Multiband antenna-receiver integration using an RF multiplexer with sensitivity-constrained design

In this paper we consider an alternative approach which exploits the fact that the single-chip transceivers from which practical multiband radios are likely to be built consist of multiple receivers operating in parallel, each of which can be directly connected to a dedicated off-chip filter. In this case an RF multiplexer can be used to segment the tuning range into multiple bands. Once partitioned in this manner, the interface for lower frequency bands - the most troublesome as noted above - can be separately optimized not for match efficiency, but rather for effective sensitivity, exploiting the high levels of environmental noise known to exist at these frequencies [4]. We demonstrate the technique by designing an antenna interface which yields acceptable performance for operation in four bands - 138-174 MHz, 220-222 MHz, 406-512 MHz, and 764-862 MHz - when used with a monopole just 20 cm long with 5 mm radius, assuming front end noise figure in the range 1-2 dB. Such noise figures are well within the capabilities of existing low-cost electronics.