A Study of the Optimum Design of Wide-Band Parametric Amplifiers and Up-Converters

Single-diode parametric amplifiers or up-converters using multiple-resonator filters as coupling networks can be made to have considerably larger bandwidths than corresponding amplifiers having single-resonator coupling circuits. Data are presented from which the coupling-filter bandwidths required for given coupling network complexity, diode parameters, and required gain can be determined for both parametric amplifiers and up-converters. In the cases of nondegenerate parametric amplifiers and up-converters, the fact that the diode must be brought to resonance at more than one frequency has an added limiting effect on bandwidth. Some trial amplifier designs are shown, and important considerations in the synthesis of the coupling filters are noted. It is seen that for the case upper-sideband up-converters, if a filter having n resonators is used in both the input and upper-sideband circuits, then the over-all response can be made to correspond to that of a filter with 2n resonators. The gain characteristics of the trial amplifier designs as determined with a digital computer are included. Computed responses ranging in bandwidth from 9 to 27 per cent are obtained for multi-resonator designs having C/sub 1// C/sub 0/ = 0.25.     

Broad-Band Cavity-Type Parametric Amplifier Design

This paper tells how maximum bandwidth can be obtained from a nondegenerate parametric amplifier which utilizes a circulator. Expressions are derived for the gain bandwidth product and maximum possible gain bandwidth product. It is then shown how the Q of the cavities used for the signal and idler circuits may be kept at a minimum without degrading the noise performance of the amplifier. It is shown that best performance results when the TEM mode is used in coax, or, if waveguide is used, when the operating frequency is far away from the waveguide cutoff frequency. The diode used should have as high a self-resonant frequency as possible and the line admittance should be approximately the diode susceptance. Using a diode with a self-resonant frequency at the idler frequency will be seen to give optimum performance. This paper also discusses double tuning the signal circuit to achieve broader bandwidths. In this case, the addition of the second tuned circuit will be seen to give much broader bandwidths than one would expect from conventional filter theory. Two sample amplifiers are considered and their bandwidths calculated. The effect of double tuning one of the amplifiers is then considered.     

Practical Design and Performance of Nearly Optimum Wide-Band Degenerate Parametric Amplifiers (Nov. 1961 [T-MTT])

The design of a two-resonator single-diode degenerate parametric amplifier is described, which incorporates features that give it nearly optimum wide-band performance. These features include the use of almost lumped circuit elements, a separate pump resonator which is very lightly coupled to the diode and pump circuits, and a diode resonated in series rather than in shunt, from which several advantages accrue. A bandwidth of 21 per cent with 15-db midband gain (double channel) is obtained at 1 Gc using two resonators, as compared with 8 per cent using one resonator. Both measured responses are found to be in excellent agreement with theoretical responses obtained with a digital computer. The measured double-channel noise figure was 1 db. Theoretical and experimental results are presented which show this type of amplifier to be remarkably insensitive to tuning errors. Good results were also obtained using two identical amplifiers in balanced operation with a 3-db coupler so as to eliminate the need for a circulator.     

A Design Theory for Wide-Band Parametric Amplifiers

A new exact design theory for a nondegenerate parametric amplifier with double-tuned signal circuit and single-tuned idler circuit is described. If the resistance of the signal circuit, which is neglected in previous papers, is considered, there exists a frequency band in which the amplifier gain is positive. In this paper the band characteristics of the gain are related to this frequency band. Slope parameters of the idler and signal circuits are normalized by the slope parameters which are associated with the diode itself. These normalized slope parameters are used to relate the actual circuit and gain-bandwidth characteristics. The slope parameter of the external signal resonator is related to the negative slope parameter of the diode, and bounds on this ratio are given over which stable amplification is possible. A design table which gives the coupling ratio and slope parameter of the external signal resonator is derived by computer calculation. Experiments were made at 19 GHz. Positive-gain bandwidth was around 4.0 GHz, and flat bandwidth at 10-dB gain was 2.4 GHz. The ratio of these bandwidths coincided with the theory.     

Maximum Bandwidth Performance of Non- degenerate Parametric Amplifier with Single-Tuned Idler Circuit

The single-tuned bandwidth and limiting flat bandwidth of a nondegenerate reflection-type diode parametric amplifier is calculated. The amplifier has a broad-banding filter structure in the signal circuit and a single-tuned idler circuit. An experimental low-noise, wide-band Z-band amplifier is described, and measurement results are presented. The amplifier has a triple-tuned signal circuit and a single-tuned idler circuit and is pumped at 11.3 Gc. A nearly flat bandwidth of 23 per cent at 7 db gain and an effective input noise temperature of 70/spl deg/K at room temperature ambient and of 29/spl deg/K at liquid nitrogen (77/spl deg/K) ambient has been obtained.     

Design Theory of Up-Converters for Use as Electronically-Tunable Filters (Sep. 1961 [T-MTT])

The up-converters discussed use a single diode, a wide-band impedance matching filter at their signal input, a moderately wide-band impedance matching filter at their pump input, and a narrow-band filter at their sideband output. With a narrow-band filter at the sideband output, the frequency which will be accepted by the amplifier can be controlled by varying the pump frequency. Analysis of the impedance matching problem involved shows that tuning ranges of the order of a half-octave to an octave are possible. Theory is presented for both the lower-sideband and upper-sideband types of tunable up-converters and for the design of the required impedance matching networks. It is shown that, because of the pump input bandwidth required, it will generally be necessary to accept some mismatch at the pump input. But, by use of a properly designed impedance matching filter, the reflection loss can be kept nearly constant across the pump band, and the incident pump power required is not unreasonable. It is seen that properly designed devices of this type using voltage-tunable pump oscillators should have wide tuning range, fast tuning capability a useful amount of gain, no image response, and a low noise figure.     

A Nondegenerate Traveling-Wave Parametric Amplifier

The traveliig-wave parametric amplifiers reported to date are not sufficiently competitive to ensure their use in advanced RADAR systems. The major hindrance is the relatively high-RADAR noise figure which is due to the fact that the signal and idler frequencies are about equal; i.e., the amplifier is degenerate. Initial experiments directed toward obtaining a nondegenerate microwave traveling-wave parametric amplifier are reported in this paper. A promising circuit has been developed and an S-band nondegenerate amplifier has been built and tested. In the first part of the paper the circuit is described and the experimental results are given. The second part of the paper describes procedures which have proved useful in the development of the circuit and which should also prove useful in future investigations.     

Wide-Band Gallium Arsenide Power MESFET Amplifiers

The performance, with emphasis on wide bandwidth, that can be expected of linear medium power GaAs microwave MESFET (metal semiconductor field-effect-transistor) amplifiers is discussed. It starts with measured scattering parameters of devices and proceeds through computer-optimized device modeling, to amplifier circuit designs and performance results. It shows computed and measured octave bandwidth performance and reveals that decade bandwidth is feasible. It discusses single-ended and balanced amplifier design approaches. Some practical designs with performance results are presented, with circuit topologies which are easily realizable in microstrip.     

The Effect of Parasitic Elements on Reflection Type Tunnel Diode Amplifier Performance

The effect of the tunnel diode series inductance and stray capacitance on the gain and bandwidth of broadband reflection type amplifiers is considered. General stability criteria imposed by these reactance are given together with realizability conditions for ideal (flat gain), Butterworth and Chebyshev responses. The main effect of the parasitic elements is to restrict the range of gain and bandwidth which may be achieved for a given number of elements in the matching network. The minimum gain is restricted together with both the maximum and minimum bandwidths. Comprehensive sets of curves are given which enable a rapid design of either Butterworth or Chebyshev response to be accomplished, and a procedure is given for conversion of the low-pass prototype network to band-pass form in the presence of the parasitic reactances. The frequency transformation is used to obtain an upper limit on the center frequency of the band-pass amplifier imposed by the parasitic. The use of the design data is illustrated by numerical examples.     

Read-Type Varactors for Parametric Amplifier Applications

The use of Read-type HI-LO doping profiles in varactors for pararnetric amplifier applications is shown to result in improved performance over conventional structures. Optimal diode doping Ievels layer thicknesses, and pump drive levels are derived which give specified frequency performance while minimizing pump power requirements, minimizing noise, maximizing dynamic range, and reducing amplifier sensitivity to pump power fluctuations. The optimum device design is based on environmental Iimitations such as pump power, circuit losses and impedance Ievels and the unavoidable diode series resistance level. Design examples are given for 10- and 100-GHZ parametric amplifiers.     

Theoretical Investigations of TRAPATT Amplifier Operation

A device-circiut interaction program has been developed for the study of TRAPATT amplifiers. The device is simulated using the programs developed by Bauhahn. A slug-tuned coaxial circuit is simulated with the circuit parameters chosen to model an amplifier for which experimental results have previously been published. Results including diode waveforms over the entire amplifier frequency band are presented. Seperate mechanisms have been identified as being responsible for the fall off in gain and power output above and below the center frequency. The maximum bandwidth which can be attained with TRAPATT amplifier is also estimated.     

Synthesis of Negative Resistance Reflection Amplifiers, Employing Band-Limited Circulators

This paper presents a theory for single-stage circulator-coupled negative resistance reflection amplifiers based on proposed realistic circuit models for frequency-dependent band-limited circulators and broadband negative resistance devices such as the tunnel diode. In particular, gain bandwidth limitations are derived which are imposed by both the inherent resonance associated with the nonreciprocal circulator junction and the reactive parasitic associated with the active device. These limitations are generally more restrictive than past results which assumed a "perfect" frequency-independent circulator and took into account only the device parasitic. In addition, a synthesis procedure is presented for realization of an absolutely stable amplifier with a prescribed nth-order Butterworth or Chebyscheff approximation to an ideally flat band-pass power gain characteristic. The approach employed is based upon the theory of reflection coefficient equalization between two reactively constrained resistances representing the pass band circulator and device immittance models. In addition, a band rejection out-of-band stabilizing network is absorbed in the pass band equalizer in accordance with an over-all synthesis procedure. Finally, the theory is verified by the construction and testing of an L-band tunnel diode amplifier having third-order maximally flat power gain centered at 1.46 Gc/s and with half-power bandwidths (430 Mcls and 355 Mc/s at 10 dB and 16dB midband gain) within six percent of those predicted by theory.     

Input Millimeter-Wave Module with Parametric Amplification

The paper presents the experimental results of an investigation into a low-noise non-cooled amplification module consisting of the parametric amplifier and the quasi-optical pumping oscillator, intended for implementation as an input circuit of the 60 GHz wave band receivers. The coaxial waveguide resonator was used as an idler frequency loop of the parametric amplifier, while the quasi-optical sphere-corner-echelette open resonator was used as the same for the oscillatory circuit of the pumping oscillator. The experimental results for the model of amplification module, which is executed using the unpacked Schottky-barrier diode and IMPATT diode, are provided. The gain is no less than 16 dB within the 1 GHz bandwidth and the noise temperature is no more than 550 K.     

An 18-GHz Double-Tuned Parametric Amplifier

A K/sub u/-band nondegenerate parametric amplifier using a single-packaged GaAs varactor diode is described. A very simple structure of the single-tuned amplifier with a new type of idler choke is employed to obtain a large voltage-gain bandwidth product and a low noise temperature. The double-tuned operation exhibits a nearly flat bandwidth of 550 MHz at a 20-dB gain and a noise temperature of 280/spl deg/K at room-temperature ambience.     

Varactor harmonic-generator chain as a pump source for a parametric amplifier

This letter gives the results of experiments on the pumping of an X band nondegenerate parametric amplifier with a Q band varactor harmonic-generator chain. It is shown that care must be taken to ensure efficient filtering in the first stage of the chain, and methods are given to obviate spurious responses in the tuning range of the parametric amplifier caused by additional harmonics from the solid-state pump source mixing in the varactor diode of the parametric amplifier.     

Analysis and design of LC amplifiers and LC oscillators using current-feedback amplifiers

The present paper discusses specific types of LC amplifier and LC oscillator using a current-feedback amplifier (CFA). The main advantage of the CFAs versus voltage-feedback amplifiers (VFAs) is their gain-bandwidth independence. Some of the monolithic CFAs provide an additional pin between the first stage (current-controlled current source) and the second stage (voltage follower), where the resistance is very high. This allows a parallel resonance LC tank to be connected to the additional op amp correction pin. The main advantage of this new configurations is the insignificant influence of the load over the parameters of the circuit (voltage gain, Q-factor, etc.). Some recommendations for designing this kind of analogue circuit are given, based on simulation results, symbol analysis of the transfer function and physical experiments as well as elements’ values calculation using centre frequency, voltage gain, bandwidth and Q-factor of the LC amplifiers as input parameters.     

A New Technique for Synthesis of Broad-Band Parametric Amplifiers

A new synthesis technique for providing precise design values for the realization of broad-band parametric amplifiers incorporating practical varactor diode models is presented. The method provides the designer considerable flexibility in choosing the topology of matching networks employed. An integral part of the synthesis scheme is the application of a least-squares optimization procedure which employs exact partial derivatives of the objective function. The partial derivatives are used in the optimization to compute the gain sensitivity of the amplifier with respect to all matching network and diode parameters. For the first time, sensitivity data is presented which quantitatively shows the effect of the device and matching network parameter variations on overall amplifier response. This permits the determination of critical parameters and provides a means for establishing tolerances for various circuit parameters. In comparison with conventional procedures, significantly improved broad-band designs are shown to result.     

Multiple-Idler Parametric Amplifiers

The input resistance and noise performance of multiple-idler parametric amplifiers are examined in this paper. General expressions applicable to any given amplifier are derived. Simplifications resulting from a sinusoidal elastance variation permit writing an expression for the input resistance of an amplifier having any given number of idlers by inspection. These expressions are then applied to examine the properties of an amplifier having two idlers. The conditions required for minimum noise performance are derived, and it is found that high pump frequencies and external resistive loading of one idler are required. When the two-idler amplifier is compared to a conventional single-idler amplifier under those conditions which permit operation of the same diode at the same signal and pump frequencies, it is found that an improvement in noise figure results. However, the single idler amplifier pumped at the optimum frequency is capable of better noise performance, because minimum noise conditions cannot be satisfied for the two-idler device at this pump frequency. When below-signal-frequency pumping is utilized in the two-idler amplifier, the reduction in required pump power is substantial, but the noise figure is degraded by a minimum of approximately 3 dB.     

Intermodulation properties of double- and triple-circuit parametric amplifiers with nonlinear barrier capacitance

There have been performed an experimental investigation of intermodulation effects in narrowband regenerative double- and triple-circuit parametric amplifiers (RDPA and RTPA) with nonlinear barrier capacitance. It has been obtained that their single-signal and double-signal intermodulation characteristics are of the conventional form, and their phase shifts in the vicinity of the resonance frequency are close to 90°, that is not enough for the compensation of nonlinear distortions in the case of amplifiers cascading. It has been demonstrated that the introduction of the additional oscillatory circuit at the double signal frequency into RDPA does allow effective compensation of the intermodulation interferences of odd order in the single-stage parametric amplifier.     

Circuit Behavior and Impedance Characteristics of Broad-Band TRAPATT-Mode Amplifiers

The characteristics of TRAPATT-mode high-efficiency oscillators and broadband amplifiers are reviewed. It is concluded that a broad-band amplifier like a high-efficiency oscillator should have capacitive circuit impedances and is distinguished from a high-efficiency oscillator principally by the number of important harmonics employed. A smaller number of harnonics for the amplifier can lead to broader bandwidth but lower efficiency. The relative merits of experimental amplifier circuits are discussed. It is shown that coaxial-line circuits employing diode packages with large lead inductances are characterized by harmonic impedances which can have large values over broad frequency bands. However, it is also shown that the device waveforms in this case are excessively degraded and relativeIy low-efficiency results. On the other hand, microstrip circuits with a Iow-impedance diode mount can provide broadband low impedances at both fundamental and third harmonic and have exhibited better performance.