FET Mixer Research Articles

An X‐to‐Ka band MMIC up‐converter in GaAs pHEMT technology for Ka‐band broadband satellite communications

ABSTRACTIn this article, an X‐band to Ka‐band up‐converter circuit designed for the transmitting chain of Satcom‐on‐the‐move terminals is presented. The circuit is implemented using a 0.25 µm GaAs pHEMT microwave monolithic integrated circuit commercial process. It operates at fixed LO frequency of 22 GHz, IF input frequency within the band (8–9) GHz and corresponding RF output frequency within (30–31) GHz band. The up‐converter circuit is composed of a resistive FET mixer, a K‐band LO buffer amplifier, and a Ka‐band medium power amplifier at the RF output. The bias operating condition of the entire multifunction chip is Vdd = 2.8 V, Idq = 322 mA, for a power consumption of 900 mW, when the Ka‐band high power amplifier (HPA) operates in linear conditions. The chip dimensions are 3.4 × 2.8 mm2. The up‐converter provides more than 12 dB conversion gain over the full bandwidth, when operated with LO input power of 0 dBm and IF fixed input power of −5 dBm. It also achieves 25 dBc of LO isolation at the RF output port. The high 1 dB compression point P1dB > 19 dBm, along with an OTOI in excess of 29 dBm, make the circuit suitable to directly drive Ka‐band high power amplifiers in very linear operating conditions. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2649–2656, 2014

A linearized amplifier using self-mixing feedback technique

A linearized amplifier using self-mixing feedback technique is presented to cancel out third-order intermodulation distortion (IMD3) terms. Second harmonic terms, which are generated by the self-mixing mixer between base and collector of a BJT amplifier, can be used as a source for IMD3 cancellation. The amplifier is based on a common emitter BJT amplifier with a passive FET mixer and an emitter follower for self-mixing feedback. The amplifier has been implemented with discrete transistors on an FR-4 PCB. Up to 16-dB IMD3 rejection has been achieved by the self-mixing feedback technique at 2GHz with peak output power of 20dBm.

Graphene FETs for Zero-Bias Linear Resistive FET Mixers

In this letter, we present the first graphene FET operation for zero-bias resistive FET mixers, utilizing modulation of graphene channel resistance rather than ambipolar mixer operations, up to 20 GHz. The graphene FETs with a gate length of 0.25 μm have an extrinsic cutoff frequency fT of 40 GHz and a maximum oscillation frequency fMAX of 37 GHz. At 2 GHz, the graphene FETs show a conversion loss of 14 dB with gate-pumped resistive FET mixing, with at least > 10-dB improvement over reported graphene mixers. The input third-order intercept points (IIP3s) of 27 dBm are demonstrated at a local oscillator (LO) power of 2.6 dBm. The excellent linearity demonstrated by graphene FETs at low LO power offers the potential for high-quality linear mixers.

Design and Stability Analysis of a Low-Voltage Subharmonic Cascode FET Mixer

A novel biasing scheme to realize a low-voltage subharmonic cascode FET mixer is presented. The proposed biasing requires a low supply voltage and effectively facilitates the generation of the second harmonic of the local oscillator (LO) signal for subharmonic mixing. Hence, the proposed subharmonic mixer (SHM) exhibits competitive performance at a lower supply voltage compared with conventional SHMs. Additionally, the large-signal stability analysis is performed to predict and eliminate the potential parametric oscillations. An experimental prototype with a radio frequency of 900 MHz and an LO frequency of 400 MHz is realized to operate at a supply of 1 V only. By applying an LO power of -4 dBm, the mixer achieves a conversion gain of 12 dB, third-order input intercept point of -11 dBm, single-sideband noise figure of -7 dB, and a power consumption of 12 mW.

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.

Noise in Current-Commutating Passive FET Mixers

Noise in the mixer of zero-IF receivers can compromise the overall receiver sensitivity. The evolution of a passive CMOS mixer based on the knowledge of the physical mechanisms of noise in an active mixer is explained. Qualitative physical models that simply explain the frequency translation of both the flicker and white noise of different FETs in the mixer have been developed. Derived equations have been verified by simulations, and mixer optimization has been explained.

Second-Order Intermodulation in Current-Commutating Passive FET Mixers

Amplitude-modulation detection in the mixer plagues the performance of the zero-intermediate-frequency receiver by downconverting the envelope of amplitude modulated blockers to baseband where the desired channel is after downconversion. Simple equations based on physical mechanisms of second-order intermodulation generation have been derived which can predict the IIP2 of the current-driven passive mixer accurately. Derived equations have been verified by SPECTRE and SPECTRE-RF simulations, and mixer optimization has been explained.

A 210 GHz Dual-Gate FET Mixer MMIC With ${>}$2 dB Conversion Gain, High LO-to-RF Isolation, and Low LO-Drive Requirements

We demonstrate the first active mixer monolithic microwave integrated circuit (MMIC) with positive conversion gain beyond 200 GHz. The presented dual-gate topology is realized in a 100 nm gate length metamorphic high electron mobility transistor technology. Without any pre- or post-amplification, the down-conversion mixer achieves > 2 dB conversion gain and > 16 dB local oscillation to radio frequency (LO-to-RF) isolation at 210 GHz, outperforming state-of-the-art resistive MMIC mixers. The conversion gain becomes positive for LO power levels larger than 0 dBm, making the mixer suitable for being driven by an MMIC-based frequency doubler. A comparison to state-of-the-art G-band mixers is given.

Retrodirective array for RFID and microwave tracking beacon applications

AbstractA novel and compact four‐element retrodirective array (RDA) prototype is realized. It demonstrates excellent performance in terms of retrodirectivity and sensitivity. Each element employs a phase conjugator (a biased FET mixer) with a conversion gain of 5.46 dB. The LO is set at 19.61 GHz and is pumped into the element while the RF operates at 9.8 GHz. The mixer generates an IF signal with a frequency offset of 10 MHz from the RF to separate the transponded signal from the interrogating signal. Retrodirectivity is observed over a wide range of incidence angles from −50° to +50°. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 409–411, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21365

Large-signal modelling including low-frequency dispersion of n-channel SiGe MODFETs and MMIC applications

This paper presents a circuit-design oriented, large-signal model for n-channel SiGe MODFET transistors, its application to the design of mixer and amplifier MMICs as well as measurement results. The model is based on an equivalent circuit approach and employs robust, globally continuous equations to describe the non-linear circuit elements. All transistor operating regions are covered without the use of partially defined equations or smoothing functions. Significant low-frequency dispersion effects similar to those found in III–V HEMT devices are observed and incorporated in a large-signal dispersion model. The bias dependency of the gate–drain and gate–source capacitance is extracted and modelled, allowing for verification of the model for frequencies up to 50 GHz. Based on the presented transistor model, an active FET mixer MMIC and a travelling-wave amplifier using the SiGe MODFET technology are designed and good agreement between simulation and measurements is achieved.

Design of a subharmonic cascode FET mixer for an IMT‐2000 base station

AbstractIn this paper, a subharmonic cascode FET mixer is proposed to improve the isolation characteristic between the local oscillator (LO) and RF ports of an unbalanced mixer. The mixer is designed by using a single‐gate FET cascode structure and driven by the second harmonic component of the LO signal. When RF power is −30 dBm and LO power is 0 dBm, the designed mixer yields a −47.17‐dBm LO‐to‐RF leakage power level and 10‐dB conversion gain. Since the LO‐to‐RF leakage power level of the designed mixer is as good as that of a double‐balanced mixer, the subharmonic cascode FET mixer can be utilized instead. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 515–518, 2003

Double Volterra series approach to FET mixers

AbstractA double Volterra series approach to analyze nonlinear microwave circuits is presented, with special emphasis on FET mixers. Considering a FET as a circuit with two input ports, a procedure to obtain closed‐form expressions for nonlinear transfer functions is presented. Based on this approach, the known time‐varying Volterra series technique can be demonstrated. Calculated conversion loss and two‐tone IMD for a FET‐resistive mixer are successfully compared with already published data. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 486–488, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11097

High-performance V -band cascode HEMT mixer and downconverter module

A high-performance V-band cascode HEMT mixer is presented together with a compact downconverter module integrating the mixer with other receiver MMICs. The cascode mixer was optimized for conversion gain and/or linearity by employing the low-pass interstage networks and by optimizing the bias voltages. The low-pass interstage network effectively filters out the unwanted harmonics and spurious signals, and therefore, enhances the gain and the linearity of the cascode mixer. On a two-tone test, the cascode mixer showed a high conversion gain of 6.3 dB with an LO power of 2.6 dBm at 60 GHz. When the gate bias to the upper common-gate HEMT was tuned for the intermodulation distortion "sweet spot" theoretically predicted by the authors , the mixer showed a high third-order intercept point of 11.2 dBm with a decent gain of 4.1 dB under a small DC power consumption of 8 mW. To benchmark the performance of the cascode mixer of this work, a waveguide-based compact V-band downconverter module was built by integrating the mixer with an MMIC LNA, a VCO, and a LO driving amplifier. The downconverter module showed a conversion gain higher than 20 dB from 57.5 to 61.7 GHz. This paper shows the potential of the cascode FET mixer for high-performance compact downconverter applications at millimeter-wave frequencies.

Intermodulation analysis of dual-gate FET mixers

A detailed intermodulation analysis of dual-gate FET (DG-FET) mixers is presented. The analysis method is based on a large-signal/small-signal analysis using time-varying Volterra-series methods. The analysis program allows one to probe the internal nodes of DG-FETs to evaluate the nonlinear current components. Therefore, it helps physical understanding of intermodulation distortion (IMD) mechanisms in DG-FET mixers. The program was used to identify the major sources of IMD generation. It was found from the analysis that the nonlinearities due to the output conductance (G/sub d3/ and G/sub d2/) of the lower common-source FET were most responsible for IMD generation. The impact of the upper common-gate FET on IMD generation was also found to be nonnegligible, especially at high local oscillator (LO) power levels. The analysis also predicted the presence of MM "sweet spots" using bias optimization, which was experimentally proved by the fabricated mixers at X- and Ka-bands. The optimized X-band hybrid mixer showed measured intermodulation characteristics (OIP/sub 3/ /spl sim/13.6 dBm) comparable to those of the resistive mixers (OIP/sub 3/ /spl sim/15.3 dBm) with low LO and dc power conditions.

Compact monolithic integrated resistive mixers with low distortion for HIPERLAN

Three ultra-compact low-cost mixers, using either a single enhancement, depletion, or deep-depletion FET are presented and compared. They are designed for HIPERLAN and 802.11a receivers with radio and intermediate frequencies around 5.2 and 0.95 GHz, respectively. An improved MESFET large-signal model has been used to allow efficient optimizations of the circuits. The fully integrated mixers have been fabricated using a commercial 0.6-/spl mu/m GaAs MESFET process and require a total chip area of only 0.5 mm/sup 2/. With an ultra-low local-oscillator (LO) power of -10 dBm, the enhancement FET mixer achieves a -4.7 dBm 1-dB input compression point, a 12.6-dB conversion loss, and a 13-dB noise figure. At a low LO power of -2.5 dBm, excellent dynamic properties are obtained for the depletion FET mixer with 2.6-dBm 1-dB input compression point, 8.3-dB conversion loss, and 8.8-dB noise figure. State-of the-art performances with 16-dBm 1-dB input compression point, 5.5-dB conversion loss, and 6.5-dB noise figure are reached for the deep depletion FET mixer at 10-dBm LO power.

Time-varying Volterra-series analysis of spectral regrowth and noise power ratio in FET mixers

This paper presents a direct and robust analysis technique for evaluating nonlinear distortion phenomena in FET mixers excited by multitone signals. Time-varying Volterra-series analysis has previously been proven to be appropriate for small-signal intermodulation-distortion calculations in mixers excited by simple RF signals. Spectral convolutions of the suitably mapped control voltages are introduced in this paper in order to solve the nonlinear current source calculations for narrow-band modulated or broad-band multicarrier RF signals. Simulations and measurements of a properly characterized resistive mixer validate the accuracy of this direct and noniterative analysis tool for spectral regrowth and noise-power-ratio prediction in such applications.

Resistive FET mixer conversion loss and IMD optimization by selective drain bias

This paper describes a dedicated nonlinear MESFET model, which was used to accurately represent the device's drain-source current nonlinearity. An analytical expression is proposed, based on the Shockley approach, with good derivative reproduction. The evolution of the Ids(Vgs, Vds) Taylor-series-expansion coefficients across V/sub GS/ and V/sub DS/ revealed not only the presence of important minimum conversion loss bias, but also of in-band intermodulation distortion sweet spots that have been used to optimize an FET resistive mixer performance. Some previously reported experimental results are also discussed through the use of the derivatives, and an alternative topology is considered for resistive mixers working on the border between the linear and saturated regions.

Noise modeling in MESFET and HEMT mixers using a uniform noisy line model

The aim of this paper is to present a noise model which predicts the noise performance of MESFET and HEMT mixers. The conversion and noise correlation matrices of a FET mixer are calculated using a uniform nonlinear noisy active line concept to describe the FET. This calculation is based on a perturbation analysis of the large-signal noiseless steady state, making it a microscopic nonlinear noise model. This method is applied to the case of a hot HEMT gate mixer and we show that the theoretical results are in agreement with experimental data.

Nonlinear models for the intermodulation analysis of FET mixers

An accurate, detailed analysis program has been developed for intermodulation distortion (IMD) simulation of FET mixers. This program is very efficient at calculating the IMD from multiple RF inputs. We have proposed a simplified nonlinear model for IMD analysis of FET gate mixers. The accuracy of the simplified model has been verified experimentally using two different MESFET mixers and one HEMT mixer at X band. All the tests show good agreement between measured results and the calculated results for second- and third-order IMD. The simplified model is based on modeling the derivative of the device transconductance by a sum of a Gaussian function and a linear function of the gate voltage. Drain bias dependence is ignored. The advantage of this model is that it can be used for both MESFET and HEMT mixers, and its fitting parameters can be easily determined from a nonlinear characterization of the devices at low frequencies.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

X-band doubly balanced resistive FET mixer with very low intermodulation

This paper describes a practical realization of a mixer that achieves low intermodulation distortion by using the channel resistance of a GaAs MESFET to provide mixing and achieves even-order spurious response rejection through the use of a doubly balanced structure. Very good results were achieved in terms of second- and third-harmonic levels of -67 and -45 dBC, respectively, at +10 dBm input level. The band-center conversion loss was 11 dB. The circuit was realized in microstrip on an alumina substrate, with a monolithic FET "quad".< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>