Peter Callaghan

Hidden Automotive Antenna Performance and Simulation

A new printed antenna system mounted in an aperture in the roof of a car is evaluated for broadcast signal reception from 88-108 MHz. Results from simulations on the vehicle are compared with measurements. The overall performance of the antenna is also compared to common types of vehicle antennas, the roof monopole and a glass based antenna. Overall the average gain of the antennas was better than -3 dBi for vertical polarization and -10 dBi for horizontal while the input return loss was generally better than -2 dB before matching sections in the tuners and comparable with common automotive antennas. The antennas in the roof aperture offer an alternative place to mount antennas on automobiles

Dual-Band Pin-Patch Antenna for Wi-Fi Applications

The pin-patch antenna provides a low-profile monopolar element suitable for wireless access point requirements. This design concept is extended here to provide dual-band operation. Experimental results are compared to predictions from a FDTD package confirming monopolar radiation in two bands at 2.4 GHz and 5.7 GHz. This band spacing can be adjusted from 1.8:1 to more than 4:1.

Automotive antenna performance and simulation

A novel antenna installed under an aperture in the roof of a sports utility vehicle below a plastic panel akin to a sun roof slot is presented. It provides an alternative location for antenna placement on a vehicle. The antenna measures 88.2 cm times 18.5 cm and is highly suited for placement in a limited size vehicle roof aperture. It has seven feeds and is capable of covering simultaneous operation of the following communications systems; FM, AM, TV, TMC and DAB audio reception. Two extra antenna elements/feeds are used for diversity reception purposes. A comparison of measurements and simulations of the proposed antenna system was carried out at 100 MHz. Simulated performance of the antenna system are shown for 200 MHz and 450-800 MHz.

Optically frequency modulated 6 GHz MMIC oscillator

Optical illumination is used to modulate a 6 GHz GaAs MMIC VCO. Tuning can be achieved by illuminating either the MESFET or the Varactor. The MESFET tuning is caused by photocurrents varying the self-bias condition. Varactor optical tuning results from both a change in the junction capacitance and by external voltages generated by a photocurrent. Although both devices achieved similar D.C. optical tuning levels, tuning via the Varactor was found to be frequency limited. Preference is therefore given to illumination of the MESFET as the optical interface component. The resulting FM modulation bandwidth achieved is sufficient for the transmission of video signals with bandwidths up to 10 MHz.

Highly linear RF amplifier design: theoretical analysis and experimental study

In this article, a high frequency amplifier design method based on the negative impedance compensation has been demonstrated analytically and experimentally. An effective nonlinear model has been used to simulate the harmonic distortion and intermodulation distortion factors in amplifier design. The simulation and measurement results show that, with this proposed technique, high linearity and high gain accuracy can be achieved. The proposed method is particularly suitable for linearisation of RF/microwave amplifiers with low open–loop gain.

Control of ground plane influence on antenna radiation pattern for mobile handheld devices

This paper presents the effects of a choke-slot on solid ground plane of an antenna, fabricated on FR4 substrate to be used in mobile communication system. Techniques have been discussed to control the ground plane current and reduce any degradation. The simulations and measurements show that introducing a slot on a conventional solid ground plane can significantly improve the radiation pattern of an antenna. Good performance at the Personal Communication Service (PCS 1900) band promises the use of this antenna on personal mobility, advance cellular phone services and wireless communication services. Achieving the maximum gain towards the expected direction for mobile phone application with the help of a choke-slot on antennas ground plane demonstrates the effectiveness of this technique.

Planar Roof Mounted Automotive Antenna

A planar antenna installed under an aperture in the roof of a sports utility vehicle is presented. It provides an alternative location for antenna placement on a vehicle. The antenna measures 88.2 cm times 18.5 cm and has seven feeds and is capable of covering simultaneous operation of the following communications systems; FM, AM, TV, TMC and DAB audio reception. A comparison of measurements and simulations of the proposed antenna system was carried out at the FM broadcast band at 100 MHz.

High frequency CMOS amplifier with improved linearity

In this paper, a novel amplifier linearisation technique based on the negative impedance compensation is presented. As demonstrated by using Volterra model, the proposed technique is suitable for linearising amplifiers with low open-loop gain, which is appropriate for RF/microwave applications. A single-chip CMOS amplifier has been designed using the proposed method, and the simulation results show that high gain accuracy (improved by 38%) and high linearity (IMD3 improved by 14 dB, OIP3 improved by 11 dB and adjacent channel power ratio (ACPR) improved by 44% for CDMA signal) can be achieved.

Multiband Low-Profile Antenna for Remote Antenna Unit Picocell Applications

The design of a compact, low-profile antenna constructed from five wire-patch elements is investigated. For a fiber-radio system a critical design parameter is the isolation between two WLAN elements. It is shown the structure can be optimized to provide in excess of 25-dB isolation. Good agreement between experiment and modeling is demonstrated including these mutual coupling effects.

Modelling and design of optically controlled MMIC oscillators

The design and performance of an optically injection-locked X-band MMIC HEMT oscillator is reported and compared with an earlier MMIC MESFET VCO. The transmission of FM signals using the optically injection-locked HEMT oscillator is demonstrated. Accurate large-signal models for illuminated active MMIC devices have been developed. The models have been implemented in a commercial, industry-standard microwave circuit simulator (HPs MDS), and have been verified through the simulation not only of device behaviour but of the overall circuit behaviour of the MESFET VCO as well.