Axel Strobel

Design of a multi-band FMCW radar module

This paper presents a multi-band frequency-modulated continuous wave (FMCW) radar module. The module can perform ranging in a wide frequency range, including the 2.4GHz and 5.8GHz ISM bands. It incorporates an application specific integrated circuit (ASIC) for processing the analogue signals and a field programmable gate array (FPGA) as digital signal processing backend, providing a reconfigurable test platform. Using multiple stations, positioning measurements are performed which demonstrate the benefits of the multi-band system in different scenarios.

A Millimeter-Wave Low-Power Active Backscatter Tag for FMCW Radar Systems

In this paper, a fully integrated active backscatter transponder based on the switched injection-locked oscillator (SILO) principle for frequency-modulated continuous-wave radar applications is presented. Furthermore, a method to characterize a SILO amplifier is extended and utilized to measure the system parameters of the presented backscatter tag that operates at 34.45 GHz. It is digitally tunable from 32.7 to 35.4 GHz and reaches an unpulsed output power of 5 dBm. Above injection power levels of

An active pulsed reflector circuit for FMCW radar application based on the switched injection-locked oscillator principle

-\hbox{53 dBm}

A mm-wave RFID system with locatable active backscatter tag

, the SILO tag responds phase coherent at its maximum output power. In system measurements, the SILO backscatter transponder was used to perform distance measurements at ranges from 0.7 to 11.5 m. A remarkably good mean distance measurement error of 7 cm with a standard deviation of 10 cm was achieved in a strong multipath environment. The single measurement precision is below 3 mm.

5.8 GHz demonstration system for evaluation of FMCW ranging

This paper presents an active pulsed reflector for a FMCW radar system based on the switched injection-locked oscillator principle at 30 GHz. The theory of the active backscatter transponder is extended and system investigations with respect to the impact of phase sampling noise were performed. The circuit has been integrated in a 0.25 µm SiGe BiCMOS technology. On-wafer measurements showed a phase coherent signal amplification of 55 dB with an output power level of −3 dBm.

Tunable interface for piezoelectric energy harvesting

Precise localization of an object with attached RFID tag is required for many future applications like the internet of things, augmented reality or distributed sensor networks. Especially precise medium range localization in dense multipath environments places high demands on the capabilities of RFID tags, which are severely limited concerning complexity and power consumption. Regarding range coverage, active backscatter transponders significantly reduce path loss in comparison to their passive counterparts. This is particularly important at high frequencies, which are attractive since their regulatory constraints offer larger allocated bandwidths compared to lower frequency bands. Therefore, with mm-wave transponders, ranging resolution, data throughput for RFID communication and multi user capability can be improved without accepting range limiting RF power restrictions like in ultra-wideband systems. In order to achieve a measurement range in the order of 10 m with a tag featuring limited complexity and power consumption, the switched injection-locked oscillator is proposed as backscatter transponder technology, which has already been successfully applied to lower frequency localization systems [2]. In contrast to a simple linear amplifier based approach, it offers much higher single stage gain in the order of about 60 dB when switched on. Furthermore, aliases caused by the switched operation allow suppressing passive reflections of the RFID readers signal completely. In this paper, a complete 34 GHz FMCW RFID ranging system concept and demonstrator implementation based on the switched injection-locked oscillator are demonstrated for the first time. The theoretical expectations regarding the operation principle are verified experimentally and the performance of the demonstrator implementation is evaluated. Measurement results in an indoor multipath indoor environment deliver an accuracy of about 3 cm within a range of 1 to 6 m.

A wideband planar microstrip to coplanar stripline transition (balun) at 35 GHz

This work describes a demonstration platform for frequency-modulated continuous wave (FMCW) based ranging systems operating in the 5.8 GHz ISM band. The goal is to gain insight into system behavior and determine critical system parts prior to integration on chip. The versatility and configurability of the presented system allows testing different synchronization and ranging principles. A synchronization scheme is proposed which is robust against imperfections of the system. Distance measurements using this scheme are carried out in an indoor and outdoor scenario.

FMCW system aspects for multipath environments

The so called Synchronous Electric Charge Extraction (SECE) interface is an electrical circuit to extract energy from a piezoelectric transducer and to put it onto a storage device like a large capacitor. The advantage of the SECE interface is the load independent power transfer. But the maximum efficiency the SECE interface in combination with the piezoelectric transducer can achieve greatly depends on the electromechanical coupling of the transducer. The SECE interface works very well with weak to mid-range electromechanically coupled piezoelectric transducers. But with strong coupled transducer the power extracted by SECE interface decreases. This paper shows how the SECE interface can be tuned to deliver the maximum power almost independent of the electromechanical coupling factor.

System considerations and VCO design for a local positioning system at 2.4 GHz for rescue of people on ships and in sea

A novel approach for wideband planar baluns is presented, which enables the realization with just two instead of three transmission lines. The analysis of the principle of operation and a suitable design procedure are described. Measurement results of test structures are compared to EM simulations. Two variants of this balun were designed for a center frequency of 35 GHz. Measurements show an absolute 3 dB-back-to-back insertion loss bandwidth of 16.7 GHz and 10.1 GHz with minimum losses of 0.38 dB and 0.71 dB respectively. The extrapolated absolute 1 dB insertion loss bandwidths of the single baluns are 14.5 GHz and 14.4 GHz respectively.

Broadband receiver frontend with high dynamic range for multi-standard digital radio

Local positioning systems (LPS) are not only of increasing interest for industrial and commercial applications, but are also required for crisis management to keep track of first responders at all times, both for security and for logistic reasons. In such systems, frequency-modulated continuous wave (FMCW) radar is widely used. However, the properties of the radio channel for the application in crisis scenarios are very difficult to predict. Therefore, the FMCW principle is going to be investigated with regard to different channels. Especially the impact of heavy multipath environments on the concept is modeled and simulated. Furthermore, a detection algorithm is proposed to cope with fading radio channels and the impact of different Fast Fourier Transform (FFT) windows is discussed.