Design principle of multi-channel receiver amplitude and phase calibration test system

Test - lowercase jpg

Kaixin micro test

Test probe P100-M3

Overview:
1. Introduction In order to obtain good performance, modern radar systems detect targets in a strong clutter environment. Usually, the received RF echo signals are down-converted to an intermediate frequency, and then decomposed into I and Q signals by a quadrature demodulator. However, due to the asymmetry of the circuit, the imperfection of the selected devices of each branch, and the changes in the operating frequency of the radar and the ambient temperature, the amplitude and phase characteristics of the I/Q branches of each channel are unbalanced and the amplitude phases between the channels are inconsistent. Causes false alarms in the system or increases system measurement errors. Therefore, the amplitude and phase consistency index of the two signals of the I component and the Q component of each channel and the amplitude and phase consistency index between the channels are one of the main factors affecting the performance of the receiving system.

2. Calibration principle of amplitude and phase calibration test system The radar receiving unit adopts a 5-channel working system, and the working frequency range covers 0.05GHz~20GHz. In order to solve the amplitude phase consistency problem under wideband receiving conditions, the receiving unit adopts phase equalization in the channel. The network and amplitude adjustment network method is used to perform amplitude and phase compensation to achieve uniformity of amplitude and phase between the channels. Figure 1 is a simplified process flow for receiving a radio frequency signal from an internal frequency signal to an intermediate frequency signal. Each of the 5 routing channels is composed of a receiving front end, a filter and a switching circuit, a channel intermediate frequency processing circuit, an AGC control circuit, a quadrature phase detecting circuit, a phase equalization network, and an amplitude adjustment network. When the receiving channel is designed, the reserved amount of the gain of the intermediate frequency receiver is increased, and the program-controlled attenuator is used for pre-fading, and the amplitude adjustment function is implemented as a regulation network in actual operation.


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