An SDR approach to developing a state-of-the-art P25 radio

By including the complete LNA to I/Q output signal path with variable gain, flexible IF filters, LO frequency dividers and dc offset controls the CMX994E supports compact, highly flexible direct conversion receiver designs.

APCO P25 is the public safety radio standard used across the USA and also deployed in a number of other countries around the world. P25 Phase 2 has a Common Air Interface (CAI) using two-slot Time Division Multiple Access (TDMA), 12.5kHz RF channels and H-CPM / H-DQPSK modulation. CML’s RF receiver and transmitter solutions have been adopted by major radio manufacturers in their new multi-mode radios.

The CMX994E also includes a PowerTrade feature that permits performance and power consumption to be traded against one another. This provides enhanced performance when needed and low power consumption at other times, providing an overall highly flexible and configurable solution that can adapt to changing demands. Integrating the transmitter in the terminal can be managed by one of CML’s I/Q transmitter ICs. The CMX971 I/Q Modulator IC is commonly used and is ideally suited to address the high performance requirements of APCO P25.

The H-DPSK modulation used by APCO P25 Phase 2 base stations is linear (non-constant envelope) therefore to ensure maximum transmitter efficiency the Power Amplifier (PA) requires linearisation. CML’s CMX998 Cartesian Feed-back Loop (CFBL) transmitter IC provides a proven solution to this complex task. These devices are just part of CML’s extensive range of integrated RF and baseband/air interface solutions in support of digital radio standards worldwide, such as: TETRA, DMR, dPMR, NXDN, ARIB STDs, PDT along  with legacy analogue FM PMR/LMR systems.