Philips Semiconductors

Product specification

NE/SA/SE5205A

Wide-band high-frequency amplifier

1992 Feb 24

10

of the power gain, and, in decibels, is equal to voltage gain as

shown below:

P

V

IN

2

Z

D

P

V

OUT

2

Z

D

N

P

OUT

P

IN

+

V

OUT

2

Z

D

V

IN

2

Z

D

+

V

OUT

2

V

IN

2

+ P

I

NE/SA/

SE5205A

Measured value for the

NP

P

OUT

P

IN

+ |S

2

+ 100

and V

V

OUT

V

IN

+ P

I

+ S

In decibels:

Also measured on the same system are the respective voltage

standing wave ratios. These are shown in Figure 21. The VSWR

can be seen to be below 1.5 across the entire operational frequency

range.

Relationships exist between the input and output return losses and

the voltage standing wave ratios. These relationships are as follows:

INPUT VSWR=

≤1.5

OUTPUT VSWR=

≤1.5

1dB GAIN COMPRESSION AND SATURATED

OUTPUT POWER

The 1dB gain compression is a measurement of the output power

level where the small-signal insertion gain magnitude decreases

1dB from its low power value. The decrease is due to nonlinearities

in the amplifier, an indication of the point of transition between

small-signal operation and the large signal mode.

The saturated output power is a measure of the amplifier’s ability to

deliver power into an external load. It is the value of the amplifier’s

output power when the input is heavily overdriven. This includes the

sum of the power in all harmonics.

INTERMODULATION INTERCEPT TESTS

The intermodulation intercept is an expression of the low level

linearity of the amplifier. The intermodulation ratio is the difference in

dB between the fundamental output signal level and the generated

distortion product level. The relationship between intercept and

intermodulation ratio is illustrated in Figure 22, which shows product

output levels plotted versus the level of the fundamental output for

two equal strength output signals at different frequencies. The upper

line shows the fundamental output plotted against itself with a 1dB to

1dB slope. The second and third order products lie below the

fundamentals and exhibit a 2:1 and 3:1 slope, respectively.

The intercept point for either product is the intersection of the

extensions of the product curve with the fundamental output.

The intercept point is determined by measuring the intermodulation

ratio at a single output level and projecting along the appropriate

product slope to the point of intersection with the fundamental.

When the intercept point is known, the intermodulation ratio can be

determined by the reverse process. The second order IMR is equal

to the difference between the second order intercept and the

fundamental output level. The third order IMR is equal to twice the

difference between the third order intercept and the fundamental

output level. These are expressed as:

second and third order intermodulation ratios in dB. The

intermodulation intercept is an indicator of intermodulation

performance only in the small signal operating range of the amplifier.

Above some output level which is below the 1dB compression point,

the active device moves into large-signal operation. At this point the

intermodulation products no longer follow the straight line output

slopes, and the intercept description is no longer valid. It is therefore

compression. One must be careful, however, not to select too low

levels because the test equipment may not be able to recover the

signal from the noise. For the NE/SA/SE5205A we have chosen an

output level of -10.5dBm with fundamental frequencies of 100.000

and 100.01MHz, respectively.