A Doubly-fed Automatic Level Control System Based on FPGA

Abstract

An FPGA-based doubly-fed automatic level control system belongs to the field of radio frequency microwave technology. The doubly fed automatic level control system includes a main link, a feedforward loop and a feedback loop. The invention provides an FPGA-based doubly-fed automatic level control system, which adopts a doubly-fed loop. In the case of an open-loop, the increase of the feedforward loop enables the system to automatically change the inherent voltage reference value according to the magnitude of the input power. , to ensure the accuracy of the output power; compared with the traditional automatic level control system, the circuit implementation is simple, in different scenarios, only need to rebuild the table, no need to change the circuit structure; adding a temperature detection module to the detection circuit, It realizes the accurate correspondence between the detection voltage and the input and output power at different temperatures, and has the characteristics of temperature compensation, which avoids the traditional complex hardware circuit design to achieve temperature compensation.

Description

technical field [0001] The invention belongs to the technical field of radio frequency microwaves, and in particular relates to an FPGA-based doubly-fed automatic level control system. Background technique [0002] The automatic level control system (ALC) is a system introduced for the instability of the performance of the component itself or the drift of the operating point caused by the environment. It can pull the signal power that deviates from the predetermined value back to the ideal value. It is widely used in In signal sources and transmitters of mobile communication systems. Specifically, the function of the automatic level control system is mainly reflected in two aspects: one is to automatically adjust and correct the fluctuating output signal power caused by unstable link devices or external interference in the previous stage link, Finally, a very stable signal is output; the second is to automatically adjust the power of the output signal in real time according...

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Problems solved by technology

However, this control method has certain defects: first, due to the nonlinear relationship between the output power and the detection voltage and the nonlinear relationship between the control voltage and the attenuation, additional logarithmic amplification and exponential amplification circuits are required, resulting in complicated circuit design; secondly , due to the existence of the loop integration circuit, the response time is long, and the loop may respond too slowly during AM modulation (amplitude modulation modulation), resulting in signal amplitude errors, complicated parameter debugging, and occupying a large amount of printed board area resources, resulting in miniaturization of the instrument difficult question

The adjustable dynamic range of this type of ALC is not large, the loop response time is at the us level, and the detection voltage is greatly affected by temperature, which cannot meet the needs of agile frequency signal sources

The digital ALC loop realizes the comparison circuit and the loop integration in the digital domain, avoiding the complicated hardware circuit, but because the circuit only has a feedback loop, the digital ALC circuit cannot capture the change of the input power when the circuit is open, and will Inaccurate output power; moreover, the output dynamic range of the digital ALC circuit is not large enough, usually only 30dB

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