Download: APPLICATION NOTE A broadband3Wamplifier for band IV/V TV transposers based on the BLW898 AN98015

APPLICATION NOTE A broadband3Wamplifier for band IV/V TV transposers based on the BLW898 AN98015,

CONTENTS

1 ABSTRACT 2 INTRODUCTION 3 AMPLIFIER ELECTRICAL DESIGN OBJECTIVES 4 DESIGN OF THE AMPLIFIER 4.1 Mounting the transistor 4.2 Positioning of the matching capacitors (see Figs 3 and 4) 5 AMPLIFIER TUNING PROCEDURE 6 AMPLIFIER PERFORMANCE 7 CONCLUSION 8 APPENDIX 1 1998 Mar 23 2, 1 ABSTRACT A broadband linear amplifier design is presented, suitable for application in TV transposers, operating in band IV and V (470 − 860) MHz. The design is based on a BLW898 bipolar transistor. Typical results at the recommended class-A bias point (25 V/1.1 A) for the total module include a 3-tone IMD level of −64 dB (fvision = −8 dB, fsideband = −16 dB and fsound = −10 dB) and an average gain of 10.5 dB at3Wpeak-sync output power in the (470 − 860) MHz frequency range. 2 INTRODUCTION The BLW898 is a bipolar linear power transistor designed to operate in the (470 − 860) MHz range. The transistor is encapsulated in a SOT171A 6-lead rectangular flange package with a ceramic cap, see Fig.1. The specified output power is3Wpeak-sync in class-A. The intermodulation distortion level (IMD) < −63 dB (fvision = −8 dB, fsideband = −16 dB and fsound = −10 dB) and gain >10 dB at 860 MHz. For application in TV transposers for Band IV/V (470 − 860) MHz a wideband linear power amplifier has been designed operating in class-A. It is suitable for driving higher power stages in TV-transposers. handbook, halfpagec1234b56ePinning PIN DESCRIPTION Top view MGH823 1 emitter 2 emitter 3 base 4 collector 5 emitter 6 emitter Fig.1 Simplified outline and symbol. 1998 Mar 23 3, 3 AMPLIFIER ELECTRICAL DESIGN OBJECTIVES Electrical characteristics (Ths = 25 °C; 25 V; 1.1 A; (470 − 860) MHz). PARAMETER SYMBOL MIN. TYP. MAX. UNIT Transducer power gain (small signal) Gp 10 − − dB Gain ripple (small signal) Gripple − − ±1 dB Intermodulation (−8 dB/−16 dB/−7 dB, IMD1 − − −60 dB Peak-sync = 3 W; note 1 Intermodulation (−8 dB/−16 dB/−10 dB, IMD2 − − −63 dB Peak-sync = 3 W; note 1 Output return loss ORL − −15 − dB Note 1. Peak-sync is a reference power level for TV-signals, in this case used fora3carrier signal. 4 DESIGN OF THE AMPLIFIER The amplifier consists of a BLW898 plus an input and output matching circuit. The input is gradually mismatched and therefore not matched to 50 Ω. To obtain a good input matching a balanced circuit with two BLW898 transistor is necessary. A schematic diagram of the BLW898 amplifier is given in Fig.2. A components list is given in “Appendix 1”. 4.1 Mounting the transistor For good thermal contact, heatsink compound should be used when mounting the transistor on a heatsink. 4.2 Positioning of the matching capacitors (see Figs 3 and 4) Input: The capacitors C4 + C5 are situated as close as possible near the transistor The capacitors C2 + C3 are situated on a distance of approx. 19 mm from the transistor The position of the ‘input’ capacitors influence the tuning for flat gain. Output: The capacitors C6 + C7 are situated on a distance of approx. 10.5 mm from the transistor The capacitors C8 + C9 are situated on a distance of approx. 21 mm from the transistor Capacitor C11 is placed approx. 11.5 mm from stripline L3 The position of the ‘output’ capacitors is critical to obtain the S22 contours as described in the amplifier tuning procedure. Note: • RF choke L6 is placed approx. 5 mm from the transistor base. • Stripline L5 is situated 2.8 mm from the transistor and 2.8 mm from L4. 5 AMPLIFIER TUNING PROCEDURE The amplifier is tuned under small signal conditions by means of a networkanalyzer. The amplifier is tuned for flat gain over the complete bandwidth (470 − 860) MHz. To obtain a flat gain, the input is gradually mismatched. The input returnloss S11 is the main parameter for setting the gain level and flatness. Tuning of the output will mainly influence IMD and to a lesser extent the gain flatness. 1998 Mar 23 4, To obtain a good IMD performance over the band it is recommended to follow the S22 tuning contours as plotted in Figs 5, 6 and 7. An S22 of about −15 dB is required over the complete bandwidth. 6 AMPLIFIER PERFORMANCE Broadband measurement data is presented in Figs 8, 9 and 10. Gain/IMD are measured versus frequency (470 − 860) MHz and versus peak-sync level (at ch69). Gain/IMD are given at two 3-tone systems: • fv = −8 dB/fsb = −16 db/fs = −10 dB • fv = −8 dB/fsb = −16 db/fs = −7 dB. Figure 3 gives gain compression (CW) versus frequency. At a nominal peak-sync level of3Wfor which the module is dimensioned the performance in the (470-860) MHz band is as follows: • 3-tone system: (−8/−16/−7) dB; IMD ≤61 dB/gain >10 dB • 3-tone system: (−8/−16/−10) dB; IMD ≤64 dB/gain >10 dB. (for both systems ripple ≤1.5 dB) 7 CONCLUSION A broadband amplifier is presented based on a BLW898, capable of operating in full band IV/V with flat gain and good linearity. Design and tuning procedure described result in good broadband behaviour. A typ. gain of 10.5 dB with good linearity (peak-sync = 3 W @ −64 dB (−8/−16/−10) dB 3-tone system) has been obtained at the class-A bias point (25 V/1.1 A). handbook, full pagewidth L7 R1 +V R2BB +VCC C12 C13 C14C15 C16 L6 L5 C11 C1 L1 L4 C10input output 50 Ω TR1 50 Ω L2C2 C L34 C6 C8 C3 C5 C7 C9 MGH824 Fig.2 Schematic diagram of the BLW898 amplifier. 1998 Mar 23 5, handbook, full pagewidth 77 77 +VBB +VCC C15 R1 L7 C12 C16 C13 L5 C11 R2 L6 C14 C1 L1 L4 C10 L2 L3 C2 + C4 + C6 + C8 + C3 C5 C7 C9 MGH826 Fig.3 Component layout of the BLW898 amplifier. 1998 Mar 23 6, handbook, full pagewidth 160 77 77 2.8 2.3 2.3 3.25 59 10 9 61 MGH825 Fig.4 Dimensions of the BLW898 amplifier. CH1 S11 log MAG 5 dB MGH827 handbook, full pagewidth BLW898 25V / 1.1 A C2 Ref 0 dB (2) (1) (3) START 100 . 000 000 MHz STOP 1 100 . 000 000 MHz (1) 470 MHz; −3.0 dB. (2) 600 MHz; −7.0 dB. (3) 860 MHz; −7.0 dB. Fig.5 Small signal results. 1998 Mar 23 7, CH1 S22 log MAG 5 dB MGH828 handbook, full pagewidth BLW898 25V / 1.1 A C2 Ref 0 dB (3) (2) (1) START 100 . 000 000 MHz STOP 1 100 . 000 000 MHz (1) 470 MHz; −20.8 dB. (2) 600 MHz; −20.8 dB. (3) 860 MHz; −15.0 dB.

Fig.6 Small signal results.

CH1 S21 log MAG 5 dB MGH829 handbook, full pagewidth BLW898 25V / 1.1 A (2) C2 (3) (1) Ref 0 dB START 100 . 000 000 MHz STOP 1 100 . 000 000 MHz (1) 470 MHz; −10.5 dB. (2) 600 MHz; −10.5 dB. (3) 860 MHz; −11.3 dB.

Fig.7 Small signal results.

1998 Mar 23 8, MGH831 −50 12 IMD gain (dB) (dB) −54 11 (1) (2) −58 10 −62 9 (3) −66 8 (4) −70 7 400 500 600 700 800 900 frequency (MHz) (1) Gain / −8; −16; −10. (2) Gain / −8; −16; −7. (3) IMD / −8; −16; −7. (4) IMD / −8; −16; −10. MGH832 −20 12 handbook, full pagewidth IMD gain (dB) (1) (dB) −30 (2) 10 −40 8 (3) −50 (4) 6 −60 4 −7020510 15 20 25 30 Po sync (W) (1) Gain / −8; −16; −10. (2) Gain / −8; −16; −7. (3) IMD / −8; −16; −7. (4) IMD / −8; −16; −10. Fig.9 Demoboard BLW898; Gain/IMD vs Po_sync/Ths = 25 C; 25 V/1.1 A/ch69. 1998 Mar 23 9, MGH833 handbook, full pagewidth (1) (2) (3) 400 500 600 700 800 900 frequency (MHz) (1) PL = 1 W. (2) PL = 5 W. (3) PL = 10 W. Fig.10 Demoboard BLW898; CW gain compression; 25 V/1.1 A/Ths = 25 C. 1998 Mar 23 10 compression (dB), 8 APPENDIX 1 Component list COMPONENT DESCRIPTION VALUE DIMENSIONS C1 multilayer ceramic chip capacitor, note 1 11 pF C2 multilayer ceramic chip capacitor, note 1 1.5 p C3, C5, C7, C9 Tekelec Giga trimmer 37271 0.6 − 4.5 pF C4 multilayer ceramic chip capacitor, note 1 15 p C6 multilayer ceramic chip capacitor, note 1 7.5 p C8 multilayer ceramic chip capacitor, note 1 2.7 p C10 multilayer ceramic chip capacitor, note 1 5.1 p C11 multilayer ceramic chip capacitor, note 1 270 p C12, C15 solid aluminium capacitor 47 µF; 63 V C13, C14, C16 multilayer ceramic chip capacitor 10 n 0805 L1 stripline, note 2 2.3 × 59 mm 50 Ω L2 stripline, note 2 3.25 × 10 mm 40 Ω L3 stripline, note 2 3.25 × 9 mm 40 Ω L4 stripline, note 2 2.3 × 61 mm 50 Ω L5 stripline, note 2 2.3 × 41.5 mm 50 Ω L6 RF choke 220 nH L7 grade 4S2 ferrocube wideband RF choke (12NC: 4330 030 36301) R1 metal film resistor 10 Ω; 0.6 W R2 metal film resistor 50 Ω; 0.6 W Notes 1. ATC capacitor type 100B or capacitor of same quality. 2. PCB manufacturer: Rogers Ultralam 2000 (BO300M1046QB) (εr = 2.55, thickness 0.76 mm), (stripline value: width × length). 1998 Mar 23 11,

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