Rapid Engineering Prototypes are real circuits that Maxim application engineers have built and measured in our labs. They can provide a starting point for new RF designs. They are not available as Evaluation Kits.
Objective: To develop and measure an external switch for maximizing power-added efficiency (PAE) with this Japanese dual-path cellular-band PA.
By using an external (off-chip) high/low power-amplifier switch, the MAX2269 dual-path power amplifier can be set up for highest PAE. Because a discrete external path switch can be made by means of a semiconductor process whose characteristics are optimized for switching, an on-chip switch would typically have slightly higher loss and poorer isolation (but the subsequent circuit costs less and is smaller). Here, the MAX2269 was tuned for efficiency using its low-power path, resulting in longest battery life. This is because use in metropolitan areas results in transmit power on an average of between -20dBm and -16dBm, and the high-powered amplifier path is required infrequently.
The MAX2269 linear RF power amplifier is designed for Japanese cellular-band CDMA, PDC, and IS-136-based TDMA modulation formats. For best low-power PAE, the MAX2269 offers a switched dual-path amplifier arrangement. Statistically, CDMA handsets operate most of the time in a low-powered path (around +16dBm output), which is where PAE needs to be optimized. Using an external FET switch or pin diode, the MAX2269 offers the industry's highest (17% typical) PAE in low-power mode.
Schematic of the MAX2269 Evaluation Kit