37

600

-15.2

27.7

194

109

54

36

700

-14.4

27.3

185

104

52

35

800

-13.6

26

159

89

45

n.a

900

-12.8

27.3

185

104

52

n.a

1000

-12

27.3

185

104

52

n.a

1100

-11.2

27.3

185

104

52

n.a

1200

-10.4

26.9

177

99

49

n.a

1300

-9.6

27.2

183

102

51

n.a

1400

-8.8

27.1

181

101

51

n.a

1500

-8

26.8

175

98

49

n.a

TBMDA2

Modulated Wideband Driver Amplifier

5 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 4 – calculated field strength for TBMDA2 driving Tekbox TEM cells

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TBMDA2

Modulated Wideband Driver Amplifier

6 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 9 – screenshot of the tracking generator control feature of EMCview

WARNING: Never connect the output of the TBMDA2 directly to the input of a

spectrum analyzer. Check the maximum input ratings of the spectrum analyzer and protect it with an appropriate attenuator.

Example: Rigol DSA815 – maximum input power rating: +20dBm

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Part Number

Description

TBMDA2

modulated driver amplifier, 2 pcs 75cm SMA-male to N-male cables, 1 pc 20dB attenuator with N-connectors, USB cable,

Version

Date

Author

Changes

V1.0

31.5.2018

Mayerhofer

Creation of the document

TBMDA2

Modulated Wideband Driver Amplifier

7 Ordering Information

8 History

Table 5 – Ordering Information

Table 6 – History