SUGISAKAMASANORI

Journal of Advances in Artificial Life Robotics
Vol. 1(3); December (2020), pp. 128–132
ON LINE ISSN 2435-8061; ISSN-L 2435-8061
https://alife-robotics.org/jallr.html

Research Article

A Design of Controllable Gain Amplification System Based onSingle Chip Computer
Fengzhi Dai1,2, Haokang Wen1

Tianjin University of Science and Technology, China,Tianjin Tianke Intelligent and Manufacture Technology CO., LTD, China

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ARTICLE INFO
Article History
Received 25 October 2019
Accepted 17 August 2020
Keywords
Radio frequency amplifier
Gain controllableSingle chip microcomputer

ABSTRACTThis paper studies and designs a gain controllable radio frequency amplifier system. As thehardware core of the whole system, the variable gain amplifier realizes the data function of theamplifier combined with the single chip microcomputer. After adjusting the gain of RF amplifier,the input signal can be amplified or attenuated, and the ideal output signal can be obtained.
Experimental results show that the gain controllable radio frequency amplifier system designedin this paper can achieve better control effects to amplify some signals. Theoretically, in real life,this amplifier has the advantage of being able to meet higher indicators, stable performance, andcertain practicality.

© 2022 The Author. Published by Sugisaka Masanori at ALife Robotics Corporation Ltd.
This is an open access article distributed under the CC BY-NC 4.0 license(http://creativecommons.org/licenses/by-nc/4.0/).

and mid-low frequency RF signal gain controllable
amplification system. The single-chip microcomputer
implements the numerical control function on this system.
Theoretically, it can meet higher indicators and can better
control gain. It can be applied to a variety of occasions,such as the front end of the RF receiver. It has a wide
range of practical significance.

1. Introduction
1.1. Research background and significanceAs a transmission module in a communication system,
RF (radio frequency) amplifiers are now widely used invarious communication systems, such as various types ofcommunication equipment and digital imagetransmission. Gain control technology is a very importantand indispensable technology in these systems.
In recent years, more low-noise amplifier designs andapplications have appeared, such as the CMOS
cascadable variable gain amplifier (VGA) withexponential gain control characteristic is presented [1].
And the amplifier with low power, low noise andelectrode DC offset suppression is presented for ECG
recording system applications [2]. But different for othertypes of design schemes, this topic is designed a stable1.2. Main content of this paper
In the hardware part, full reference is made to various
types of RF amplifier modules to build a gaincontrollable amplifier system that meets the requirements.
In the software part, the AT89C52 is used as the maincontrol microcontroller to implement the key control
function for the entire variable gain system. At the sametime, a display module is added to display the input signal,output signal and gain of the amplifier in the receiver inreal time.
2. RF Receiver Overview

Corresponding author’s E-mail: daifz@tust.edu.cn URL: www.tust.edu.cn

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The common basic architecture of the RF receiver isshown in Fig.1. It is mainly composed of five parts: filter,
low-noise amplifier, mixer, band-pass filter, and analogto-digital conversion.
The LNA low-noise amplifier module in Fig. 1 has
multiple design schemes. According to the design of thecontrollable gain system in this article, this LNA can bereplaced with VGA.
Fig.3 AD8361 module circuit diagram
3.2. Variable gain amplifier
There are many types of RF amplifiers with stableperformance on the market. In this subject, because thegoal is to achieve the amplification of low-frequency RFsignals, the amplifier module with AD8367 chip as thecore is selected in this subject. This module is a variable
gain intermediate frequency amplifier. The module ismainly composed of two parts, one is a 9th orderresistance attenuation network, and the other is a fixed
gain amplifier. The AD8367 is an example of a VGA thatuses variable attenuation followed by a post-gain
amplifier [4]. Providing the module with DC voltage
enables it to work in VGA mode, which is the working
mode used in this project. The module's peripheral circuit
is designed with a shielded shell and an anti-reverse
protection diode, which has a good protection function
for the module. As shown in Fig.4.

Fig.1 RF receiver basic structure

3. Controllable gain system design
Fig. 2 shows the block diagram of the system designed inthis paper, which mainly includes detectors, variable gain
amplifiers, AD converters, DA converters, andmicrocontrollers.

Fig.2 System structure block diagram
3.1. Detector
The AD8361 selected in this paper is an average response
power detector, suitable for high-frequency receivers up
to 2.5GHz. The AD8361 is a wideband linear RMS radiofrequency (RF) detector IC that is widely used in the RF
industry [3]. The module uses a single power supply. The
module has the characteristics of low power consumption.
The circuit design of the module is shown in the Fig.3.

Fig.4 Variable gain amplifier module
3.3. AD module
The analog-to-digital conversion module in this subject
is the PCF8591 module shown in the Fig.5. PCF8591 isan 8-bit data acquisition device [5]. The PCF8591
module has a track and hold circuit, and the AD
conversion principle of this module is 8-bit successive
approximation type. It mainly has the characteristics of129

monolithic integration, 5V DC voltage power supply, andlow power consumption, and is widely used in dataacquisition modules. All data in the module is seriallyinput or output through the I2C. Through the setting of
the single-chip microcomputer, data collection andconversion functions can be realized.

Fig.6 DAC0832 schematic diagram
4. System test
After building the entire system and connecting themodules, the actual tests were performed. The
experimental effect is obvious, and obvious waveformchanges can be obtained on the spectrum analyzer. Next,
list some data, objects and graphics in actual tests.
In this subject, first set the RF input signal shown in
the Fig.7: 250MHz, -30dBm.

Fig.5 PCF8591 schematic
3.4. DA module
The system hardware designed in this paper adopts amodular design, taking the 89C52 single-chip
microcomputer as the core of the system, controlling theDA conversion circuit, AD conversion circuit, and key
control circuit to form the entire control system. The
function of DA is to output the analog voltage signal
through the single chip microcomputer, and send it backto the variable gain amplifier VGA module. Through thecontrol of the single-chip microcomputer, the outputs areanalog voltage value, so as to control the variable gainamplifier and realize different gains.
The DA module is composed of the DA chip andamplifying circuit. DAC0832 shown in the Fig.6 is anelectric current exports type 8 bits D/A converter,
adopting to reversing T type resistor network [6].
Through this module, it is possible to output different
point flows with three keys and output corresponding
analog voltage values through the load resistor. This
voltage signal is supplied to the variable gain amplifier,which can make the variable gain amplifier module
AD8367 have different gain, and finally realize thecontrol function of the microcontroller to the amplifier.
In this project, the button control is combined with DA
analog-to-digital conversion, through actual tests, theactual system requirements can be achieved, the test
results are good, and the control performance is stable.

Fig.7 Input signal
As shown in Fig.8, the output signal passing throughthe amplifier is: 250MHz with an amplitude of -9.28dBm.

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the amplifier, and realizes the design of a variable gain
amplifier system at the front end of the RF receiver.
However, there were some discrepancies in the liquid
crystal display and gain calculation of the system's analog
quantity transmitted to the single chip microcomputer.
After actual testing, this system can amplify radio
frequency signals in the range of 0-500MHz, which canachieve better control effects to amplify these signals, but
for signals that are too high in frequency or too small in
amplitude, the tested data has a large deviation.
Acknowledgements

Fig.8 Output signal

The research is partly supported by the Project of Tianjin
Enterprise Science and Technology Commissioner toTianjin Tianke Intelligent and Manufacture Technology
Co., Ltd (19JCTPJC53700). It is also supported by theIndustry-University Cooperation and Education Project(201802286009) from Ministry of Education, China.

As shown in Fig.9, The liquid crystal display of thesingle-chip microcomputer: IN: 026; OUT: 060; DEV:00043.

References
1. Po-Chiun Huang, Li-Yu Chiou and Chorng-Kuang Wang,
A 3.3-V CMOS wideband exponential control variablegain-amplifier, Proceedings of 1998 IEEE International
Symposium on Circuits and Systems, Monterey, CA, 1998,
Vol. 1, pp. 285-288.
2. Xiao Yang, Qi Cheng, Li-fei Lin, Wei-wei Huang, Chaodong Ling, Design of low power low noise amplifier for
portable electrocardiogram recording system applications,
Proceedings of the 2011 IEEE International Conference
on Anti-Counterfeiting, Security and Identification, 2011,
pp. 89-92.
3. N. Greenough, Improving the linearity of the AD8361“Tru-Pwr” RF detector IC, Proceedings of 2011
IEEE/NPSS 24th Symposium on Fusion Engineering,
Chicago, IL, 2011, pp. 1-4.
4. Newman E J., X-Amp,™ A New 45-dB, 500-MHz
Variable-Gain Amplifier (VGA) Simplifies Adaptive
Receiver Designs. Analog Dialog, 2002, 36(1): pp. 1-3.
5. Gay, W., PCF8591 ADC, In Custom Raspberry PiInterfaces (pp. 67-90). Apress, Berkeley, CA, 2017.
6. Xu, Y. H., Zhang, D. T., Research on One Kind ofIntellectualization High Accuracy Digital Adjustment
Direct Source. Applied Mechanics and Materials, 2014,
599: pp. 608-611.

Fig.9 LCD display
In the liquid crystal display section, IN is the input RFsignal source (V) of the system, and OUT is the amplified
output value (V) of the system. DEV is the gain, which isthe ratio of the OUT value to the IN value. The displayedvalue is 100 times the actual ratio.
Under the test conditions, the input signal is 250MHz
with an amplitude of -30dBm and the output signal is
250MHz with an amplitude of -9.28dBm. It can be
deduced that the actual gain is 20.72dB and the actual
magnification is about 11 times. The single chip
microcomputer collects and converts the value on theLCD after being collected by AD and converted into a
digital quantity. The ratio of the two numbers is 0.43, andthe gain of the amplifier is 2.3 times.
5. ConclusionThe full text starts from the design of the variable gain
amplifier and aims to achieve the gain controllability of131

Authors Introduction
Dr. Fengzhi Dai

7. He received an M.E. and Doctorof Engineering (PhD) from theBeijing Institute of Technology,
China in 1998 and Oita
University, Japan in 2004
respectively. His main researchinterests
areartificialintelligence, pattern recognition
and robotics. He worked inNational Institute of Technology, Matsue College, Japan
from 2003 to 2009. Since October 2009, he has been thestaff in Tianjin University of Science and Technology,
China, where he is currently an associate Professor of theCollege of Electronic Information and Automation.
Mr. Haokang Wen

He is the first-year graduate
student of Tianjin University ofScience and Technology. His
major is information processingandInternet of Things
technology. His main research
fieldisdigital
imageprocessing. During his studies
in school, he published several research papers.

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