In this paper, we study the performance of low-power impulse radio ultra-wideband (IR-UWB) correlation receivers with suboptimal rectangular templates in additive-white-Gaussian-noise (AWGN), and independent and correlated Nakagami-m channels. Furthermore, we give numerical results based on simulations as well as actual measurements for different Federal Communication Commission (FCC) compliant pulses. Although the rectangular template has been suggested previously, no attempt has been made to analytically examine its bit-error-rate (BER) performance in AWGN or multipath channels. In this paper we fill that void. Specifically, we show that low-power is traded for a minimal performance loss of ≈ 0.3 dB for equally-correlated pulse-position-modulation EC-PPM modulation.