The antenna symbol used is that of a Marconi style antenna - an isolated wire in an RF-field. Another name: monopole antenna. It generates an RF signal at one end with respect to ground (earth). It is often an odd # of quarter-wavelengths long. Earth is a required part of this antenna, and the earth connection should have a low RF impedance, ideally lower than the 40-ohm impedance of the quarter-wavelength monopole. Sometimes a quarter-wavelength wire substitutes for an earth connection (but now you've lost half your signal).
As suggested, a transformer would be an appropriate solution.
simulate this circuit – Schematic created using CircuitLab
A loop style of antenna is a self-contained antenna that can work properly with a diode-type rectifier: the DC voltage will appear across the load resistor, since loops generally have a very low DC resistance (much lower than the load resistor). A loop antenna can be multi-turn, self-resonant at a desired frequency.
Recognize that the diodes of the bridge rectifier need an input RF voltage high enough to overcome forward voltage (for silicon: about 0.6V, for Schottky: about 0.3V). For a bridge rectifier, two diodes require double RF voltage...a single diode rectifier may yield more voltage across the load resistor rather than a 4-diode rectifier for small RF signals. A very big antenna signal is required for this direct RF detector.
If you persist:
Since only large RF voltages are efficiently rectified by the bridge, some effort to match antenna impedance to a large-value load resistor makes the rectifier more efficient. For example, a quarter-wavelength monopole antenna might have an equivalent source resistance of 40 ohms: a 1:5 turns-ratio step-up transformer would efficiently match to a 1000 ohm Rload. This assumes that the earth ground is a good one, with low RF impedance.
An op amp can amplify the DC voltage across the load resistor. Most op amps haven't the bandwidth to amplify RF signals above 100 kHz. Local ground would be connected to the opamp's DC supply.
The diode within an optocoupler requires even more RF voltage than silicon diodes, and is not optimized for high frequency (RF) use.