Microwave Radar Detectors

Uniden LRD 6199SW
Valentine One Radar Locator

Introduction

Radar -- an acronym for RAdio Detection And Ranging -- was invented during World War II and was used to locate enemy planes and ships. The radar device emits a microwave signal and detects the arrival of the reflected signal. The microwave is reflected by objects such as aircraft, and the elapsed time between emission and return is a function of the distance of the object from the radar device. In addition, the speed and direction of a moving object can be determined by analyzing the shift in the frequency of the microwave signal (Doppler effect).

Radar detectors are essentially radios that are tuned to the exact microwave frequencies employed in traffic radar. They detect radar signals, sound an alert, and inform the driver of the strength and sometimes location of the radar source. Most radar detectors will identify the three common microwave frequencies empoyed in traffic radars:

X Band: 10.49 - 10.56 GHz
K Band: 24.04 - 24.26 GHz
Ka Band: 33.40 - 36.00 GHz

More recently, traffic controls have started using laser guns to identify speeders. A series of short (nanosecond) pulses of infrared laser light is emitted, and the laser gun once again measures the time it takes for the laser light to be reflected.

This bulletin covers two radar detectors-- the Uniden LRD 6199SW and the Valentine One Radar Locator.

  • The Uniden LRD 6199SW detects X, K, and KA band radar and laser sources from all directions. Multiple visual and audible adjustible alarms indicate the strength and distance of the radar or laser source. The unit can be mounted on the windshield and is powered by the cigarette lighter through an adapter. The unit retails for $99.
  • The Valentine One Radar Locator is a high-end radar/laser detector that retails for $399. It not only detects radar and laser signals, but can also identify the location (ahead, behind, side) of the source and the number of sources. The Valentine has both a forward and a rearward antenna.

Construction

Both units are small enough to be attached to the windshield with suction cups, but the Uniden has a sleek, thin design compared to the boxy style of the Valentine. The latter also weighs almost twice as much as the Uniden.

Altogether, the Uniden contains four printed circuit boards:

  • A main board with the logic functions, switches, connectors, and diodes
  • A small laser board with a single laser detecting component
  • Two waveguide boards inside the waveguide for radar detection

The Valentine, on the other hand, consists of seven printed circuit boards:

  • A main board with the logic functions, switches, and connectors
  • A laser board with six individual laser detectors
  • Two waveguide boards mounted back-to-back onto the waveguide
  • Two boards placed into separate shielded compartments of the waveguide
  • A counter board with LED display

The printed circuit assemblies found in either detector are not very complex. The Uniden detector uses slightly denser boards and components to minimize the number of boards used and to lower costs.

All wireless applications -- especially those in the microwave range (e.g., DBS and LMDS transceivers) -- have particular needs with respect to shielding and low loss substrates. These radar detectors illustrate possible approaches.

EMI Shielding

The Uniden and Valentine radar detectors are faced with significant EMI challenges, and employ various measures of containment --

  • Metal waveguides surround the EMI-generating components, acting as a shield. Furthermore, the Valentine uses a metal outer housing.
  • Individual components are packaged in TO39 metal cans, and some boards are separately packed into individual compartments that are part of the waveguide assembly.
  • The plated copper area on the printed circuit boards is maximized.
  • Plated-through holes along the edges enhance EMI shielding.

Specialty Laminates

Most printed circuit boards are made of glass epoxy laminates, if not of cheaper composite or paper laminates. For certain high-end applications, however, the electrical or mechanical requirements demand specialty laminates such as cyanate ester, polyimide, Getek, PTFE, or others. One of the Uniden's waveguide boards and both of the Valentine's waveguide boards are based on PTFE.

PTFE is a low loss laminate that is used primarily in wireless applications where both the frequency and the transmitted power is high. Military and aerospace applications are currently the largest users of PTFE, but consumer applications are quickly becoming major consumers of PTFE.

Radar detectors require PTFE substrates due to the high frequency of radar (greater than 10 GHz). The Uniden uses a PTFE laminate with woven fiberglass reinforcement, whereas both of the Valentine's waveguide boards use PTFE laminate with a non-woven fiberglass reinforcement.

Laser Detection

Both the Uniden and the Valentine units are capable of detecting laser beams. The Valentine uses six individual infrared laser photo diodes mounted on the laser board and facing the front of the car (two at an angle to obtain greater coverage).

The Uniden unit, on the other hand, uses a single photo diode component in a 20-lead DIP package. A lightguide funnels the light to the photodiode for 360 coverage.

Conclusion

Radar detectors are interesting products because they combine the need for low cost, high volume manufacturing with the technical requirements associated with high frequency communications. The Uniden targets the mainstream, very cost-sensitive segment of the radar detector market, whereas the Valentine radar locator is for the die-hard radar afficionado.

Even though the Uniden by no means uses leading edge packaging technology, it was able to significantly decrease the number of printed circuit assemblies by using slightly denser designs and greater component integration. The Uniden also confines the use of PTFE boards to only those components that absolutely require a low loss substrate.

Copyright 1996 Integrated Electronics Engineering Center and Prismark Partners LLC.

12/96

Warranty Disclaimer -- All information used in the preparation of this report was obtained from sources believed to be reliable at the time the information was collected. Prismark Partners LLC, its employees, its agents, and assignees have exercised their best efforts in preparing this report. Prismark Partners LLC extends no warranties with respect to this information and shall bear no liability whatsoever to the report recipient or to any other party as a result of the use of this report or the information contained herein.

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Copyright © 2000 [IEEC]. All rights reserved. Revised: February 28, 2002 .