**5.3. 6 and 8 GHz SMT SILO**

For reference and for first experiments, SILO implementations based on surface mounted planar technology were realized. They are based on an ordinary common-collector Colpitts oscillator and designed for a natural frequency of 6 GHz respectively 7.5 GHz. In order to implement injection-locking, a directional coupler was added to apply the injection signal to the oscillator's output (see Fig. 12). The maximum achievable (10 dB) bandwidth is about 600 MHz at 7.5 ns pulse width.

Apart from parasitic technological limitations of lumped planar implementations, the single-ended design features an inherent source of self-locking to a harmonic of the switched power supply. Therefore, the pulse width is limited to about 10 to 20 ns in order to achieve a good compromise between bandwidth and minimum injection level. In consequence,

14 UKoLoS 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>

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.

Concepts and Components for Pulsed Angle Modulated Ultra Wideband Communication and Radar Systems 357

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*

The peak generator was designed for a pulse duration of 1 ns by selecting the size of the

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 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

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

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

*τcurrent* = *RBCBE*3. (17)

of the charging circuit:

resistor *RB* = 5 kΩ.

the implementation.

**5.5. 63 GHz integrated circuit**

**Figure 12.** SILO SMT implementation; left: schematic of 7.5 GHz version; upper right: 7.5 GHz implementation; lower right: 6 GHz implementation

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 performance.
