Nils Pohl

An Ultra-Wideband 80 GHz FMCW Radar System Using a SiGe Bipolar Transceiver Chip Stabilized by a Fractional-N PLL Synthesizer

A radar system with an ultra-wide FMCW ramp bandwidth of 25.6 GHz (≈32%) around a center frequency of 80 GHz is presented. The system is based on a monostatic fully integrated SiGe transceiver chip, which is stabilized using conventional fractional-N PLL chips at a reference frequency of 100 MHz. The achieved in-loop phase noise is ≈ -88 dBc/Hz (10 kHz offset frequency) for the center frequency and below ≈-80 dBc/Hz in the wide frequency band of 25.6 GHz for all offset frequencies >;1 kHz. The ultra-wide PLL-stabilization was achieved using a reverse frequency position mixer in the PLL (offset-PLL) resulting in a compensation of the variation of the oscillators tuning sensitivity with the variation of the N-divider in the PLL. The output power of the transceiver chip, as well as of the mm-wave module (containing a waveguide transition), is sufficiently flat versus the output frequency (variation <;3 dB). In radar measurements using the full bandwidth an ultra-high spatial resolution of 7.12 mm was achieved. The standard deviation between repeated measurements of the same target is 0.36 μm.

A dielectric lens antenna with enhanced aperture efficiency for industrial radar applications

A dielectric lens antenna for 25 GHz industrial radar measurements in industrial tanks is presented. Due to the limited diameter, the aperture efficiency is an important benchmark for these applications. The presented approach uses a massive PTFE lens body, which results in a measured aperture efficiency of 104% at a diameter of 74 mm. This corresponds to a gain of 25.9 dBi. The main lobe has a tight 3 dB angular width of 8.4°/ 8.6° with a side lobe level of −17.0 dB /−17.6 dB.

SiGe Bipolar VCO With Ultra-Wide Tuning Range at 80 GHz Center Frequency

A SiGe millimeter-wave VCO with a center frequency around 80 GHz and an extremely wide (continuous) tuning range of 24.5 GHz ( ap 30%) is presented. The phase noise at 1 MHz offset is -97 dBc/Hz at the center frequency (and less than -94 dBc/Hz in a frequency range of 21 GHz). The maximum total output power is about 12 dBm. A cascode buffer improves decoupling from the output load at reasonable VCO power consumption (240 mW at 5 V supply voltage). A low-power frequency divider (operating up to 100 GHz) provides, in addition, a divided-by-four signal. As a further intention of this paper, the basic reasons for the limitation of the tuning range in millimeter-wave VCOs are shown and the improvement by using two (instead of one) varactor pairs is demonstrated.

High-Precision D-Band FMCW-Radar Sensor Based on a Wideband SiGe-Transceiver MMIC

In this paper, a miniaturized D-band frequency-modulated continuous-wave (FMCW) radar sensor with 48-GHz bandwidth (32.8%, 122-170 GHz) and a high measurement rate of > 1 kHz for multi-target vibration measurements is presented. The sensor is based on a SiGe transceiver monolithic microwave integrated circuit manufactured via Infineons B7HF200 bipolar production technology with an fT of 170 GHz and fmax of 250 GHz. Gilbert cell, push-pull, and varactor-based doubler concepts on manufactured chips are compared, and the most promising signal source is embedded into a transceiver chip, which forms the main component of the presented radar sensor. The maximum output power of the system is ≈ -10 dBm and a phase noise of ≈ -80 dBc/Hz is achieved. Measurements are provided to demonstrate the sensor characteristics and show the promising results of FMCW radar in highest precision distance and multi-target vibration measurement applications. Due to the covered wide bandwidth, a range resolution of 5.88 mm is achieved ( -6-dB width, Tukey window). The sensors distance measurement repeatability is 290 nm (65 nm with 10 × averaging and 0.5-m target distance), and the distance measurement accuracy is m for a target in 65-cm distance moving 1 cm. Additionally, vibration measurement results and range-Doppler plots for advanced multi-target applications are presented.

A 240 GHz ultra-wideband FMCW radar system with on-chip antennas for high resolution radar imaging

Nowadays emerging industrial radar applications demand for high-resolution, high-precision and at the same time low-cost radar sensors. Recent advances in semiconductor technology allow highly integrated radar sensors at frequencies up to several hundred GHz in mass-production suitable and cost-effective SiGe bipolar technologies. In this contribution, a SiGe MMIC-based 240 GHz radar sensor with more than 60GHz bandwidth is presented. It consists of a MMIC chip including the high-frequency components and a digital control module with the PLL stabilisation, ramp generation, and data acquisition. The antenna is realized by on-chip patch antennas, which are focused by using an additional dielectric lens. The radar allows fast and highly linear frequency sweeps from 204 GHz to 265 GHz with an maximum output power of ≈ -1dBm EIRP (patch only). A phase noise of <;-65 dBc/Hz (>1 kHz offset) is achieved over the complete tuning range. Additionally range profile, jitter and imaging measurements are presented to demonstrate the achieved system performance.

A Low-Power Wideband Transmitter Front-End Chip for 80 GHz FMCW Radar Systems With Integrated 23 GHz Downconverter VCO

A low-power FMCW 80 GHz radar transmitter front-end chip is presented, which was fabricated in a SiGe bipolar production technology ( fT=180 GHz, fmax=250 GHz ). Additionally to the fundamental 80 GHz VCO, a 4:1-frequency divider (up to 100 GHz), a 23 GHz local oscillator (VCO) with a low phase noise of -112 dBc/Hz (1 MHz offset), a PLL-mixer and a static frequency divider is integrated together with several output buffers. This chip was designed for low power consumption (in total <; 0.5 W, i.e., 100 mA at 5 V supply voltage), which is dominated by the 80 GHz VCO due to the demands for high output power (≈ 12 dBm) and low phase noise (minimum -97 dBc/Hz at 1 MHz offset) within the total wide tuning range from 68 GHz to 92.5 GHz (Δf = 24.5 GHz). Measurements of the double-PLL system at 80 GHz showed a low phase noise of -88 dBc/Hz at 10 kHz offset frequency.

High Precision Radar Distance Measurements in Overmoded Circular Waveguides

Distance measurements in overmoded waveguides are an important application for industrial radar systems. The accuracy of the measurements is deteriorated by the appearance of higher order modes in the metal tube, although the frequency-modulated continuous-wave method is used with a large bandwidth. This paper describes the problems caused by dispersion and multimode propagation and presents a solution in the form of mode-matched antennas for feeding the overmoded waveguide. It is shown that different modes, e.g., the H11 and H01 modes, are equally well suited for precision distance measurements, as is demonstrated both by simulations and measurements.

A 240 GHz single-chip radar transceiver in a SiGe bipolar technology with on-chip antennas and ultra-wide tuning range

This paper presents an ultra-wideband single-chip radar transceiver MMIC around 240 GHz in a SiGe:C bipolar laboratory technology with an fT of 240 GHz and fmax of 380 GHz. The presented transceiver architecture consists of a fundamental 120 GHz VCO, two 240 GHz frequency doublers, a fundamental 240 GHz down-conversion mixer, a divide-by-four stage, a PLL-mixer and two on-chip patch antennas. The complete transceiver architecture is fully differential. The chip facilitates a -1 dBm peak output power (EIRP) at the transmit patch antenna and a tuning range of 61 GHz. The phase noise at 1 MHz offset is -84 dBc/Hz at 240 GHz (and better than -76 dBc/Hz over the full tuning range). The 240 GHz mixer offers a simulated noise figure below 17 dB, a simulated conversion gain of better than 5 dB, and an input refered compression point of -1.3 dBm. The results are achieved with a power consumption of 750 mW from a single 5 V supply.

A SiGe Fractional-

A millimeter-wave (mm-wave) frequency synthesizer is presented focusing on an ultra-high-speed fractional- N frequency divider and a highly linear phase-frequency detector (PFD). All circuits are integrated into a high-frequency SiGe bipolar technology. The programmable frequency divider can be operated at input frequencies between dc and 57 GHz for division factors in the entire integer range from 12 to 259. The PFD is optimized for fractional- N synthesis, which requires an extremely linear characteristic due to the modulation of its input frequency. The frequency divider and the PFD are used together with an 80-GHz wideband voltage-controlled oscillator (VCO) and transceiver for a high precision mm-wave frequency-modulated continuous-wave (FMCW) radar sensor. As shown by the experimental results the realized circuits stabilize the mm-wave VCO with an extremely low phase noise below -97 dBc/Hz at 10-kHz offset around its center frequency of 80 GHz and can generate a highly linear frequency ramp with a bandwidth of 24 GHz. Furthermore, the accuracy of the synthesizer is demonstrated by FMCW radar distance measurements inside a waveguide and in free space. Inside the waveguide a standard deviation of the phase of the target below 0.0018 ° (which corresponds to 9.4 nm) was measured.

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This paper presents two differential signal source chips for 150 GHz and 220 GHz in SiGe:C bipolar technologies. The presented architectures consist of a fundamental VCO with a frequency doubling output stage based on the differential Gilbert-Cell. The 150 GHz chip is fabricated in a production technology with an fT of 170 GHz and fmax of 250 GHz, the 220 GHz in an advanced laboratory technology with fT/fmax = 240 GHz/380 GHz. The main goal of this work is to achieve signal sources near the cut-off frequencies of the used technologies with differential outputs. The signal sources achieve a relative 3 dB bandwidth of >; 20% with an output power of 0 dBm and -6 dBm for the 150 GHz chip and 220 GHz chip, respectively. The power consumptions are kept at a moderate level with 430 mW for the 150 GHz chip and 580 mW for the 220 GHz chip from a 5 V supply.