Design dual band internal antennasdesignfeature By Leslie J Reading, Galtronics YOU CAN FIT MOST CELLULAR PHONES WITH AN INTERNAL ANTENNA IF YOU GAIN A THOROUGH UNDERSTANDING OF THE PHYSICS OF THE PROBLEM AND IF YOUR PERFORMANCE EXPECTATIONS REMAIN CONSISTENT WITHIN SOME FUNDAMENTAL LIMITS. Designing dual-band internal antennas A s cellular telephones have evolved over the issues conflict with each other (see sidebar “Factors years, so have their components, particularly the to consider in internal-antenna design”). antennas. The first cellular telephones were big, heavy, and clumsy but worked well using large, coax- THE BASIC MODEL fed, half-wavelength antennas. As cellular-phone Figure 1 illustrates a dual-band internal antenna handsets became smaller, so did the antennas. By us- in its elementary form. This simple mod……