This paper describes a link margin enhancement method for high data rate impulse-radio ultra-wideband (IR-UWB) transceiver systems. To overcome a trade-off between link margin and spectrum compliance in the pulse based UWB system, a spectrum-efficient frequency hopping (FH) technique is proposed to increase average transmission power without violating the spectrum mask. An energy detection receiver is used to convert a frequency hopping signal to a baseband signal with the original bandwidth, thus improving the signal-to-noise ratio. A 500 Mb/s 7.25-9.5 GHz UWB transceiver is implemented in 65 nm CMOS. Having eight sub-bands with 50% overlap, the transceiver exhibits a meter-range communication capability with a 9 dB link margin enhancement. The transceiver consumes 13.3 mW from a 1 V supply, achieving an energy efficiency of 26.6 pJ/bit.