I have a GPS antenna (lozenge shaped ca. 4.5mm x 3.0mm, magnetic, Frequency 1575.42 +/-2MHz, Gain 27dB, Voltage 3~5 vDC, fitted with a coaxial cable (one conductor and shield) terminating in a BNC plug).
I would like to connect this as an external signal source to my phone using the USB plug in the hope of increasing the sensitivity of the device. How should the connection be made? Is a power source required for the antenna and what additional circuitry is required?

I suppose the best way is to buy a reradiation antenne.

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Thanks for your reply.
Essentially what I have is similar to what is shown in the pic, but without the car plug and without the long wire on which it's not clear whether there is a plug (Lightning or 36 pin for iPhone or micro USB for other phones) or whether it's effectively just a signal amplifier. I certainly don't want to shell out £39 on a device, what I want is a "quick fix".

you can't connect the antenna to the usb port because the usb doesn't provide power. it's just used to charge and/or exchange data. also we don't know what kind of antenna you have and might not be appropriate to increase the gps signal frequency.
also there's 2 kinds of antennas, passive or active (unpowered or powered). powered antennas can most times be powered by the antenna connector itself.
also tomtom devices uses MCX connector for the antenas and you have BNC. you need an adapter. more adapters and longer the cable you have more losses occur and you get less signal.
also we don't know if your connector is male or female. but basically you need something like this:
https://www.amazon.com/DHT-Electronics-coaxial-adapter-connector/dp/B00CWDKAXA
or this
https://www.aliexpress.com/item/New-BNC-Female-Jack-Connector-Switch-MCX-Male-Plug-Convertor-RG316-Wholesale-Fast-Ship-15CM-6/32231910514.html?spm=2114.01010208.3.1.2oYmAc&ws_ab_test=searchweb0_0,searchweb201602_4_10056_10065_10055_10068_10054_10069_10059_10073_10017_10070_10060_10061_10052_10062_10053_10050_10051,searchweb201603_3&btsid=a21767ff-f722-43fd-af40-252070584ad5
and this it's a passive gps antenna with the connector you need:
https://www.aliexpress.com/item/GPS-Antenna-active-MCX-male-right-angle-connector-with-3M-extension-cable-magnetic-NEW-wholesale-price/32304891554.html?spm=2114.01010208.3.46.d34SGK&ws_ab_test=searchweb0_0,searchweb201602_4_10056_10065_10055_10068_10054_10069_10059_10073_10017_10070_10060_10061_10052_10062_10053_10050_10051,searchweb201603_3&btsid=a71ab1a6-ff06-4df9-ab79-30b8e6a1666b

Thanks for your response.
I fully realise that some kind of adaptor or rewiring would be necessary to allow the device to be plugged into my phone../that was the purpose of the OP!
5v is available at the micro usb socket on the phone with the other two conductors permitting signal input. In any case power could be provided by a battery if required.
The device I have is identical to that given in your link:
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except for the connector.
Are you suggesting that it could be connected directly to the signal pins of a micro usb plug without any power supply. If that is the case, why does it say "voltage 3-5VDC"?
Devices with a similar appearance are available on eBay with a USB plug on, but cost around $40 compared with the one in your link at less than $10.
I don't understand the statement that you don't know the kind of antenna I have; I gave all the details in the OP. What do you mean about increasing the signal frequency, that is also given in my OP?