D.G. Thomas

Optimization of active microwave frequency multiplier performance utilizing harmonic terminating impedances

A primary factor affecting optimum performance of microwave multipliers employing nonlinear devices is the proper termination of the fundamental and other harmonic frequency components. The objective of this paper is to present a quantitative analysis leading to the assessment of optimum terminating impedances in the design of active frequency multipliers with special attention given to harmonics other than those desired. The analysis includes computer modeled HEMT data and supporting measured data for corresponding circuit realizations. Circuit designs are presented utilizing HEMT transistors as the active element to verify modeled results. Based on available literature, the results demonstrate, for the first time, the quantitative effects of harmonic termination on active multiplier conversion gain and fundamental and higher harmonic suppression. An experimental design reveals an improvement in multiplier gain of 124% over the conventional approach and data is presented which quantitatively illustrates the advantages of impedance termination considerations under optimal bias conditions.

A reduced size planar balun structure for wireless microwave and RF applications

An extremely important component in the realization of certain RF and microwave system topologies is the high frequency balun network. In addition to its application in radiating structures, it has broad utility in numerous wireless communication system topologies. This paper describes a small and compact coupled microstrip line design for use primarily in the exploding portable wireless market. The main advantage of the design to be discussed is that its size is considerably smaller than traditional planar circuit realizations. Size reduction is achieved by utilizing the property of effective length enhancement of a transmission line by employing additive capactive effects. The design technique is illustrated by presentation of computed and measured data on a /spl sim/0.9 GHz realization developed for wireless applications.

Design of microstrip T junction power divider circuits for enhanced performance

This paper details the development of novel power-divider T junction circuits which have unique prescribed transmission characteristics. Subsequent to a description of the design technique, the paper describes experimental results obtained on a series of fabricated circuit designs. These circuits were fabricated on microstrip material having a relative dielectric of 2.17, and substrate thickness of 20 mils. The measured results are shown to compare well with computer simulations over a frequency range from 50 MHz to 8 GHz.

Radio‐Frequency Multipliers

The sections in this article are 1 Applications of Frequency Multipliers 2 Passive Frequency Multipliers 3 Active Frequency Multipliers

Reduced-size low noise-low power consumption amplifier designs for communications and RF applications

Low-noise amplifiers are extremely significant components in most RF cellular and communications devices. While current design techniques achieve either low noise or high gain, exclusively, little research has been done to reduce their power consumption while simultaneously meeting both of the aforementioned objectives. This paper presents important techniques for the design and development of spatially compact amplifiers that simultaneously provide low noise figure, high gain, low-power consumption, and low VSWR. The design method is illustrated by the realization of both distributed and discrete amplifier circuits centered in the 1.8 GHz frequency range.

Single-ended HEMT RF/microwave frequency doubler design using reflector networks

Microwave and RF frequency multipliers are widely used in a large number of communications, radar, civilian and military systems. This paper presents the development of active doublers operating in the S and C frequency bands. These devices are unique in that HEMTs are employed with specialized embedding networks to provide optimized performance. Conversion gains of approximately 7 dB have been attained for narrowband designs (5% bandwidth), 5 dB for medium bandwidth designs (15%), and 4 dB for wide bandwidth designs (35%). The fundamental and third harmonic rejection is approximately 40 dBc for the narrowband designs and greater than 50 dBc for the medium and wideband designs.

Design of low-noise RF/microwave amplifiers for communication systems requiring very low power consumption

As miniaturization becomes a dominant factor in the development of microwave communication systems, power consumption emerges as an extremely critical design parameter for battery-operated wireless communication devices. With circuits requiring low power consumption, the resultant decrease in power supply battery size provides significant overall system volume and weight reduction. Low-noise amplifiers are essential in the design of many classes of communication receivers employed in microwave technology. For a broad class of wireless systems, there is a significant requirement for low-bias power, low-noise amplifiers operating in the 1 GHz frequency range. This paper presents the development of low-bias (V/sub CE/=1 volt, I/sub C/=1 mA), single-stage, low-noise amplifiers operating in the 1 GHz frequency range. These bipolar designs are unique in that they achieve excellent gain (>10 dB) and noise figure (/spl sim/1 dB) while simultaneously requiring significantly lower bias power than standard designs.

Analysis of harmonic termination impedance on RF/microwave multiplier efficiency

Harmonic terminating impedances have been shown to drastically effect the performance of RF/microwave frequency multipliers. In the literature, various apparently differing conclusions have been obtained on the proper terminating impedances for active multipliers to achieve optimum performance. This paper presents a rigorous and concise approach leading to the determination of harmonic terminating impedances for optimum efficiency. The approach is illustrated in HEMT frequency multipliers in S and C bands. Results have been obtained which have conversion gains of 6 dB with harmonic suppression of greater than 25 dBc utilizing this approach.

Nonlinearities in FET/HEMT microwave devices for circuit synthesis applications

Numerous microwave circuits utilize the properties of active elements that operate under large signal conditions. In particular, active frequency conversion circuits employ the nonlinearities resident in microwave transistors such as MESFETs and HEMTs. This paper analyzes the various nonlinear mechanisms possessed by MESFETs and HEMTs with the goal of utilizing these to provide for optimal designs. The major emphasis is placed on the quantitative contribution of each nonlinearity (e.g., I/sub ds/, g/sub d/, C/sub gs/, etc.) to overall harmonic generation. Numerical results are provided utilizing nonlinear simulation software.

Miniaturized RF/cellular low noise amplifier design having low bias power

A key building block in RF and communications devices, amplifiers play an essential role in the efficiency and flexibility of circuits. This paper details techniques in the design and development of a low power consumption amplifier that achieves the contradictory characteristics of extremely low noise figure and high gain. The method is illustrated by the realization discrete 900 MHz spatially compact amplifier circuit.