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PDF ECO7806 Data sheet ( Hoja de datos )
| Número de pieza | ECO7806 | |
| Descripción | WideBand Linear Power Amplifiers | |
| Fabricantes | Philips | |
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APPLICATION NOTE
Wide-band linear power
amplifiers (470 − 860 MHz) with
the transistors BLW32 and
mBLW33
www.DataSheet4U.coECO7806
www.DataSheet4U.com
1 page  
Philips Semiconductors
Wide-band linear power amplifiers (470 − 860 MHz)
with the transistors BLW32 and BLW33
Application Note
ECO7806
3.2 The output networks
The circuits will be designed on printed circuit boards with P.T.F.E.-fibre-glass as a dielectric with an εr = 2.74 and a
thickness of 1/16 inch.
The input and output network start with a piece of stripline having a width of 6 mm, being the width of the base and
collector leads. For a dielectric of 1/16 inch the characteristic impedance ZC is 37.6 Ω. The length for the collector leads
amounts to 3 mm. The base leads are different in length.
As the output impedance of both transistors is rather high a Chebyshev bandpass-filter configuration will be chosen to
match it to the 50 Ω load. As will be shown later 6 elements are sufficient to obtain an acceptable VSWR through the
band.
The bandpass filter is derived from a low-pass prototype having a cut-off frequency equal to the bandwidth of the final
filter, i.e. 860 − 470 = 390 MHz and a characteristic resistance of 50 Ω (see Ref.1). The transformation procedure is
depicted in Figs 3 to 7. These figures are for the BLW32.
To determine C1 = C3 in Fig.3 we have to keep in mind that the input (and output) RC-product remains constant with
impedance transformation, so: C1 = C3 = 82 × 4.2/50 = 6.9 pF.
Next, we determine the quantity γ being equal to: γ = ω-----c----×----C-1----1----×-----R---
In which ωc is the cut-off frequency of the low-pass prototype and C1 × R is the already mentioned time constant, so:
γ = 2-----×-----π-----×-----3---9---0-----×-----1---0----6---1-×-----6---,--9-----×-----1---0----–--1--2----×-----5----0- = 1,183
Then L2 can be calculated according to: L2 = { ω--R---c-} { -γ--2----+--2---0-γ--,--7---5-- }
in which R is the characteristic resistance of the filter being 50 Ω, so:
L2 = { 2-----×-----π-----×-----53---09---0-----×-----1----0---6-} { 1----,-2-3---9-×--9---1--+-,--1--0-8--,--3-7----5- } = 22,46 nH
The transformation from low-pass to bandpass is made by:
1. Shunting each capacitor by an inductor and
2. Putting the capacitor in series with each inductor, such that resonance is obtained at the geometric mean frequency
of the band: fO = 860.470 = 635.8 MHz
1998 mar 23
5
5 Page 
Philips Semiconductors
Wide-band linear power amplifiers (470 − 860 MHz)
with the transistors BLW32 and BLW33
Application Note
ECO7806
4.3 Measured results
Figures 16 to 21 show the practical results for resp. the BLW32 and BLW33 amplifiers.
The results for two units are both given. They are numbered (1) and (2).
For a clear interpretation of the S11 and S22 readings the expression for the reflection damping and some figures are
given in Table 4:
Table 4 Refl. damping = 20 log (S + 1)/(S − 1) dB in which S is the voltage standing wave ratio (VSWR)
REFL. DAMPING
(dB)
0
4
8
12
16
20
24
28
1
0.631
0.398
0.251
0.158
0.1
0.063
0.04
REFL. COEFF.
∞
4.42
2.32
1.67
1.38
1.22
1.13
1.08
S
Examining Figs 16 and 19 one will see that in both cases, the reflection damping is about 20 dB so the input VSWR is
about 1.2 near 860 MHz, whilst the output VSWR, with respect to 50 Ω, varies between 3 and 1.06 over the band.
After optimization at small signals, the i.m.d. has been measured in a 2-tone set-up. Although it is advised to apply the
3-tone test method for determining the i.m.d. in case of TV systems, the 2-tone test shows a good correlation with the
former (see Ref.3).
In practice this means that for a 3-tone test with the tones at −7, −8 and −16 dB below the 0 dB peak sync. level, the
in-band i.m. product has to be at least −60 dB down, whilst the same amplifier has to show a distance of two i.m. products
d3 of at least −47 dB with respect to one of the equal tones in case of the 2-tone test with equal peak output power.
The results are given in the curves of Figs 22 to 25.
For these amplifiers, of which two each have been constructed and measured, the results are according to the expected
ones for wide-band operation. At three channels the peak sync power for a 3-tone i.m.d. of −60, −56 and −52 dB has
been measured too. Table 5 gives an impression of the average −60 dB results of the BLW32 and BLW33.
Table 5
CHANNEL NO.
BLW32
21 (471.25 MHz)
445 mW
39 (615.25 MHz)
671 mW
70 (863.25 MHz)
500 mW
PO sync. for −60 dB i.m.d. (average of two amplifiers)
1286 mW
1308 mW
941 mW
BLW33
Tables 10 and 11 show the more complete test results.
Comparing the afore mentioned 3-tone (−60 dB) results with the 2-tone (−47 dB) figures it appears that: As for the single
amplifiers the typical low frequency decoupling elements are divided over the bias circuit and the amplifier circuit. This
was done because in case of concentrating all low-frequency decoupling elements on the bias board, parasitic
oscillations occurred.
1998 mar 23
11
11 Page | ||
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| PDF Descargar | [ Datasheet ECO7806.PDF ] | |
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