I need to design af pulsing oscilator to be used for some testing.
It must be able to turn on/off a raw carrier wave of 2.4 Ghz in random intervals of about 2 ms, and it must be possible to adjust the amplitude of the carrier wave.
My idear was to solve it by an oscillator, a PA (power amplifier), and a switch.
The switch is controlled by a little microcontroller, and guides the wave either into the antenna (on) or into a load resistor (off)
I believe Analog Devices has most of the components that I need.
Any one who can recomend some devices for me?
I would recommend the ADF4360-0 as the base oscillator. It is very simple to use, but check if its phase noise meets your requirements.
It is possible the turn off and on the output signal by switching the PLL to power-down mode, but it seems the lock time is too large for you (5..0.6msec, page 17). Some amplifiers have on/off control input, if you are lucky you can find one meeting your requirements. In other case I would use the ADG901 or similar RF switch. Please consider * The isolation in OFF state is about -20dB at the given frequency, therefore you should use two (or more) of them if you want smaller leakage in OFF state. * Its input power is limited, so place between the pll and the amplifier, and not at the output of the amplifier. (there are high power rf switches in high price range...)
Up to +10dBm, the output amplifier could be a custom MMIC. You can achieve larger output power (up to +20dBm) with these devices, but overtones could be a problem. There are many manufacturers, see below. In the 1W range, use a suitable power amplifier.
What do you mean of "adjusting the amplitude of the carrier wave"? * The cheaper (and best) your oscillator provides fixed output power, and you change an external attenuator manually.* Some power amplifiers have a gain control input, usually providing a several (2..4) ~10dB gain steps.* There are voltage variable (EVA-3000) or digital step attenuators (DAT-15R5-P), but they are not cheap.
best regards, vili
pll:http://www.analog.com/static/imported-files/data_sheets/ADF4360-0.pdfswitch:http://www.analog.com/static/imported-files/data_sheets/ADG901_902.pdfmmic:www.avago.com (MGA-62563)www.minicircuits.com (GALI-)www.analog.com (ADL5542)power amplifier:www.rfmd.com (SZM-2066Z, 2W)www.ti.com (TRF1123, 1W)
Regarding the amplifier how much gain, output power ,etc, do you require in your application?
Thanks for your advices.
The ADF4360-0 sounds like a good solution for the Oscillaator part. However it would be great if output could be disbaled more rapidly, so that the swtches would not bee needed. Any alternatives?
Can switches be avoided by selecting a oscillator/PA with an enable pin?
Regarding "adjusting the amplitude of the carrier wave"? I simply mean that it must be possible to adjust the output power to the antenna
If thios can be done by a simple potentiometer controlling the gain op the PA it would be great.
But an attenuator with a potentiometer is also ok. Any Analog Devices antenuator sugestions?
Output power of the generator should be about the same as a WiFi transmitter:
When the signal is off (dead time) it should be reduced by at least 40 dB
I would suggest the ADL5243 RF VGA as a possible solution for the Amp. P1 dB is 26 dBm @ 2140 MHz.