Adaptive receivers
View Patent ↗An adaptive receiver for receiving a radio frequency (RF) signal and converting the RF signal at an RF frequency F RF toward a low intermediate frequency F IF is disclosed. The adaptive receiver comprises a pair of band pass filters with a nominal center frequency F c equal to F IF , a look-up table (LUT) configured to estimate a frequency offset Δ f , representing the center frequency of the band pass filter due to an operating temperature change and/or process variation, a micro controller configured to estimate the operating center frequency of the band pass filter (=F IF +Δ f with the frequency offset included) and use this new center frequency as the adaptive intermediate frequency F IF,AD , and a local oscillator generates oscillating signals at a frequency F LO equal to F RF minus F IF,AD . A temperature sensing device may also be included in this adaptive receiver.
1. An adaptive receiver for receiving a radio frequency (RF) signal and converting the RF signal at a frequency F RF toward an intermediate frequency (IF) signal at a frequency F IF,AD , the adaptive receiver comprising:
a pair of band pass filters, each with a nominal center frequency at F IF ,
a two-dimensional look-up table configured to provide frequency offset (Δ f ) values of the center frequency of the band pass filters for environmental temperature and process corner variations;
a temperature sensing device to provide temperature information;
a micro controller configured to, based on the frequency offset (Δ f ) values from the look-up table, the temperature information from the temperature sensing device and pre-stored information on the process corner, estimate an adaptive intermediate frequency F IF,AD equal to the nominal center frequency of the band pass filter, F IF , plus the frequency offset Δ f ; and
a local oscillator to generate sinusoidal signals at a frequency F LO equal to F RF minus F IF,AD .
2. The adaptive receiver of claim 1 further comprising two mixers each comprising:
a first input to receive the received RF signal; and
a second input to receive one of a first and a second local oscillator (LO) signals at the frequency F LO =F RF −F IF,AD =F RF −(F IF +Δ f ), wherein the first LO signal and the second LO signal are orthogonal to one another in phase.
3. The adaptive receiver of claim 2 further comprising a low noise amplifier to amplify the received RF signal.
4. An adaptive receiver for receiving a radio frequency (RF) signal and converting the RF signal at a frequency F RF toward an intermediate frequency (IF) signal at a frequency F IF,AD , the adaptive receiver comprising:
a pair of band pass filters, each with a nominal center frequency at F IF ,
a one-dimensional look-up table configured to provide an intermediate frequency offset Δ f as a function of the difference between two tone voltages, ΔV FX2-FX1 ;
wherein the voltage difference ΔV FX2-FX1 (=V FX2 −V FX1 ) is determined based on measured voltages V FX2 and V FX1 for two frequencies;
a micro controller configured to, using the ΔV FX2-FX1 value, determine the frequency offset Δ f from the one-dimensional look-up table and compute an adaptive intermediate frequency F IF,AD equal to the sum of the nominal intermediate frequency F IF and Δ f ; and
a local oscillator to generate sinusoidal signals at a frequency F LO equal to F RF minus F IF,AD .
5. The adaptive receiver of claim 4 further comprising two mixers each comprising:
a first input to receive the received RF signal after amplification by a low noise amplifier; and
a second input to receive one of a first and a second local oscillator (LO) signals with the same frequency (F LO =F RF −F IF,AD =F RF −(F IF +Δ f )) and a 90-degree phase difference.
6. An adaptive receiver for receiving a radio frequency (RF) signal and converting the RF signal at a frequency F toward an intermediate frequency (IF) signal at a frequency F IF,AD , the adaptive receiver comprising:
a band pass filter with a nominal center frequency at F IF ,
a one-dimensional look-up table configured to provide an intermediate frequency offset Δ f as a function of the difference of two tone voltages, ΔV FX2-FX1 ;
wherein the voltage difference ΔV FX2-FX1 (=V FX2 −V FX1 ) is determined after the adaptive receiver is powered on at temperature T on , based on measured voltages V FX2 and V FX1 for two frequencies;
a temperature sensing device to detect the temperature difference Δ T (=T on −T op ) between an operating temperature T op and the temperature T on ;
a micro controller configured to, using the ΔV FX2-FX1 value, determine the frequency offset Δ f from the one-dimensional look-up table and compute an adaptive intermediate frequency F IF,AD equal to the sum of the nominal intermediate frequency F IF , Δ f and F slope ×Δ T , where F slope is the F IF +Δ f slope coefficient related to temperature difference Δ T ; and
a local oscillator to generate sinusoidal signals at a frequency F LO equal to F RF minus F IF,AD .
7. The adaptive receiver of claim 6 further comprising two mixers each comprising:
a first input to receive the received RF signal after amplification by a low noise amplifier; and
a second input to receive one of a first and a second local oscillator (LO) signals with the same frequency (F LO =F RF −F IF,AD =F RF −(F IF +Δ f +F slope ×Δ T )) and a 90-degree phase difference.