narrow band matching network for ad8307

i want to receive a pulse modulated signal with Logarithmic Detector to detect the signal.ADI has AD8313(to 2.5GHz) and AD8307(to 500MHz),so i can detect the RF signal with AD8313 or down the RF signal to IF signal then detect it with AD8307.i don't which is better?i need sensitivity -75dbm.thanks.

AD8313 has better response time that would help detecting your pulse signal.

AD8313 is at the Front end of the receiver,that is the RF signal passes through a RF filter then detected with AD8313.if the signal is small ,is it ok?does the noise influence the detector?

The datasheet of AD8313 specify that the wide band low signal sensitivity is -65dBm, and this limit can be increased with 6dB (-71dBm) if a narrow band input matching network is used. That means you cannot detect a -75dB input signal without a spare amplifier in the front of the detector.

AD8307 has better sensitivity (-88dBm), but as I said the trade off is the response time.

I starts to design a logarithmic amplifier.
Can anyone tell me what the logamp response time is and how to simulate that spec?
More over, some commercial logamps state that they can be used to measure RF power of modulated signals like UTMS/CDMA/WCDMA, WLAN...
I am using ADS. In the modulated source menu, there is some kind of sources (CDMA, 3GPP,...) with only freq, power and impedance parameters. Anyone can show me how to have WCDMA n-channel.
Thanks all.

8307 is good,and y should add LNA in front of it and y need add a narrow band filter before the ad8307!
donnot forget push the bottom to add point to me!
good luck