Coupled-slotline-hybrid sampling mixer integrated with step-recovery-diode pulse generator for UWB applications

A new compact low-cost sampling mixer with internal local strobe-pulse generator for (carrierless) ultra-wideband (UWB) applications, especially for sub-sampling of UWB video pulse signals, is presented along with detailed design information. The sampler employs a double-sided planar structure to facilitate interface with the strobe-pulse generator and the baseband circuit without using wire connections or air bridges, enabling hybrid microwave integrated-circuit integration with significant reduction in assembly effort. A novel coupling structure for both coupling and termination of the RF and local-oscillator signals to the Schottky-diode sampling bridge was designed to suppress ringing in the strobe pulse signal, resulting in harmonic-distortion reduction in the baseband output signal. Development of strobe-pulse generators using step recovery diodes for good output power efficiency is also presented along with design information for relatively low clock frequencies. The developed sampler achieves an unprecedented conversion loss of 4.5-7.5 dB (without a baseband amplifier) and conversion gain from 6.5 to 9.5 dB (with an amplifier) over a 5.5-GHz RF bandwidth, a dynamic range of over 50 dB, and low harmonic distortion in the baseband output. A new intrinsic conversion-loss equation that allows the sampler's conversion loss and operating RF bandwidth to be predicted accurately was also derived.