| The MIL-STD-188-181A dictates that all transmissions over US-owned UHF SATCOM channels be adjacent channel emissions (ACE) compliant. The ACE requirements are specified for both the 5 kHz and 25 kHz channels, in terms of relative energy spilling out in adjacent channels above and below the main transmitting channel. The two main modulations recommended by the mil standard are 50% SBPSK and 50% SOQPSK. The SOQPSK technique offers outstanding side lobe suppression such that the ACE requirements are readily met with the standard 50% SOQPSK waveform.. The 50% shaped SBPSK waveform as recommended in MIL-STD-188-181A, however does not offer much ACE margin in the first two 5 kHz offset channels, nor for 9600 bps in the first two 25 kHz offset channels. Hardware limitations may further degrade ACE performance. This paper introduces new phase shaping methods that have far superior ACE suppressions with little or no additional modem implementation loss when the transmitted waveform is demodulated by a coherent BPSK demodulator. The new shaping waveforms introduced in this paper use a piece-wise-linear approach to generate the phase transitions while keeping the transition time equal to that used in the MIL-STD 188-181. The ACE characteristics are predicted by a computer model, then verified via spectral measurement of the transmitted RF signal. This transmitted RF signal is fed to an off-the-shelf RF receiver/demodulator and BER measurements are obtained. Computer simulation results show good agreement with measured experimental results in terms of both ACE characteristics and modem implementation loss. |