Pagination in custom query in a category page

Meta query must be done with a nested array. So it may look more like this:

$query = new WP_Query(
                array( 
                    'meta_query' => array(
                                        array(
                                            'key' => 'duedate',
                                            'value'=> $today,
                                            'compare' => '>=', 
                                        ),
                    ),
                    'paged' => $paged,
                    'posts_per_page'=>'20'
                )
            );