Product Manual

© MiMOMax Wireless Ltd
Tornado Product Manual
27
7 DUPLEXER TUNING GUIDE
The MiMOMax Tornado radio unit has two transmitters and two receivers; these connect to two antenna ports via two
duplexers.
The duplexer serves three primary functions.
• It allows one transmitter and one receiver to be connected to a single antenna port.
• It reduces the high-power transmitter signal getting into the sensitive receiver, and the received signal getting into
the transmitter.
• In the case of the Tornado duplexer, the Low Noise Amplifier for the Receive path has been integrated onto the
duplexer printed circuit board.
This manual covers internal duplexer tuning for 400 – 470 MHz radios. 700 MHz radios do not require duplexer tuning and
duplexers should not be tuned in the 900 MHz range. VHF radios do not have internal duplexers.
7.1 DUPLEXER TUNING
The 400-470 MHz internal duplexers are designed for a TX to Rx frequency difference of greater than 5 MHz. The filters are
band pass filters with tuneable notches at +/-the difference in frequency. Given that notches appear either side of the pass
band, the duplexer can support TX high or TX low configurations. Note: TX high means the transmitter frequency is above the
receive frequency. TX low means the transmitter frequency is below the receive frequency.
The 3dB pass band is nominally designed to be 3.5MHz. However this will vary slightly across the band. It will be slightly wider
at the top of the band and narrower at the bottom of the band. The insertion loss is typically 3.4dB in the pass band. Insertion
loss will vary across the band, being less at the top of the band and more at the bottom of the band. The Tx notch depth is
designed to be >60dB at +/-5MHz. Note that this improves as the other path is tuned up and typically with both Tx and Rx
tuned properly the notch depth will approach 65dB.
7.2 400-470 MHZ DUPLEXER TUNING GUIDE
NB: full anti-static precautions are to be taken.
7.3 400MHZ INTERNAL DUPLEXERS
The 400MHz duplexers are band pass duplexers with notches on each of the alternate signal paths. The transmitter path will
have a notch tuned to the receiver frequency. The receiver path will have a notch tuned to the transmitter frequency. Each of
these Duplexers is made up of ten tuneable elements, five for the transmitter path and five for the receiver path.
Top View of Channel 1 Duplexer
Channel 2 duplexers are electrically identical, however, from the top view they are considered almost symmetrical about the
longest axis. The duplexers are mounted to pillars in the radio housing. M3x10mm T10 Torx head Taptite screws are used to
secure the duplexer. The duplexer is further secured through fixing the N-Type connector to the front face of the chassis using
the N-Type 19mm hex mounting nut and spring washer.
The duplexer electrically connects to the transmitter and receiver via semi-flexible coax. The coax is terminated in SMB female
RF connectors to mate with the opposite gender on the RF and duplexer printed circuit boards. Due to mechanical constraints
the duplexers cannot be interchanged between Channels 1 and 2.
The duplexers would be fitted in the chassis as seen below. The symmetry is more obvious from this view. As mentioned
earlier, in addition to the normal duplexing function the LNA is integrated into the duplexer. The power supply (+5V) for channel
1 and 2 LNA’s are provided by the red and black twisted cable seen connecting the top corner of the duplexers to the RF
printed circuit board. In this view Channel 1 is seen on the left side of the radio and Channel 2 on the right. With the radio