**Software Radio (SDR) Concept**
Software Radio, also known as Software Defined Radio (SDR), is a communication technology that uses a general-purpose hardware platform to implement various communication functions through software. This approach allows for greater flexibility and adaptability compared to traditional radio systems.
The two key elements of SDR are the "Universal Hardware Platform" and "Software." The "Universal Hardware Platform" means that the same hardware can support multiple communication protocols and functions, rather than being limited to one specific function. This contrasts with traditional radios, which rely on dedicated hardware circuits for each function. In contrast, SDR uses software to implement communication modules, allowing for faster development, lower costs, and easier updates and maintenance.
To better understand the difference between traditional and SDR-based base stations, we can look at Figure 1. On the left, a traditional large base station is shown, requiring numerous custom-designed hardware components. On the right, an SDR-based miniaturized base station is depicted, where most of the functionality is implemented in software, making it more compact and flexible.
SDR is considered the third major revolution in communications. The first was the transition from wired to wireless communication in 1G systems, and the second was the shift from analog to digital in 2G systems. SDR represents the future of communication systems, offering greater adaptability and efficiency.
**Principle of SDR System**
Now let's explore how an SDR system works. A typical GPP-based SDR system includes a general-purpose processor (GPP) and peripheral devices. To illustrate this, we'll use a laptop connected to a USRP B200 as an example.
**Transmitter**
Figure 2 shows the transmitter system. On the left, we have the laptop running the SDR application, while on the right, the USRP B200 handles the transmission. The SDR program on the laptop implements the communication protocol stack, such as LTE or WiFi, using high-level programming languages like C or C++ for real-time performance.
The UHD driver manages communication with the USRP B200. The interface between the laptop and the USRP is USB 3.0, which provides sufficient bandwidth for most communication systems. The USRP B200 contains FPGA-based modules, including the transmit control and digital up-conversion (DUC) modules. These convert baseband data into RF signals, which are then amplified and transmitted.
**Receiver**
In the receiver section (Figure 3), the signal is first amplified by a low-noise amplifier before being down-converted to an intermediate frequency (IF). The IF signal is then digitized using an ADC, processed by the FPGA, and sent back to the laptop for further processing. The digital down-conversion (DDC) module reduces the IF signal to baseband, enabling efficient processing.
Why do we perform two frequency conversions? As shown in Figure 4, the first conversion brings the RF signal down to an intermediate frequency suitable for ADC sampling. The second conversion moves the signal to baseband, simplifying further processing. This method avoids the complexities of zero-IF receivers, especially at higher frequencies.
Each component of the SDR system involves deep technical knowledge, and this overview only scratches the surface. For those interested in diving deeper, there are many resources available to explore the full potential of SDR technology.
Earth Leakage Breaker ELCB
ELCB is an acronym for Earth leakage circuit breaker, which is a device placed inside a water heater, commonly referred to as ELCB electric leakage breaker. This circuit breaker has the function of disconnecting the device from the circuit whenever an electrical leak occurs through the human body when touching the electrical parts of the device.
ELCB is to limit the incident of electric shock inside the machine, disconnecting the power when there is a problem, ensuring safety for human life as well as fire and explosion prevention.
How many types of ELCB?
ELCB is often used in both civil and industrial applications.
For the domestic electricity system, the installation problem is not difficult, but in industry, the anti-shock for workers and the prevention of electrical leakage for electrical equipment with large capacity requires a bridge. Automatic anti-shock, high-power leakage protection, and often has a much higher price.
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