Futurecom Systems Group ULC. CMDUHF Manuale Utente
8M074X01-01 Rev.1
7
The programming software allows to display on the computer screen the measured values of received
signal power level, actual transmitted power level, VSWR on the Tx output port, and the internal
temperature of the unit.
signal power level, actual transmitted power level, VSWR on the Tx output port, and the internal
temperature of the unit.
6.0 BLOCK DIAGRAM AND DESCRIPTION
The block diagram of the Channel Module is shown in 8D074A14 drawing. The Channel Module
consists of the following blocks: Transceiver, Power Amplifier and Controller module.
consists of the following blocks: Transceiver, Power Amplifier and Controller module.
6. 1 TRANSCEIVER
Transceiver starts with a band-pass filter that filters out of band unwanted frequencies. It is followed by
a low noise amplifier, which can be switched in/out of the signal path under software control. A
software-controlled 30 dB attenuator is next. It is used to control input sensitivity and to lower
intermodulation products for stronger input signals. (Procedure to set up this attenuator can be found in
the following section).
Transceiver starts with a band-pass filter that filters out of band unwanted frequencies. It is followed by
a low noise amplifier, which can be switched in/out of the signal path under software control. A
software-controlled 30 dB attenuator is next. It is used to control input sensitivity and to lower
intermodulation products for stronger input signals. (Procedure to set up this attenuator can be found in
the following section).
The next two stages consist of a Voltage Controlled Oscillator (VCO), mixer, band-pass filter and an
amplifier. These two stages implement double heterodyne down conversion to Intermediate Frequency
of 450 kHz. Voltage Controlled Oscillator frequencies are based on a single Temperature
Compensated Crystal Oscillator (TCXO).
amplifier. These two stages implement double heterodyne down conversion to Intermediate Frequency
of 450 kHz. Voltage Controlled Oscillator frequencies are based on a single Temperature
Compensated Crystal Oscillator (TCXO).
Proper selectivity of the Channel Module is achieved by the Intermediate Frequency stage. The
selectivity is assured by the input filter together with other filters in this stage. The IF signal is also used
to produce baseband audio signal and provides Received Signal Strength (RSSI) indication.
selectivity is assured by the input filter together with other filters in this stage. The IF signal is also used
to produce baseband audio signal and provides Received Signal Strength (RSSI) indication.
The rest of the Transceiver section is mainly an up-conversion circuitry with associated filters. An
additional Voltage Controlled Oscillator can be switched into the last mixer. This VCO can be
modulated with audio modulation. It can add a programmable subaudible controlling tone.
The output from the Transceiver section is the signal on final output frequency.
additional Voltage Controlled Oscillator can be switched into the last mixer. This VCO can be
modulated with audio modulation. It can add a programmable subaudible controlling tone.
The output from the Transceiver section is the signal on final output frequency.