[Reprint] Amplifier parameter test

Original address: http://www.pesmatrix.com/news/html/?415.html

In the transmitter, the RF signal generated by the oscillator is generally relatively small, after a variety of modulation, in the feed to the antenna before the signal radiated out of the need for a number of stages of power amplification. At the same time, the sensitivity of the receiver is more and more high, often received very faint signal, before the subsequent demodulation and decoding analysis also need high-gain pre-level low noise design. Therefore, the RF amplifier is a lot of circuits, especially communication circuit in the inevitable key components, in the design and production needs to undergo careful testing to ensure that the parameters meet the design requirements.

Amplifier has a lot of indicators to be inspected, including two major types of parameters, one is linear parameters, the other is nonlinear parameters. Linear parameters include amplifier operating frequency range, power gain, gain flatness, noise figure, nonlinear parameters include 1dB compression point output power, third-order truncation point, saturated output power, harmonic distortion and so on. In addition, today's portable devices are increasingly demanding for power consumption, so they are often tested for parameters such as operating voltage and current. This article will show you how to use the RF signal source and spectrum analyzer to test the amplifier's main.

Amplifier operating frequency range refers to the amplifier to meet all levels of the operating frequency range of indicators. The actual operating frequency range of the amplifier may be greater than the defined operating frequency range.  Power gain gain refers to the ratio of amplifier output power to input power, which is commonly used in "DB" units. Gain flatness (ΔG) refers to the range of amplifier gain variation over a specified temperature over the entire operating frequency range. We use the RF signal source as the excitation, using the frequency scanning function, it is easy to get the amplifier in the operating frequency of the amplitude and frequency characteristics of the situation. In the test results of the spectrometer below, we can see that the gain of the amplifier changes over the 6db,3db bandwidth by about 2GHz in the 3GHz range. At the same time, we notice that the standing wave is obviously deteriorated when the frequency is high.

The amplifier has a linear dynamic range, in which the output power of the amplifier increases linearly with the input power. This amplifier is called a linear amplifier, and the ratio of these two power is the power gain g. As the input power continues to increase, the amplifier enters the non-linear region, and its output power no longer increases linearly with the input power, that is, its output power is lower than the expected value of the small signal gain. The output power value is usually defined as the 1dB compression point of the output power when the gain drops to 1dB lower than the linear gain, expressed in p1db. We use the power sweep function of the RF signal source to easily test this characteristic of the amplifier. For example, we can read out that its p1db is about 7dBm. At the same time, we can get the saturation power of this amplifier around 9dBm.

The noise figure refers to the ratio of the signal to noise ratio of the input side to the signal-to-noise ratio at the amplifier output, which is commonly used in "DB". The noise figure is represented by the following formula: NF=10LG (input signal-to-noise ratio/output signal-to-noise ratio). The noise figure of the amplifier can also be tested using a spectrum analyzer, but often requires a more complex formula for conversion, and the Huarui integration specifically provides the corresponding test software to automate this conversion. According to the calculation, the noise figure of this amplifier is around 3dB.

From this article we can see that the main parameters of the amplifier can be tested using RF signal source and spectrum meter, besides power gain, 1dB compression point, noise figure, etc., it can also test harmonics distortion, intermodulation distortion, Third order truncation point and other indexes. In addition, the power dissipation of the amplifier is also a key indicator, especially in portable products, and often requires specialized testing and validation. However, due to the need for complex equipment setup, so in the actual production of capacity requirements, the more appropriate way is to use the program control to complete the automatic test.

Beijing Huarui Integration Technology Co., Ltd. is a test integration and solution provider, we focus on testing and measurement, to help you solve the testing problems at hand, provide consulting, analysis, sales, support and training of test equipment and testing solutions.

Tel: 010-89940679

E-mail:[email protected]

Website: www.pesmatrix.com

[Reprint] Amplifier parameter test