Hi Lingjun. Using the Neural Network Toolbox, you can create a convolutional neural net, and specify the number of filters to apply at each convolutional layer. The number of filters is analogous to the number of output channels, or feature maps. The following page has a good explanation of how this fits into the overall conv net structure:
https://www.mathworks.com/help/nnet/ug/layers-of-a-convolutional-neural-network.html
And here is the documentation for the convolution2dLayer function that you can use to specify the convolutional layer and the feature maps:
https://www.mathworks.com/help/nnet/ref/convolution2dlayer.html
