Compact Co-Planar Dual-Band Microstrip Patch Antennas for Modernized GPS

A new navigational signal designated as L5 with a center frequency of 1176 MHz and a bandwidth of 20 MHz has been introduced as part of GPS Modernization. This new signal is in the Aeronautical Radio Navigation Service Band and will primarily benefit aviation users by allowing precision navigation when used with the existing L1 signal for ionospheric corrections. In addition, U.S. military users will be primary beneficiaries of the new M code signal with a bandwidth of 24 MHz introduced into the L1 and L2 bands. The unique feature of this code is its spectral separation from the civil signals in these two bands. New antennas will be needed to support both civil and military users of a modernized GPS system when it becomes fully operational. The L1/L5 antenna used in avionics has to meet stringent size and performance requirements imposed by the RTCA. Military antennas also need to have adequate bandwidth and gain to allow high fidelity reception of M code signals. This paper describes two new microstrip antenna designs for very compact, co-planar dual-band antennas suitable for operation in either the L1/L5 bands for civil avionics applications or in the L1/L2 bands for use in small CRPA antenna arrays used for military applications. Both antenna designs meet their expected performance requirements and offer significant advantages over conventional GPS microstrip antenna designs that are currently being used.