Martin Jahn

A Four-Channel 94-GHz SiGe-Based Digital Beamforming FMCW Radar

This paper presents a multi-channel frequency-modulated continuous-wave (FMCW) radar sensor operating in the frequency range from 91 to 97 GHz. The millimeter-wave radar sensor utilizes an SiGe chipset comprising a single signal-generation chip and multiple monostatic transceiver (TRX) chips, which are based on a 200-GHz fT HBT technology. The front end is built on an RF soft substrate in chip-on-board technology and employs a nonuniformly distributed antenna array to improve the angular resolution. The synthesis of ten virtual antennas achieved by a multiple-input multiple-output technique allows the virtual array aperture to be maximized. The fundamental-wave voltage-controlled oscillator achieves a single-sideband phase noise of -88 dBc/Hz at 1-MHz offset frequency. The TX provides a saturated output power of 6.5 dBm, and the mixer within the TRX achieves a gain and a double sideband noise figure of 11.5 and 12 dB, respectively. Possible applications include radar sensing for range and angle detection, material characterization, and imaging.

Precise distance measurement with cooperative FMCW radar units

In many applications the precise distance between different units has to be measured. The proposed measurement system operates with frequency modulated continuous wave (FMCW) radar sensors for distance measurement in a cooperative but unsynchronized way. Due to the missing synchronization a data transfer between the units is performed by means of the radar hardware. On the other hand, this principle could be easily implemented in communication systems. A prototype system in the 5.8-GHz ISM band has been built, and measurement results up to about 780 meters distance with accuracies of few centimeters are shown. Furthermore, the distance can be calculated at both transponder units.

125 to 181 GHz fundamental-wave VCO chips in SiGe technology

This paper presents four signal-generation chips that comprise a fundamental-wave voltage-controlled oscillator (VCO), an output buffer, and a divide-by-32 prescaler. The VCOs with contiguous tuning ranges cover almost the full waveguide band from 110 to 170GHz (D-band). The fastest VCO operates at up to 181GHz in combination with the prescaler. The VCOs run on 1.8V, draw ~35 mA, and achieve a single-sideband phase noise ranging from -92 to -82 dBc/Hz at 1MHz offset frequency. Power consumption of the high-speed frequency divider in the first prescaler stage is 70mW. The circuits are based on an Infineon SiGe technology, which features HBTs with an fmax of 340 GHz.

Highly integrated 79, 94, and 120-GHz SiGe radar frontends

This paper reflects on design aspects for multichannel frequency-continuous wave (FMCW) radar frontends from conception to application on board. In the 79-GHz domain, multi-channel applications are recapitulated, and in the 94-GHz domain, a broadband transceiver is presented along with a voltage-controlled oscillator (VCO) that covers a tuning range of 12 GHz. The functionality of the 94-GHz chipset was verified by means of a four-channel multiple-input multiple-output (MIMO) radar prototype. Finally, a highly integrated 120-GHz transceiver with on-chip signal generation is presented.

A 122-GHz SiGe-Based Signal-Generation Chip Employing a Fundamental-Wave Oscillator With Capacitive Feedback Frequency-Enhancement

This paper presents a highly integrated and fully balanced signal generation block comprising a fundamental-wave voltage-controlled oscillator (VCO), an output buffer, and a configurable frequency divider stage (prescaler). The VCO introduces a negative resistance structure in conjunction with capacitive cross-coupling. This compound structure allows fundamental oscillation to be sustained at high frequencies while providing wide tuning ranges. The capabilities of the capacitive feedback were analyzed using a linear transistor model, and boundary conditions, which support the early design phase, were derived. The chip was fabricated in a SiGe technology with 300-GHz fmax HBTs. The output frequency of the monolithic microwave integrated circuit is centered at 122 GHz and provides a tuning range of 16 GHz at an average single-sideband phase noise of -95 dBc/Hz at 1 MHz offset frequency. Possible applications include ISM applications at 122 GHz and short-range radar systems with wide tuning ranges.

Performance analysis of cooperative FMCW radar distance measurement systems

In recent years, cooperative frequency-modulated continuous-wave radar based ranging and positioning systems attained significant attraction. In this paper, we present a novel analysis approach of the performance of these incoherent systems, with a special focus set on phase noise effects. We show the behavior in different signal to noise ratio conditions and compare two competing evaluation concepts. The results are verified on real measurement data, taken with a prototype ranging system in the 5.8 GHz ISM band.

DC-Offset Compensation Concept for Monostatic FMCW Radar Transceivers

A novel dc-offset compensation technique for monostatic frequency-modulated continuous-wave (FMCW) transceivers is presented. This approach uses the intermediate frequency (IF) port of the active direct-conversion mixer to access its collector resistors. Additional external variable resistors in parallel connection can vary the total load resistance in each branch and hence compensate or generate a dc-offset voltage at the output. Since the wiring is located on the low-frequency side of the mixer, the variable resistors can also be external (off-chip), which offers great flexibility and eases application. The concept was successfully tested with an integrated 77 GHz automotive radar mixer fabricated in a 200 GHz fT Silicon Germanium (SiGe) bipolar technology.

A sige-based 140-GHz four-channel radar sensor with digital beamforming capability

This paper presents a multi-channel radar sensor operating at 140 GHz. The sensor employs fundamental-wave SiGe-based chips that feature HBTs with 340-GHz ƒmax. A separate voltage-controlled oscillator chip provides the LO signal with frequencies from 136 to 150GHz for four cascaded transceiver chips. The saturated transceiver output power is approximately 4 dBm, the maximum receiver gain is 19.5 dB, and the minimum double-sideband noise figure is 13.5 dB. The equivalent isotropically radiated power of a single channel is 5 dBm. The sensor was field-tested with frequency-modulated continuous-wave chirps from 140 to 145 GHz. Targets were resolved in range and angle by means of digital beamforming.

Characterization of Differential Transmission Lines for Integrated Millimeter-Wave Applications

This letter focuses on the characterization of differential transmission lines (T-lines) typically used in millimeter-wave integrated circuits. Common- and differential-mode propagation constants were calculated and validated in two experimental steps. A four-port scattering parameter (S-parameter) measurement followed by a multi-line calibration was performed. In addition, several two-port S-parameter measurements were conducted using a set of three marchand baluns. Comparison of the values extracted from simulations and two experiments shows very good agreement over a broad frequency range from 65 to 170 GHz.

On-wafer passives de-embedding based on open-pad and Transmission Line measurement

In this paper, a new de-embedding technique based on open-pad and Transmission Line (TL) measurement is discussed. This technique can be used as an alternative to the conventional de-embedding approaches in order to characterize on-chip passives in the millimeter wave range of frequencies. Using open-pad measurement, parallel parasitics are extracted and removed in the first step. Cross-talk parasitics between two pads that are kept at a constant distance can be assumed constant, and thus both cross-talk and parallel parasitics can be removed. Subsequently, the transfer function matrix of a single-ended TL is used to de-embed series parasitics from the measurement results. The measurement results are in a close agreement with the simulations up to 110 GHz.