**5.4. 7 GHz integrated circuit**

**Figure 13.** 7 GHz SILO circuits; left: Schmitt-trigger with peak generator, right: VCO with *Q*-degeneration resistor

The circuit consists of two active baluns for single-ended to differential and differential to single-ended conversion, a Schmitt-trigger with modified current mirror load for current peak generation and a simple cross-coupled oscillator for signal generation. It has an externally controllable pulse repetition rate and a pulse duration of approx. 1 ns. During operation it consumes 33 mA at 3.3 V supply voltage, while generating a > 330 mVppsignal. The generated signal has a 10 dB-bandwidth of over 2 GHz at 7.5 GHz center frequency.

Both Schmitt trigger with current peak generator and VCO with *Q*-degeneration circuits are shown in Fig. 13.

356 Ultra-Wideband Radio Technologies for Communications, Localization and Sensor Applications Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems <sup>15</sup> Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems 357

> As efficient integrated circuits are built in a differential configuration but external circuitry and measurement equipment usually are only available in single-ended configuration, single-ended to differential (S2D) and differential to single-ended (D2S) conversion circuits are needed in the IC. We designed a simple active balun circuit that can act as both S2D-and D2S-converter. When employed as a S2D-converter, both outputs and one input are connected, when used as a D2S-converter, one output and both inputs are connected.

> In order to control the pulse repetition rate externally, a Schmitt-trigger circuit with current peak generator was designed based on [13]. The circuit enables a wide variety of pulse repetition rates (1 − 80 MHz could be achieved with the measurement equipment at hand). The resistor *RB* together with base-emitter capacitance *CBE*<sup>3</sup> controls the time constant *τcurrent* of the charging circuit:

$$
\pi\_{\text{current}} = R\_B \mathbb{C}\_{BE3}.\tag{17}
$$

The peak generator was designed for a pulse duration of 1 ns by selecting the size of the resistor *RB* = 5 kΩ.

For the oscillator, a simple cross-coupled topology was chosen. As the oscillator has to lock to the injected phase, a low *Q* is preferable. In order to degenerate the *Q*, a resistor was connected in parallel to the *LC*-tank circuit. The current is provided by the peak generator. Fig. 13 shows the implementation.

A simple common-collector circuit is used as an output buffer to drive the 50 Ω load.

### **5.5. 63 GHz integrated circuit**

14 UKoLoS

**Figure 12.** SILO SMT implementation; left: schematic of 7.5 GHz version; upper right: 7.5 GHz

**Figure 13.** 7 GHz SILO circuits; left: Schmitt-trigger with peak generator, right: VCO with

signal has a 10 dB-bandwidth of over 2 GHz at 7.5 GHz center frequency.

The circuit consists of two active baluns for single-ended to differential and differential to single-ended conversion, a Schmitt-trigger with modified current mirror load for current peak generation and a simple cross-coupled oscillator for signal generation. It has an externally controllable pulse repetition rate and a pulse duration of approx. 1 ns. During operation it consumes 33 mA at 3.3 V supply voltage, while generating a > 330 mVppsignal. The generated

Both Schmitt trigger with current peak generator and VCO with *Q*-degeneration circuits are

differential integrated circuit implementations are expected to deliver a significantly better self-locking suppression allowing much shorter pulsed in the order of 1 ns with comparable

implementation; lower right: 6 GHz implementation

performance.

*Q*-degeneration resistor

shown in Fig. 13.

**5.4. 7 GHz integrated circuit**


 

 
 -

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> The system developed for pulsed angle modulated signal generation at mm-wave frequency is shown in Fig. 14. The input signal of 5.8 GHz is coupled into the harmonics generator, which consists of a bipolar transistor with a resonant load. The load consisting of a transmission line of inductance *L*<sup>1</sup> and capacitors *C*<sup>1</sup> and *C*<sup>2</sup> is designed to couple the wanted 11th harmonic into the transformer. Fig. 17 shows the output power for the 1st, 10th, 11th and 12th harmonic depending on the input power. For an input power > −3 dBm, the 11th harmonic is the strongest. The now differential signal is used to lock the VCO shown in Fig. 15.

**Figure 14.** 63 GHz-system consisting of harmonics generator, baluns and VCO with pulse generator

16 UKoLoS 358 Ultra-Wideband Radio Technologies for Communications, Localization and Sensor Applications Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems <sup>17</sup>

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 oscillator.

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

**Figure 17.** Power of the generated harmonics over the input power of the harmonics generator


 

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

 

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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].

Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems 359

**6. Measurement setup and results**

**6.1. Verification of sampling theory**

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

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.

358 Ultra-Wideband Radio Technologies for Communications, Localization and Sensor Applications Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems <sup>17</sup> Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems 359

**Figure 17.** Power of the generated harmonics over the input power of the harmonics generator
