Can't tell the difference? The difference between RF analog signal source and vector signal source

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Can't tell the difference? The difference between RF analog signal source and vector signal source [Copy link]

Today, Boyu Xunming engineers will introduce you to RF signal sources. RF signal sources are often used as signal drivers and clock substitutes for circuits due to their low phase noise and high frequency stability. However, RF signal sources include not only analog signal sources but also vector signal sources, and people often cannot distinguish between these two types of RF signal sources.

　　These two types of RF signal sources are commonly used test instruments by engineers, but the appearance of analog signal sources and vector signal sources is basically the same. So, how to distinguish between RF analog signal sources and vector signal sources? Let's take a look~~

　　What is an analog signal source?

　　The analog signal source mainly outputs continuous sine waves, and then generates amplitude modulation, frequency modulation, phase modulation and pulse signals. The output frequency of a single machine can currently reach 67GHz, which can be expanded to millimeter waves; the frequency range of the RF source is generally within 9kHz~8GHz. The frequency synthesizer, also known as the frequency synthesizer, is the core of the analog source. Frequency modulation FM and phase modulation PM can be directly implemented in the frequency synthesizer; the pulse modulator is a controllable pulse switch that controls the on and off of the RF signal; the amplitude modulation modulator is mixed with the automatic level control ALC circuit; the basic function of ALC is to maintain the stability of the RF output level through feedback monitoring and comparison. If equipped with an external mixing device, the output frequency can reach terahertz.

　　

Terahertz spectrum expansion device

　　What is a vector signal generator?

　　Vector signal source mainly generates IQ signals and digital modulation signals, and the frequency range can reach 44GHz. The frequency range of RF vector source is generally within 9kHz~8GHz. Its modulation bandwidth is its important indicator, usually 100M~2G.

　　It is commonly used in the popular 5G mobile communication signals, as well as simulation of various radar and navigation signals. The core principle of the vector source is to generate a vector modulated RF signal through an I/Q mixer, i.e., an orthogonal modulator. The baseband source is a digital file generated by the target modulation algorithm, which is converted into an analog I/Q signal by a DAC and input into the modulator. The local oscillator LO of the modulator comes from the frequency synthesizer with the same setting as the RF frequency. The instantaneous voltage of the two orthogonal signals I/Q with a phase difference of 90° can be used to control the instantaneous amplitude and phase of the RF output, thereby achieving the purpose of arbitrary vector modulation.

　　

QAM signal generated by vector signal source

　　The difference between RF analog signal source and vector signal source

　　1. A pure RF signal source is only used to generate analog RF single-frequency signals and is generally not used to generate modulated signals, especially digital modulated signals. This type of signal source generally has a wider frequency band and a larger power dynamic range.

　　2. Vector signal source is mainly used to generate vector signal, i.e., the modulation signal commonly used in digital communication, supporting I/Q modulation: ASK, FSK, MSK, PSK, QAM, custom I/Q, 3GPP LTE FDD and TDD, 3GPP FDD/HSPA/HSPA+, GSM/EDGE/EDGE evolution, TD-SCDMA, WiMAX and other standards. For vector signal source, since it has a built-in modulator, the frequency is generally not too high (about 6GHz). The corresponding modulator index (such as built-in baseband signal bandwidth) and the number of signal channels are an important index.

　　In simple terms, a vector signal source has an additional baseband generator compared to an analog signal source. So when choosing a vector signal source, we are more concerned about the size of the baseband generator and what kind of digital signal it can generate. Through the above explanation by Boyu Xunming engineers, can you distinguish between analog signal sources and vector signal sources?