**6. Measurement setup and results**

16 UKoLoS

The signal is coupled to the collector load transmission lines of the Colpitts oscillator using a transformer with a center tap. The center tap is connected to the pulsed current source of the

**Figure 15.** 63.8 GHz Colpitts voltage controlled oscillator schematic. *Z*<sup>1</sup> to *Z*<sup>5</sup> denote transmission lines

The simulation of the whole system was not possible. This is due to the fact that the system works in three frequency ranges, which differ by the order of magnitudes: The 5.8 GHz input signal, the 63.8 GHz output signal and the SILO pulse repetition frequency (10 − 100 MHz). Combined with the unknown modeling of switched injection-locking in the EDA software made it more viable to design each component (harmonics generator, VCO, pulse generator)

separately. 16 shows the layout of the SILO circuit with its sub-components.

oscillator.

**Figure 16.** Layout of 63.8 GHz SILO

### **6.1. Verification of sampling theory**

In order to verify the theoretical predictions concerning the switched injection locked harmonic sampling approach according to section 3.3, a demonstrator based on lumped planar components was built (see Fig. 18 and 19). It consists of a 480 MHz, 0 dBm signal source, a 10 MHz DAC modulated phase shifter, a single biased bipolar transistor frequency multiplier, a band pass filter (200 MHz @ 5.8 GHz) and the 5.8 GHz switched injection locked oscillator, which is turned on and off by the digital baseband synchronously to DAC modulation. Fig. 20 depicts the spectrum at the SILO's output. It features the typical sinc shaped peak comb in pulsed mode, which is aligned to and follows the injection frequency of 5.76 GHz when changed. When tuning the oscillators natural frequency (which is according to Fig. (20) different from the injection frequency) using a varactor diode, the sinc shape of the spectrum moves on the frequency axis while the peak positions do not change. These results prove most of the main claims of the generalized sampling theory according to (5) [4].

**Figure 18.** Implementation of communication and radar signal generator [4]

18 UKoLoS 360 Ultra-Wideband Radio Technologies for Communications, Localization and Sensor Applications Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems <sup>19</sup>

**6.2. Synthesis of communication signals**

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

inphase component (I)

time in us

quadrature component (Q)

<sup>0</sup> 0.2 0.4 0.6 0.8 <sup>1</sup> 1.2 1.4 1.6 1.8 <sup>2</sup> −0.3

component, right: IQ diagram [4]

 

 

 

*! "* 

**6.3. Synthesis of radar signals**

time in us


 

 

 

−0.3 −0.2 −0.1 0 0.1 0.2 0.3

−0.2 −0.1 0 0.1 0.2 0.3

sufficient.

 *-* 

SILO [3]

amplitude in V

amplitude in V

The synthesis of time domain communication signals was demonstrated using an 8 PSK modulation with cyclic transmission of all symbol values and maximum symbol rate, i.e. one symbol per pulse. The output signal of the demonstrator (Fig. 18, 19) was mixed to baseband using a quadrature mixer and displayed using an oscilloscope. Its waveform (Fig. 21) clearly shows the phase states and their repeatability in the IQ diagram. These results prove for the first time that it is feasible to generate UWB signals with more complex phase modulation

Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems 361

−0.3 −0.2 −0.1 0 0.1 0.2 0.3 0.4

quadrature amplitude in V

**Figure 21.** Generator output with 8 PSK modulation mixed to DC; left: inphase and quadrature

 *-* 

**Figure 22.** Measurement setup (on-waver) for the synthesis of radar signals using an integrated circuit

According to sections 3.5 and 4.3, the same simple hardware implementation used for communication signal synthesis (Fig. (18), (19)) can be employed to generate pulsed frequency modulated radar signals by repeatedly transmitting a limited list of phase samples. For a pulse rate of 10 MHz and a ramp slope of 20 MHz/*μs*, only 50 phase samples (one per pulse) are

> - - *-*

 *-* 

 -

 

- 

!" #

−0.4 −0.3 −0.2 −0.1 <sup>0</sup> 0.1 0.2 0.3 0.4 −0.4

inphase amplitude in V

  *-*   

 

 

 

time domain waveform in IQ plane

than BPSK while at the same time keeping complexity and power consumption low.

**Figure 19.** Hardware components for the 6 GHz transmitter system demonstrator (using lumped planar components SILO implementation)

**Figure 20.** Spectrum of SILO based demonstrator with CW modulation; large peak: oscillator permanently on, comb: pulsed oscillator, background: comb zoomed out to show envelope, span 1.5 GHz [4]

360 Ultra-Wideband Radio Technologies for Communications, Localization and Sensor Applications Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems <sup>19</sup> Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems 361

### **6.2. Synthesis of communication signals**

18 UKoLoS

**Figure 19.** Hardware components for the 6 GHz transmitter system demonstrator (using lumped planar

5.2 5.4 5.6 5.8 6 6.2 6.4

frequency in GHz

pulsed CW

5.76 5.78 5.8 5.82 5.84

frequency in GHz

**Figure 20.** Spectrum of SILO based demonstrator with CW modulation; large peak: oscillator permanently on, comb: pulsed oscillator, background: comb zoomed out to show envelope, span 1.5

components SILO implementation)

power in dBm

−80

−80

−60

−40

power in dBm

GHz [4]

−20

0

−70

−60

−50

−40

The synthesis of time domain communication signals was demonstrated using an 8 PSK modulation with cyclic transmission of all symbol values and maximum symbol rate, i.e. one symbol per pulse. The output signal of the demonstrator (Fig. 18, 19) was mixed to baseband using a quadrature mixer and displayed using an oscilloscope. Its waveform (Fig. 21) clearly shows the phase states and their repeatability in the IQ diagram. These results prove for the first time that it is feasible to generate UWB signals with more complex phase modulation than BPSK while at the same time keeping complexity and power consumption low.

**Figure 21.** Generator output with 8 PSK modulation mixed to DC; left: inphase and quadrature component, right: IQ diagram [4]

### **6.3. Synthesis of radar signals**

According to sections 3.5 and 4.3, the same simple hardware implementation used for communication signal synthesis (Fig. (18), (19)) can be employed to generate pulsed frequency modulated radar signals by repeatedly transmitting a limited list of phase samples. For a pulse rate of 10 MHz and a ramp slope of 20 MHz/*μs*, only 50 phase samples (one per pulse) are sufficient.

**Figure 22.** Measurement setup (on-waver) for the synthesis of radar signals using an integrated circuit SILO [3]

**Figure 23.** Beat spectrum (6-8 GHz SILO chip) of measured radar signal after mixing with linear sweep and before low pass filtering [3]

1.009 1.01 1.011 1.012 1.013 1.014 1.015 1.016

frequency in Hz

For verification, this approach was realized both using the previously employed lumped components SILO (6 GHz, 600 MHz bandwidth) and the first large bandwidth integrated circuit implementations (7 GHz, >2 GHz bandwidth) in order to demonstrate the resolution benefit for ranging. The setup for both experiments is depicted in Fig. 22; the generated and delayed signal is acquired using an oscilloscope and evaluated on a PC using a numerical computation software where it is mixed with a linear FMCW signal and analyzed in frequency

Fig. 23 and 24 show the resulting beat frequency spectrum for the integrated circuit implementation using 1 ns pulses and 10 MHz pulse repetition rate. It corresponds to equation (10) except the small peaks that result from imperfections in the oscillator design leading to a

Comparing the results of the lumped and integrated circuit implementations (see Fig. 25), the benefit of much higher bandwidths regarding resolution becomes obvious. If the oscillator's spectral bandwidth is too small in relation to the sweep bandwidth, the beat frequency peak is broadened because of additional windowing through the narrowband SILO spectrum. Therefore, the oscillator bandwidth / pulse width should be adjusted to the desired sweep

The manufactured circuit is depicted in Fig.26. It measures 710 × 1455 *μ*m². For reasons of nonavailability of differential equipment, all measurements were done single-ended with the

Fig. 27 shows the output power over the tuning range. The 10 dB decrease of output power compared to the previously published [8] VCO is attributed to the different VCO output buffer

slight turn-on pulse self-locking effect. Future designs are expected to fix this issue.

bandwidth in order to maximize spectral efficiency [3].

unused output terminated to ground with a 50 Ω resistor.

**Figure 25.** Comparison of 6-8 GHz chip (2 GHz bandwidth) with lumped implementation (wider

FMCW beat spectrum (downsweep)

Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems 363

5ns pulse 7.5ns pulse 10ns pulse

5ns pulse, 1m extra cable 7.5ns pulse, 1m extra cable 10ns pulse, 1m extra cable

−50

pulses, smaller bandwidth) [3]

**6.4. VCO with switch IC**

and the insertion loss of the switch.

domain (FFT).

−40

−30

−20

relative power in dB

−10

0

10

x 10<sup>7</sup>

**Figure 24.** Zoomed beat spectrum (6-8 GHz SILO chip), comparison of two waveforms with different transmission delays [3]

**Figure 25.** Comparison of 6-8 GHz chip (2 GHz bandwidth) with lumped implementation (wider pulses, smaller bandwidth) [3]

For verification, this approach was realized both using the previously employed lumped components SILO (6 GHz, 600 MHz bandwidth) and the first large bandwidth integrated circuit implementations (7 GHz, >2 GHz bandwidth) in order to demonstrate the resolution benefit for ranging. The setup for both experiments is depicted in Fig. 22; the generated and delayed signal is acquired using an oscilloscope and evaluated on a PC using a numerical computation software where it is mixed with a linear FMCW signal and analyzed in frequency domain (FFT).

Fig. 23 and 24 show the resulting beat frequency spectrum for the integrated circuit implementation using 1 ns pulses and 10 MHz pulse repetition rate. It corresponds to equation (10) except the small peaks that result from imperfections in the oscillator design leading to a slight turn-on pulse self-locking effect. Future designs are expected to fix this issue.

Comparing the results of the lumped and integrated circuit implementations (see Fig. 25), the benefit of much higher bandwidths regarding resolution becomes obvious. If the oscillator's spectral bandwidth is too small in relation to the sweep bandwidth, the beat frequency peak is broadened because of additional windowing through the narrowband SILO spectrum. Therefore, the oscillator bandwidth / pulse width should be adjusted to the desired sweep bandwidth in order to maximize spectral efficiency [3].

## **6.4. VCO with switch IC**

20 UKoLoS

FMCW beat spectrum (upsweep)

0 2 4 6 8 10

frequency in Hz

FMCW beat spectrum (upsweep)

1ns pulse

1ns pulse, 1m extra cable

1.89 1.9 1.91 1.92 1.93 1.94 1.95 1.96 1.97

frequency in Hz

**Figure 24.** Zoomed beat spectrum (6-8 GHz SILO chip), comparison of two waveforms with different

**Figure 23.** Beat spectrum (6-8 GHz SILO chip) of measured radar signal after mixing with linear sweep

−30

−50

transmission delays [3]

−40

−30

−20

relative power in dB

−10

0

10

and before low pass filtering [3]

−25

−20

−15

−10

relative power in dB

−5

0

5

10

x 107

x 106

1ns pulse

The manufactured circuit is depicted in Fig.26. It measures 710 × 1455 *μ*m². For reasons of nonavailability of differential equipment, all measurements were done single-ended with the unused output terminated to ground with a 50 Ω resistor.

Fig. 27 shows the output power over the tuning range. The 10 dB decrease of output power compared to the previously published [8] VCO is attributed to the different VCO output buffer and the insertion loss of the switch.

22 UKoLoS 364 Ultra-Wideband Radio Technologies for Communications, Localization and Sensor Applications Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems <sup>23</sup>

**Figure 26.** VCO with switch circuit IC photograph

**Figure 28.** Measured phase noise of VCO with switch circuit

**Figure 29.** Manufactured 7 GHz SILO IC

measurement probes.

digital baseband and analog RF circuits. Fig. 29 shows a chip photograph with connected

Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems 365

The 10 dB-bandwidth stretches from 5to 8 GHz. A single pulse is shown in Fig. 31. A single

Fig. 30 shows the output power spectrum of the manufactured SILO.

cycle of oscillator start up, oscillation and decay has a duration of 1.5 ns.

**Figure 27.** Measured output power of 1st, 2nd and 3rd harmonic of VCO with switch

The phase noise performance of the VCO with switch has deteriorated significantly from the previous [8] stand-alone VCO. This is mainly attributed to the new buffer structure which performed worse than anticipated.

### **6.5. 7 GHz SILO IC**

The IHP Technologies SGB25V 250 nm SiGe:C BiCMOS process was chosen for manufacturing. It provides a cheap and flexible platform including one or two thick top metal layers consisting of aluminum. The advantage of using a BiCMOS process for a transmitter circuit is the possibility to build a system-on-a-chip (SoC) solution that integrates 364 Ultra-Wideband Radio Technologies for Communications, Localization and Sensor Applications Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems <sup>23</sup> Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems 365

**Figure 28.** Measured phase noise of VCO with switch circuit

22 UKoLoS

**Figure 26.** VCO with switch circuit IC photograph

performed worse than anticipated.

**6.5. 7 GHz SILO IC**

**Figure 27.** Measured output power of 1st, 2nd and 3rd harmonic of VCO with switch

The phase noise performance of the VCO with switch has deteriorated significantly from the previous [8] stand-alone VCO. This is mainly attributed to the new buffer structure which

The IHP Technologies SGB25V 250 nm SiGe:C BiCMOS process was chosen for manufacturing. It provides a cheap and flexible platform including one or two thick top metal layers consisting of aluminum. The advantage of using a BiCMOS process for a transmitter circuit is the possibility to build a system-on-a-chip (SoC) solution that integrates

**Figure 29.** Manufactured 7 GHz SILO IC

digital baseband and analog RF circuits. Fig. 29 shows a chip photograph with connected measurement probes.

Fig. 30 shows the output power spectrum of the manufactured SILO.

The 10 dB-bandwidth stretches from 5to 8 GHz. A single pulse is shown in Fig. 31. A single cycle of oscillator start up, oscillation and decay has a duration of 1.5 ns.

be refined for an even better performance and higher integration level. Last but not least,

Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems 367

This work was supported by the German Research Foundation (DFG - priority program SPP1202, grant VO 1453/3-2) within the project "Components and concepts for low-power

[1] Barrett, T. W. [2000]. History of UltraWideBand (UWB) Radar & Communications:

[2] Carlowitz, C., Esswein, A., Weigel, R. & Vossiek, M. [2012a]. A low power Pulse Frequency Modulated UWB radar transmitter concept based on switched injection locked harmonic sampling, *Microwave Conference (GeMiC), 2012 The 7th German*, pp. 1

[3] Carlowitz, C., Esswein, A., Weigel, R. & Vossiek, M. [2012b]. Synthesis of Pulsed Frequency Modulated Ultra Wideband Radar Signals Based on Stepped Phase Shifting,

[4] Carlowitz, C. & Vossiek, M. [2012]. Synthesis of Angle Modulated Ultra Wideband Signals Based on Regenerative Sampling, *IEEE International Microwave Symposium 2012*. [5] Chandrakasan, A., Lee, F., Wentzloff, D., Sze, V., Ginsburg, B., Mercier, P., Daly, D. & Blazquez, R. [2009]. Low-Power Impulse UWB Architectures and Circuits, *Proceedings of*

[6] Deparis, N., Loyez, C., Rolland, N. & Rolland, P.-A. [2008]. UWB in Millimeter Wave Band With Pulsed ILO, *Circuits and Systems II: Express Briefs, IEEE Transactions on*

[7] Deparis, N., Siligarisy, A., Vincent, P. & Rolland, N. [2009]. A 2 pJ/bit pulsed ILO UWB transmitter at 60 GHz in 65-nm CMOS-SOI, *Ultra-Wideband, 2009. ICUWB 2009. IEEE*

[8] Esswein, A., Dehm-Andone, G., Weigel, R., Aleksieieva, A. & Vossiek, M. [2010]. A low phase-noise SiGe Colpitts VCO with wide tuning range for UWB applications, *Wireless*

[9] Grass, E., Siaud, I., Glisic, S., Ehrig, M., Sun, Y., Lehmann, J., Hamon, M., Ulmer-Moll, A., Pagani, P., Kraemer, R. & Scheytt, C. [2008]. Asymmetric dual-band UWB / 60 GHz demonstrator, *Personal, Indoor and Mobile Radio Communications, 2008. PIMRC 2008. IEEE*

[10] Hancock, T. & Rebeiz, G. [2005]. Design and Analysis of a 70-ps SiGe Differential RF Switch, *Microwave Theory and Techniques, IEEE Transactions on* 53(7): 2403 – 2410.

mm-wave pulsed angle modulated ultra wideband communication and ranging".

*Institute for Electronics Engineering, University of Erlangen-Nuremberg, Germany*

*Institute of Microwaves and Photonics, University of Erlangen-Nuremberg, Germany*

*IEEE International Conference on Ultra-Wideband (ICUWB)* .

*Technology Conference (EuWIT), 2010 European*, pp. 229 –232.

hardware concepts for receiver technology are being developed.

**Acknowledgement**

**Author details**

**8. References**

–4.

Alexander Esswein and Robert Weigel

Christian Carlowitz and Martin Vossiek

Pioneers and Innovators.

*the IEEE* 97(2): 332–352.

*International Conference on*, pp. 113 –117.

*19th International Symposium on*, pp. 1 –6.

55(4): 339 –343.

**Figure 30.** Measured output spectrum of 7 GHz SILO IC

**Figure 31.** Transient output of 7 GHz SILO IC

### **7. Future work**

Since this project is still ongoing, future work will cover further aspects that enhance theory and hardware implementation. Regarding pulsed angle modulated signals, more complex modulation schemes will be developed in conjunction with a more comprehensive study of error sources and their compensation. Furthermore, the first designs of the SILO circuit will 366 Ultra-Wideband Radio Technologies for Communications, Localization and Sensor Applications Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems <sup>25</sup> Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems 367

> be refined for an even better performance and higher integration level. Last but not least, hardware concepts for receiver technology are being developed.
