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Home > Other > Basic characteristics, principles and applications of RDA6216 power am

Basic characteristics, principles and applications of RDA6216 power amplifier module

Published time: 2020-07-28 10:36:58

As we all know, the GSM system is currently the most widely used mobile communication standard in the world. With the introduction of the high-speed, high-reliability third-generation mobile communication system and gradually entering the commercial stage, the upgrade of the GSM system is imminent. As an upgraded version of the second-generation mobile communication system GSM, EDGE has its unique advantages. The EDGE system uses a linear 8-PSK modulation method, which can greatly increase the communication rate. At the same time, the EDGE system follows the GSM time division multiplexing architecture , Only need to upgrade a few components on the basis of the existing GSM system to realize the EDGE function, and the upgrade cost is very low.

As of the end of 2006, more than 200 operators in more than 100 countries around the world have publicly pledged to adopt EDGE technology, and they represent more than 1 billion mobile users. Among them, more than 100 operators have opened EDGE networks and services. Covering 60 regions around the world. EDGE has shown strong development strength. According to expert analysis, EDGE and GSM networks will have a symbiosis phenomenon for a long time. In order to adapt to such market development conditions, the majority of operators, terminal product providers and chip design companies have begun Research and launch products and solutions that can simultaneously support EDGE/GSM systems.

Although EDGE and GSM have a certain degree of homology in technology, EDGE is an evolution system of GSM after all. There are certain differences in the design of the core chip of handheld wireless communication products. This is especially manifested in the radio frequency module: due to EDGE It is a linear modulation system, and its transceiver module must also be a linear module. The power amplifiers in traditional GSM mobile phones are basically non-linear devices and cannot realize the EDGE function. Therefore, a new RF power amplifier module needs to be designed to support the EDGE system.

How can a high-efficiency and multi-band GSM/EDGE power amplifier module be realized?

Basic characteristics of RDA6216 power amplifier module

RDA6216 is a four-band power amplifier module developed by RDA Microelectronics that supports both EDGE system and GSM system. The power amplifier and controller in this chip adopt high-stability InGap/GaAs HBT process and CMOS process respectively. The chip package is 6mm×6mm LGA. The RF input and output terminals are matched to 50 ohms. The Ramping control terminal integrates transient State spectrum filter, the chip peripheral circuit only needs one filter capacitor, which can simplify PCB design and reduce the space occupied by PCB.

Currently, EDGE power amplifiers on the market usually have two structures, one adopts the Polar-loop structure, and the other adopts the power back method. The first structure has higher power added efficiency, but requires power detection, and requires a complex feedback network to adjust the output phase and amplitude of the power amplifier, so the design is complicated, the cost is high, and the chip area is large. The second structure is simple to implement, low in cost, and small in chip area. The disadvantage is that the static current is large and the efficiency is low.

RDA6216 adopts the second kind of scheme, so the area of the whole module is very small, namely it is 6mm * 6mm LGA to capsulate. At the same time, by optimizing the output matching network of the power amplifier and the quiescent current of the power amplifier in the design, the shortcomings of the second scheme are improved as much as possible. In fact, in EDGE mode, the quiescent current of RDA6216 is very low, GSM/EGSM band quiescent current is 150mA, DCS/PCS band quiescent current is 85mA, and RDA6216 also has a higher maximum linear power added efficiency, GSM/EGSM band is 28%, the DCS/PCS frequency band is 29%.

The RDA6216 also integrates a CMOS control chip. When used as a GSM power amplifier, the power supply voltage of the power amplifier can be controlled by controlling the VRAMP terminal to control the output power of the power amplifier. At the same time, a transient spectrum filter is also integrated at the VRAMP pin. The converter can effectively suppress the switching spectrum formed when the power amplifier is switched. In GSM mode, the maximum output power of the GSM/EGSM band is 34.5dBm, and the maximum power added efficiency is 50%. The maximum linear output power of the DCS/PCS band is 32.5dBm, and the maximum power added efficiency is 53%. In addition, the switching between EDGE/GSM in RDA6216 is very flexible, and this function can be realized only by selecting the pin potential through the control mode.

The working principle of RDA6216 power amplifier module

Figure 1 shows the functional module diagram of RDA6216, which is composed of a GSM/EGSM power amplifier, DCS/PCS power amplifier, CMOS controller and two output matching networks. BANDS is the selection pin for GSM/EGSM and DCS/PCS, TXENA is the switch pin for controlling the entire chip module, VMODE is the selection pin for GSM/EDGE mode, VRAMP is the control pin for RF output power, GSM/EGSM RFIN GSM/EGSM RFOUT and GSM/EGSM RFOUT are the RF input and output terminals of the GSM/EGSM frequency band, and DCS/PCS RFIN and DCS/PCS RFOUT are the RF input and output terminals of the DCS/PCS frequency band respectively.

Figure 1. Functional block diagram of RDA6216

When VMODE is high, the power amplifier module realizes the linear amplification function, so it can amplify the EDGE signal. At this time, the output of the CMOS controller is a voltage close to the power supply voltage, the gain of the power amplifier module is fixed, and the output power is directly controlled by the input power . Due to the good linear amplification function, the input signal has very little distortion after passing through the power amplifier, which can effectively amplify the EDGE signal. You can select GSM/EGSM frequency band and DCS/PCS frequency band by selecting BANDS pin, and then select TXENA to control the opening and closing of the power amplifier of the corresponding frequency band.

When VMODE is low, the power amplifier module is used to amplify the GSM signal. At this time, the output voltage of the CMOS controller is related to the VRAMP voltage, and the output power is related to the output voltage of the CMOS controller. Therefore, the output power can be adjusted by controlling the VRAMP terminal. the goal of. In the process of GSM switching, the base band can control the rising and falling speed of VRAMP, effectively reducing the switching spectrum brought by the switching moment. Similarly, you can select the GSM/EGSM frequency band and the DCS/PCS frequency band by selecting the BANDS pin, and then select TXENA to control the opening and closing of the corresponding frequency band power amplifier.

Application of RDA6216 power amplifier module

Figure 2 is a demonstration PCB board for RDA6216. The peripheral circuit of this chip is very simple, just add a 22μF filter capacitor at the power supply terminal VCCCT. This is mainly due to the high integration of RDA6216. Simple peripheral circuits can reduce the PCB space, which is beneficial to the miniaturization of mobile phones, and can reduce the crosstalk between signals caused by complex peripheral circuits, thus simplifying the design of mobile phone motherboards and speeding up the development cycle of mobile phones.

Figure 2. PCB board for demonstration of RDA6216

Because the RDA6216 peripheral circuit and control logic are very simple, and the RF input and output are matched at 50 ohms, it is easily compatible with most RF transceivers and baseband chips on the market.

 

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