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.     

Noise properties of HTS Josephson mixers at 345 GHz and operating temperatures at 20 K

The authors report on the mixing properties of high-temperature superconductor bicrystal Josephson junctions at 345 GHz and high-operating temperatures. A variable backshort and E-plane tuner enabled the control of impedance matching between the junction and the RF environment. The local oscillator frequency and intermediate frequency were 345 and 1.4 GHz, respectively. The double-side band (DSB) mixer noise temperature and the conversion efficiency were determined using the hot/cold method. The authors observed that the noise temperature was strongly dependent on the matching conditions. The lowest noise temperatures were observed for tuner positions supporting the formation of a subharmonic step which appeared between the zeroth and first Shapiro step. At T = 20 K they obtained a lowest DSB mixer noise temperature of 1003 K and a conversion efficiency of -1.2 dB. They have investigated the dependence of the noise temperature on the operating temperature in detail. The impact of resonances on the device performance will be discussed.     

Image-cancelling mixers at 2 GHz

Image-cancelling mixers are a form of image-recovery mixer that avoid the use of a high-Q factor tuned input circuit. Two identical mixers are pumped in quadrature, and their input circuits are connected to cancel the image current or voltage. Results on double-balanced mixers operating at 2 GHz are presented, and a conversion loss of about 1 dB is obtained.     

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     

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     

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.     

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     

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/.     

12 GHz receiver with self-oscillating dual-gate MESFET mixer

A hybrid integrated 12 GHz receiver, fabricated on a 1 ×2N alumina substrate, contains a two single-gate FET preamplifier, one dual-gate FET self-oscillating mixer, IF matching and bias filters of all FETs. 11?14 dB conversion gain for a bandwidth of 400 MHz and an associated noise figure of 4.5?5 dB have been obtained.     

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.     

Heterodyne mixing at 70 GHz with superconductor-insulator-superconductor tunnel junctions

A laboratory heterodyne receiver working at 70 GHz was built up using superconductor-insulator-superconductor tunnel junction as mixing element. Single sideband conversion loss L_C as low as 1.92±0.23 and mixer noise temperature T_M of less than 100 K have been achieved while local oscillator pump power is 4·10^?8W.     

Josephson effect gain and noise in SIS mixers

The authors report measurements of gain and noise in SIS mixers at 230 and 492 GHz. Measurements were made of relatively high gain and noise associated with Josephson currents that have not been previously reported. These measurements show that Josephson currents are increasingly important as operating frequencies are raised. The techniques used to make these measurements are discussed. Measurements made with hot and cold black-bodies are shown to be inaccurate at high frequencies. The problem is that SIS mixers do not always respond linearly to the signal power incident on them. This is particularly important when (1) very broad band mixers are used and (2) Josephson effect currents are important. Both of these circumstances are present in the quasioptical SIS mixers favored for 500 GHz and higher. Monochromatic signals were used to measure gain and noise to get around these problems     

Picosecond applications of Josephson junctions

The behavior of simple superconducting circuits in the picosecond regime is described in a comprehensive way, with primary emphasis being given to the step function and pulse responses of these circuits. Topics receiving detailed discussion include Josephson-junction modeling with both the microscopic and shunted-junction models. Limitations of the shunted-junction model are explored by comparing it with experimental results and with the microscopic model. An approximate evaluation is given of the important dynamical properties of junctions made with the dominant fabrication technology (Pb-alloy systems), as a function of tunneling barrier thickness. Rounding out the device aspects of the discussion, we describe in detail the properties of superconducting microstrip transmission lines, with an emphasis on their high-speed behavior. Turning to simple circuits we review experimental results on the measurement of picosecond regime transient signals. The concept of turn-on delay is analyzed anew, providing simplified and extended results. Details of concepts for pulse height and pulsewidth measurements are explored, leading to the conclusion that the time resolution of superconducting circuits is limited to approximately the period of one plasma oscillation. With present Pb-alloy fabrication technology this limit is 2 ps.     

Noise and mixing properties of high-Tc Josephson junctions at W-band frequencies

We report on the noise and Josephson mixing properties of high-T_c superconductor (HTS) Josephson junctions. Direct radiation measurements and heterodyne mixing experiments in the frequency range 45–141 GHz have been performed by using YBa₂Cu₃O_7−x (YBCO) step-edge junctions (SEJ) on LaAlO₃ and MgO and bicrystal junctions (BCJ) on MgO substrates. Junctions with current voltage characteristics (CVC) close to predictions of the resistivity shunted junction (RSJ) model were mounted into a high sensitive radiometer system. From linewidth measurements we calculated an effective noise temperature of our junctions. In heterodyne mixing experiments we obtained conversion efficiencies around −14 dB in the 11 GHz intermediate frequency (IF) band under the radiation of two monochromatic signals. In the fundamental mixing regime we observed response at IF at working temperatures up to 72 K. The measured receiver and mixer noise temperature of the Josephson mixer at 94 GHz local oscillator (LO) frequency, an IF of 1.4 GHz and at a working temperature of 10 K was 4700 and 3400 K, respectively.     

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.     

Superconducting memory device using Josephson junctions

A superconducting storage device is proposed in which a Josephson tunnelling junction, switched by a control film strip, replaces the cryotron in a one-cryotron-per-bit storage cell. The device should be fast, work at 4.2° K and require a simple technology, which must, however, yield reproducible thin Josephson tunnelling layers.     

General energy relations for Josephson junctions

The Josephson junction acts as a nonlinear lossless inductor and can be applied for mixing and parametric amplification in the microwave region. Since an alternating current can be generated in the junction by an applied dc voltage, a dc power flow must be taken into consideration. Energy relations for the Josephson junction are derived which are similar to the Manley-Rowe equations but with an additional term for the dc power. These equations show the possibility of realizing dc-pumped parametric amplifiers.     

Logic gates with shaped Josephson junctions

Long (L//spl lambda//SUB j/>5) in-line Josephson junctions, with varying width along the length L of the device, are investigated as logic gates (/spl lambda//SUB j/ being the Josephson penetration depth). The devices realized have an asymmetric threshold characteristic with almost suppressed sidelobes, providing good logic gain and permitting logic fan-in with multiple control lines. Optimum conditions are found for junctions with width varying approximately sinusoidally along the device length. The so-called shaped junctions are incorporated in various flip-flop circuits to evaluate the transfer time and transfer efficiency of loop circuits, and in a self-resetting inverter circuit to demonstrate the feasibility of self-resetting logic. The principle of current steering and the relatively large operating currents (I/SUB G//spl sime/6 mA) make the circuits suitable for medium-speed applications such as in the decode and control logic of a main-memory chip. For a fan-out of four, the minimum circuit delay is 300 ps, resulting in a power-delay product in the order of 3/spl times/10/SUP -15/ J.     

140 GHz broadband crossbar stripline mixers with over 20 GHz instantaneous RF bandwidth

The letter presents the design and performance of a 140 GHz broadband crossbar stripline mixer using beam-lead diodes. With the LO fixed at 140 GHz, a conversion loss of 7?11 dB has been achieved with the RF swept from 140 to 160 GHz, and 6 to 8 dB with the RF swept from 133 to 147 GHz.     

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.