A waveguide bi-directional amplifier module is illuminated by a downstream illumination source and an upstream illumination source. The illumination sources are coupled to an array having waveguide to microstrip converters that provide for upstream and downstream electrical signals. Switchable amplifiers provide for amplification in both directions for the electrical signals and the converters coherently combine the output of the amplifiers to provide increased power to the electromagnetic wave entering the waveguide.

Bi-directional amplifier module for insertion between microwave transmission channels

A phase-locked second harmonic Gunn oscillator, mechanically tunable from 65 to 115 GHz, has been developed for use as a Iocal oscillator (LO) in millimeter radio astronomy. The oscillator's output power is greater than 2 mW over most of its operating range, and exceeds 10 mW from 80 to 102 GHz. Its frequency can be electronically tuned approximately +-200 MHz by varying the bias voltage on the Gunn diode it is phase locked by exploiting this bias tuning. The oscillator consists of a commercially available, packaged GaAs Gunn diode which is mounted in a coaxial resonator of adjustable length. Descriptions of the mechanical design and phase-lock circuit are given. Extensive experimental measurements of the tuning range and power output for oscillators with different resonator dimensions also are reported.

A Continuously Tunable 65--15-GHz Gunn Oscillator

A very-small-size printed loop antenna for mobile phone application is proposed. The antenna has a loop strip of length 62 mm only, which is folded into an L-shape and occupies a small area of 96.5 mm2 on the top no-ground portion of the system circuit board of the mobile phone. By incorporating a simple matching circuit formed by a chip capacitor and a chip inductor, both in series, the loop antenna can generate three resonant modes (0.25-, 0.5-, and 1.0-wavelength modes) at about 925, 1800, and 2200 MHz. The 0.25-wavelength mode forms the antenna's lower band covering GSM operation, whereas the 0.5- and 1.0-wavelength modes form the antenna's upper band covering DCS/PCS/UMTS operation. Quad-band operation is hence obtained for the printed loop antenna, although it has a very small size. Details of the proposed antenna are presented. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 184–192, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24008

https://onlinelibrary.wiley.com/doi/pdf/10.1002/mop.24008

Very-small-size printed loop antenna for GSM/DCS/PCS/UMTS operation in the mobile phone

Pulsed and CW measurements in the range 26-110 GHz were performed on gallium arsenide (GaAs) Gunn diodes having active lengths of 1.8-2.6 µm, bonded into commercially available packages. The diodes were operated in full-height waveguides in the V-(WR-15), E-(WR-12), and W-(WR- 10) bands, using coaxial-bias circuits aud a disc-post resonator to provide the required resonance at their fundamental frequency in the range from about 25-65 GHz. Frequency and power measurements were performed up to 110 GHz on the fundamental, second, and third harmonics. The main emphasis of this experimental investigation has been the study of frequency changes caused by changes made in the various parameters of the disc, post, diode, diode package, and embedding waveguide sections.

Fundamental and Harmonic Operation of Millimeter-Wave Gunn Diodes

Design considerations for developing a highly directive broadband bidirectional distributed amplifier are discussed. Through effective binomial scaling of the individual device transconductances, directivities on the order of -25 to -35 dB have been demonstrated using computer simulation and measured S-parameter data for the NEC 9000 transistor. The circuit is broadband, with the potential for operation over an octave or more in frequency. Finally, it is noted that the circuit is bidirectional in that it may be driven from both ends of the gate line simultaneously with high directivity exhibited at each respective port on the drain line. >

A highly directive, broadband, bidirectional distributed amplifier

Research into a novel class of distributed amplifiers which have a high isolation bandstop response in the reverse gain direction is described. These devices may be used as duplexer/circulator or bidirectional amplifier elements which, for many applications, can perform the function of ferrite isolator and circulator elements. The paper details the design of such an amplifier, working in the S-band, and gives measured test data.

Distributed amplifiers as duplexer/low crosstalk bidirectional elements in S-band

A novel design of varactor-tuned millimetre-wave second-harmonic Gunn oscillator is reported in which a varactor is mounted in a secondary cavity resonant at the fundamental frequency of the Gunn diode. This has the advantage that the varactor does not significantly load the Gunn diode at the output second-harmonic frequency, and enables the oscillator to produce the maximum possible output power from the diode while still offering varactor tuning and high Q.

Novel varactor-tuned millimetre-wave Gunn oscillator

Measurements performed on a 2nd-harmonic transferred-electron oscillator and a scale model are reported. A method is described for determining the resonant frequency of the oscillator once the diode parasitic reactances are defined.

Determination of resonant frequency for 2nd-harmonic-mode millimetre-wave transferred-electron oscillators

An injection-locking technique whereby a varactor-tuned Gunn oscillator is connected directly to a high-power impatt oscillator is described. The technique does not require a circulator and results in a compact, high-power, electronically tunable source.

Novel 93 GHz injection-locked impatt oscillator

The signal flow characteristics of distributed amplifiers are studied, and it is found that such modules can be designed to suit certain solid-state duplexer/circulator or bi-directional amplifier applications. A module with a measured S/sub 31/ (transmit to receive) isolation of typically 10 dB is described, and found to have a gain of about 6.0 dB in the S/sub 34/ direction and 7.5 dB in the S/sub 21/ direction. A major motivation of this research is to seek all solid-state design solutions for low power FMCW radar and duplex communications equipment; thereby obviating the use of ferrite circulator components. >

R.N. Bates

Papers

Distributed amplifiers as duplexer/low crosstalk bidirectional elements in S-band

Novel varactor-tuned millimetre-wave Gunn oscillator

Determination of resonant frequency for 2nd-harmonic-mode millimetre-wave transferred-electron oscillators

Novel 93 GHz injection-locked impatt oscillator

Distributed amplifiers as duplexer/circulator components at S-band