
368 Microwave Engineering
If substitution using linear detection: This method is good upto 100–150 dB.
In Figure 10.31, frequencies of signal source (f
1
) and local oscillator
(f
2
) and their respective eld strengths E
1
and E
2
are shown. As E
1
≪ E
2
,
E E E E
1 2
, ,
1
2
2
2
< these eld strengths give
( )E E E E E E E E E
1 2
2
1 2 1 2
2 2+ = + + ≈ +
1
2
2
2
2
2
(10.12)
Thus, the output is linearly related with E
1
.
10.8.7.3 Cavity Resonance Method
Cavity resonators have been discussed at length in Chapter 4. A long resonator
can be formed by shortening a transmission line (say waveguide) at both ends.
If L is the length of the line, R is ...