config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Expertmagento_Adminhtml>
            <version>0.1.0</version>
        </Expertmagento_Adminhtml>
    </modules>
    <global>
        <blocks>
            <adminhtml>
                <rewrite>
                    <catalog_product_edit_tabs>Expertmagento_Adminhtml_Block_Tabs</catalog_product_edit_tabs>
                </rewrite>
            </adminhtml>
        </blocks>
    </global>    
    
</config>

Tabs.php

<?php
class Expertmagento_Adminhtml_Block_Tabs extends Mage_Adminhtml_Block_Catalog_Product_Edit_Tabs
{
    protected function _prepareLayout()
    {
      parent::_prepareLayout();           
            $this->addTab('knowledgebase', array(
                'label'     => Mage::helper('catalog')->__('Knowledge Base Articles'),
                'content'   => 'Success',
            ));
            
    }
}

?>