Self-oscillating Mixer Research Articles

Nonlinear optimization tools for the design of microwave high-conversion gain harmonic self-oscillating mixers

A new optimization method is presented for the design of microwave high-conversion gain harmonic self-oscillating mixers (SOMs). It is based on the control of the harmonic content of the transistor input-voltage waveform of the self-oscillation, through the use of a nonperturbing auxiliary generator and a substitution generator. The combination of the two generators allows obtaining the optimum harmonic content of the transistor-gate voltage waveform for a maximum conversion gain. Two different downconverter circuits have been designed using this method, a second harmonic SOM and a third harmonic SOM, obtaining a high conversion gain. A good agreement between the simulated and experimental results has been found

Design of novel balanced high-order subharmonic self-oscillating mixer

The design of RF and millimetre-wave receivers demands low-cost features and compact architecture. Self-oscillating mixers (SOMs) are excellent choices for such a design as both the oscillating source and the mixer are combined in one single device. Moreover, subharmonic operation reduces LO frequency requirements and therefore opens up interesting perspectives for high-end millimetre-wave systems. A fully-balanced third-harmonic SOM structure is presented, operating at 5.8 GHz with high measured conversion gain (max. 8.75 dB) that is used as a frequency-scaled prototype for future millimetre-wave circuits. To the authors' knowledge, this is the first presentation of such a circuit structure.

Self-oscillating mixing technique and its application to low-cost receiver architectures

Self-oscillating mixers (SOMs) are an excellent choice for low-cost modern receiver architectures because the oscillating source and the mixer are combined in a single device. Moreover, subharmonic operation reduces local oscillator (LO) frequency requirements and therefore provides a very good option for millimetre-wave systems. In this paper, a fully balanced SOM structure at high harmonics with high conversion gain is presented. The balanced structure provides inherent RF-LO isolation and suppression of harmonics and noise. In addition, it removes the input balun from the design, thereby permitting integration into a monolithic microwave integrated circuit (MMIC).

A low-power oscillator mixer in 0.18-/spl mu/m CMOS technology

A downconversion double-balanced oscillator mixer using 0.18-/spl mu/m CMOS technology is proposed in this paper. This oscillator mixer consists of an individual mixer stacked on a voltage-controlled oscillator (VCO). The stacked structure allows entire mixer current to be reused by the VCO cross-coupled pair to reduce the total current consumption of the individual VCO and mixer. Using individual supply voltages and eliminating the tail current source, the stacked topology requires 1.0-V low supply voltage. The oscillator mixer achieves a voltage conversion gain of 10.9 dB at 4.2-GHz RF frequency. The oscillator mixer exhibits a tuning range of 11.5% and a single-sideband noise figure of 14.5 dB. The dc power consumption is 0.2 mW for the mixer and 2.94 mW for the VCO. This oscillator mixer requires a lower supply voltage and achieves a higher operating frequency among recently reported Si-based self-oscillating mixers and mixer oscillators. The mixer in this oscillator mixer also achieves a low power consumption compared with recently reported low-power mixers.

A phase‐conjugating pair of coupled, dual‐gate, self‐oscillating mixers

AbstractA novel phase conjugator for active retro‐directive operation is made by using twin, dual‐gate, self‐oscillating mixers mutually locked through a 12‐dB hybrid coupler. The coupling network incorporates the load of both oscillators. Reduced LO penetration is achieved at the IF port in two steps: (i) by trapping the LO signal within the dc bias lines of each self oscillating mixer and (ii) by the out‐of‐phase addition of any LO signal leakage. The input RF signal leaking through the mixers has also been suppressed by out‐of‐phase addition at the IF port. The measured results are presented for a phase conjugator designed for nominal operation at 900 MHz. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 59–62, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21081

Active Integrated Antenna Techniques for Beam Control

Active integrated antenna techniques have high potential for giving smaller size, lighter weight, lower cost and higher efficiency, in particular to millimeter-wave circuit-antenna systems. This paper gives a review of active integrated antenna techniques with emphasis on beam steering and retrodirective antenna arrays. Various beam steering operations of integrated antenna oscillator arrays using locking phenomena are presented. Beam steering arrays of such type have the feature that phase shifters are not necessary in the arrays. Arrays with higher harmonic output radiation can enlarge the beam steering range. Arrays of locked active antennas which operate as self-oscillating mixers can be beam controllable receiving antennas.

Beam Control in Unilaterally Coupled Active Antennas with Self-Oscillating Harmonic Mixers

Beam control using active antenna arrays with self-oscillating harmonic mixers has been investigated. The active antenna is composed of a patch antenna receiving RF signal and a parallel feedback type oscillator which operates as the self-oscillating harmonic mixer, and down-converts the received RF signal into IF signal. The mixer has two ports for local oscillating (LO) signal. One is an output port extracting the LO signal. The other is an input port for an injection signal to synchronize the local oscillation. The mixers can be coupled unilaterally without other nonreciprocal components by connecting the output port to the input port in the next mixer. In the unilaterally coupled array, the phase differences of the LO signals between the adjacent mixers can be varied without phase shifters in injection locking state by changing the local free-running frequencies of the self-oscillating mixers. The receiving pattern can be controlled by combining the IF signals from the individual active antennas, which have phases associated with the LO signals. The IF is difference between the RF and double of the LO frequency so that arbitrary phase differences from 0 to 2π radian can be provided to the output IF signals. The experiments using the two- and three-element arrays demonstrated beam control capability.

V-band high-order harmonic injection-locked frequency-divider MMICs with wide bandwidth and low-power dissipation

In this paper, V-band high-order frequency divider monolithic microwave integrated circuits (MMICs) showing wide bandwidth and low-power dissipation are presented. For high-order (divide-by-four) frequency division, a super-harmonic signal is injected into a self-oscillating subharmonic mixer loop consisting of cascode field-effect transistors (FETs). Cascode FET-based harmonic injection locking allows high-frequency operation, simple circuit configuration, reduced FET count, and thus, low dc power consumption. Bias circuits and quarter-wavelength stubs are used to effectively suppress unwanted harmonic and spurious signals in the oscillation loop. A simple analysis method employing two-tone harmonic-balance simulation and an ideal directional coupler is developed to optimize the performance of the high-order divider. The designed V-band frequency dividers are fabricated with a commercial 0.15-/spl mu/m GaAs pseudomorphic high electron-mobility transistor foundry. The measurement of a divide-by-four MMIC shows a bandwidth of 2.81 GHz around 64.0 GHz under very small dc power consumption of 7.5 mW. The circuit concept has been extended to a divide-by-five MMIC by adding a frequency doubler in the feedback loop, which shows the bandwidth of 1.02 GHz at V-band. To the best of our knowledge, the frequency dividers of this study show the best performance in terms of division order and dc power consumption among the reported millimeter-wave analog frequency dividers at V-band and above.

A 2.5-GHz InGaP/GaAs differential cross-coupled self-oscillating mixer (SOM) IC

This letter presents a monolithic differential cross-coupled self-oscillating mixer (SOM). The SOM chip is fabricated using an InGaP/GaAs heterojunction bipolar transistor (HBT) foundry process and operates at 2.5 GHz. The chip provides voltage controlled oscillator (VCO) operation, up- and down-conversion mixing, and injection locking functionalities. The voltage down-conversion gain and the power up-conversion gain of up to 15 and 11.5 dB, respectively, are measured for the circuit. There is a compromise between obtaining a high conversion gain, and the oscillator power (-0.3 dBm for a 5-V supply) and phase noise (-84 dBc/Hz at 100 kHz). However, phase noise improvement of 32dB is observed by injection of a -30-dBm stable reference.

Application of the envelope-transient method to the analysis and design of autonomous circuits

The envelope transient enables a very efficient simulation of circuits with two different time scales, such as those that contain modulated signals (for example, amplifier or mixers), where an accurate prediction of intermodulation distortion is needed. The method has also been extended to oscillator analysis, where it requires additional techniques in order to avoid convergence to degenerate mathematical solutions, for which the circuit is not actually oscillating. It allows an efficient analysis of transients in these circuits and an accurate prediction of the phase-noise spectrum. This article presents an overview of the envelope-transient method and its most recent applications to the simulation of autonomous circuits, such as free and forced oscillators, frequency dividers, and phase-locked loops. Using this method, the operation bands of these circuits (which are delimited by qualitative stability changes or bifurcations) can be determined in a straightforward manner. This technique can also be applied to predict intermodulation distortion in self-oscillating mixers and to simulate the response of synchronized oscillators containing modulated signals. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.

Radial Cavity-Fed Spatial Power Combiner With Retrodirective Array Behavior

This paper discusses the design and operational properties of a circular array of slot coupled active GaAs metal-semiconductor field-effect transistor (MESFET) rectangular microstrip patch antennas arranged for quasioptical power combining at X band. The active antenna radiating elements are injection locked by slot coupling to a radial cavity waveguide. Spatial power combining efficiency of 75% and dc to radio frequency (RF) conversion efficiency of 10% at 28 dBm EIRP was achieved at 10.38 GHz. Retrodirective action was also demonstrated by using the active elements as self-oscillating mixers pumped at 20.76 GHz.

Envelope Transient Analysis of Self-Oscillating Mixers

In this paper, the envelope-transient method is applied to the analysis of intermodulation distortion in self-oscillating mixers (SOM). A two-tone Fourier-series expansion of the circuit variables with time-varying harmonic components is used with a new initialization technique of the oscillation to avoid convergence toward unstable forced solutions. The two cases of an autonomous oscillation and a sub-synchronized oscillation are studied and compared. In the sub-synchronized SOM, the ranges of sub-synchronized operation in terms of the sub-synchronization generator power and frequency are determined through harmonic balance. The techniques are applied to a SOM with 5.5-GHz input frequency and 0.5-GHz IF. In the case of an autonomous oscillation, two different values of the quality factor of the load circuit are considered. For sub-synchronized operation, a generator is introduced at approximately one-third the self-oscillation frequency. In order to validate the analysis techniques, the circuit has been experimentally characterized in both autonomous and sub-synchronized operation, obtaining very good agreement with the simulation results.

A Retro-Directive Antenna Array With Phase Conjugation Circuit Using Subharmonically Injection-Locked Self-Oscillating Mixers

In this paper, a novel phase conjugation circuit and its application to retro-directive antennas are presented. The phase conjugation circuit uses a balanced circuit structure with subharmonically injection locked self-oscillating mixers oscillating at /spl omega/. In the operation, an input signal at /spl omega//2 is converted to its conjugated signal with no external source required for LO signal pumping, and the output signal frequency is locked at the same frequency of the input signal. The developed phase conjugation circuit is implemented with active antennas to become a retro-directive antenna array. Both the theoretical and measured results of phase conjugation and retro-directive performance are shown in good agreement.

A 16-element two-dimensional active self-steering array using self-oscillating mixers

A 16-element two-dimensional (2-D) retrodirective array using self-oscillating mixers (SOMs) is presented. SOMs allow for easier implementation of larger 2-D arrays by eliminating the complex local-oscillator (LO) feed structure. A 4 /spl times/ 4 element retrodirective array using SOMs is demonstrated at an LO frequency of 7.68 GHz. Each element is phased locked at the LO frequency with an accompanying RF frequency isolation of 17.9 dB between adjacent horizontal elements and 22.2 dB between adjacent vertical elements. A -10-dBm external injection-locking signal is applied to reduce the phase noise of the 16-element array to -68.2 dBc/Hz at 10-kHz offset. Retrodirectivity is observed in the /spl phi/=0/spl deg/, /spl phi/=-45/spl deg/, and /spl phi/=-90 plane for scattering angles of /spl theta/=-15/spl deg/, /spl theta/=0/spl deg/, and /spl theta/=+30/spl deg/.

Experimental study for optimizing self‐oscillating mixer with electromagnetically coupled antenna element

AbstractRecently, extensive research has been carried out on active antennas using microwave transistors such as GaAs FETs for mobile communications and millimeter‐wave applications. The active antenna including a built‐in oscillator using GaAs FET devices does not require a mixer and has the advantage of reduced attenuation in transmission lines. In this paper, with a view to enhancing the output level of the IF when an active antenna is used as a self‐oscillating mixer, the addition of an electromagnetically coupled antenna such as a dipole, monopole, loop, and patch is proposed. Experimental studies are carried out on the self‐oscillating mixer with such an electromagnetically coupled element. In order to enhance the output level of the IF, conditions for optimum shapes and positions of the parasitic element are obtained. From the results of an experiment using a dipole and a loop for which the coupling of the parasitic element near the active device significantly affects the IF output level, it is confirmed that the oscillation becomes unstable if the spacing between the FET and the parasitic element is less than 3 mm. In a monopole with a structure that can increase the spacing from the active device, improvement of IF output by about 20 dB at the maximum can be obtained. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(11): 30–37, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10118

Hybrid active integrated antenna arrays with a 23‐GHz MMIC oscillator

AbstractAn ultrasmall active integrated antenna 2.5 cm square was fabricated by combining an MMIC oscillator and planar slot antennas. The design of array antennas by simulation and analysis of their injection locking characteristics are presented. Beam steering and the effect of packaging are considered in the measurement, and the effect of the metal reflector plate behind the array antenna is studied. A small active integrated antenna is placed at the focal point of a parabolic antenna. Its operation as a receiving integrated antenna with a self‐oscillating mixer for communication satellite is confirmed. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(11): 46–56, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10115

New nonlinear design tools for self-oscillating mixers

New nonlinear design tools for self-oscillating mixers are presented here, with the aim to increase the designer's control over their behavior. The new tools enable fixing the self-oscillation frequency and selecting the optimum self-oscillation amplitude for maximum conversion gain. They can also be applied for the optimized design of harmonic self-oscillating mixers. Using bifurcation-theory concepts, it has been possible to increase the input-power range with self-oscillating-mixer operation. A self-oscillating mixer with 5.5 GHz input frequency has been designed and simulated obtaining very good agreement with the experimental results.

A low-power-consuming SOM for wireless communications

This paper presents theoretical and experimental results of a low-power-consuming hybrid push-pull self-oscillating mixer (SOM) circuit at the UHF frequency band. The frequency-stable SOM circuit is designed and fabricated using matched-pair Si bipolar junction transistors and high-Q resonators, where measured phase noise of this free-running voltage-controlled oscillator is -101.2 dBc/Hz at 100-kHz offset. A 20-dB up-conversion gain, a compression dynamic range (CDR) of 65 dB/spl middot/MHz, and a spurious-free dynamic range of 50 dB/spl middot/MHz/sup 2/3/ are also measured for the mixer portion of this SOM. Moreover, a down-conversion gain of /spl ap/-2 dB with a CDR of 100 dB/spl middot/MHz is also measured.

A subharmonic self-oscillating mixer with integrated antenna for 60-GHz wireless applications

A balanced integrated-antenna self-oscillating mixer at 60 GHz is presented in this paper. The modal radiation characteristics of a dual-feed planar quasi-Yagi antenna are used to achieve RF-local oscillator (RF-LO) isolation between closely spaced frequencies. The balanced mixer is symmetric, inherently broad band, and does not need an RF balun. Pseudomorphic high electron-mobility transistors are used in a 30-GHz push-pull circuit to generate the second harmonic and a 30-GHz dielectric resonator was used to stabilize the fundamental oscillation frequency. This allows the possibility of building a balanced low-cost self-contained antenna integrated receiver with low LO leakage for short-range narrow-band communication. Phase locking can be done with half of the RF frequency. The circuit exhibits a conversion loss less than 15 dB from 60 to 61.5 GHz, radiation leakage of -26 dBm at 60 GHz, and IF phase noise of -95 dBc/Hz at 100-kHz offset.

Demonstration of a 77-GHz heterojunction bipolar transferred electron device

We demonstrate for the first time a heterojunction bipolar transferred electron device (HBTED), a device with a bipolar transistor-like structure in which Gunn oscillations occur. The use of a graded doping profile in the collector region is, we believe, a key factor in the device design. AlGaAs/GaAs HBTEDs fabricated on semi-insulating GaAs substrates exhibit free-running oscillations at a frequency of around 77 GHz. The third (emitter) terminal enables this device to be injection-locked and to function as a self-oscillating mixer.