Use following code :
[{
"SQAD_RATE_ID": "12494158",
"SQAD_MARKET": "ZANESVILLE1",
"SQAD_MARKET_ID": "0",
"SQAD_DAYPART": "PR",
"SQAD_DEMO": "W55+",
"SQAD_QTRYR": "3Q%20%2711",
"SQAD_LEVEL": "AVG",
"SQAD_CPP": "26"
}]
Remove first & last double quotes...
Check it here :
JSONLint - The JSON Validator.[
^]