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Microwave AM detector
MMD850
Detects AM wave of 2 to 8GHz in 30dB dynamic range.
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| Microwave AM detector MMD850 performs AM detection of signal of 2 to 8GHz
(available for 1 to 15GHz range as special order) in 30dB dynamic range.
It may be used for evaluation of W-CDMA, CDMA, GSM, PDC, PHS, wireless
LAN, Bluetooth and wireless communication equipment including evaluation
of ETC signals. |
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Faults of coaxial type AM detector |
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Coaxial type AM detector has two disadvantages in the application indicated below :
The first is that the dynamic range is narrow. The curve is non-linear
when the input is more than +5dBm or less than -10dBm as shown below. Therefore,
the workable range is only +15dBm. It is provided, however, that when the
peak level of input is less than +5dB, -6dBm for instance, the dynamic
range is even narrower and drops to 4dB. Narrow dynamic range means that
the waveform is collapsed.
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| Coaxial type AM detector in / out characteristics |
The second is video output frequency band. The equivalent circuit of coaxial
type AM detector (Rv = 1.5kohm, Co = 30pF) of a certain manufacturer is
shown below. The case where observation is performed with this AM detector
connected to an oscilloscope (RL = 1Mohm, CL2 = 25pF) using 1 meter coaxial cable (CL1 = 100pF) is taken into account.
Tr = 0.35 / fb = 2.2RvRL (Co + CL1 + CL2) / (Rv + RL)
Therefore, rising time Tr = 511 [ns] and frequency band fb = 685 [kHz]. It is learnt that the band is lower than what was imagined.
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| Coaxial type AM detector equivalent circuit |
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The block diagram of microwave AM detector MMD850 is shown below. When
a microwave amplifier and linearizer are added to it, 30dB dynamic range
is secured against signals of peak level more than -6dBm and up, and in
addition, 10MHz bandwidth is secured without being affected by the load.
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| MMD850 block diagram |
Against signals of peak level more than -6dBm, it is possible to observe signals without spoiling the dynamic range when fixed attenuator is located to the input. If three attenuators of 3dB, 6dB and 12dB are prepared, for example, it is possible to perform observation in at least 27dB dynamic range, against signals of peak level -6dBm to +15dBm. Furthermore, due to the fact that the output impedance of the linearizer is 50ohm, it is possible to perform observation without being affected by the load, when the output is terminated with 50ohm.
Input signals and detected output waveforms are indicated below. Example
1 is the case where continuous wave or FM wave of -6dBm is input. +1V DC
voltage is produced as the detected output. Example 2 is the case where
ASK signals of peak level -6dBm and bottom level -36dBm (modulation factor
94%) is input. A waveform of peak level +1V and bottom level +31.6mV is
output.
Input signal and detected output waveform
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Input characteristics
Input frequency range
Optimum input level
Dynamic range
VSWR
Input damage level
Output characteristics
Output frequency range
Output voltage
Polarity
Output impedance
General
Power source
Dimensions
Standard accessories |
2 to 8GHz
*Available for 1 to 15GHz range as special order
-6dBm @ peak level
30dB @ -6dBm input
less than 1.4
+13dBm
DC to 10MHz @ -3dBm
+1.0V @ 50ohm load and -6dBm input
positive polarity
50ohm
90 to 132VAC, 50 / 60Hz
320 (W) × 56 (H) × 350 (D) mm (excluding projections)
Operation manual (1pc), Fuse (1pc), Power cable (1pc) |
| Optional |
•(180 to 250 VAC) Power source
•Coaxial cable MC201
•Coaxial cable MC202
•Coaxial cable MC203
•Fixed microwave attenuators (1 to 10, 12, 13, 15, 20dB)
•50 ohm termination |
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