View of STUDY OF NOTCH FILTER UNILATERALLY INJECTION-LOCKED GUNN

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ACCENT JOURNAL OF ECONOMICS ECOLOGY & ENGINEERING Available Online:www.ajeee.co.in Vol. 02, Issue 11, November 2017, ISSN -2456-1037 (INTERNATIONAL JOURNAL) UGC APPROVED NO. 48767

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STUDY OF NOTCH FILTER UNILATERALLY INJECTION-LOCKED GUNN Prof. Sanjay Shrivastava

Ass. Prof., Guru Ramdas Khalsa Institute of Science & Technology Jabalpur, MP, India Email Id:-harshilshri@gmail.com

Abstract:-In this paper, we present the theory and design of a novel microwave active notch filter operating at X-band (8 GHz-12.4 GHz). The notch filter has a notch frequency of 10.22 GHz and a 3 dB calculated bandwidth of 87 MHz, the corresponding 3 dB experimental bandwidth is 120 MHz. The filter is designed using a magic tee and two tunable X-band Gunn oscillators injection-locked to the input interference to be eliminated. The special features of this filter are that it is of low noise, tunable and signal tracking character and possesses considerable power handling capacity.

Key words: Gunn Oscillator, Injection locking, Microwave, Notch filter, Notch Frequency.

1. INTRODUCTION

Notch filters are essential components of a microwave communication system.

Microwaves, according to IEEE convention, span over the frequency range 3 GHz-30 GHz of the electromagnetic spectrum. Notch filters are used to eliminate monotone or narrowband interference in a receiver. This interference can appear automatically from adjacent channels and it can also be man- made when the interference is introduced deliberately for jamming a communication receiver. A good notch filter must have low insertion loss, negligible radiation loss and high power handling capacity which are of major concern at microwave frequencies. A notch filter can be treated as a special case of band reject filter where the stop band becomes very narrow and the attenuation becomes high. Design of microwave notch filters [1-6] is being investigated over a few decades. To make the notch filters reconfigurable and to operate at higher microwave frequencies, research work is going on the design of notch filter all over the globe till now. Jackowski et al., have proposed a frequency agile, constant bandwidth, reconfigurable notch filter with a tuning range of an octave [7, 8]. A notch filter has been designed at 13.2 GHz with a bandwidth of 50 MHz and 25 dB rejection at the notch frequency by Narayana et al., . Notch filters have been designed using Barium strontium Titanate thin film varactor technology by Ramadugu.

The low frequency notch filter discussed above are all passive, in general.

Active notch filters [4-6] incorporate one or more amplifying devices such as negative resistance oscillators. These negative resistance oscillators when operated in the injection-locked mode possess amplitude noise reduction property as well as higher power handling capacity. In this paper, we have used a pair of unilaterally injection locked Gunn oscillator operating at X-band.

The Gunn oscillators are locked to the input interference received at the receiver and follows the interfering signal. The Gunn oscillator pair is thus made coherent and their outputs are subtracted at the E-arm of the magic tee resulting in a cancellation of the interference accompanying the input signal assuming the Gunn oscillator pair to be identical. The desired signal falls outside the rejection band of the notch filter and passes through it.

2. MECHANISM OF OPERATION

It incorporates a magic tee and two coherent Gunn Oscillators connected with the collinear arms of the magic tee. The input of the notch filter is the H-arm and the output port is the E-arm of the magic tee. The schottky diode detector is not any part of the notch filter. It only detects the microwave power and delivers an output voltage proportional to the input microwave power. It gives a method of indirect measurement of output microwave power.

The detector output voltage is measured in an oscilloscope (CRO).

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2 3. ANALYSIS

For injection locking at microwave frequencies, there must exist a free running microwave oscillator, called the slave oscillator, which is injected by the output power of another microwave oscillator, called as the master oscillator. Depending upon the frequency detuning of the injection signal frequency from the free running slave oscillator frequency and the relative power of the injection signal, the slave oscillator gets injection locked to the master oscillator. Under locked condition, the slave oscillator frequency becomes identical with that of the master oscillator and the input-output phase error assumes a constant value. If the injection signal power is much less than the free running slave oscillator power, the latter is said to be under driven. On the other hand, the locked oscillator is said to be overdriven if the injection signal power is comparable or greater than the free running slave oscillator output power.

The injection locked Gunn oscillators (GO#2 and GO#3) have amplitude limiting property. Any amplitude modulation of the injection signal is shaked-off by the locked oscillators. So, we will not use amplitude modulation as modulation format of the input signal. Rather, we will consider FM signal input and study the response of the sub-system to such frequency modulated signal. The interference to be removed from the receiver is assumed to be monotone in nature. We will make a static analysis of the sub-system considering a slow variation of input master signal frequency. The input signal is delivered by a tunable Gunn oscillator.

4. EXPERIMENT

The Gunn oscillators having model no. XG- 11 have been procured from M/S SICO Ltd;

India. Magic tee and directional couples used for microwave power measurement and variable attenuator for input signal power attenuation have been purchased from M/S VidyutYantraUdyog Limited, India. Schottky barrier diode and the microwave power meter have been procured from M/S Salicon Nanotechnology Limited, India. The measured lock band for Gunn oscillator GO#2 with free running frequency

of 10.22 GHz and free running power of 8.75 mW is 118 MHz for an injection power of 4.25 mW. This corresponds to a loaded Q factor. QL=60. GO#3 has a free running power of 7.5 mW at the free running frequency of 10.22 GHz. It has a Q-value of 59. The notch Frequency can be tuned by tuning the free running frequencies of slave oscillators GO#2 and GO#3.

5. CONCLUSION

The theory and design of an active microwave notch filter has been presented in this paper. The notch frequency is 10.22 GHz with a 3-dB experimental bandwidth of 120 MHz. This filter has negligible insertion loss and considerable power handling capacity. Besides, since injection locking has been used in the design, the notch filter will strongly reduce amplitude noise of the received signal. The notch filter has also input signal tracking property.

6. REFERENCES

[1] I.C. Hunter and J.D. Rhodes, “Electronically tunable microwave band stop filters”, IEEE Transactions on Microwave theory and Techniques, vol. MTT-30, pp. 1361-1367, Sept. 1982.

[2] R. Levy, R.V. Snyder and G. Mathali, “Design of microwave filters”, IEEE Transactions on Microwave theory and Techniques, vol. MTT- 50, no. 3 pp. 783-793, Mar 2002.

[3] T-Lin. Wu, “Microwave filter design”, Chap.6, Department of Electrical Engineering, National Taiwan University, John Wiley &

Sons, Inc., 2001.

[4] R.V Snyder, “Evaluation of of passive and active microwave filters”, Microwave Symposium Digest, pp. 1-3, 2012.

[5] B.Y. Kapilevich, “Variety of approaches to designing microwave active filters”, 27 th European Microwave Conference, Jerusalem, Israel, vol. 1,pp.397-408, 8-12 Sept. 1997.

[6] C.Y. Chang and T. Itoh, “Microwaves active filters based on coupled negative resistance method”, IEEE Trans.On Microwave Theory and Techniques, vol. MTT-38, no. 12, pp.1879-1884, Dec. 1990.

[7] D.R. Jackwoski and A.C. Guyette, “Sub-octave- tunable microstrip notch filter”, IEEE EMC Society Symposium on Electromagnetic Compatibility, pp. 99-102, Astin, Texas, VSA, Aug. 17-21, 2009.

[8] D.R. Jackwoski, “Passive enhancement of resonator Q in microwave notch filters”, 2004 IEEE MTT-s International Microwave Symposium Digest, pp. 1315-1318, June 2004.

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[9] M.S. Narayana and N. Gogia, “Accurate Design

of a notch filter using electromagnetic simulators”, Applied Microwave and Wireless, pp. 44-49, vol. 12,Part 11, 2000.

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[10] J.C. Ramadugu, Design of microwave bandstop and bandpass filters on Barium Strontium Titanate thin film varactor technology”, Ph. D. Thesis, University of Dayton, Dayton, Ohio, USA, Dec. 2013.

[11] Arvind Kumar, A Bhattacharya and D K Singh. Microwave Image Reconstruction of Two Dimension Dielectric Scatterers Using Swarm Particle Optimization, International Journal of Electronics and Communication Engineering & Technology, 4(6), 2013, pp. 57-61.

[12] Prof. B.N. Biswas, S. Chatterjee and S Pal. Laser Induced Microwave Oscillator, International Journal of Electronics and Communication Engineering & Technology, 3(1), 2012, pp. 211 - 219.

[13] P. Bhattacharyya, S. K. Dawn and T. Chattopadhyay, “Low noise bandpass filter using an X-band injection–locked Gunn oscillators”, International Journal of Research in Engineering and Technology, vol. 04, issue-12, pp. 1-6, Dec. 2015.