Quasi-optical HEMT and MESFET self-oscillating mixers

Planar quasi-optical receivers that compactly integrate a coupled slot antenna and a HEMT or MESFET balanced self-oscillating mixer and on the same substrate for applications in microwave and millimeter-wave receiver arrays are discussed. Both the HEMT and the MESFET circuit are designed and demonstrated at X-band. The HEMT circuit exhibits an isotropic conversion gain of 4.5 dB and a noise figure of 6.5 dB. The isotropic conversion gain of the HEMT circuit is 7.5 dB higher than the mixer diode circuit previously reported     

Conversion matrix and gain of self-oscillating mixers

The conversion matrix of self-oscillating mixers is derived from the bias-, amplitude-, and frequency-dependent admittance of the active device together with its dynamic current-voltage characteristic. Components at the image frequency are also taken into account. With this matrix and the circuit admittances at the different frequencies involved, the conversion gain can be expressed. For better insight into the relevant mechanisms, the conversion gain is subdivided into the amplitude response of the self-excited oscillation to an input signal and the demodulation caused by the device internal rectification. The formalism is applied to a simplified model of an oscillating BARITT diode. The resulting analytical expressions allow a discussion of the influence of different device and circuit parameters as well as a qualitative and quantitative comparison with experimental results from a self-oscillating BARITT-diode mixer operating in the V-band at 60 GHz     

60 GHz BARITT diodes as self-oscillating mixers

The fabrication of Pt np+ silicon baritt diodes for V-band frequencies is described. An oscillating output power of 1 mW at 60 GHz could be attained. The diodes were investigated as self-oscillating mixers in Doppler-radar and local-oscillator applications. A conversion gain of 26 dB and a minimum detectable signal of ?160 dBm (1 Hz bandwidth) could be measured near the carrier.     

Ka-band self-oscillating mixers with Schottky BARITT diodes

The fabrication of Pt n-p+ silicon Baritt diodes is described which can deliver more than 4 mW at Ka-band frequencies. The diodes were investigated as self-oscillating mixers. A minimum detectable signal of ?154 dBm as well as a conversion gain of 26 dB could be realised.     

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     

Large-signal computer-aided analysis and design of silicon bipolarMMIC oscillators and self-oscillating mixers

A large-signal analysis and design of silicon bipolar monolithic microwave integrated circuit (MMIC) feedback oscillators and self-oscillating mixers are discussed. Emphasis is placed on the modeling of the active and passive devices and the large-signal analysis and design of nonlinear circuits using SPICE. Measured and simulated data of a C-band self-oscillating mixer are presented     

Josephson junctions as self-oscillating mixers at 34 GHz

Adjustable point-contact Josephson junctions have been used as self-oscillating mixers at 34 GHz, with an intermediate frequency of 300 MHz. The average conversion loss was about 18 dB, but mismatch losses and waveguide losses may amount to 10 dB at present.     

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/.     

Use of mutually coupled harmonic self-oscillating mixers for receiving phased-array antennas

A topology based on mutually coupled harmonic self-oscillating mixers for beam steering purposes in a receiver configuration is presented. The use of harmonic self-oscillating mixers increases the maximum inter-element phase-shift allowing greater steering angles. A 3 times 1 array has been manufactured showing good agreement between experimental and simulated results.     

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.     

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.     

Dual-gate m.e.s.f.e.t. self-oscillating X-band mixers

GaAs dual-gate m.e.s.f.e.t.s have been successfully used as self-oscillating down-convertors in X-band. A single device replaces the preamplifier, mixer and local oscillator. The best conversion gain achieved by mixing from 10 GHz down to 1 GHz was 12 dB. The input (gate 1) to output (drain) port isolation amounted to 16 dB. Slug-tuner and `disc?-resonator circuits were tested and showed comparable gain and noise performance. Best d.s.b. noise figures of 5.5 dB could be realised at an i.f. of 1 GHz with an associated conversion gain of 4 dB.     

Performance of self-oscillating GaAs m.e.s.f.e.t. mixers at X-band

A new mode of m.e.s.f.e.t. operation, the self-oscillating mixer is reported. Conversion gains of up to 2 dB at 10 GHz and noise figures as good as 15 dB have been demonstrated by using a simple circuit.     

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_d3 and G_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 (OIP₃ ~13.6 dBm) comparable to those of the resistive mixers (OIP₃ ~15.3 dBm) with low LO and dc power conditions     

Behavioral analysis of self-oscillating class D line drivers

Self-oscillating power amplifiers (SOPAs) provide an elegant way to power signals which have high crest factors with a high efficiency. Recently, it has been shown that by pushing this concept to its limits, the stringent specifications of digital subscriber line (xDSL) could be met. For the design of these high bandwidth, low distortion amplifiers in a digital CMOS technology, a thorough analysis of the hard nonlinear system is mandatory. This paper describes behavioral models based on the describing function method and Bessel series expansion of nonlinear modulations. Models have been derived for the self-oscillation, the bandwidth, the dominant third-order distortion and all inter-modulation products of a SOPA line driver. All spectral peaks at the output of a single ended SOPA amplifier are qualitatively and quantitatively explained by these models with a very high accuracy. A calculation speed-up with three orders of magnitude could be obtained compared with a dedicated numerical simulator.     

Modelling and analysis of dual-gate MESFET mixers

A method is presented for the modelling and analysis of dual-gate MESFET mixers. The method can handle all the dominant nonlinear mixing processes, and is valid for arbitrary DC-bias conditions. Good agreement between theory and experiment is demonstrated.     

采用迟滞比较器的自激振荡功率放大器行为特性分析

采用迟滞比较器的自激振荡功率放大器,在音频功放、DSL线路驱动器及数据转换器等方面得到了较好的应用。但由于其强非线性的特性,分析其行为特性较为困难。本文从时域出发分析了1阶和2阶系统的振荡频率,以线性化的比较器增益为基础分析了系统增益,给出了3次谐波失真的经验公式,不仅简洁、直观,而且具有较高的精度。这些结果经Matlab仿真验证,可以给电路设计者较好的指导作用。     

Accurate analysis and design of millimeter wave mixers

The present study is based on the method introduced by B. Shuppert (1986) for nonlinear analysis of mixers, but it differs in the linear part. In particular, the circuit characterization of the mixer harmonics is emphasized, removing the usual approximation of matched terminations and employing models that effectively represent network characteristics in the microwave and millimeter wave domain. This goal is achieved through the accurate knowledge of the various components used in the mixer and the use of accurate equivalent circuits. In order to validate the model, two subharmonic mixers operating at K-band (18-26 GHz) were realized. Reasonable agreement between theoretical and experimental results is achieved     

Modeling MESFETs for intermodulation analysis of mixers andamplifiers

The problem of modeling GaAs MESFETs for calculations of intermodulation and spurious responses is examined. It is shown that an adequate model must express not only the absolute I/V characteristics of the device, but also the derivatives of those characteristics. It is demonstrated that these derivatives are dominant in determining intermodulation levels, and that the common approaches to modeling MESFETs do not model those derivatives very well. Finally, a new model for the MESFET gate I/V characteristic (the dominant nonlinearity in most FETs) that is accurate through at least the third derivative is proposed     

Computer-aided noise analysis of MESFET and HEMT mixers

A numerical approach to the noise analysis of MESFET and HEMT mixers of arbitrary topology is discussed. A qualitative picture of the complex physical mechanisms responsible for the generation of the intermediate frequency (IF) noise is outlined, and the corresponding computational algorithms are presented. The derivation of a noisy nonlinear model for the microwave FET is addressed, and it is shown that a satisfactory solution to this problem can be obtained by combining a conventional time-domain model with standard noise information. The method has been implemented in a computer program designed to work in conjunction with an existing general-purpose harmonic-balance simulator. An application is described in detail to demonstrate the excellent performance of this software tool