Features

• High Sensitivity
• Built-in IF Matching Network
• Mechanically Rugged
• Built-in Protection Diode and Shorting Switch

Applications

• Radio Astronomy
• Plasma Diagnostics
• Atmospheric Sounding
• Laboratory Spectroscopy

Description

Farran Technology produces a complete range of corner cube mixers for use in the submillimeter wavelength region. The corner cube mixer consists of a long wire antenna, backed by a corner cube reflector, contacting a low capacitance Schottky barrier diode. This configuration has been recognised as being that providing the most sensitive and broadband response to radiation at submillimeter wavelengths.

Farran Technology uses low noise diodes whose performance is the key to high sensitivity in this wavelength region. All corner cubes supplied by FTL are mechanically rugged units and each incorporates a shorting switch to provide protection to the unit from static discharges when it is not being used. A built-in protection diode reduces the risk of burnout from transients when the mixer is in use.

Each corner cube mixer is custom made for the frequency specified by the customer. The corresponding wavelength determines the length of antenna in the corner cubes as well as the parameters of the Schottky diode to be used. In this way, our customers can be confident that the corner cube they are purchasing has been customized specially for their applications.

The corner cube mixers are intended for heterodyne reception with a local oscillator (LO). The output signal from the mixer is at an intermediate frequency (IF) in a specific IF bandwidth. The mixers have a built-in IF matching network to ensure that the highest sensitivity is achieved. The IF output impedance is 50W. It is important that the customer specifies the IF centre frequency and IF bandwidth:

1. IF centre frequency range: 0.5GHz to 15GHz as standard
2. IF bandwidth range: 100MHz to 1000MHz as standard.

The corner cube mixers can be ordered with fixed tuned corner reflector, model CMB, or with tunable corner reflector, model CMT. The standard FTL corner cube model CMB has the antenna structure optimized for a particular operating frequency, since the contacting whisker is located a fixed distance from the apex of the 90 degree back reflector.

Although the bandwidth of this device is rather broad, for applications where sensititvity is important there is a substantial improvement to be obtained by making the position of the 90 degree reflector adjustable with respect to the whisker.

This ensures that at any frequency other than the design frequency, the correct ratio of the whisker length to whisker spacing can be guaranteed and thus the performance optimized. The tunable corner cube mixers CMT have the same centre frequency specifications as for the CMB models with fixed corner reflector. They include an IF-matching network with integral DC-bias port and safety switch with protection diode.

The corner cube mixers require a DC-bias for the diode in order to achieve the lowest conversio loss. The DC-bias network is an integral part of the IF matching network and is supplied via a separate DC-bias input connector. The Farran Technology Precision DC Bias Supply FDB-F4 is recommended to ensure maximum safe operation.

CM(X)-1

300-600

1.0 - 0.5

9 / 12

3000

5

4 x 10^-20

CM(X)-2

600-800

0.5 - 0.4

12 / 14

7500

7

1 x 10^-19

CM(X)-3

800-1000

0.4 - 0.3

14 / 16

10000

10

1.5 x 10^-19

1000-2000

0.3 - 0.15

16 / 18

20000

15

3 x 10^-19

2000-3000

0.15 - 0.10

18 / 20

40000

30

6 x 10^-19

Notes

1. X=B: Fixed tuned;
   X=T: Tunable reflector
2. IF=1.2 - 1.4 GHz;
   T_IF=100K
3. These detectors have been constructed to be mechanically robust and to provide trouble-free operation if they are handled with reasonable care. However, in common with all whisker-contacted structures they can be accidentally damaged. Farran Technology provides a fast turnaround time on recontacting or whisker replacement for units which are returned to the factory.

Typical Outline