1. High Power Monocycle Pulse Transmitter for Ultra Wideband Radar Sensor
Ahajjam Younes1,2, Jose M. Catalá-Civera1 Felipe L. Peñaranda-Foix1,, Abdellah Driouach2
1 ITACA. Universitat Politècnica de València. Camino de Vera s/n Valencia, España.
2Information System and Remote Sensing Laboratory ,University Abdelmalek Essaâdi, Tétouan, Morocco.
Abstract
In this paper, a high power sub-nanosecond pulse transmitter for Ultra-wideband radar sensor is presented. The basis of the generator is considered as a step recovery diode and unique pulse forming the circuit, which gives rise to an ultra-wide band Gaussian pulse. Both transistor driver and transmission line pulse forming network are investigated to transform on one hand, a TTL trigger signal to a driving pulse with the timing and the amplitude parameters required by the SRD and on the other hand, to form an output monocycle pulse respectively. For a good range radar, a high amplitude pulse are indispensable, especially when penetrating thick Lossy material. In order to increase the output amplitude of the transmitter, the outputs of two identical pulse generators have been connected in parallel. This technique leads to a simple and useful solution.
The pulse transmitter circuit is completely fabricated using micro-strip structure technology characteristics. Waveforms of the generated monocycle pulses over 15V in amplitude have been obtained. Good agreement has been achieved between the simulation and the measurement results.
Fig 2. circuit diagram of the Gaussian radar transmitter
The pulse generator was implemented on an ARLON AD450 substrate 0,7262 mm in thickness. Waveform was measured using an Agilent C sampling oscilloscope at 50Ω load.
Introduction
Recently, and according to Ultra-wideband technology development, increased demands on wireless personal area networks as well as on high-resolution positioning facility is required. Therefore, attracted attentions by many researchers have been concentrated more and more on sub-nanosecond pulses; because Ultra-short pulses with well-defined output waveform plays a crucial role in the UWB transmitter design. When penetrating think lossy obstacle, high amplitude pulses are very advantageous. However, high power UWB pulse generators are very expensive, and are in most cases not compatible with modern planar technology and miniaturization effort. A way to increase the transmitter’s output power is to combine the output waveform from multiple sources. Combining ultra-wideband Gaussian pulses is a challenging task. Traditional power combining structures, e.g. the Wilkinson power divider, are fundamentally narrowband and distort UWB waveforms. Some dividers/combiners using planar multilayer techniques, which show proper UWB performance, have also been described in the literature [1],[2]. Unfortunately, these designs are suitable primarily for the higher UWB band (3, 1-10, 6 GHz) and tend to differentiate the pulses.
In our design we preferred to combine UWB pulses with a minimum distortion loss. This requirement is well accomplished using Mini-circuit “power splitter ZN2PD2” which works in the band MHz. To test the whole functionality of the full system, we have assembled two identical pulse generators on a single board.
Combing UWB pulses and results
To obtain the sum of the pulses without any disturbance, it's important that both generators have to provide an output pulse exactly at the same time. The pulse amplitude is now over 15V.
Fig 3. Output waveform of the proposed radar transmitter
General Structure of the transmitter
A block diagram of the proposed monocycle pulse transmitter is shown in Fig.1. The transmitter consists of two identical Gaussian pulse generators and monocycle pulse forming network (PFN). Both generators are trigged by one timing source.
Fig 1. Block diagram of the proposed radar transmitter.
The pulse generator was designed and simulated by the AWR Microwave office and Multisim transient simulator. A detailed circuit diagram is shown in Fig.2.
References
A. M. Abbosh, “Multilayer Phase divider for UWB applications,” Microwave. Opt- Techn. Let., Vol. 50, No.5, pp ,2008.
,” Design of ultra-wideband three-way arbitrary power dividers,” IEEE Trans. Microwave Therory Tech, vol. 56, no. 1 pp , 2008
3. Ahmed abbas Husseien Ameri. “Long-Range Ultra-wideband Radar Sensor for Industrial Applications” Doctoral Diss, Kassel University, November 2012.
4. Yu Guo; Guofu Zhu; Zhimin Zhou "A novel design and implementation of sub- nanosecond sampling pulse generator for ultra-wideband equivalent sampling receiver", Computing, Communication and Networking Technologies (ICCCNT), 2014 International Conference on, on page(s): 1 – 5
Conclusions
In this poster, a new circuit solution of an UWB transmitter has been presented. In order to increase the output power of the transmitter, we assembled two identical generator units on a single board with parallel output connected. The simulation results show that the peak power of summed pulses is nearly twice of the peak power of the single one. With an additional output PFN, the monocycle pulses 15 V in amplitude and 800 ps in total width were also measured.