Purported iPhone 4S part photos display modified antenna base

A series of purporting to be the structural case design for a revamped, cheaper new iPhone 4 indicate changes in its antenna design.

The images, published by MacRumors and iPatchiPods, appear to show a unibody frame without case seams on the top or either side of the top of the phone.

Existing GSM iPhone 4 models sold by AT&T and other global carriers have a single seam on the top, while the Verizon CDMA model has two seams on either side of the top end.

The seams separate the external edge of the iPhone 4 into antenna segments; the GSM model has two antennas (one for mobile use and one for WiFi/Bluetooth/GPS, as shown below) while the CDMA model has three (dual mobile antennas required in the CDMA specification and a WiFi/Bluetooth/GPS segment).

The modified case also incorporates a SIM card, something that only the existing GSM version of the current iPhone 4 has or needs.

It’s not yet known whether the anticipated new cheaper iPhone 4 (sometimes referred to as the “iPhone 4S”) will be dual band, allowing it to work on both major mobile network types. It is expected that the separate iPhone 5 model, bearing an original new design, will support both networks.

The primary feature of the new iPhone 4 phone design is expected to be its reduced cost, achieved through the use of streamlined components and a smaller 8GB of storage capacity.

A similarly purported “iPhone 5” prototype case design appeared in January, similarly lacking seams on the top two sides, instead bearing a single seam on the top.

The report also portrays a bottom frame segment that appears to lack a defined Home button, suggesting that Apple may change the appearance and design of the Home button on the phones it releases later this fall.

Stay tuned for additional details as they become available.