Converter technology is advancing every year. The sampling rates of ADC and DAC from major semiconductor companies are orders of magnitude faster than products from a decade ago. For example, in 2005, the world's fastest 12-bit resolution ADC had a sampling rate of 250 MS/s; By 2018, the 12-bit ADC sampling rate had reached 6.4 GS/s. As a result of these performance improvements, converters can directly digitize RF frequency signals and provide adequate dynamic range for modern communications and radar systems.
While there are trade-offs when using high sampling rate (mostly dynamic range) converters, this technique allows you to replace a widely used heterodyne RF architecture with a direct RF architecture to support a specific application. For example, for wideband RF applications requiring smaller dimensions or reduced cost, direct RF sampling instruments with simplified front ends are ideal. In particular, the technology has been further developed in some defense and aerospace applications such as radar and electronic warfare.
1. What is sampling of indoor broadband antenna news?
If you want to understand the direct RF architecture, you need to understand how it differs from other RF architectures. In the heterodyne structure, the receiver receives the signal at RF frequency, converts the signal down to a lower intermediate frequency (IF), and digitizes, filters, and demodulates it. Figure 1 shows a block diagram of a heterodyne receiver. As you can see, the RF front end of the instrument contains a bandpass filter, a low noise amplifier, a mixer, and a local oscillator (LO).
The direct RF sampling receiver architecture consists only of a low noise amplifier, an appropriate filter, and an ADC. The receiver in Figure 2 does not need to use a mixer and LO; The ADC directly digitizes the RF signal and sends it to the processor. In this architecture, you can implement many analog components of the receiver on digital signal processing (DSP) chips. For example, you can use direct digital conversion (DDC) to isolate a target signal without using a mixer. In addition, in most cases, you can replace most analog filters with digital filters in addition to anti-aliasing or reconstruction filters.
Since analog frequency conversion is not required, the overall hardware design of direct RF sampling receivers is much simpler, allowing for smaller overall dimensions and lower design costs.
2. How to realize direct sampling?
Prior to the rapid development of converter technology in recent years, the direct sampling architecture was not practical due to the limited sampling rate and resolution of the converter. Semiconductor companies use new technologies to improve resolution at higher sampling frequencies to reduce noise within the converter. With the advent of ultra-high speed converters with higher resolution, RF input signals can be directly converted into signals at thousands of megabhertz.
This conversion rate enables engineers to digitize in the L and S bands with very high instantaneous bandwidth. As converters continue to evolve, sampling indoor broadband antenna news in other frequency bands, such as C-band and X-band, is not utopian.
3. When should you consider using direct RF sampling architecture?
The main advantage of direct RF sampling is that it simplifies the RF signal chain and reduces the cost per channel as well as the channel density. Instruments based on the direct RF sampling architecture are typically smaller in size and more power efficient because they use fewer analog components. If building a high-channel system, direct RF sampling can reduce the footprint and cost of the system. This is especially important when building systems such as fully active phased array radars, which form a beam by phasing signals transmitted from up to hundreds or even thousands of antennas. Since the same system contains multiple RF signal generators and analyzers, the size and cost of each channel becomes an important consideration.
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