A brief discussion on the main performance indicators and selection parameters of signal sources

Signal source refers to devices such as radio head, high frequency head, recording cassette, video cassette. Microcomputer and auxiliary equipment complete functions such as signal extraction, digital-to-analog conversion, and digital signal processing. Signal source is an important part of radar system. Radar system often requires signal source to be stable, reliable, easy to implement, with pre-distortion function, signal generation and signal parameter change are simple and flexible. Signal generator, also known as signal source or oscillator, is an instrument used to generate various electronic signals, which has a wide range of applications in production practice and science and technology. Signal source has developed to today, and its coverage is very wide. We can classify it according to the frequency range: ultra-low frequency (0.1m~1kHz), audio (20Hz~20kHz), video (20kHz~10MHz), radio frequency and high frequency (200k~3000MHz), microwave (≥3000MHz), light wave signal source, etc.; according to the working principle, it can be divided into: LC source, phase-locked source, synthetic source, etc.

Audio signal source (AG), function signal source (FG), power function generator (PFG), pulse signal source (PG), arbitrary function generator (AFG), arbitrary waveform generator (AWG), standard high frequency signal source (SG), radio frequency signal source (RG), television signal generator (TVSG), noise signal source (Noise), modulation signal generator (MSG), digital signal source (DG).

Generally speaking, arbitrary waveform generators (AFGs) can provide 12 standard function waveforms, pulse waveforms, modulation waveforms, frequency sweeps and burst signals, etc., and can quickly edit arbitrary waveforms. They are very representative among mid-range signal sources and are revolutionary digital products. A waveform generator is a data signal generator. When debugging hardware, it is often necessary to add some signals to observe whether the circuit is working properly. Using a general signal generator is not only bulky, but also only sends some simple waveforms, which cannot meet the needs. For example, when a user wants to debug a serial communication program, he must write a program on the computer and then connect the computer and the user's experimental board with a wire. If it is not normal, it is not known whether there is a problem with the communication line or the program. Using the waveform generator function of E2000/L, you can define serial port data. Through the output of the logic probe, debugging is simple and fast. Its basic technical indicators are the same as those of other signal sources, but there are also special requirements. The following is an explanation of the relevant performance indicators of the arbitrary waveform generator (AFG):

Bandwidth (Fw): Bandwidth is a technical indicator that must be considered for all AC measuring instruments. It refers to the frequency at which the instrument outputs or can measure the signal amplitude attenuation of -3dB.

Output amplitude (Vpp): The voltage range of the signal source output signal, generally expressed as peak-to-peak value.

Output channel (CH): The number of channels through which the signal source outputs to the outside world.

Vertical resolution (DAC): Vertical resolution is related to the binary word length (unit: bit) of the instrument's digital-to-analog conversion. The more bits, the higher the resolution. The vertical resolution of the digital-to-analog conversion determines the amplitude accuracy and distortion of the reproduced waveform. Digital-to-analog conversion with insufficient resolution will cause quantization errors, resulting in unsatisfactory waveform generation.

Horizontal Resolution (HA): Horizontal resolution represents the time increment that can be used to create a waveform. Generally speaking, it is calculated using the following formula:

T = 1/F (T is the timing resolution in seconds, and F is the sampling rate).

Memory Depth (Wsiz): Memory depth is used together with the clock frequency to determine the number of points in a waveform. Memory depth determines the number of sample points that can be stored. Each sample point of a waveform occupies one memory location. Each location is equal to the time of the sampling interval at the current clock frequency.

Sampling rate (fs): Sampling rate is usually expressed in megasamples or gigasamples per second, indicating the clock or sampling rate at which the instrument can run. The sampling rate affects the frequency bandwidth and fidelity of the primary output signal, as shown in the following formula:

Signal output frequency bandwidth = sampling rate ÷ storage depth, that is, Fw = fs ÷ Wsize

Of course, the performance indicators and selection parameters of various signal sources are not exactly the same, but when using a signal generator, you must try your best to consider the above indicators when selecting a model to meet your requirements.