Klas Yhland

A Subharmonic Graphene FET Mixer

We demonstrate a subharmonic resistive graphene FET mixer utilizing the symmetrical channel-resistance versus gate-voltage characteristic. A down-conversion loss of 24 dB is obtained with fRF = 2 GHz, fLO= 1.01 GHz, and fIF= 20 MHz in a 50- Ω-impedance system. Unlike conventional subharmonic resistive FET mixers, this type of mixer operates with only one transistor and does not need any balun at the local oscillator (LO) port, which makes it more compact.

An in-circuit noncontacting measurement method for S-parameters and power in planar circuits

A method for measuring the reflection coefficient and absolute power in the propagating waves from a circuit embedded in a planar circuit environment is presented. The method utilizes a pair of inductive and capacitive probes. The standard one-port vector-network-analyzer calibration is extended to allow the measurement of power in the forward and backward waves. Experimental results are presented for measurements between 700 MHz and 20 GHz. Good agreement between the new noncontacting method and a standard coaxial measurement method is demonstrated up to 12 GHz for power and up to 14 GHz for the reflection coefficient. The method is useful for in-circuit testing of open transmission-line structures, e.g., microstrip.

A symmetrical nonlinear HFET/MESFET model suitable for intermodulation analysis of amplifiers and resistive mixers

We propose a new symmetrical heterojunction FET (HFET)/MESFET model to predict intermodulation distortion in amplifiers and resistive mixers. The model is symmetric. That is, drain and source of the intrinsic FET are interchangeable. This reflects the characteristics of most microwave FETs. The model has few fitting parameters and they are simple and straightforward to extract. The model was installed into Hewlett-Packards harmonic-balance program microwave design system and verified by measurements. The verification shows excellent results for an MESFET and an HFET in both amplifier and resistive mixer configurations.

Novel single device balanced resistive HEMT mixers

A novel single device balanced resistive HEMT mixer operating at 18 GHz has been designed and characterized. The mixer has 180 degree baluns at the RF and IF ports. Measurements show a conversion loss of 6 to 7 dB and an LO to RF isolation of up to 37 dB. The main advantages of this type of mixer are that no device pairing is necessary, since only one HEMT is used and that no high frequency grounding is necessary. These advantages make this topology suitable for microstrip MICs, crossbar, fin-line and quasi optical mixers.<<ETX>>

A new extraction method for the two-parameter FET temperature noise model

This paper presents a direct extraction method for the associated noise temperatures T/sub d/ and T/sub g/ in the field-effect transistor (FET) temperature noise model. The method is related to nodal analysis of circuits. T/sub d/ and T/sub g/ are extracted from the small-signal model parameters and the noise parameters of the device. It is also theoretically shown that there exist source admittances that cancel the thermal noise contribution at the output from either T/sub d/ or T/sub g/ in the model. Finally, a commercially available GaAs pseudomorphic high electron-mobility transistor (pHEMT) is measured and modeled for a wide range of bias points. Comparisons between measured and modeled noise parameters are presented in the 2-26 GHz frequency range.

pHEMT and mHEMT ultra wideband millimeterwave balanced resistive mixers

Two ultra wideband millimeterwave single balanced resistive mixers utilizing a Marchand balun for the LO-hybrid are simulated, fabricated and characterized for 30-60 GHz in both up and down conversion. Two different versions of the mixer were manufactured in a commercial pHEMT-MMIC and a mHEMT-MMIC process respectively. A measured down conversion loss of approximately 6 to 12 dB over the whole band is obtained for both versions of the mixer with external IF power combining. In spite of the balanced design, the required LO power is quite low, 2 dBm is sufficient for low conversion loss. The LO-RF isolation is excellent, often more than 30 dB for both type of mixers. Low noise figure and high IIP3 figures are obtained. It is also shown that by applying selective drain bias, up to 5 dB improvement of IIP3 can be obtained for the mHEMT mixer with small LO powers.

A new FET frequency multiplier

A new FET frequency multiplier is presented. The FET multiplier works in a similar way as a resistive mixer. The FET can be operated either as a series or a parallel switch. The multiplier has essentially no DC power dissipation and its stability properties are good, since the drain-to-source bias-voltage is zero. The multiplier is insensitive to device parameter variations. Different configurations are analysed. The preliminary measurements show a conversion loss of 4.5 dB. The authors believe that the conversion efficiency can be further improved.

Noncontacting measurement of reflection coefficient and power in planar circuits up to 40 GHz

This paper describes the use of loop-coupler probes for noncontacting measurement of power and reflection coefficient in microstrip circuits up to 40 GHz. The inherent directivity of the loop-coupler probe makes it suitable for use with scalar measuring instruments such as power meters and spectrum analyzers. The probe coupling and directivity and their sensitivity to probe positioning errors are investigated. The results are summarized in a simple uncertainty budget. Measurements of reflection coefficient with a vector network analyzer are also presented and verified by coaxially contacting measurements.

Measurement Uncertainty in Power Splitter Effective Source Match

The authors present an uncertainty calculation together with a technique to assess the residual error when calibrating the effective source match of power splitters. The technique is applied to the Juroshek method, which is the most convenient way of measuring the effective source match. The technique uses an airline as impedance reference and is similar to the ripple technique used when evaluating the residual errors in vector network analyzers

Submillimeter Wave

We demonstrate S-parameter characterization of membrane circuits in the WR-03 frequency band (220-325 GHz) utilizing thru-reflect-line (TRL) -calibration technique. The TRL calibration kit design features 3 μm thick GaAs membrane circuits packaged in E-plane split waveguide blocks with the reference planes inside the membrane circuit structure. A 300 GHz membrane ring resonator filter circuit has been characterized by applying the proposed calibration kit, showing good agreement with simulations.