BPSK modulation using a Mixer
I'm trying to generate a BPSK signal based upon a 120 MHz carrier signal and a TTL signal with a modulation rate of 36 microseconds.
I am looking at my options and I'm pretty sure that I can either use a double balanced mixer. I'm curious that will require a modulation signal that is bi-polar in nature instead of the TTL signal. TTL (0 to 5) Bipolar (-5 to 5)
I'm also interested in using other schemes but I have never done this before and I'm not sure where to start. Any information or help would greatly be appreciated.
Thanks in Advance
Shane
Minicircuits used to have a diagram for BPSK with a DBM but I can't find it. Yes, it has to be bipolar current into the IF port (which is DC coupled). You place a resistor in series with the IF to limit the current. You may want to be able to control the peak to peak current and the DC offset (which will affect carrier supression).
I buit once once with PIN diodes a rat-race coupler. This is good for high power. There are probably other ways to do it with switches and transmission lines. There are also some MMICs but most everything is an I/Q modulator.
http://www.minicircuits.com/appnote/mod11-2.pdf
Right now I am leading towards a hybrid with 2 pin diodes. One of the diode an open circuit and the other diodes a short circuit.
Either the coupler or the dc coupled mixer are what I'm more comfortable working with as most of my experience lies in RF (but I?m still new to all this), I have never done this so we'll see how it works out.
Does anyone have any information about a particular MMIC for generating BPSK and a date sheet or something so I can get an idea of their performance (especially what level they require to operate)? I'm trying to use a low level input to the BPSK because of other elements further down the transmit chain. (Hoping to get away with -15 dBm)