Pulse generator for UWB communication and ... - Semantic Scholar
Pulse generator for UWB communication and radar applications with PPM and Time Hopping possibilities Deparis N., Loyez C., Rolland N., Rolland P-A. Departement Hyperfrequence et Semiconducteurs (D.H.S.) I.E.M.N. C.N.R.S UMR 8520 F-59652 Cité Scientifique, Avenue Henri Poincare - BP60069, Villeneuve d'Ascq Cedex, France [email protected] This paper summarizes some experimental results of two digital pulse generators which exhibits rise and fall times of 25 ps. The first one is single ended, whereas the second one has differential outputs. The position and width of the pulse are adjustable. These pulse generators can be compliant with the FCC part 15 frequency mask with a specific and simple filter.
Abstract— Two simple and compact ultra-wideband, ultrashort-pulse transmitters have been developed using a monolithic microwave integrated circuit (MMIC). These pulse generators include a digital approach for the pulse forming based on a logic gate. They produce pulses with a variable width as low as 65 ps and rise and fall time about 25 ps (measured). The pulse position modulation (PPM) with pulse frequency rate (PRF) from frequency below 1 MHz to several GHz is also possible. Finally, an analog filtering solution for its shape is proposed in order to be compliant with the FCC part 15 frequency mask.
II. A.
Principle The main idea of the pulse generator is the use of a logic gate (such as a NAND, NOR or XOR gate) with two delayed inputs. For example, with a NAND gate, when the two inputs INA and INB are both in low state, the output is "high". With a XOR gate, the output is high only when INA and INB are in different states, the PRF will be twice the INA IN B inputs frequency (Fig. 1).
I. INTRODUCTION Ultra short pulse generation is a challenge for lot of kind of applications. Each application has its own specifications: RADAR with high output peak voltage [1], sampling at millimeter waves with very short fall/rise times and duration [2], TDR/TDT at millimeter waves [3], and recently wireless communications with specific pulse shape (FCC part 15 frequency mask) [4],[5]. Various methods for pulse generation have been presented, including optical systems – which have the fastest transient specification [6],[7] but a difficult implementation – hybrid methods – with step recovery diodes (SRD) [8]-[11] and avalanche transistors [12] – and with integrated circuit (IC) – such as with NLTL [13] and digital method [14]-[19]. Many other methods exist and will not be presented here [20].
IN
τ
τ
IN
τ
τ
τ
Figure 1. Basic structure of pulse generator
SRD (linked with schottky diode for the pulse shaping) is the most popular and easiest way for pulses generation. The main limitation of this technique is the pulse repetition frequency (PRF) due to time life of the carriers. This method is not recommended for high data rate communications.
For our application, we use a NOR gate with two complementary inputs delayed with τ. The choice of such logic gate is function of the high speed IC process and its logic family advantages and drawbacks. Using a NOR gate, the two complementary inputs can be obtained using a differential output buffer.
More recently, [15],[16] introduces an ultra short pulse generator using a logic gate in pHEMT technology. [17][19], also present simulation results using the same method with low cost CMOS process, but without pulse width tuning capability.
0-7803-9390-2/06/$20.00 ©2006 IEEE
SINGLE ENDED DIGITAL PULSE GENERATORS
This delay τ can be realized with a propagation line, multiple delay taps [18],[21], or with a mixed analog and digital IC. This IC can be composed, for example, with a
661
ISCAS 2006
triangular generator and a comparator [17], or with a varactor diode [16],[19] (Fig. 2). Another way to create this delay is to use two comparators with two shifted analog sources. This shift can be programmed with two Direct Digital Synthesis (DDS) whose relative phase can be precisely controlled [14]. Using the varactor diode, a special study must be made on its dimension in order to fix the minimum or the maximum pulse width. In fact, the pulse width limits are determined by the equivalent Cmax/Cmin factor. It is also possible to adjust the pulse width, using a BDCFL logic family, by changing the voltage threshold of the NOR gate (Vth). This can be done by tuning the value of the R var value in the design of the BDCFL gate (Fig. 2a).
Figure 4. Pulse Generator using a varactor diode, die size : 0.7x1.5 mm²
In order to have two complementary outputs at the input of the NOR Gate, the first inverters – which are used as fast edge compressor – have been designed in SCFL logic family. The NOR gate and the outputs stage have been designed in BDCFL logic, in order to have a high voltage margin (3 V). The consumption is about 180 mW. It can be seriously decreased using high speed CMOS process for wireless communication.
OUTA 0
IN A
Vwidth
OUT A Rvar
-1 Vth -2 -3
(a)
-Vss
0.0
0.5
1.0
(b)
1.5
C. Experimental results In this section, experimental results about the pulse generator designed with the ED02AH foundry are presented.
2.0 2.5 t [nsec]
Figure 2. Principle of delaying using a varactor diode: (a) BDCFL inverter with threshold adjustable (b) output of the BDCFL inverter for different voltages applied to the varactor diode.
1) Time Domain On the Fig. 5a are represented a 3 dBm sinusoidal analog clock at 250 MHz and different position of pulses. These positions were obtained for a voltage control from -300 mV to 150 mV at the input of the comparator (Fig. 3). The pulse position deviation is about 420 ps for 450 mV, so the sensibility is about 1 ps/mV. The pulse width and shape is still constant, whatever the position of the pulse.
In order to enable the Time Hopping possibility in wireless communication [4],[5], a third input is added to the input of the gate. When CtrlTH. value is on high state pulses are generated. This signal must be synchronized with the analog clock and bufferized. Finally, for the PPM, an analog voltage controls the position of the pulse with the first stage, i.e. the comparator. The final simplified block diagram of the pulse generator is presented in Fig. 3. Ctrl T.H. Analog clock VPPM comparator
SCFL
Vwidth
BDCFL
(a)
(b)
Figure 5. (a) Pulse position control width from left to right Vctrl from -300 to 150 mV. (b) 750 MHz PRF. Scale : 100mV/ div and 100ps/div.
Varactor diode Figure 3. Functional block diagram designed for a single ended digital pulse generator using a varactor diode with T.H and PPM possibilities
We can also see on Fig. 5 the ringing that is due to the mismatched between the pulse generator and the 50 impedance of the digital scope. The pulse repetition frequency (PRF) has also been validated and can be as low as 1 MHz up to 1 GHz (Fig. 5b). Fig. 6 represents the control of the pulse width. The minimum width is about 75 ps and can reach 800 ps. For width lower than 100 ps, the amplitude decreases,
B. Design The OMMIC ED02AH foundry has been chosen. This process provides low noise, pseudomorphic HEMT devices using 0.2 µm GaAs HEMT. Depletion and enhancement transistors are available with Ft=63 GHz so 25 ps rise/fall times can be reached. A microphotograph of the pulse generator is presented below (Fig. 4).
662
as a delay line and the order of the filter (i.e. number of stub) defines the shape of the pulse.
otherwise, it is still constant, about 800 mV with 50 Ω impedance load. The jitter has also been measured and is less than 1.5 ps rms. Width [ps]
90 0 80 0 70 0 60 0 50 0 40 0 30 0 20 0 10 0
Vdiode [V]
0 -1, 50
-1, 25
-1, 00
-0, 75
-0, 50
-0, 25
0, 00
0, 25
(a)
0, 50
(b) Figure 8. High-pass filter with short-circuited stub
Figure 6. (a) Pulse width control. (b) Shape of the pulse for different widths Scale : 100 mV/div and 50 ps/div.
Varying the length of the different stubs will change the shape, and so the spectral frequency occupations. Two temporal representations are presented in Fig. 10.
2) Frequency domain With rise and fall times of about 25 ps, several dozen of gigahertz bandwidth is occupied (Fig. 7a). The pulse width also defines the spectral occupation.
(a)
(b)
Figure 9. Pulse shaping with differents orders of filter. (a) first order (b) second order. Scale : 100 mV/ div and 200ps/div.
(a)
Fig. 9 shows the measured pulses waveform. They have pulse duration of 300 ps. The amplitude peak-to-peak is 800 mV using the first order filter and 400 mV for second order filter. The ringing level is due to the mismatch between the pulse generator and the oscilloscope. The amplitude and shape symmetry are good. The measurement was made using a 100-MHz sinusoidal wave signal and Agilent DCA-J 86100C digital communication analyzer.
(b)
Figure 7. (a) spectral occupation of 100 MHz PRF unipolar pulse (b) spectral occupation of 100 MHz PRF unipolar pulse with PPM
In order to validate the pulse position modulation, we measure the output spectral occupation of the pulse generator with 50 Mbps PPM (Fig. 7b). The shape smooth of the waveform validates the pulse position modulation. D. Pulse shaping In order to be compliant with the FCC part 15 frequency mask, the occupied bandwidth of the pulse must be in the [3.1 – 10] GHz band. A method to produce this specific pulse shape is to filter the output of the pulse generator with a high pass filter. This can be done with lumped elements, such as a simple RC high-pass filter [11] but these two parameters are not enough to assure the specific pulse shape. This can be also done with LC band pass filter [19], but above a few GHz, specific model of lumped elements must be used, and simulation results are too far from experimental results.
(a)
(b)
Figure 10. Spectral occupation of 100 MHz PRF pulse filetered. (a) without modulation (b) with PPM at 50 Mbps.
The spectral occupation of the pulse shown in Fig. 9b., i.e., using the second order filter is presented Fig. 10. The bandwidth occupation is equal to [3.2 – 8.4] GHz (with 20 dB rejection). Some optimizations are still required to validate the pulse generator with the FCC frequency mask. The pulse position modulation is also validated (Fig. 10b).
The other way is the use of a microstrip filter composed of short-circuited stubs and a transmission line with specific impedances. In order to have a monocycle, τ must be equal to the input pulse width (Fig. 8). The short-circuited stub acts
663
III. DIFFERENTIAL O UTPUTS WITH BPSK MODULATION Another method to produce a monocycle is to sum up pulses with different polarities with a time delay corresponding to the width of the pulse [20]. A. Architecture Using the D01PH foundry, a new design of pulse generator has been made. This process provides HEMT with Ft=100 GHz so 20 ps rise/fall times can be reached. The principle is still the same, using high speed logic gate and a varactor diode, but the logic families are now fully differential (SCFL). This pulse generator photography is presented on Fig. 11.
Figure 13. 200 ps monocycle pulse width spectrum, FPRF = 100 MHz, Fcenter = 6.5 GHz, SPAN = 7 GHz, RL = -25 dBm
According to Fig. 13., some filtering is still necessary to be compliant with the FFC part 15 frequency mask. The spectrum of a 60 ps pulse width with 2 PRF – 100 MHz and 5 GHz - is presented in Fig. 14. We can see that a - 40 dBm power can be available at millimeter wave (40 GHz).
Figure 11. Pulse Generator with differential outputs, die size : 0.7x1.5 mm²
With two pulse generators using this kind of architecture, a BPSK modulation can be achieved [20] (see Fig. 12b). In fact, each pulse generator pulse position can be controlled undependably and by summing the outputs, specials shape can be obtained.
(a) FPRF = 100 MHz, SPAN = 25 GHz
IV. CONCLUSION Two RF pulse generators using digital approach for multiples application have been developed in pHEMT technology and validated. They achieves 25 ps of rise and fall time. Their width can vary from 60 ps to 800 ps. The PPM modulation has also been validated for wireless communications and sampling [22]. A simple passive pulse shape using microstrip filter has been presented in order to be compliant with the FCC part 15 reglementation. Another pulse generator has also been presented for special shape and BPSK modulation.
B. Experimental Results The differential output measurements of the pulse generator are shown in Fig. 12.a. The output spectrum are presented in Fig. 13 and 14. A 60 ps minimum pulse width can be reached, which means that more than 20 GHz bandwidth is occupied. It has been validated according to Fig. 14.a. Three signals are presented in Fig. 12.b., the two on the right are the differential outputs of two pulse generators. The position can be controlled by adjusting a voltage control on the device. The signal on the left is the sum. A 200 ps monocycle pulse width is obtained.
REFERENCES [1] [2]
[3] (a) 20 ps/div
(b) FPRF = 5 GHz, SPAN = 50 GHz
Figure 14. Pulse generator output spectrum, Ref Level = 0 dBm, 10 dB/div,
(b) 100 ps/div
[4]
Figure 12. Pulse Generator with differential outputs, die size : 0.7x1.5 mm²
[5]
664
Daniels D.J, “Surface penetrating radar”, Electronics & Communication Engineering Journal, Vol 8, Issue 4, Aug. 1996 P. Abele, M. Birk, D. Behammer, H. Kibbe1, A. Tkasser, P. Maier, K.-B. Schad, E. Sonmez, and H. Schumacher, “Sampling Circuit on Silicon Substrate for Frequencies beyond 50 GHz”, IEEE MTT-S, 2002 James R. Andrews, “Time Domain Reflectometry (TDR) and Time Domain Transmission (TDT) Measurement Fundamentals,” Picosecond Pulse Labs, AN-15, November 2004 R. A. Scholtz, “Multiple access with time hopping impulse modulation,” Proceeding IEEE MILCOM Conf., pp. 447–450, 1993 M. Z. Win, R. A. Scholtz, “Ultra-Wide Bandwidth Time-Hopping Spread-Spectrum Impulse Radio for Wireless Multiple-Access
[6]
[7]
[8]
[9] [10]
[11]
[12]
[13]
[14]
Communications,” IEEE Trans. Communications, vol. 48, N°. 4, April 2000. M. Kamegawa, K. Giboney, J. Karin, S. Allen, M. Case, R. Yu, M. J. W. Rodwell, and J. E. Bowers, “Picosecond GaAs Monolithic Optoelectronic Sampling Circuit,” IEEE Photonics Technology Letters, Vol. 3. No. 6, June 1991 K. Takahata, R. Takahashi, T. Nakahara, H. Takenouchi, and H. Suzuki, “3.3 ps electrical pulse generation from a discharge-based metal-semiconductormetal photodetector,” Electrnoics Letters, Vol. 41, No.1, January 2005. J.S. Lee and C. Nguyen, “Novel Low-Cost Ultra-Wideband, UltraShort-Pulse, Transmitter with MESFET Impulse-Shaping Circuitry for Reduced Distortion and Improved Pulse Repetition Rate,” IEEE Microwave and Wireless Components Letters., vol. 11, no. 5, pp. 208-210, May 2001. J.S. Lee and C. Nguyen, “Uniplanar picosecond pulse generator using step-recovery diode”, Electronics Letters, Vol. 37, No. 8, April2001 J.S. Lee, C. Nguyen, and T. Scullion, “New Uniplanar Subnanosecond Monocycle Pulse Generator and Transformer for Time-Domain Microwave Applications,” IEEE Transactions On Microwave Theory And Techniques, Vol. 49, No. 6, June 2001 J. Han, C. Nguyen, “A New Ultra-Wideband, Ultra-Short Monocycle Pulse Generator with Reduced Ringing”, IEEE Microwave and Wireless Components Letters, Volume: 12 , No: 6 , June 2002 R. J. Focia, E. Schamiloglu, C. B. Fleddermann, F. J. Agee, and J. Gaudet, “Silicon diodes in avalanche pulse sharpening applications,” IEEE Trans. Plasma Sci., vol. 25, Apr. 1997. M.J.W. Rodwell, M. Amegawa, R.YU, M. Case, E. Carman, K.S. Giboney, “GaAs nonlinear transmission lines for picosecond pulse generation and millimeter-wave sampling,” IEEE Trans. Microw. Theory Tech., 1991, MTT-39, pp. 1194-1204 N. Deparis, A. Boé, M. Fryziel, C. Loyez, L. Clavier, N. Rolland, P.A. Rolland, “Transposition of Impulse Radio UWB signals in Millimetre Wave for WPAN,” 4th ESA Workshop on Millimetre
[15]
[16]
[17]
[18]
[19]
[20] [21]
[22]
665
Wave Technology and Applications, February 15-17, 2006, Espoo, Finland N. Deparis, A. Bendjabballah, A. Boe, M. Fryziel, C. Loyez, L. Clavier, N. Rolland, P.-A. Rolland, “ Transposition of a baseband UWB signal at 60 GHz for high data rate indoor WLAN,” IEEE Microwave And Wireless Components Letters, Vol. 15, No. 10, October 2005 N. Deparis, C. Loyez, M. Fryziel, A. Boe, N. Rolland, P.A. Rolland, “Transposition of a base band Ultra Wide Band Width Impulse Radio signal at 60 GHz for high data rates multiple access indoor communication systems,” EuMW-ECWT proceedings, Amsterdam, 2004. S. Bagga, G. de Vita, S.A.P. Haddad1, W.A. Serdijn and J.R. Long, “A PPM Gaussian pulse generator for ultra-wideband communications communication,” Circuits and Systems, 2004. ISCAS '04. Proceedings of the 2004 International Symposium on, Volume 1, May 2004. Y. Jeong, S. Jung and Jin Liu, “A CMOS impulse generator for uwb wireless communication systems”, Circuits and Systems, 2004. ISCAS '04. Proceedings of the 2004 International Symposium on, Volume 4, May 2004. B. Jung, Y.H. Tseng, J. Harvey and Ramesh Harjani, “Pulse Generator Design For UWB IR Communication Systems,” Circuits and Systems, 2005. ISCAS 2005. IEEE International Symposium on, May 2005 I. opperman, M. Hämäläinen, J. Linatti, “UWB Therory and Aplpications,” John Wiley & Sons, Ltd, 2004 K. Marsden, H.J Lee, D.S am Ha and Hyung-Soo Lee, “Low Power CMOS Re-programmable Pulse Generator for UWB Systems,” Int. Conf. on Ultra Wideband Systems and Technologies, pp. 443-447, November 2003, Reston, Virginia N. Deparis, C. Loyez, N. Rolland, P-A. Rolland, “Receiver and Synchronization for UWB impulse radio signals”, accepted for Microwave Symposium Digest, 2006 IEEE MTT-S International
Abstract— Two simple and compact ultra-wideband, ultrashort-pulse transmitters have been developed using a monolithic microwave integrated circuit (MMIC). These pulse generators include a digital approach for the pulse forming based on a logic gate. They produce pulses with a variable width as low as 65 ps and rise and fall time about 25 ps (measured). The pulse position modulation (PPM) with pulse frequency rate (PRF) from frequency below 1 MHz to several GHz is also possible. Finally, an analog filtering solution for its shape is proposed in order to be compliant with the FCC part 15 frequency mask.
II. A.
Principle The main idea of the pulse generator is the use of a logic gate (such as a NAND, NOR or XOR gate) with two delayed inputs. For example, with a NAND gate, when the two inputs INA and INB are both in low state, the output is "high". With a XOR gate, the output is high only when INA and INB are in different states, the PRF will be twice the INA IN B inputs frequency (Fig. 1).
I. INTRODUCTION Ultra short pulse generation is a challenge for lot of kind of applications. Each application has its own specifications: RADAR with high output peak voltage [1], sampling at millimeter waves with very short fall/rise times and duration [2], TDR/TDT at millimeter waves [3], and recently wireless communications with specific pulse shape (FCC part 15 frequency mask) [4],[5]. Various methods for pulse generation have been presented, including optical systems – which have the fastest transient specification [6],[7] but a difficult implementation – hybrid methods – with step recovery diodes (SRD) [8]-[11] and avalanche transistors [12] – and with integrated circuit (IC) – such as with NLTL [13] and digital method [14]-[19]. Many other methods exist and will not be presented here [20].
IN
τ
τ
IN
τ
τ
τ
Figure 1. Basic structure of pulse generator
SRD (linked with schottky diode for the pulse shaping) is the most popular and easiest way for pulses generation. The main limitation of this technique is the pulse repetition frequency (PRF) due to time life of the carriers. This method is not recommended for high data rate communications.
For our application, we use a NOR gate with two complementary inputs delayed with τ. The choice of such logic gate is function of the high speed IC process and its logic family advantages and drawbacks. Using a NOR gate, the two complementary inputs can be obtained using a differential output buffer.
More recently, [15],[16] introduces an ultra short pulse generator using a logic gate in pHEMT technology. [17][19], also present simulation results using the same method with low cost CMOS process, but without pulse width tuning capability.
0-7803-9390-2/06/$20.00 ©2006 IEEE
SINGLE ENDED DIGITAL PULSE GENERATORS
This delay τ can be realized with a propagation line, multiple delay taps [18],[21], or with a mixed analog and digital IC. This IC can be composed, for example, with a
661
ISCAS 2006
triangular generator and a comparator [17], or with a varactor diode [16],[19] (Fig. 2). Another way to create this delay is to use two comparators with two shifted analog sources. This shift can be programmed with two Direct Digital Synthesis (DDS) whose relative phase can be precisely controlled [14]. Using the varactor diode, a special study must be made on its dimension in order to fix the minimum or the maximum pulse width. In fact, the pulse width limits are determined by the equivalent Cmax/Cmin factor. It is also possible to adjust the pulse width, using a BDCFL logic family, by changing the voltage threshold of the NOR gate (Vth). This can be done by tuning the value of the R var value in the design of the BDCFL gate (Fig. 2a).
Figure 4. Pulse Generator using a varactor diode, die size : 0.7x1.5 mm²
In order to have two complementary outputs at the input of the NOR Gate, the first inverters – which are used as fast edge compressor – have been designed in SCFL logic family. The NOR gate and the outputs stage have been designed in BDCFL logic, in order to have a high voltage margin (3 V). The consumption is about 180 mW. It can be seriously decreased using high speed CMOS process for wireless communication.
OUTA 0
IN A
Vwidth
OUT A Rvar
-1 Vth -2 -3
(a)
-Vss
0.0
0.5
1.0
(b)
1.5
C. Experimental results In this section, experimental results about the pulse generator designed with the ED02AH foundry are presented.
2.0 2.5 t [nsec]
Figure 2. Principle of delaying using a varactor diode: (a) BDCFL inverter with threshold adjustable (b) output of the BDCFL inverter for different voltages applied to the varactor diode.
1) Time Domain On the Fig. 5a are represented a 3 dBm sinusoidal analog clock at 250 MHz and different position of pulses. These positions were obtained for a voltage control from -300 mV to 150 mV at the input of the comparator (Fig. 3). The pulse position deviation is about 420 ps for 450 mV, so the sensibility is about 1 ps/mV. The pulse width and shape is still constant, whatever the position of the pulse.
In order to enable the Time Hopping possibility in wireless communication [4],[5], a third input is added to the input of the gate. When CtrlTH. value is on high state pulses are generated. This signal must be synchronized with the analog clock and bufferized. Finally, for the PPM, an analog voltage controls the position of the pulse with the first stage, i.e. the comparator. The final simplified block diagram of the pulse generator is presented in Fig. 3. Ctrl T.H. Analog clock VPPM comparator
SCFL
Vwidth
BDCFL
(a)
(b)
Figure 5. (a) Pulse position control width from left to right Vctrl from -300 to 150 mV. (b) 750 MHz PRF. Scale : 100mV/ div and 100ps/div.
Varactor diode Figure 3. Functional block diagram designed for a single ended digital pulse generator using a varactor diode with T.H and PPM possibilities
We can also see on Fig. 5 the ringing that is due to the mismatched between the pulse generator and the 50 impedance of the digital scope. The pulse repetition frequency (PRF) has also been validated and can be as low as 1 MHz up to 1 GHz (Fig. 5b). Fig. 6 represents the control of the pulse width. The minimum width is about 75 ps and can reach 800 ps. For width lower than 100 ps, the amplitude decreases,
B. Design The OMMIC ED02AH foundry has been chosen. This process provides low noise, pseudomorphic HEMT devices using 0.2 µm GaAs HEMT. Depletion and enhancement transistors are available with Ft=63 GHz so 25 ps rise/fall times can be reached. A microphotograph of the pulse generator is presented below (Fig. 4).
662
as a delay line and the order of the filter (i.e. number of stub) defines the shape of the pulse.
otherwise, it is still constant, about 800 mV with 50 Ω impedance load. The jitter has also been measured and is less than 1.5 ps rms. Width [ps]
90 0 80 0 70 0 60 0 50 0 40 0 30 0 20 0 10 0
Vdiode [V]
0 -1, 50
-1, 25
-1, 00
-0, 75
-0, 50
-0, 25
0, 00
0, 25
(a)
0, 50
(b) Figure 8. High-pass filter with short-circuited stub
Figure 6. (a) Pulse width control. (b) Shape of the pulse for different widths Scale : 100 mV/div and 50 ps/div.
Varying the length of the different stubs will change the shape, and so the spectral frequency occupations. Two temporal representations are presented in Fig. 10.
2) Frequency domain With rise and fall times of about 25 ps, several dozen of gigahertz bandwidth is occupied (Fig. 7a). The pulse width also defines the spectral occupation.
(a)
(b)
Figure 9. Pulse shaping with differents orders of filter. (a) first order (b) second order. Scale : 100 mV/ div and 200ps/div.
(a)
Fig. 9 shows the measured pulses waveform. They have pulse duration of 300 ps. The amplitude peak-to-peak is 800 mV using the first order filter and 400 mV for second order filter. The ringing level is due to the mismatch between the pulse generator and the oscilloscope. The amplitude and shape symmetry are good. The measurement was made using a 100-MHz sinusoidal wave signal and Agilent DCA-J 86100C digital communication analyzer.
(b)
Figure 7. (a) spectral occupation of 100 MHz PRF unipolar pulse (b) spectral occupation of 100 MHz PRF unipolar pulse with PPM
In order to validate the pulse position modulation, we measure the output spectral occupation of the pulse generator with 50 Mbps PPM (Fig. 7b). The shape smooth of the waveform validates the pulse position modulation. D. Pulse shaping In order to be compliant with the FCC part 15 frequency mask, the occupied bandwidth of the pulse must be in the [3.1 – 10] GHz band. A method to produce this specific pulse shape is to filter the output of the pulse generator with a high pass filter. This can be done with lumped elements, such as a simple RC high-pass filter [11] but these two parameters are not enough to assure the specific pulse shape. This can be also done with LC band pass filter [19], but above a few GHz, specific model of lumped elements must be used, and simulation results are too far from experimental results.
(a)
(b)
Figure 10. Spectral occupation of 100 MHz PRF pulse filetered. (a) without modulation (b) with PPM at 50 Mbps.
The spectral occupation of the pulse shown in Fig. 9b., i.e., using the second order filter is presented Fig. 10. The bandwidth occupation is equal to [3.2 – 8.4] GHz (with 20 dB rejection). Some optimizations are still required to validate the pulse generator with the FCC frequency mask. The pulse position modulation is also validated (Fig. 10b).
The other way is the use of a microstrip filter composed of short-circuited stubs and a transmission line with specific impedances. In order to have a monocycle, τ must be equal to the input pulse width (Fig. 8). The short-circuited stub acts
663
III. DIFFERENTIAL O UTPUTS WITH BPSK MODULATION Another method to produce a monocycle is to sum up pulses with different polarities with a time delay corresponding to the width of the pulse [20]. A. Architecture Using the D01PH foundry, a new design of pulse generator has been made. This process provides HEMT with Ft=100 GHz so 20 ps rise/fall times can be reached. The principle is still the same, using high speed logic gate and a varactor diode, but the logic families are now fully differential (SCFL). This pulse generator photography is presented on Fig. 11.
Figure 13. 200 ps monocycle pulse width spectrum, FPRF = 100 MHz, Fcenter = 6.5 GHz, SPAN = 7 GHz, RL = -25 dBm
According to Fig. 13., some filtering is still necessary to be compliant with the FFC part 15 frequency mask. The spectrum of a 60 ps pulse width with 2 PRF – 100 MHz and 5 GHz - is presented in Fig. 14. We can see that a - 40 dBm power can be available at millimeter wave (40 GHz).
Figure 11. Pulse Generator with differential outputs, die size : 0.7x1.5 mm²
With two pulse generators using this kind of architecture, a BPSK modulation can be achieved [20] (see Fig. 12b). In fact, each pulse generator pulse position can be controlled undependably and by summing the outputs, specials shape can be obtained.
(a) FPRF = 100 MHz, SPAN = 25 GHz
IV. CONCLUSION Two RF pulse generators using digital approach for multiples application have been developed in pHEMT technology and validated. They achieves 25 ps of rise and fall time. Their width can vary from 60 ps to 800 ps. The PPM modulation has also been validated for wireless communications and sampling [22]. A simple passive pulse shape using microstrip filter has been presented in order to be compliant with the FCC part 15 reglementation. Another pulse generator has also been presented for special shape and BPSK modulation.
B. Experimental Results The differential output measurements of the pulse generator are shown in Fig. 12.a. The output spectrum are presented in Fig. 13 and 14. A 60 ps minimum pulse width can be reached, which means that more than 20 GHz bandwidth is occupied. It has been validated according to Fig. 14.a. Three signals are presented in Fig. 12.b., the two on the right are the differential outputs of two pulse generators. The position can be controlled by adjusting a voltage control on the device. The signal on the left is the sum. A 200 ps monocycle pulse width is obtained.
REFERENCES [1] [2]
[3] (a) 20 ps/div
(b) FPRF = 5 GHz, SPAN = 50 GHz
Figure 14. Pulse generator output spectrum, Ref Level = 0 dBm, 10 dB/div,
(b) 100 ps/div
[4]
Figure 12. Pulse Generator with differential outputs, die size : 0.7x1.5 mm²
[5]
664
Daniels D.J, “Surface penetrating radar”, Electronics & Communication Engineering Journal, Vol 8, Issue 4, Aug. 1996 P. Abele, M. Birk, D. Behammer, H. Kibbe1, A. Tkasser, P. Maier, K.-B. Schad, E. Sonmez, and H. Schumacher, “Sampling Circuit on Silicon Substrate for Frequencies beyond 50 GHz”, IEEE MTT-S, 2002 James R. Andrews, “Time Domain Reflectometry (TDR) and Time Domain Transmission (TDT) Measurement Fundamentals,” Picosecond Pulse Labs, AN-15, November 2004 R. A. Scholtz, “Multiple access with time hopping impulse modulation,” Proceeding IEEE MILCOM Conf., pp. 447–450, 1993 M. Z. Win, R. A. Scholtz, “Ultra-Wide Bandwidth Time-Hopping Spread-Spectrum Impulse Radio for Wireless Multiple-Access
[6]
[7]
[8]
[9] [10]
[11]
[12]
[13]
[14]
Communications,” IEEE Trans. Communications, vol. 48, N°. 4, April 2000. M. Kamegawa, K. Giboney, J. Karin, S. Allen, M. Case, R. Yu, M. J. W. Rodwell, and J. E. Bowers, “Picosecond GaAs Monolithic Optoelectronic Sampling Circuit,” IEEE Photonics Technology Letters, Vol. 3. No. 6, June 1991 K. Takahata, R. Takahashi, T. Nakahara, H. Takenouchi, and H. Suzuki, “3.3 ps electrical pulse generation from a discharge-based metal-semiconductormetal photodetector,” Electrnoics Letters, Vol. 41, No.1, January 2005. J.S. Lee and C. Nguyen, “Novel Low-Cost Ultra-Wideband, UltraShort-Pulse, Transmitter with MESFET Impulse-Shaping Circuitry for Reduced Distortion and Improved Pulse Repetition Rate,” IEEE Microwave and Wireless Components Letters., vol. 11, no. 5, pp. 208-210, May 2001. J.S. Lee and C. Nguyen, “Uniplanar picosecond pulse generator using step-recovery diode”, Electronics Letters, Vol. 37, No. 8, April2001 J.S. Lee, C. Nguyen, and T. Scullion, “New Uniplanar Subnanosecond Monocycle Pulse Generator and Transformer for Time-Domain Microwave Applications,” IEEE Transactions On Microwave Theory And Techniques, Vol. 49, No. 6, June 2001 J. Han, C. Nguyen, “A New Ultra-Wideband, Ultra-Short Monocycle Pulse Generator with Reduced Ringing”, IEEE Microwave and Wireless Components Letters, Volume: 12 , No: 6 , June 2002 R. J. Focia, E. Schamiloglu, C. B. Fleddermann, F. J. Agee, and J. Gaudet, “Silicon diodes in avalanche pulse sharpening applications,” IEEE Trans. Plasma Sci., vol. 25, Apr. 1997. M.J.W. Rodwell, M. Amegawa, R.YU, M. Case, E. Carman, K.S. Giboney, “GaAs nonlinear transmission lines for picosecond pulse generation and millimeter-wave sampling,” IEEE Trans. Microw. Theory Tech., 1991, MTT-39, pp. 1194-1204 N. Deparis, A. Boé, M. Fryziel, C. Loyez, L. Clavier, N. Rolland, P.A. Rolland, “Transposition of Impulse Radio UWB signals in Millimetre Wave for WPAN,” 4th ESA Workshop on Millimetre
[15]
[16]
[17]
[18]
[19]
[20] [21]
[22]
665
Wave Technology and Applications, February 15-17, 2006, Espoo, Finland N. Deparis, A. Bendjabballah, A. Boe, M. Fryziel, C. Loyez, L. Clavier, N. Rolland, P.-A. Rolland, “ Transposition of a baseband UWB signal at 60 GHz for high data rate indoor WLAN,” IEEE Microwave And Wireless Components Letters, Vol. 15, No. 10, October 2005 N. Deparis, C. Loyez, M. Fryziel, A. Boe, N. Rolland, P.A. Rolland, “Transposition of a base band Ultra Wide Band Width Impulse Radio signal at 60 GHz for high data rates multiple access indoor communication systems,” EuMW-ECWT proceedings, Amsterdam, 2004. S. Bagga, G. de Vita, S.A.P. Haddad1, W.A. Serdijn and J.R. Long, “A PPM Gaussian pulse generator for ultra-wideband communications communication,” Circuits and Systems, 2004. ISCAS '04. Proceedings of the 2004 International Symposium on, Volume 1, May 2004. Y. Jeong, S. Jung and Jin Liu, “A CMOS impulse generator for uwb wireless communication systems”, Circuits and Systems, 2004. ISCAS '04. Proceedings of the 2004 International Symposium on, Volume 4, May 2004. B. Jung, Y.H. Tseng, J. Harvey and Ramesh Harjani, “Pulse Generator Design For UWB IR Communication Systems,” Circuits and Systems, 2005. ISCAS 2005. IEEE International Symposium on, May 2005 I. opperman, M. Hämäläinen, J. Linatti, “UWB Therory and Aplpications,” John Wiley & Sons, Ltd, 2004 K. Marsden, H.J Lee, D.S am Ha and Hyung-Soo Lee, “Low Power CMOS Re-programmable Pulse Generator for UWB Systems,” Int. Conf. on Ultra Wideband Systems and Technologies, pp. 443-447, November 2003, Reston, Virginia N. Deparis, C. Loyez, N. Rolland, P-A. Rolland, “Receiver and Synchronization for UWB impulse radio signals”, accepted for Microwave Symposium Digest, 2006 IEEE MTT-S International
