Jeongwoo Han

A new ultra-wideband, ultra-short monocycle pulse generator with reduced ringing

We introduce a new ultra-wideband (UWB), ultra-short, step recovery diode monocycle pulse generator. This pulse generator uses a simple RC high-pass filter as a differentiator to generate the monocycle pulse directly. The pulse-shaping network employs a resistive circuit to achieve UWB matching and substantial removal of the pulse ringing, and rectifying and switching diodes to further suppress the ringing. An ultra-short monocycle pulse of 300-ps pulse duration, -17-dB ringing level, and good symmetry has been demonstrated. Good agreement between the measured and calculated results was achieved.

Ultra-wideband electronically tunable pulse generators

We report on the development of new low-cost, compact ultra-wideband microstrip pulse generators capable of varying the pulse duration electronically. These electronically tunable pulse generators generate an initial step function using a step recovery diode, which is then converted into pulses of various durations by alternately switching on one of the switches, realized by PIN diode or MESFET, spatially located along a short-circuited transmission line. Representative pulse-duration variations from 300 to 800 ps have been demonstrated experimentally and theoretically. Good symmetry and low distortion have been achieved for the pulses. Measured results also confirm the simulations.

On the development of a compact sub-nanosecond tunable monocycle pulse transmitter for UWB applications

Development of a new sub-nanosecond monocycle pulse transmitter with tunable pulse duration for short-range low-power ultra-wideband radar and communication systems is presented along with detailed design and analysis. The developed pulse transmitter is simple, compact, and can be realized using planar or uniplanar integrated circuits. A novel RC coupling circuit along with a high driving current, provided by a high-speed amplifier and buffers, are used to obtain an increase in the output power. A decoupling circuit is implemented to reduce ringing on the monocycle pulse and provide necessary pulse clamping. Tuning of the output monocycle-pulse duration is achieved by using two distributed delay lines, coupled together by the decoupling network, each spatially loaded with antiparallel p-i-n diodes that are alternately switched on and off. Measurement results show tunable monocycle pulse durations in range of 0.4-1.2 ns, approximately corresponding to the operating frequency range of 0.15-3.7 GHz, and 200-400 mW of pulse peak power. The calculated and measured pulse durations also agree reasonably well

Development of a Tunable Multiband UWB Radar Sensor and Its Applications to Subsurface Sensing

Development of a new tunable multiband ultra-wideband (UWB) radar sensor is presented. The UWB sensor integrates the transmitter, receiver, and antennas completely in a single package using microwave integrated circuits and operates over multiple pulse durations or frequency bands. The sensor can transmit pulses with duration varying from 450 to 1170 ps and peak power from 200 to 400 mW and can detect signals with a conversion gain of 6.5-9.5 dB and a dynamic range of 50dB over a 5.5-GHz RF bandwidth. It has a range resolution of around 1 in. The sensor performs well through tests of various samples, demonstrating its success for subsurface sensing. The multipulse/multiband feature allows the sensor to achieve both fine-range resolution and long operating range and enhanced target detection and classification

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 samplers conversion loss and operating RF bandwidth to be predicted accurately was also derived.

Integrated balanced sampling circuit for ultra-wideband communications and radar systems

A balanced sampling circuit realized using step recovery and Schottky diodes on coplanar waveguide, coplanar strips, and slotlines is presented for ultra-wideband communications and radar applications. An efficient design was implemented to achieve improved performance. The impulse generator, providing signal for the sampling gate, was designed with a new LO feeding structure. The fabricated circuit shows 16-19 dB conversion loss without amplifier and 1-4 dB conversion gain with amplifier across 9-GHz RF bandwidth with 500-MHz sampling frequency.

Tunable monocycle pulse generator using switch controlled delay line and tunable RC network for UWB systems

A new ultra wideband (UWB) tunable monocycle pulse generator has been developed. The monocycle pulse was generated through differentiation of an UWB Gaussian or rectangular pulse, which was obtained by differentiating a step pulse generated by step-recovery diode. The tunable differentiation of step pulse was obtained based on a tunable delay line structure using electronic controlled switches. The tunable differentiation of Gaussian or rectangular pulse was done using a monocycle pulse shaping circuit with an RC network based on varactor diode. Measurement result shows good-shape monocycle pulse with pulse width of 400–850 ps and low ringing level.

Recent development of SRD- and FET-based sub-nanosecond pulse generators for ultra-wideband communications

Various low-cost, compact planar ultra-wideband (UWB), ultra-short pulse generators have been developed using step recovery and PIN diodes and MESFET. These include fixed and electronically tunable pulse generators. Fixed pulses ranging from 115 to 300 ps and tunable pulses Varying from 300 to 800 ps have been demonstrated experimentally and theoretically. Good agreement between measured and calculated results is also achieved. These pulse generators find applications in UWB communications systems, both transmitter and receiver.

Development of a low-cost, compact planar synchronous receiver for UWB systems

A new compact, low-cost ultra-wideband (UWB) synchronous receiver for UWB applications is presented. The developed receiver employs a double-sided planar structure, enabling low-cost hybrid MIC integration. It achieves an unprecedented conversion loss of 4.5-7.5 dB (without baseband amplifier) and conversion gain from 6.5-9.5 dB (with amplifier) over a 5.5 GHz RF bandwidth, a dynamic range of more than 50 dB and low harmonic distortion in the baseband output signal. The receivers down-converted signals match very close to those down-converted by a commercial digitized oscilloscope, demonstrating its high performance and hence usefulness for various UWB systems

Time-Domain Ultra-Wideband Radar, Sensor and Components

Introduction.- System Analysis.- UWB Transmitter Design.- UWB Receiver Design.- UWB Antenna Design.- UWB System Integration and Test.- Summary and Conclusion.