Microwave Power Amplifiers - Giga

Microwave Power Amplifiers
‡‡ Power Loss, Transmitted % and Voltage Refl. Coeff vs VSWR and
Return Loss
Key Amplifier Terms
Frequency Range
The frequency range over which the amplifier is specified to operate
Output Power Level
Psat = saturated output power level = the maximum power available from the amplifier
P1dB = output power level at which the gain has decreased 1 dB from its small signal value
P3dB = output power level at which the gain has decreased 3 dB from its small signal value
Gain
Gain = the small signal gain of the amplifier when operating in the linear region well below saturation
Gain Flatness
Gain flatness = the variation in small signal gain across the amplifier’s frequency range
VSWR
Input VSWR = The deviation from an ideal impedance match with the amplifier’s input port
Output VSWR = The deviation from an ideal impedance match with the amplifier’s output port
Noise Figure
Noise Figure (NF) = a measure of added noise from the amplifier (in dB) = the ratio of output noise to that
noise which would be present if the amplifier itself did not introduce any noise
Noise Factor
Noise Factor (F) equals the ratio of the signal-to-noise at the input over the signal to noise at the output.
Noise Figure (NF) = 10 log10 (F)
Harmonics
As an amplifier approaches saturation, harmonics (multiples) of the input signal are generated.
Intermodulation
No amplifier is perfectly linear. When two or more signals are amplified, intermodulation frequencies are
generated. For frequencies F1 and F2, intermodulation products are at F1 ± F2, 2 F1, 2 F2, 2(± F1 ± F2).
Stability
Giga-tronics’ Instrumentation Amplifiers are unconditionally stable; however, it is a best practice to always
power off amplifiers when not connected to a load
Voltage vs Power in 50 ohms
Vrms
dBm
Watts
70.7
50
100
22.4
40
10
7.07
30
1
2.24
20
100 mW
0.707
10
10 mW
0.224
0
1 mW
Power Conversion
dBm
30
27
23
20
17
13
10
7
3
0
Watt
1
500 mW
200 mW
100 mW
50 mW
20 mW
10 mW
5 mW
2 mW
1 mW
Watt
1000
100
10
1
100 mW
10 mW
1 mW
0.1 mW
0.01 mW
0.001 mW
VSWR
RL (dB)
Loss (dB)
Trans. (%)
Γ
1.1
26.4
0.01
99.8
0.05
1.2
20.8
0.036
99.2
0.09
1.3
17.7
0.075
98.3
0.13
1.4
15.6
0.122
97.2
0.17
1.5
14
0.177
96
0.2
1.6
12.7
0.238
94.7
0.23
1.7
11.7
0.302
93.3
0.26
1.8
10.9
0.37
91.8
0.29
1.9
10.2
0.44
90.4
0.31
2
9.5
0.51
89
0.33
2.5
7.4
0.88
82
0.43
3
6
1.25
75
0.50
4
4.4
1.94
64
0.60
5
3.5
2.55
55
0.67
Applications
Boost power out of a VNA for Load Pull testing and
components testing requiring higher drive levels.
Use amplifiers as preamps to lower noise figure and
increase the sensitivity of spectrum analyzers.
Fsystem = Famplifier + (Fanalyzer - 1)/GAINamplifier
Vector Network
Analyzer
For example:
Amplifier
NFamplifier = 6 dB
Famplifier = 3.98
NFanalyzer = 20 dB
Fanalyzer = 100
GAINamplifier = 40 dB
GAINamplifier = 10,000
NFsystem = 6.01 dB
Fsystem = 3.99
Preamp
Signal
Device-Under-Test
‡‡Advantage of amplifier near DUT
Spectrum
Analyzer
GT-1000B Option 06
5W, 100 MHz to 18 GHz
GT-1020A
1/2 W, 100 MHz to 20 GHz
GT-1026A
1/2 W, 100 MHz to 26.5 GHz
GT-1040A
1/4 W, 10 MHz to 40 GHz
GT-1050A
1/4 W, 2 GHz to 50 GHz
GT-1051A
1/4 W, 10 MHz to 50 GHz
The best quality low-loss
microwave cable is about
0.35 dB/ft at 20 GHz and
1 dB/ft at 40 GHz
dBm
60
50
40
30
20
10
0
-10
-20
-30
~ 3 dB
+27 dB
DUT
With 3 feet of cable at 40 GHz, half the power lost in the cable, but full power
at the DUT
www.gigatronics.com/Power-Amplifiers
2500B Series Microwave Signal Generators
with Automation Xpress ATE Software
(100 kHz to 50 GHz)
GT-1000 Series Microwave Power
Amplifiers (100 MHz to 50 GHz)