Burkhard Schiek

A modulated subcarrier technique with instantaneous amplitude and phase information

An accurate and instantaneous microwave phase and amplitude measurement technique is described, that makes use of a single-sideband generator and a single-sideband detector. The phase and amplitude values of a microwave signal are transposed to an IF signal of a convenient frequency. The dynamic range may be as high as 80 dB and the phase and amplitude errors in this range are below 1° and 0.1 dB, respectively.

Microwave Distance Meter with ± 2.5 mm Resolution

A range resolution of ± 2.5 mm has been obtained with a FMCW radar and a sophisticated signal processing. The system operates at X-band with 1.5 GHz frequency sweep. It makes use of the fact, that the total phase length ¿¿ of the IF waveform produced by superposition of the transmitted and reflected FMCW signal is an exact measure of the distance, if reflections of only one target are present. The measurement of the total phase length is performed by counting the zeros of m subsequent IF pulses, while the start phase of each pulse is changed in steps of 2/¿m. This procedure results in an accuracy of the ¿¿ measurement ¿ 2¿/m. The signal processing is realized by a combination of a single-sideband mixer and a low frequency modulator followed by digital electronics.

Broadband Matching of Microstrip Differential Phase Shifters

Meanderline phase shifters in microstrip are badly matched (vswr ¿ 2), due to the difference in phase velocity of the odd and even mode of the coupled transmission lines. This is overcome by a stepped impedance design, allowing to realize e.g. a 90° phase shifter with a return loss better than 30 db across an octave bandwidth. Straightforward design equations are derived and confirmed by measurements on MICs in the frequency range 4 to 8 GHz and X-band.

Direct and Accurate Measurements of Mixer Equivalent Noise Temperatures

A new measuring technique has been developed, which enables the effective noise temperature Teff and intrinsic conversion loss Li of a lossy 2-port network to be determined directly. This technique when applied to a mixer, yields results which are in agreement with theoretical predictions (0.5 ¿ Teff ¿ To; To ambient temperature) and may be measured with greater accuracy than has previously been possible using other methods. Practical results will be presented together with theoretical predictions based on a new approach to mixer noise analysis. This approach gives greater insight into the noise generation mechanisms and is more readily interpreted than other methods published to date in the literature.

A Microwave F.M. Noise Measuring System with a Simplified Calibration Procedure

The f.m. noise of a microwave oscillator is discriminated with the combination of a circulator and a high-Q reflection type cavity and detected in a balanced mixer. The L.O.-signal for the mixer is also derived from the oscillator under test. The resonator can be frequency modulated with a small ferrite insert. With a constant current input to the ferrite coil, the frequency deviation is flat for modulation frequencies up to 600 kHz and over a 10% microwave frequency range. The frequency modulation capability of the resonator is used for an automatic calibration of the f.m. noise of the microwave oscillator under test. An experimental prototype of this system operating at X-band has a limiting sensitivity of 0.01 Hz/ ¿Hz above 1 kHz from the carrier frequency.