Paul Hallbjörner

The significance of radiation efficiencies when using S-parameters to calculate the received signal correlation from two antennas

The correlation coefficient between signals received by two antennas can be calculated from port S-parameters. Antenna radiation efficiencies must, however, also be considered. They result in an uncertainty in the calculated received signal correlation, if the correlation between the losses is unknown, which is often the case. Relations are presented for the effect antenna efficiencies have on the calculated correlation.

Printed Slot Planar Inverted Cone Antenna for Ultrawideband Applications

A novel ultrawideband (UWB) printed wide-slot antenna is presented. The design is based on the planar inverted cone antenna (PICA), introduced by Suh. The presented design comprises PICA-like structures, etched from a double-layer substrate. Compared to the original PICA, it is lower in profile, more compact and maintains comparable performance. A prototype integrated in a printed circuit board and fed by a microstrip line is fabricated and measured. The results show that the proposed antenna provides at least 13:1 impedance bandwidth at 10-dB return loss.

60 GHz Single-Chip Front-End MMICs and Systems for Multi-Gb/s Wireless Communication

Single-chip 60 GHz transmitter (TX) and receiver (RX) MMICs have been designed and characterized in a 0.15mum (fT~ 120 GHz/f MAX> 200 GHz) GaAs mHEMT MMIC process. This paper describes the second generation of single-chip TX and RX MMICs together with work on packaging (e.g., flip-chip) and system measurements. Compared to the first generation of the designs in a commercial pHEMT technology, the MMICs presented in this paper show the same high level of integration but occupy smaller chip area and have higher gain and output power at only half the DC power consumption. The system operates with a LO signal in the range of 7-8 GHz. This LO signal is multiplied in an integrated multiply-by-eight (X8) LO multiplier chain, resulting in an IF center frequency of 2.5 GHz. Packaging and interconnects are discussed and as an alternative to wire bonding, flip-chip assembly tests are presented and discussed. System measurements are also described where bit error rate (BER) and eye diagrams are measured when the presented TX and RX MMICs transmits and receives a modulated signal. A data rate of 1.5 Gb/s with simple ASK modulation was achieved, restricted by the measurement setup rather than the TX and RX MMICs. These tests indicate that the presented MMICs are especially well suited for transmission and reception of wireless signals at data rates of several Gb/s

Extracting electrical material parameters of electrically large dielectric objects from reverberation chamber measurements of absorption cross section

Reverberation chambers can be used to measure the absorption cross section of a dielectric object. The absorption cross section of a dielectric object depends on its size, shape, and electrical material parameters. By comparing with a theoretical model of the absorption cross section, material parameters can be extracted from measurements. A model based on a plane wave approach of incident fields is used here, valid for electrically large material samples in an isotropic environment such as that in a reverberation chamber. Which material parameter can be extracted depends on the properties of the material sample. The presented method combines the accuracy of cavity methods with the flexibility of being able to measure samples of arbitrary size and shape. Because both the reverberation chamber and the material sample are electrically large, the method is particularly useful at millimeter-wave frequencies.

Electrically Steerable Single-Layer Microstrip Traveling Wave Antenna With Varactor Diode Based Phase Shifters

The design of electrically steerable traveling wave microstrip antenna arrays is presented. Varactor diode based phase shifters implemented on the same metallic layer as the patch elements are used to provide a variable progressive phase shift in the array. Two antennas for the 5.8 GHz ISM band, manufactured as single layer printed designs on a standard PTFE soft substrate, are demonstrated. A ten-element beam-tilting vertical array using transmission type phase shifters is realized, yielding between 11.8 to 13.9 dBi gain for the 0deg to 11deg beam tilt tuning range. Using wide phase tuning range reflection type phase shifters a five-element horizontally scanning array with -32deg to 32deg steering range and 10.9-11.3 dBi gain has been realized.

Compact reflective microstrip phase shifter for traveling wave antenna applications

A varactor diode based microstrip phase shifter for 5.8GHz is presented. It is designed for use in microstrip traveling wave antennas where there is a strict limitation on the available space for the phase shifters. To meet all requirements, a reflective type phase shifter is chosen. Such a phase shifter includes a hybrid coupler. A compact branch line coupler is designed to make the phase shifter fit between the radiating elements in the antenna, while maintaining sufficient electrical performance. Phase shifters are designed with different types of stubs connecting the diodes to ground. A phase tuning range of 62deg is measured for a phase shifter with parallel open stubs, and 92deg with shorted stubs. Insertion loss is in both cases less than 0.6dB. A complete five-element array antenna is built and characterized. Measurements show beam scanning angles within plusmn32deg from broadside

Maximum Doppler Frequency in Reverberation Chamber with Continuously Moving Stirrer

Reverberation chambers equipped with a continuously moving mechanical mode stirrer cause Doppler spread in the measured signal. In order not to affect the signal, the instrument used for recording the measurement samples should have an IF bandwidth that exceeds the maximum Doppler frequency of the reverberation chamber. The actual stirrer speed cannot be used to calculate the maximum Doppler frequency the usual way, because the resonances in the chamber enhance the effect of stirrer motion. A relation for the maximum Doppler frequency in reverberation chambers is derived, and measurements are performed to verify it.

Technical Solutions for Automotive Intermodulation Radar for Detecting Vulnerable Road Users

Technical solutions for automotive intermodulation radar for detecting vulnerable road users

Estimating the number of independent samples in reverberation chamber measurements from sample differences

Reverberation chamber measurements suffer from statistical fluctuations in the average power of a measured sequence. The standard deviation of these fluctuations depends on the number of independent samples N/sub ind/ in the sequence. A common method for estimating N/sub ind/ is based on calculating the autocorrelation function of the sequence. A method is presented here that is simpler, yet comparable in accuracy and precision. In the presented method, N/sub ind/ is calculated from the sequence of differences between neighboring measurement samples. Simulated sequences are used to compare different variants of the presented method and the autocorrelation function method. Examples with measured data are also presented.

Electrically small unbalanced four-arm wire antenna

An electrically small antenna element is presented. It is an unbalanced antenna, consisting of four wire arms arching over a groundplane. One of the wire ends is the feed, and the other three are connected to the groundplane, via a capacitance, short, and load, respectively. The resonance frequency is tuned by varying the capacitance, which can be set fixed or used to accomplish electronic tunability with a tuning range of several octaves. The momentary bandwidth of the antenna is approximately 3%. Applications are typically antennas for very small terminals in narrowband systems, or alternatively broadband systems where electronical tuning can be implemented in the antenna. The exact shape of the wires is not critical and can be chosen to conform to mechanical design requirements.